- Palladium-Catalyzed Cross-Coupling of Superbase-Generated C(sp3) Nucleophiles
-
A range of methods has been investigated recently for the arylation of weakly acidic C(sp3)-H bonds, primarily exploiting directed metalation with a transition metal catalyst or radical formation via hydrogen atom transfer. In this work, a classical base-mediated approach is taken, exploiting the ability of organometallic superbases to metalate very weakly acidic (pKa> 40) C-H bonds. Conditions are developed with eithern-BuLi/diamine orn-BuLi/KOtBu superbases to enable metalation to occur with high selectivity. Organolithium nucleophiles can be directly used in cross-coupling, or organozincs can be formed to enable reactions with functional group-dense organohalides.
- Freure, Garrett P. R.,Lavertu, Jean-Danick E.,Newman, Stephen G.,Skrotzki, Eric A.
-
p. 12258 - 12263
(2021/10/26)
-
- Borane-catalyzed C(sp3)-F bond arylation and esterification enabled by transborylation
-
The activation and functionalization of carbon- fluorine bonds represent a significant synthetic challenge, given the high thermodynamic barrier to C-F bond cleavage. Stoichiometric hydridoborane-mediated C-F functionalization has recently emerged, but is yet to be rendered catalytic. Herein, the borane-catalyzed coupling of alkyl fluorides with arenes (carbon-carbon bond formation) and carboxylic acids (carbon-oxygen bond formation) has been developed using transborylation reactions to achieve catalytic turnover. Successful C-C and C-O coupling across a variety of structurally and electronically differentiated arenes and carboxylic acids was achieved using 9-borabicyclo[3.3.1]nonane (H-B-9-BBN) as the catalyst and pinacolborane (HBpin), with broad functional group tolerance. Experimental and computational studies suggest a mechanistic dichotomy for the carbon-carbon and carbon-oxygen coupling reactions. B-F transborylation (B-F/B-H metathesis) between F-B-9-BBN and HBpin enabled catalytic turnover for carbon-carbon bond formation, whereas direct exchange between the alkyl fluoride and acyloxyboronic ester (C-F/B-O metathesis) was proposed for carbon-oxygen coupling, where H-B-9-BBN catalyzed the dehydrocoupling of the carboxylic acid with HBpin.
- Willcox, Dominic R.,Nichol, Gary S.,Thomas, Stephen P.
-
p. 3190 - 3197
(2021/04/06)
-
- Interactions of C?F Bonds with Hydridoboranes: Reduction, Borylation and Friedel–Crafts Alkylation
-
The stoichiometric reactions of the alkylfluorides 1-fluoroadamantane (Ad-F), fluorocyclohexane (Cy-F), 1-fluoropentane (Pent-F) and benzyl fluorides with secondary boranes pinacolborane (HBpin), catecholborane (HBcat), 9-borabicyclo(3.3.1)nonane (9-BBN)
- Bamford, Karlee L.,Chitnis, Saurabh S.,Qu, Zheng-wang,Stephan, Douglas W.
-
supporting information
p. 16014 - 16018
(2018/10/15)
-
- Immobilization of an Aminobisphosphine–PdII Complex over Graphene Oxide: An Efficient and Reusable Catalyst for Suzuki–Miyaura, Ullmann Coupling and Cyanation Reactions
-
The grafting of an aminobis(phosphine)–PdII complex (PNP–PdII) [PdCl2{(Ph2P)2N(CH2)3Si(OMe)3}] (2) on graphene oxide (GO) has been carried out by a condensation reaction between methoxysilane groups of 2 and hydroxyl groups of GO. The composite material was characterized by FTIR spectroscopy, solid-state 31P NMR spectroscopy, SEM, TEM, XPS and ICP-AES techniques. All these tools support the clean immobilization of compound 2 on GO. The composite material showed high catalytic activity in Suzuki–Miyaura, Ullmann coupling and cyanation reactions. The heterogeneity of the composite was confirmed by a hot filtration test. The immobilized PNP–PdII shows comparable activity to its homogeneous analogue 2. The recycling ability of the catalyst was examined for five consecutive runs, which showed little or no reduction in its catalytic efficiency.
- Sengupta, Debasish,Pandey, Madhusudan K.,Mondal, Dipanjan,Radhakrishna, Latchupatula,Balakrishna, Maravanji S.
-
p. 3374 - 3383
(2018/05/08)
-
- A Zwitterionic Palladium(II) Complex as a Precatalyst for Neat-Water-Mediated Cross-Coupling Reactions of Heteroaryl, Benzyl, and Aryl Acid Chlorides with Organoboron Reagents
-
The Suzuki–Miyaura cross-coupling (SMC) reactions of several heteroaryl chlorides, benzyl chlorides, and aryl acid chlorides with (hetero)arylboron reagents have been investigated in the presence of [Pd(HL1)(PPh3)Cl2] (I) [HL1 = 3-[(2,6-diisopropylphenyl)-1-imidazolio]-2-quinoxalinide] as catalyst and K2CO3 as base in neat water. The synthesis of the heterocycle-containing biaryls required the addition of 2 mol-% of a phosphine ligand (PPh3 or X-Phos). A combination of more than 115 substrates were screened and it was found that I is a versatile catalyst that can produce heterocycle-containing biaryls, diarylmethanes, and benzophenones in moderate-to-excellent yields.
- Ramakrishna, Visannagari,Rani, Morla Jhansi,Reddy, Nareddula Dastagiri
-
p. 7238 - 7255
(2018/01/01)
-
- Synthesis of zwitterionic palladium complexes and their application as catalysts in cross-coupling reactions of aryl, heteroaryl and benzyl bromides with organoboron reagents in neat water
-
N-(3-Chloro-2-quinoxalinyl)-N′-arylimidazolium salts (aryl = 2,6-diisopropylphenyl [HL1Cl]Cl, aryl = mesityl [HL2Cl]Cl) have been synthesized by treating 2,3-dichloroquinoxaline with the corresponding N′-arylimidazole in neat water. Facile reactions of these imidazolium salts with Pd(PPh3)4 and Pd2(dba)3/PPh3 (dba = dibenzyledene acetone) at 50 °C have afforded zwitterionic palladium(ii) complexes [Pd(HL1)(PPh3)Cl2] (I) and [Pd(HL2)(PPh3)Cl2] (II) in excellent yields. I and II have been tested for their ability to catalyze Suzuki-Miyaura cross coupling (SMC) reactions in neat water/K2CO3 and are found to be highly active for carrying out these reactions between aryl bromides and organoboron reagents. Furthermore, the scope of the catalyst I was also examined by employing (hetero)aryl bromides, hydrophilic aryl bromides, benzyl bromides and various organoboron reagents. More than 80 aryl/benzyl bromide-arylboronic acid combinations were screened in neat water/K2CO3 and it was found that I was a versatile catalyst, which produced biaryls/diarylmethanes in excellent yields. A TON of 82 000 was achieved by using I. Studies on the mechanism have also been carried out to investigate the involvement of carbene complexes in the catalytic path. Poison tests and a two-phase test were also conducted and the results are reported.
- Ramakrishna,Dastagiri Reddy
-
p. 8598 - 8610
(2017/07/12)
-
- Use of Trifluoromethyl Groups for Catalytic Benzylation and Alkylation with Subsequent Hydrodefluorination
-
The electrophilic organofluorophosphonium catalyst [(C6F5)3PF][B(C6F5)4] is shown to effect benzylation or alkylation by aryl and alkyl CF3 groups with subsequent hydrodefluorination, thus resulting in a net transformation of CF3 into CH2-aryl fragments. In the case of alkyl CF3 groups, Friedel-Crafts alkylation by the difluorocarbocation proceeded without cation rearrangement, in contrast to the corresponding reactions of alkyl monofluorides.
- Zhu, Jiangtao,Prez, Manuel,Caputo, Christopher B.,Stephan, Douglas W.
-
supporting information
p. 1417 - 1421
(2016/02/14)
-
- Towards iron-catalysed suzuki biaryl cross-coupling: Unusual reactivity of 2-halobenzyl halides
-
The reaction of 2-halobenzyl halides with the borate anion Li[(Ph)(t-Bu)Bpin] leads not only to the expected arylation at the benzyl position, but also to some Suzuki biaryl cross-coupling. Preliminary mechanistic investigations hint towards the intermediacy of benzyl iron intermediates that can either: (a) directly cross-couple with the aryl boron reagent to give observed monoarylated species, or (b) undergo oxidative addition of the aryl halide to generate the diarylated species on reaction with the boron-based nucleophile.
- Bedford, Robin B.,Gallagher, Timothy,Pye, Dominic R.,Savage, William
-
p. 1761 - 1765
(2015/06/16)
-
- Iron-catalyzed arylation of aromatic ketones and aldehydes mediated by organosilanes
-
A simple and efficient iron-catalyzed method for arylation of aromatic carbonyl compounds is reported. The use of 4-% FeCl3 or Fe(acac) 3 as the catalyst, in combination with a slight excess of chlorotrimethylsilane and triethylsilane, chlorination of benzylic ketones and aldehydes with subsequent Friedel-Crafts alkylation of arenes is achieved. Although the method is limited by the general constraints associated with Friedel-Crafts alkylation reactions, robust applications for the synthesis of pharmaceutical intermediates and so on can be envisioned. A robust one-pot, iron-catalyzed chlorination Friedel-Crafts alkylation reaction of benzylic carbonyl compounds, mediated by chlorotrimethylsilane and triethylsilane, has been developed to yield substituted diaryl and triaryl building blocks. Copyright
- Savela, Risto,Majewski, Marcin,Leino, Reko
-
p. 4137 - 4147
(2014/07/08)
-
- InBr3-catalyzed deoxygenation of carboxylic acids with a hydrosilane: Reductive conversion of aliphatic or aromatic carboxylic acids to primary alcohols or diphenylmethanes
-
A simple and practical procedure for the direct reduction of aliphatic carboxylic acids with a variety of functional groups to a primary alcohol using the mild reducing reagent tetramethyldisiloxane (TMDS), in the presence of a catalytic amount of InBr3 has been developed. This simple reducing system, when used together with a hydrosilane, allows the preparation of the diphenylmethane derivative directly from an aromatic carboxylic acid and an aromatic compound. Copyright
- Sakai, Norio,Kawana, Keita,Ikeda, Reiko,Nakaike, Yumi,Konakahara, Takeo
-
experimental part
p. 3178 - 3183
(2011/06/28)
-
- Suzuki-Miyaura cross-coupling of aryl carbamates and sulfamates: Experimental and computational studies
-
The first Suzuki-Miyaura cross-coupling reactions of the synthetically versatile aryl O-carbamate and O-sulfamate groups are described. The transformations utilize the inexpensive, bench-stable catalyst NiCl 2(PCy3)2 to furnish biaryls in good to excellent yields. A broad scope for this methodology has been demonstrated. Substrates with electron-donating and electron-withdrawing groups are tolerated, in addition to those that possess ortho substituents. Furthermore, heteroaryl substrates may be employed as coupling partners. A computational study providing the full catalytic cycles for these cross-coupling reactions is described. The oxidative addition with carbamates or sulfamates occurs via a five-centered transition state, resulting in the exclusive cleavage of the aryl C-O bond. Water is found to stabilize the Ni-carbamate catalyst resting state, which thus provides rationalization of the relative decreased rate of coupling of carbamates. Several synthetic applications are presented to showcase the utility of the methodology in the synthesis of polysubstituted aromatic compounds of natural product and bioactive molecule interest.
- Quasdorf, Kyle W.,Antoft-Finch, Aurora,Liu, Peng,Silberstein, Amanda L.,Komaromi, Anna,Blackburn, Tom,Ramgren, Stephen D.,Houk,Snieckus, Victor,Garg, Neil K.
-
scheme or table
p. 6352 - 6363
(2011/06/19)
-
- Synthesis of methylene-bridge polyarenes through palladium-catalyzed activation of benzylic carbon-hydrogen bond
-
In the presence of palladium(II) acetate [Pd(OAc)2] and an N-heterocyclic carbene (NHC) ligand, fluorene derivatives can be generated in good to excellent yields from 2-halo-2′-methylbiaryls through the benzylic C-H bond activation (14 examples; 81-97% yields). The scope and limitations of this protocol have been examined. A wide range of functional groups, such as alkyl, alkoxy, ester, nitrile, and others, is able to tolerate the reaction conditions herein. The cyclization of an isotope-labelled biphenyl gave the corresponding product with a primary kinetic isotope effect (k H/kD=4.8:1), which indicates that the rate-determining step of this reaction is the activation of the benzylic C-H bond. Moreover, indenofluorenes were also accessed in excellent results from terphenyls (3 examples; 91-92% yields). The cascade reaction of 2,6-dichloro-2′- methylbiphenyl with diphenylacetylene produced 8,9-diphenyl-4H-cyclopenta[def] phenanthrene in 60% yield through the activation of an aryl and a benzylic C-H bond. Copyright
- Hsiao, Chien-Chi,Lin, Yi-Kuan,Liu, Chia-Ju,Wu, Tsun-Cheng,Wu, Yao-Ting
-
experimental part
p. 3267 - 3274
(2011/02/23)
-
- Extremely efficient cross-coupling of benzylic halides with aryltitanium tris(isopropoxide) catalyzed by low loadings of a simple palladium(II) acctate/Tris(p-tolyl)phosphine system
-
Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O-i-Pr)3] catalyzed by a simple palladium(II) Acctate/tris(p-tolyl)phosphine [Pd(OAc)2/ P(p-tolyl)3] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2 mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electronwithdrawing cyano (CN) or trifluoromethyl (CF 3) substituents, the reactions require a higher catalyst loading of 1 mol%, or the reactions are carried out at 60°C. The catalytic system also tolerates (1-bromoethyl)benzene bearing β-hydrogen atoms while using a catalyst loading of 1 mol% to afford the coupling product in a 70% yield.
- Chen, Chi-Ren,Zhou, Shuangliu,Biradar, Deepak Baburao,Gau, Han-Mou
-
experimental part
p. 1718 - 1727
(2010/09/18)
-
- Palladium nanoparticle catalyzed hiyama coupling reaction of benzyl halides
-
An efficient Hiyama coupling reaction between benzylic halide and aryltrialkoxysilane using Pd nanoparticles has been developed. This procedure accommodates various functional groups to yield a diverse range of diarylmethanes which are ubiquitous units of natural products and pharmaceuticals.
- Srimani, Dipankar,Bej, Ansuman,Sarkar, Amitabha
-
supporting information; experimental part
p. 4296 - 4299
(2010/09/04)
-
- N,N-diethyl O-carbamate: Directed metalation group and orthogonal Suzuki-Miyaura cross-coupling partner
-
(Chemical Equation Presented) The first Suzuki-Miyaura cross-coupling of an aryl O-carbamate, a versatile and powerful directed metalation group (DMG) in directed ortho metalation (DoM) chemistry, is described using the inexpensive, bench-stable catalyst NiCl2(PCy3)2. Broad synthetic scope and good efficiency are demonstrated for aryl and heteroaryl O-carbamates. The role of water and hydrolysis equilibrium between free boronic acid and boroxine was established to be a crucial parameter for this transformation. When combined with DoM and traditional Pd-catalyzed Suzuki-Miyaura strategies, the methodology offers concise routes to uniquely substituted molecules, avoiding the need for protection/deprotection of the phenol and the use of strongly nucleophilic cross-coupling partners.
- Antoft-Finch, Aurora,Blackburn, Tom,Snieckus, Victor
-
supporting information; experimental part
p. 17750 - 17752
(2010/03/25)
-
- Benzylation of arenes through FeCl3-catalyzed Friedel-Crafts reaction via C-O activation of benzyl ether
-
Various benzyl ethers were converted to benzyl arenes via a FeCl3-catalyzed Friedel-Crafts alkylation reaction under mild condition in good yields. This method also offered a simple and practical approach to synthesize di- or tri-aryl methanes and aryl heteroaryl methanes through the activation of C-O bonds.
- Wang, Bi-Qin,Xiang, Shi-Kai,Sun, Zuo-Peng,Guan, Bing-Tao,Hu, Ping,Zhao, Ke-Qing,Shi, Zhang-Jie
-
p. 4310 - 4312
(2008/09/21)
-
- Suzuki-miyaura cross-coupling of benzylic carbonates with arylboronic acids
-
(Chemical Equation Presented) The cross-coupling of benzylic carbonates with arylboronic acids gave the corresponding diarylmethanes in high yields by use of the palladium catalyst generated in situ from [Pd(n3-C 3H5)Cl]2 and 1,5-bis(diphenylphosphino)pentane (DPPPent). The Suzuki-Miyaura reaction using DPPPent-palladium catalyst is applicable to syntheses of a broad range of functionalized diarylmethanes.
- Kuwano, Ryoichi,Yokogi, Masashi
-
p. 945 - 947
(2007/10/03)
-
- Suzuki-Miyaura cross-coupling of benzylic phosphates with arylboronic acids
-
(Chemical Equation Presented) Suzuki-Miyaura cross-coupling of benzylic phosphates with arylboronic acids was investigated. Optimum conditions employed the simple catalytic system of palladium(II) acetate (1 mol %) and triphenylphosphine (4 mol %) with either potassium phosphate or potassium carbonate as the base and toluene as the solvent at 90°C. Using the developed conditions, a series of structurally diverse diarylmethanes were prepared.
- McLaughlin, Mark
-
p. 4875 - 4878
(2007/10/03)
-
- Synthesis of unsymmetrical diarylmethanes by cross-coupling between aryl triflates and tetrabutylammonium difluorotribenzylstannate
-
(Matrix Presented) The benzylation of aryl triflates can be achieved by cross-coupling between aryl triflates and the new hypervalent tin reagent (n-Bu4N)+(Bn3-SnF2)-.
- Garcia Martinez, Antonio,Osio Barcina, Jose,Heras, Maria Del Rosario Colorado,De Fresno Cerezo, Alvaro
-
p. 1377 - 1378
(2007/10/03)
-
- Generation of allyl- and benzyllithiums from the corresponding halides by the aid of lithium-tellurium exchange reactions
-
A variety of allyl- and benzyllithiums were prepared by lithium-tellurium exchange reactions of allylic and benzylic tellurides generated in situ from the corresponding halides.The produced organolithiums were trapped successfully with electrophiles such as aldehydes, ketones, and trimethylchlorosilane.Benzyllithiums having an alkyl, alkoxy,fluoro, chloro, or cyano substituent(s) on their aromatic ring were generated efficiently in THF.Benzylic tellurides bearing a bromo or iodo substituent afforded a mixture of products under similar conditions arising from the competing lithium-halogen exchange and/or the displacement of the halogen atom with organolithiums used, but they were converted selectively to benzyllithiums in ether without affecting halogen substituents on the benzene ring.Several allyllithiums including dilithioisobutene were generated from allylic halides in a similar way via allylic tellurides.Wurtz-type coupling was negligible in any reactions examined. Key words: Tellurium; Lithium; Allyl; Benzyl; Halide
- Kanda, Takahiro,Kato, Shinzi,Sugino, Takushi,Kambe, Nobuaki,Sonoda, Noboru
-
-
- Synthesis of 4-alkyl-4-(4-methoxyphenyl)cyclohex-2-en-1-ones and 5-alkyl-5-phenyl-1,3-cyclohexadienes from bis(tricarbonylchromium)-coordinated biphenyls
-
(η6:η6-Biphenyl)[Cr(CO)3] 2 and (η6η64,4'-dimethoxybiphenyl) [Cr(CO)3]2 were chemically reduced with lithium anthracenide or lithium naphthalenide in THF to generate s
- Rieke, Reuben D.,Schulte, Louis D.,Dawson, Bryan T.,Yang, Sheng Sbeng
-
p. 8388 - 8398
(2007/10/02)
-