cas 702-23-8, 4-METHOXYPHENETHYL ALCOHOL | Articles data

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Formation and stability of the 4-methoxyphenonium ion in aqueous solution
The reaction of 2-methoxyphenylethyl tosylate (MeO-1-Ts) is first-order in [N3-]. A carbon-13 NMR analysis of the products of the reactions of MeO-1-[α-13C]Ts shows the formation of MeO-1-[β-13C]OH and MeO-1-[β-13C]N3 from the trapping of a symmetrical 4-methoxyphenonium ion reaction intermediate 2+. An analysis of the rate and product data provides a value of kaz/ks = 83 M- 1 for partitioning of 2 + between addition of azide ion and solvent. These data set a limit for the lifetime of 2+ in aqueous solution.
Tsuji, Yutaka,Hara, Daisuke,Hagimoto, Rui,Richard, John P.
p. 9568 - 9571
(2011)
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Cu-Catalyzed Phenol O-Methylation with Methylboronic Acid
A Cu-catalyzed oxidative cross-coupling of phenols with methylboronic acid to form aryl methyl ethers has been developed, expanding the scope of Chan-Evans-Lam alkylation. Electron-deficient phenol derivatives with a broad array of functional groups are methylated in high yields. Increased reaction temperature and catalyst loading enables the methylation of substrates incorporating pyridine and dihydroquinolone motifs. Electron-rich phenol derivatives are poor substrates for the methylation; the characterization of C?H homodimerization products formed from these substrates illuminates a competing mechanistic pathway.
Bartlett, Mairead E.,Chavez, Angela K.,Gaffney, Uma Bhagwat,Gorin, David J.,Lee, Joyce,Sharew, Betemariam,Wu, Miranda,Zhu, Yingchuan
supporting information
p. 5661 - 5664
(2021/11/11)

Evaluation of 2-(piperidine-1-yl)-ethyl (PIP) as a protecting group for phenols: Stability to ortho-lithiation conditions and boiling concentrated hydrobromic acid, orthogonality with most common protecting group classes, and deprotection via Cope elimination or by mild Lewis acids
A new protecting group, 2-(piperidine-1-yl)-ethyl (PIP), was evaluated as a protecting group for phenols. The PIP group was stable to ortho-lithiation conditions and refluxing with concentrated hydrobromic acid. Deprotection was accomplished by two routes, oxidation to N-oxides followed by Cope elimination (CE) and subsequent hydrolysis or ozonolysis of the vinyl ether or one-step deprotection by BBr3?Me2S. The PIP group is orthogonal to the O-benzyl, O-acetyl, O-t-butyldiphenylsilyl, O-methyl, O-p-methoxybenzyl, O-allyl, O-tetrahydropyranyl and N-t-butoxy carbonyl groups. The CE step was systematically studied and was found to give higher yields when the reaction was performed in the presence of silylating agents.
Norén, Rolf
(2021/04/07)

Nickel Hydride Catalyzed Cleavage of Allyl Ethers Induced by Isomerization
This report discloses the deallylation of O - and N -allyl functional groups by using a combination of a Ni-H precatalyst and excess Bronsted acid. Key steps are the isomerization of the O - or N -allyl group through Ni-catalyzed double-bond migration followed by Bronsted acid induced O/N-C bond hydrolysis. A variety of functional groups are tolerated in this protocol, highlighting its synthetic value.
Kathe, Prasad M.,Berkefeld, Andreas,Fleischer, Ivana
supporting information
p. 1629 - 1632
(2021/02/09)

Borane evolution and its application to organic synthesis using the phase-vanishing method
Although borane is a useful reagent, it is difficult to handle. In this study, borane was generated in situ from NaBH4 or nBu4NBH4 with several oxidants using a phase-vanishing (PV) method. The borane generated was directly reacted with alkenes, affording the desired alcohols in good yields after oxidation with H2O2 under basic conditions. The selective reduction of carboxylic acids with the evolved borane was examined. The organoboranes generated by the PV method successfully underwent Suzuki–Miyaura coupling. Using this PV system, reactions with borane can be carried out easily and safely in a common test tube.
Soga, Nene,Yoshiki, Tomo,Sato, Aoi,Kawamoto, Takuji,Ryu, Ilhyong,Matsubara, Hiroshi
supporting information

(2021/03/26)

Hydrosilylation of Esters Catalyzed by Bisphosphine Manganese(I) Complex: Selective Transformation of Esters to Alcohols
Selective and efficient hydrosilylations of esters to alcohols by a well-defined manganese(I) complex with a commercially available bisphosphine ligand are described. These reactions are easy alternatives for stoichiometric hydride reduction or hydrogenation, and employing cheap, abundant, and nonprecious metal is attractive. The hydrosilylations were performed at 100 °C under solvent-free conditions with low catalyst loading. A large variety of aromatic, aliphatic, and cyclic esters bearing different functional groups were selectively converted into the corresponding alcohols in good yields.
Bagh, Bidraha,Behera, Rakesh R.,Ghosh, Rahul,Khamari, Subrat,Panda, Surajit
supporting information
p. 3642 - 3648
(2020/04/20)

Synthesis method of p-hydroxyphenylethanol
The invention relates to the field of organic synthesis, and discloses a synthesis method of p-hydroxyphenylethanol, which comprises the following steps: (1) mixing methanol, sodium methoxide and a catalyst, and performing stirring; (2) adding 4-chlorophenethyl alcohol, and carrying out a heating reaction; (3) cooling to room temperature, carrying out filtering, and drying by distillation to obtain a 4-methoxyphenethyl alcohol crude product; (4) adding the crude product into a solvent, and performing stirring; (5) dropwise adding hydrobromic acid, carrying out heating reflux, and carrying outa heat preservation reaction until the reaction is finished; (6) cooling to 55-65 DEG C, slowly adding an alkaline solution, and adjusting the pH value to 6-7; and (7) cooling to 8-12 DEG C, stirringfor 0.5-1.5h, filtering the material to obtain a wet filter cake, adding a solvent, heating for dissolution, separating water, and carrying out recrystallizing, filtering, and spin-drying to obtain the final product. The product purity can reach 99% or more, the yield can reach 90% or more, and the whole synthesis process has the advantages of simple and mild reaction conditions, simple post-treatment, and low cost.
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Paragraph 0030-0032; 0038-0040; 0046-0048

(2020/07/21)

Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
p. 13659 - 13667
(2020/11/30)

Diaminodiphosphine tetradentate ligand and ruthenium complex thereof, and preparation methods and applications of ligand and complex
The invention discloses a diaminodiphosphine tetradentate ligand and a ruthenium complex thereof, and preparation methods and applications of the ligand and the complex, and provides a ruthenium complex represented by a formula I, wherein L is a diaminodiphosphine tetradentate ligand represented by a formula II, and X and Y are respectively and independently chlorine ion, bromine ion, iodine ion,hydrogen negative ion or BH4. According to the present invention, the ruthenium complex exhibits excellent catalytic activity in the catalytic hydrogenation reactions of ester compounds, has high yield and high chemical selectivity, is compatible with conjugated and non-conjugated carbon-carbon double bond, carbon-carbon triple bond, epoxy, halogen, carbonyl and other functional groups, and hasgreat application prospects.
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Paragraph 0301-0303; 0305

(2019/11/04)

A deprotection procedure using SO3H silica gel to remove non-silyl protecting groups
Protecting groups are indispensable in organic synthesis and there is a great need for a variety of deprotection methods. Here, we investigated the scope of the application of a deprotection procedure using SO3H silica gel, which we have previously reported as a desilylation procedure. Under these conditions, -OMOM, -OSEM, -OTHP, and -OAc groups and dimethyl acetal were cleaved. Pivaloyloxy, benzyloxy and methoxy carbonyl groups remained intact and selective deprotection of TBS groups in the presence of other protecting groups was accomplished. We succeeded in cleaving an acetyl group on a secondary alcohol in a highly polar nortropine derivative. Our findings here provide another deprotection option and would be helpful in the synthesis of multifunctional compounds.
Karaki, Fumika,Kuwada, Miki,Tajiri, Saki,Kanda, Misaki,Yanai, Mari,Kamimura, Mitsuhiro,Itoh, Kennosuke,Fujii, Hideaki
p. 212 - 220
(2019/05/06)

Cleavage of lignin C-O bonds over a heterogeneous rhenium catalyst through hydrogen transfer reactions
Hydrogenolysis is one of the most popular strategies applied in the depolymerization of lignin for the production of aromatic chemicals. Currently, this strategy is mainly conducted under high hydrogen pressure, which can pose safety risks and is not sustainable and economical. Herein, we reported that heterogeneous rhenium oxide supported on active carbon (ReOx/AC) exhibited excellent activity in the selective cleavage of lignin C-O bonds in isopropanol. High yields of monophenols (up to 99.0%) from various lignin model compounds and aromatic liquid oils (>50%) from lignin feedstock were obtained under mild conditions in the absence of H2. The characterization of the catalyst by X-ray absorption fine structure, X-ray photoelectron spectroscopy and H2-temperature-programed reduction suggested that the activity of ReOx/AC could be attributed to the presence of ReIV-VI. The interaction between the surface oxygen groups of the active carbon and rhenium oxide could also play an important role in the cleavage of the C-O bonds. Notably, an ReOx/AC-catalyzed C-O bond cleavage pathway beyond a typical deoxydehydration mechanism was disclosed. More importantly, 2D-HSQC-NMR and GPC characterizations showed that ReOx/AC exhibited high activity not only in β-O-4 cleavage, but also in the deconstruction of more resistant β-5 and β-β linkages in lignin without destroying the aromatic ring. This study paves the way for the development of rhenium-based catalysts for the controlled reductive valorization of realistic lignin materials through a hydrogen transfer pathway.
Zhang, Bo,Qi, Zaojuan,Li, Xinxin,Ji, Jianwei,Zhang, Leilei,Wang, Hua,Liu, Xiaoyan,Li, Changzhi
supporting information
p. 5556 - 5564
(2019/10/28)

Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
Matt, Christof,K?lblin, Frederic,Streuff, Jan
supporting information
p. 6983 - 6988
(2019/09/09)

Rhodium-Catalyzed Parallel Kinetic Resolution of Racemic Internal Allenes Towards Enantiopure Allylic 1,3-Diketones
A rare case of a parallel kinetic resolution of racemic 1,3-disubstituted allenes by means of a rhodium-catalyzed addition to 1,3-diketones furnishing enantiopure allylic 1,3-diketones is described. Mechanistic experiments demonstrate that the different allene enantiomers react in parallel to either the diastereomeric E- or Z-allylic 1,3-diketones with the same absolute configuration of the newly formed stereogenic center. A broad substrate scope demonstrates the synthetic utility of this new method.
Hilpert, Lukas J.,Breit, Bernhard
supporting information
p. 9939 - 9943
(2019/06/24)

Selective aerobic oxidation of alkyl aromatics on Bi2MoO6 nanoplates decorated with Pt nanoparticles under visible light irradiation
Pt/Bi2MoO6 nanoplates are efficient photocatalysts for the selective oxidation of saturated C-H bonds in alkyl aromatics under visible light illumination using O2 as an oxidant. This study opens a new window for direct C-H functionalization through the photocatalytic method based on cheap Bi2MoO6 semiconductor materials.
Zhang, Bao,Yang, Xiaojing,Li, Jun,Cheng, Gang
supporting information
p. 12194 - 12197
(2018/11/21)

Highly sulphated cellulose: a versatile, reusable and selective desilylating agent for deprotection of alcoholic TBDMS ethers
A mild, efficient and rapid protocol was developed for the deprotection of alcoholic TBDMS ethers using a recyclable, eco-friendly highly sulphated cellulose sulphate acid catalyst in methanol. This acid catalyst selectively cleaves alcoholic TBDMS ethers in bis-TBDMS ethers containing both alcoholic and phenolic TBDMS ether moieties.
Dachavaram, Soma Shekar,Penthala, Narsimha R.,Calahan, Julie L.,Munson, Eric J.,Crooks, Peter A.
p. 6057 - 6062
(2018/09/06)

Selective Cleavage of C?O Bonds in Lignin Catalyzed by Rhenium(VII) Oxide (Re2O7)
The selective cleavage of C?O bonds in typical model lignin β-O-4 compounds and deconstruction of a realistic lignin feedstock catalyzed by Re2O7 is described. High yields of C?O cleavage products (up to 97.8 %) from model compounds and oils (76.3 %) from organosolv pinewood lignin were obtained under mild conditions. Evidence for the pathway of this catalytic process is also provided.
Qi, Zaojuan,Zhang, Bo,Ji, Jianwei,Li, Xinxin,Dai, Tao,Guo, Haiwei,Wang, Aiqin,Lu, Lican,Li, Changzhi
p. 500 - 505
(2018/03/27)

Discovery, synthesis, and structure-activity relations of 3,4-dihydro-1H-spiro(naphthalene-2,2′-piperidin)-1-ones as potassium-competitive acid blockers
With the aim to discover a gastric antisecretory agent more potent than the existing proton pump inhibitors, novel 3,4-dihydro-1H-spiro(naphthalene-2,2′-piperidin)-1-one derivatives, which could occupy two important lipophilic pockets (described as LP-1 and LP-2) of H+,K+-ATPase and can strongly bind to the K+-binding site, were designed based on a docking model. Among the compounds synthesized, compound 4d showed a strong H+,K+-ATPase-inhibitory activity and a high stomach concentration in rats, resulting in potent inhibitory action on histamine-stimulated gastric acid secretion in rats. Furthermore, 4d exerted significant inhibitory action on histamine-stimulated gastric-acid secretion in rats with a rapid onset and moderate duration of action after the administration. These findings may lead to a new insight into the drug design of potassium-competitive acid blockers.
Imaeda, Toshihiro,Ono, Koji,Nakai, Kazuo,Hori, Yasunobu,Matsukawa, Jun,Takagi, Terufumi,Fujioka, Yasushi,Tarui, Naoki,Kondo, Mitsuyo,Imanishi, Akio,Inatomi, Nobuhiro,Kajino, Masahiro,Itoh, Fumio,Nishida, Haruyuki
p. 3719 - 3735
(2017/06/13)

Nucleophilic addition of arylmethylzinc reagents (ArCH2ZnCl) to formaldehyde: An easy access to 2-(hetro)arylethyl alcohols
The selective addition of arylmethylmagnesium halides with formaldehyde giving arylethyl alcohols is extremely challenging. To circumvent the difficulties, in the current communication, we have reported on the nucleophilic addition of benzyl zinc reagents derived from inexpensive and abundant benzyl chlorides to paraformaldehyde. The reaction investigated herein is hitherto unknown and was found to be selective, operationally simple, atom- and step-economical and high yielding to deliver phenethyl alcohols utilized as key perfumery ingredients in 60–83% yields. After successful establishment of the reaction condition, the reaction was also scaled up successfully to deliver a large-scale preparation of the phenethyl alcohol.
Bhatt,Samant,Pednekar, Suhas
supporting information
p. 968 - 974
(2017/05/04)

Regioselective hydrosilylation of epoxides catalysed by nickel(II) hydrido complexes
Bench-stable nickel fluoride complexes bearing NNN pincer ligands have been employed as precursors for the regioselective hydrosilylation of epoxides at room temperature. A nickel hydride assisted epoxide opening is followed by the cleavage of the newly formed nickel oxygen bond by σ-bond metathesis with a silane.
Wenz, Jan,Wadepohl, Hubert,Gade, Lutz H.
supporting information
p. 4308 - 4311
(2017/04/21)

Biocatalytic Formal Anti-Markovnikov Hydroamination and Hydration of Aryl Alkenes
Biocatalytic anti-Markovnikov alkene hydroamination and hydration were achieved based on two concepts involving enzyme cascades: epoxidation-isomerization-amination for hydroamination and epoxidation-isomerization-reduction for hydration. An Escherichia coli strain coexpressing styrene monooxygenase (SMO), styrene oxide isomerase (SOI), ω-transaminase (CvTA), and alanine dehydrogenase (AlaDH) catalyzed the hydroamination of 12 aryl alkenes to give the corresponding valuable terminal amines in high conversion (many ≥86%) and exclusive anti-Markovnikov selectivity (>99:1). Another E. coli strain coexpressing SMO, SOI, and phenylacetaldehyde reductase (PAR) catalyzed the hydration of 12 aryl alkenes to the corresponding useful terminal alcohols in high conversion (many ≥80%) and very high anti-Markovnikov selectivity (>99:1). Importantly, SOI was discovered for stereoselective isomerization of a chiral epoxide to a chiral aldehyde, providing some insights on enzymatic epoxide rearrangement. Harnessing this stereoselective rearrangement, highly enantioselective anti-Markovnikov hydroamination and hydration were demonstrated to convert α-methylstyrene to the corresponding (S)-amine and (S)-alcohol in 84-81% conversion with 97-92% ee, respectively. The biocatalytic anti-Markovnikov hydroamination and hydration of alkenes, utilizing cheap and nontoxic chemicals (O2, NH3, and glucose) and cells, provide an environmentally friendly, highly selective, and high-yielding synthesis of terminal amines and alcohols.
Wu, Shuke,Liu, Ji,Li, Zhi
p. 5225 - 5233
(2017/08/17)

Antiproliferative activity and SARs of caffeic acid esters with mono-substituted phenylethanols moiety
A series of CAPE derivatives with mono-substituted phenylethanols moiety were synthesized and evaluated by MTT assay on growth of 4 human cancer cell lines (Hela, DU-145, MCF-7 and ECA-109). The substituent effects on the antiproliferative activity were systematically investigated for the first time. It was found that electron-donating and hydrophobic substituents at 2′-position of phenylethanol moiety could significantly enhance CAPE's antiproliferative activity. 2′-Propoxyl derivative, as a novel caffeic acid ester, exhibited exquisite potency (IC50?=?0.4?±?0.02 & 0.6?±?0.03?μM against Hela and DU-145 respectively).
Xie, Jin,Yang, Fengzhi,Zhang, Man,Lam, Celine,Qiao, Yixue,Xiao, Jia,Zhang, Dongdong,Ge, Yuxuan,Fu, Lei,Xie, Dongsheng
p. 131 - 134
(2016/12/27)

A new compound and its preparation method (by machine translation)
The invention provides a new compound and a preparation method thereof. The compound is a new impurity of venlafaxine, and particularly is (+/-)-1-{2-[(4-methoxy phenyl ethyl) (methyl) amino]-1-(4-methoxy phenyl) ethyl} cyclohexanol. The compound and the preparation method thereof provide support for more accurate control of impurities in venlafaxine and acquisition of venlafaxine which is more safe and reliable and has a definite curative effect.
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(2016/10/09)

Highly efficient and chemoselective zinc-catalyzed hydrosilylation of esters under mild conditions
A mild and highly efficient catalytic hydrosilylation protocol for room-temperature ester reductions has been developed using diethylzinc as the catalyst. The methodology is operationally simple, displays high functional group tolerance and provides for a facile access to a broad range of different alcohols in excellent yields.
Kovalenko, Oleksandr O.,Adolfsson, Hans
supporting information
p. 2785 - 2788
(2015/02/05)

Ring Expansion of Epoxides under Br?nsted Base Catalysis: Formal [3+2] Cycloaddition of β,γ-Epoxy Esters with Imines Providing 2,4,5-Trisubstituted 1,3-Oxazolidines
A novel ring-expansion reaction of epoxides under Br?nsted base catalysis was developed. The formal [3+2] cycloaddition reaction of β,γ-epoxy esters with imines proceeds in the presence of triazabicyclodecene (TBD) as a superior Br?nsted base catalyst to afford 2,4,5-trisubstituted 1,3-oxazolidines in a highly diastereoselective manner. This reaction involves the ring opening of the epoxides with the aid of the Br?nsted base catalyst to generate α,β-unsaturated esters having an alkoxide at the allylic position, which would formally serve as a synthetic equivalent of the 1,3-dipole, followed by a cycloaddition reaction with imines in a stepwise fashion. This methodology enables the facile synthesis of enantioenriched 1,3-oxazolidines from easily accessible enantioenriched epoxides.
Kondoh, Azusa,Odaira, Kenta,Terada, Masahiro
supporting information
p. 11240 - 11244
(2016/07/06)

One-Carbon Homologation of Primary Alcohols and the Reductive Homologation of Aldehydes Involving a Jocic-Type Reaction
(Trichloromethyl)carbinols, which are formed in one operation from either alcohols or aldehydes, can be converted into primary alcohols in a Jocic-type reaction involving LiBH4. The net result is a convenient two-step, one-carbon homologation of primary alcohols or a reductive one-carbon homologation of aldehydes featuring a broad substrate scope. The method is step-economical, and it nicely complements established one-carbon homologation strategies. (Trichloromethyl)carbinols, which are formed in one operation from either alcohols or aldehydes, can be converted into primary alcohols in a Jocic-type reaction involving LiBH4. The net result is a convenient two-step, one-carbon homologation of primary alcohols or a reductive one-carbon homologation of aldehydes featuring a broad substrate scope.
Li, Zhexi,Gupta, Manoj K.,Snowden, Timothy S.
p. 7009 - 7019
(2015/11/16)

Mild deprotection of PMB ethers using tert-butyl bromide
A convenient and high yielding method for the cleavage and scavenging of p-methoxybenzyl protecting group of several alcohols using tert-butyl bromide in refluxing acetonitrile is described. Under these mild conditions other protecting groups such as acid sensitive allyl, benzyl, and Me3CPh2Si ethers, or isopropylidene acetals were unchanged. Interestingly, a selective alkoxy-PMB cleavage was observed in the presence of a PMB phenoxy ether.
Rival, Nicolas,Albornoz Grados, Arantxa,Schiavo, Lucie,Colobert, Fran?oise,Hanquet, Gilles
p. 6823 - 6826
(2015/11/27)

Highly chemoselective reduction of amides (primary, secondary, tertiary) to alcohols using SmI2/amine/H2O under mild conditions
Highly chemoselective direct reduction of primary, secondary, and tertiary amides to alcohols using SmI2/amine/H2O is reported. The reaction proceeds with C-N bond cleavage in the carbinolamine intermediate, shows excellent functional group tolerance, and delivers the alcohol products in very high yields. The expected C-O cleavage products are not formed under the reaction conditions. The observed reactivity is opposite to the electrophilicity of polar carbonyl groups resulting from the nX → πC=O (X = O, N) conjugation. Mechanistic studies suggest that coordination of Sm to the carbonyl and then to Lewis basic nitrogen in the tetrahedral intermediate facilitate electron transfer and control the selectivity of the C-N/C-O cleavage. Notably, the method provides direct access to acyl-type radicals from unactivated amides under mild electron transfer conditions.
Szostak, Michal,Spain, Malcolm,Eberhart, Andrew J.,Procter, David J.
supporting information
p. 2268 - 2271
(2014/03/21)

Mechanism of SmI2/amine/H2O-promoted chemoselective reductions of carboxylic acid derivatives (esters, acids, and amides) to alcohols
Samarium(II) iodide-water-amine reagents have emerged as some of the most powerful reagents (E° = -2.8 V) for the reduction of unactivated carboxylic acid derivatives to primary alcohols under single electron transfer conditions, a transformation that had been considered to lie outside the scope of the classic SmI2 reductant for more than 30 years. In this article, we present a detailed mechanistic investigation of the reduction of unactivated esters, carboxylic acids, and amides using SmI2-water-amine reagents, in which we compare the reactivity of three functional groups. The mechanism has been studied using the following: (i) kinetic, (ii) reactivity, (iii) radical clock, and (iv) isotopic labeling experiments. The kinetic data indicate that for the three functional groups all reaction components (SmI2, amine, water) are involved in the rate equation and that the rate of electron transfer is facilitated by base assisted deprotonation of water. Notably, the mechanistic details presented herein indicate that complexation between SmI2, water, and amines can result in a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to a variety of carboxylic acid derivatives. These observations will have important implications for the design and optimization of new processes involving Sm(II)-reduction of ketyl radicals. (Chemical Equation Presented).
Szostak, Michal,Spain, Malcolm,Eberhart, Andrew J.,Procter, David J.
p. 11988 - 12003
(2015/01/16)

On the role of pre- and post-electron-transfer steps in the SmI 2/Amine/H2O-mediated reduction of esters: New mechanistic insights and kinetic studies
The mechanism of the SmI2-mediated reduction of unactivated esters has been studied using a combination of kinetic, radical clocks and reactivity experiments. The kinetic data indicate that all reaction components (SmI2, amine, H2O) are involved in the rate equation and that electron transfer is facilitated by Bronsted base assisted deprotonation of water in the transition state. The use of validated cyclopropyl-containing radical clocks demonstrates that the reaction occurs via fast, reversible first electron transfer, and that the electron transfer from simple Sm(II) complexes to aliphatic esters is rapid. Notably, the mechanistic details presented herein indicate that complexation between SmI2, H2O and amines affords a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to carboxylic acid derivatives as an attractive alternative to the classical hydride-mediated reductions and as a source of acyl-radical equivalents for C-C bond forming processes. Electron donors: The mechanism of the SmI 2-mediated reduction of unactivated esters has been studied by using a combination of kinetic, radical clock, and reactivity experiments. Notably, the mechanistic details presented herein indicate that complexation between SmI2, H2O, and amines gives a new class of structurally diverse, thermodynamically powerful reductants for efficient electron transfer to carboxylic acid derivatives as an attractive alternative to the classical hydride-mediated reductions and as a source of acyl-radical equivalents for C-C bond-forming processes (see scheme).
Szostak, Michal,Spain, Malcolm,Procter, David J.
supporting information
p. 4222 - 4226
(2014/05/06)

Neutral sulfur nucleophiles: Synthesis of thioethers and thioesters by substitution reactions of N-heterocyclic carbene boryl sulfides and thioamides
Newly discovered boryl sulfides and N-borylthioamides are shown to serve as neutral sources of sulfur nucleophiles in substitutions reactions. For example, heating of diMe-Imd-BH(SPh)2 with benzyl bromides, primary bromides, or acid chlorides provides the corresponding thioethers or thioesters in high yields. Likewise, N-phenyltetrazole thioethers/esters are made from a readily available N-borylthionotetrazole. The formation of the boryl sulfide and its onward nucleophilic substitution can be telescoped down to a one-pot reaction whose components are an NHC-borane (NHC-BH3), a disulfide, and an electrophile.
Pan, Xiangcheng,Curran, Dennis P.
supporting information
p. 2728 - 2731
(2014/06/09)

Temporal separation of catalytic activities allows anti-Markovnikov reductive functionalization of terminal alkynes
There is currently great interest in the development of multistep catalytic processes in which one or several catalysts act sequentially to rapidly build complex molecular structures. Many enzymes - often the inspiration for new synthetic transformations - are capable of processing a single substrate through a chain of discrete, mechanistically distinct catalytic steps. Here, we describe an approach to emulate the efficiency of these natural reaction cascades within a synthetic catalyst by the temporal separation of catalytic activities. In this approach, a single catalyst exhibits multiple catalytic activities sequentially, allowing for the efficient processing of a substrate through a cascade pathway. Application of this design strategy has led to the development of a method to effect the anti-Markovnikov (linear-selective) reductive functionalization of terminal alkynes. The strategy of temporal separation may facilitate the development of other efficient synthetic reaction cascades.
Li, Le,Herzon, Seth B.
p. 22 - 27
(2014/01/17)

A highly active and air-stable ruthenium complex for the ambient temperature anti-markovnikov reductive hydration of terminal alkynes
The conversion of terminal alkynes to functionalized products by the direct addition of heteroatom-based nucleophiles is an important aim in catalysis. We report the design, synthesis, and mechanistic studies of the half-sandwich ruthenium complex 12, which is a highly active catalyst for the anti-Markovnikov reductive hydration of alkynes. The key design element of 12 involves a tridentate nitrogen-based ligand that contains a hemilabile 3-(dimethylamino) propyl substituent. Under neutral conditions, the dimethylamino substituent coordinates to the ruthenium center to generate an air-stable, 18-electron, κ3-complex. Mechanistic studies show that the dimethylamino substituent is partially dissociated from the ruthenium center (by protonation) in the reaction media, thereby generating a vacant coordination site for catalysis. These studies also show that this substituent increases hydrogenation activity by promoting activation of the reductant. At least three catalytic cycles, involving the decarboxylation of formic acid, hydration of the alkyne, and hydrogenation of the intermediate aldehyde, operate concurrently in reactions mediated by 12. A wide array of terminal alkynes are efficiently processed to linear alcohols using as little as 2 mol % of 12 at ambient temperature, and the complex 12 is stable for at least two weeks under air. The studies outlined herein establish 12 as the most active and practical catalyst for anti-Markovnikov reductive hydration discovered to date, define the structural parameters of 12 underlying its activity and stability, and delineate design strategies for synthesis of other multifunctional catalysts.
Zeng, Mingshuo,Li, Le,Herzon, Seth B.
supporting information
p. 7058 - 7067
(2014/06/09)

Iron-catalyzed reduction of carboxylic esters to alcohols
A novel catalytic system formed from Fe(stearate)2/NH 2CH2CH2NH2 and polymethylhydrosiloxane was directly developed for the hydrosilylation of carboxylic acid esters to alcohols. The catalytic method exhibits broad substrate scope, including 20 aliphatic, aromatic, and heterocyclic esters. The corresponding alcohols are obtained in moderate to very good yields. The first iron-catalyzed hydrosilylation of carboxylic acid esters to alcohols is described. A catalytic system formed by Fe(stearate)2/NH 2CH2CH2NH2 and polymethylhydrosiloxane (PMHS) is used for this transformation, which has a broad substrate scope, including 20 aliphatic, aromatic, and heterocyclic esters. The corresponding alcohols are obtained in moderate to very good yields. Copyright
Junge, Kathrin,Wendt, Bianca,Zhou, Shaolin,Beller, Matthias
p. 2061 - 2065
(2013/05/09)

1,2,3-Trimethoxypropane, a glycerol-based solvent with low toxicity: New utilization for the reduction of nitrile, nitro, ester, and acid functional groups with TMDS and a metal catalyst
1,2,3-Trimethoxypropane (1,2,3-TMP) was prepared from glycerol in one step in good yield and selectivity by phase transfer catalysis. According to OECD guidelines, a toxicity study was realized for this compound. It revealed that 1,2,3-TMP has a low acute toxicity, no skin sensitization, no mutagenicity and no ecotoxicity in an aquatic environment. This compound was also used as a solvent for the reduction of organic functions using either aluminium hydride or 1,1,3,3-tetramethyldisiloxane (TMDS) as a benign hydride source. In particular, a new process for the reduction of nitriles to amines in 2-MeTHF and in 1,2,3-TMP was developed, using TMDS in combination with copper triflate (Cu(OTf)2).
Sutter, Marc,Pehlivan, Leyla,Lafon, Romain,Dayoub, Wissam,Raoul, Yann,Metay, Estelle,Lemaire, Marc
supporting information
p. 3020 - 3026
(2013/11/06)

Iron-catalyzed hydrosilylation of esters
The first hydrosilylation of esters catalyzed by a well defined iron complex has been developed. Esters are converted to the corresponding alcohols at 100 °C, under solvent-free conditions and visible light activation. Copyright
Bezier, David,Venkanna, Gopaladasu T.,Castro, Luis C. Misal,Zheng, Jianxia,Roisnel, Thierry,Sortais, Jean-Baptiste,Darcel, Christophe
supporting information; experimental part
p. 1879 - 1884
(2012/09/22)

Enantioselective hydrosilylation of aromatic alkenes catalyzed by chiral bis(oxazolinyl)phenyl-rhodium acetate complexes
Highly efficient and enantioselective hydrosilylation of aromatic alkenes catalyzed by the chiral rhodium acetate complexes with the bis(oxazolinyl)phenyl ligands has been reported that afforded chiral silane derivatives with up to 99% ee. Georg Thieme Ve
Naito, Tatsuo,Yoneda, Takuma,Ito, Jun-Ichi,Nishiyama, Hisao
p. 2957 - 2960
(2013/02/22)

Selective switchable iron-catalyzed hydrosilylation of carboxylic acids
Selective reduction of carboxylic acids either to aldehydes or alcohols is achieved using a one pot procedure based on iron-catalyzed hydrosilylations. Using phenylsilane and (COD)Fe(CO)3 catalyst under UV-irradiation at rt, alcohols were obtained specifically in good yields, whereas aldehydes were selectively obtained using TMDS and (t-PBO)Fe(CO)3 catalyst under thermal activation.
Misal Castro, Luis C.,Li, Haoquan,Sortais, Jean-Baptiste,Darcel, Christophe
supporting information
p. 10514 - 10516,3
(2020/09/02)

Copper(II) triflate-catalyzed reduction of carboxylic acids to alcohols and reductive etherification of carbonyl compounds
A protocol is described for the reduction of carboxylic acids to primary alcohols using 1,1,3,3-tetramethyldisiloxane (TMDS) and a catalytic amount of Cu(OTf)2. Aliphatic as well as aromatic carboxylic acids are reduced in high selectivity and good yields. TMDS/Cu(OTf)2 has also been found to be an efficient catalytic reducing system for the preparation of symmetrical ethers from carbonyl compounds under mild conditions.
Zhang, Yin-Jie,Dayoub, Wissam,Chen, Guo-Rong,Lemaire, Marc
experimental part
p. 7400 - 7407
(2012/09/10)

Zinc-catalyzed chemoselective reduction of esters to alcohols
Economical alcohols! A general and chemoselective catalytic reduction of esters to alcohols using inexpensive zinc acetate and silanes has been developed. The operational simplicity and the high functional group tolerance, without the need for protecting and deprotecting steps, make this procedure particularly attractive for organic synthesis. Copyright
Das, Shoubhik,Moeller, Konstanze,Junge, Kathrin,Beller, Matthias
experimental part
p. 7414 - 7417
(2011/08/05)

Synthesis of a novel ester of hydroxytyrosol and α-lipoic acid exhibiting an antiproliferative effect on human colon cancer HT-29 cells
A novel ester of hydroxytyrosol and α-lipoic acid was synthesized in satisfactory yield by original and simple procedures and evaluated about its antiproliferative activity on the human colorectal adenocarcinoma HT-29 cell line. The compound exhibited a cell growth inhibitory activity significantly more potent than the corresponding parent natural compounds, very likely due to the induction of cell cycle arrest in the G2/M phase. These data suggest that the novel ester might exert a more effective antitumour activity than hydroxytyrosol and α-lipoic acid.
Bernini, Roberta,Crisante, Fernanda,Merendino, Nicol,Molinari, Romina,Soldatelli, Maria Chiara,Velotti, Francesca
experimental part
p. 439 - 446
(2011/02/25)

Microwave-assisted synthesis of 5-substituted 2-aminothiophenes starting from arylacetaldehydes
An easy three-step pathway for the synthesis of arylacet-aldehydes from the corresponding carboxylic acids in very high yields is described. Their use as precursors of 5-substituted-2-aminothiophenes is illustrated via a microwave-assisted Gewald reaction. This method allows obtaining the expected compounds in a shorter time and with better yields and purities than the classical procedures. Georg Thieme Verlag Stuttgart - New York.
Revelant, Germain,Dunand, Sandrine,Hesse, Stephanie,Kirsch, Gilbert
experimental part
p. 2935 - 2940
(2011/11/01)

Synthesis of mycinose from 1,2:5,6-Di-O-isopropylidene-α-D- glucofuranose
A facile synthesis of mycinose from commercially available 1,2:5,6-Di-O-isopropylidene-α-D-glucofuranose was developed. A selective and direct reductive debromination of α-hydroxy bromides in a simple NaBH4/EtOH/H2O system was found.
Bao, Kai,Gao, Hao,Zhu, Zhibin,Wang, Jinhong,Zhang, Guoning,Sun, Jun,Zhang, Weige,Yao, Xinsheng
scheme or table
p. 592 - 595
(2012/05/31)

Reduction of carboxylic acids using esters of benzotriazole as high-reactivity intermediates
Herein, we describe a simple and practical protocol for the reduction of carboxylic acids via the in situ formation of hydroxybenzotriazole esters followed by reaction with sodium borohydride to give the corresponding alcohols. The reaction proceeds with excellent yields in the presence of water. Georg Thieme Verlag Stuttgart - New York.
Morales-Serna, Jose Antonio,Garcia-Rios, Erendira,Bernal, Jorge,Paleo, Ehecatl,Gavino, Ruben,Cardenas, Jorge
scheme or table
p. 1375 - 1382
(2011/06/19)

RENIN INHIBITORS
Renin inhibitors, which are spirocyclic piperidine amides, of structural formula (I) and pharmaceutical compositions thereof useful in the treatment of cardiovascular diseases and renal insufficiency, wherein n, for each instance in which it occurs, is independently 0, 1, or 2; R1 is hydrogen, C1-6 -alkyl or C3-6 -cycloalkyl, wherein said C1-6 -alkyl or C3-6 -cycloalkyl group can be independently substituted with 1-3 halogens; A is (i) a five- or six-membered saturated or unsaturated heterocyclic or carbocyclic monocyclic ring or (ii) a five- or six-membered saturated or unsaturated heterocyclic or carbocyclic ring which is fused to another five- or six-membered saturated or unsaturated heterocyclic or carbocyclic ring, V is a bond or -(C=O)-, -CH(OH)-, -CH2- or =CH-; U is a bond or -CH2-, or for the case when V is =CH-, U is -CH=; X is =CH-, =CF-, =C(OR3)-, or -C=O-; and Y is =CH-, =CF-, =N-, or for the case when X is -C=O-, Y is -N(R3)-.
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Page/Page column 25

(2011/04/13)

Cleavage of benzyl ethers by triphenylphosphine hydrobromide
Triphenylphosphine hydrobromide was found to cleave the benzyl ethers derived from 1°, 2° alkyl, and aryl alcohols to the corresponding alcohols and benzyltriphenylphosphonium bromide in good yields. Alkene and allyl phosphonium salts were produced from the benzyl ethers with 3° alkyl and allyl groups, respectively. These results indicate that the formation of the product is determined by the relative stability of the carbocationic intermediate. The anhydrous, stoichiometric amount of PPh3·HBr offers a new and effective method for the deprotection of benzyl ethers.
Ramanathan, Mani,Hou, Duen-Ren
experimental part
p. 6143 - 6145
(2010/12/24)

Enantiopure trans -3-arylaziridine-2-carboxamides: Preparation by bacterial hydrolysis and ring-openings toward enantiopure, unnatural D -α-amino acids
Several racemic trans-3-arylaziridine-2-carboxamides were prepared and then resolved by Rhodococcus rhodochrous IFO 15564-catalyzed hydrolysis. The resulting enantiopure (2R,3S)-3-arylaziridine-2-carboxamides are adequate substrates to undergo fully stereoselective nucleophilic ring-openings at the C-3 ring position to finally yield enantiopure, unnatural d-α- aminocarboxylic acids. Experimental evidence is provided that suggests the fate of the (2S,3R)-3-arylaziridine-2-carboxylic acids concomitantly formed during the resolution processes. In this context, the similar bacterial resolution of racemic 1-arylaziridine-2-carboxamides and -carbonitriles, previously investigated by our research group, has been partially re-examined.
Moran-Ramallal, Roberto,Liz, Ramon,Gotor, Vicente
supporting information; body text
p. 6614 - 6624
(2010/11/17)

Rhodium-catalysed hydroboration employing new Quinazolinap ligands; An investigation into electronic effects
As part of an ongoing effort to improve the efficiency and substrate scope of our Quinazolinap ligand series in the rhodium-catalysed asymmetric hydroboration of vinyl arenes, 2-(p-trifluoromethylphenyl)-Quinazolinap and 2-(p-methoxyphenyl)-Quinazolinap have been synthesised and resolved in good yield. These, along with the previously reported 2-(2-pyridyl)-Quinazolinap and 2-(2-pyrazinyl)-Quinazolinap, form part of an electronic series of Quinazolinap ligands synthesised in order to explore electronic effects in this ligand class. The application of this series of ligands to the rhodium-catalysed asymmetric hydroboration of a range of vinylarenes is described. Good conversions and regioselectivities as well as excellent enantioselectivities up to 97% were obtained. 2-(p-Methoxyphenyl)-Quinazolinap demonstrated consistently high enantioselectivities in the hydroboration of sterically demanding vinylarenes.
Maxwell, Aoife C.,Flanagan, Susan P.,Goddard, Richard,Guiry, Patrick J.
experimental part
p. 1458 - 1473
(2010/11/03)

Synthesis and post-resolution modification of new axially chiral ligands for asymmetric catalysis
The synthesis of four new members of the Quinazolinap series of ligands is described. Three of these ligands were prepared by post-resolution modification of the known ligand (R)-7-chloro-2-isopropyl-Quinazolinap, a new approach which offers an expedient route to a range of enantiopure ligands as it precludes the need for resolution of each ligand prepared. The remaining ligand, 7-chloro-2-methyl-Quinazolinap, was prepared in a seven-step synthetic sequence incorporating palladium- and nickel-catalyzed transformations as the key steps. A diastereomerically pure palladacycle of this ligand was characterised by X-ray crystallography. (R)-7-Chloro-2-isopropyl-Quinazolinap was applied to the rhodium-catalyzed hydroboration of vinylarenes with regioselectivities of up to > 99:1 and ee values of up to 68%. Each of the Quinazolinap ligands prepared were applied to the palladium-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate resulting in conversions of up to 100% and ee values of up to 85%. Solution-phase NMR studies on a palladium complex of one of the ligands provided a rationale for the sense of asymmetric induction. Foue new members of the Quinazolinap series of ligands are prepared, three by post-resolution modification. They were applied to the rhodium-catalyzed hydroboration of vinylarenes with regioselectivities of catalyzed allylic of up to >99:1 and ee values of up to 68%. Each of the Quinazolinap ligands prepared were applied to the palladium-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate in a synthetic and mechanistic study which helped to rationalize the sense of asymmetric induction observed.
Fleming, William J.,Mueller-Bunz, Helge,Guiry, Patrick J.
experimental part
p. 5996 - 6004
(2011/03/17)

An improved bouveault-blanc ester reduction with stabilized alkali metals
Significantly improved Bouveault-Blanc conditions for ester reduction have been developed using sodium in silica gel (Na-SG), a free-flowing powder that can be easily handled in the open atmosphere. Primary alcohols were prepared in excellent yield from a variety of aliphatic esters under mild reaction conditions. The chemistry presented here is far safer than the classic Bouveault-Blanc reduction and is competitive with more modern hydride reduction methods.
Bodnar, Brian S.,Vogt, Paul F.
supporting information; experimental part
p. 2598 - 2600
(2009/08/07)

Electronically varied quinazolinaps for asymmetric catalysis
The synthesis and resolution of electronically varied axially chiral Quinazolinaps is reported. These ligands bear different aryl groups on the donor phosphorus atom and were synthesised as part of our investigations into electronic effects within this ligand class. A diastereomerically pure palladacycle of one ligand was characterised by X-ray crystallography. The application of these Quinazolinaps to the rhodium-catalysed hydroboration of vinylarenes resulted in enantioselectivities of up to 92%. Their application to the palladium-catalysed allylic alkylation of 1,3-diphenylprop-2-enyl acetate resulted in conversions of up to 99% and enantioselectivities of up to 94%. The Royal Society of Chemistry 2008.
Maxwell, Aoife C.,Franc, Celine,Pouchain, Laurent,Mueller-Bunz, Helge,Guiry, Patrick J.
supporting information; experimental part
p. 3848 - 3853
(2009/02/05)