- POLAR EFFECTS IN FREE-RADICAL REACTIONS. NEW SYNTHETIC DEVELOPMENTS IN THE FUNCTIONALIZATION OF HETEROAROMATIC BASES BY NUCLEOPHILIC RADICALS
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The synthetic interest of the direct substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals is furtheron developed by the following new achievements: i) utilization of the redox system N(+)H3OH/Ti(III) in several solvents; ii) utilization of benzoyl peroxide in alcohols; iii) carbamoylation by HCONH2 and H2O2 in the presence of catalytic amounts of Fe(II).These systems allow to obtain either substitution till now tried without success or reactions of industrial interest.Polar effects play a dominat role in determining reactivity, selectivity and synthetic applications; in particular the role of the strongly nucleophilic intermediate radicals of pyridinyl type in the rearomatization step is emphasized.
- Minisci, Francesco,Citterio, Attilio,Vismara, Elena,Giordano, Claudio
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- A novel, selective free-radical carbamoylation of heteroaromatic bases by Ce(IV) oxidation of formamide, catalysed by N-hydroxyphthalimide
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The Ce(IV)-NHPI system was used to generate a carbamoyl radical by oxidation of formamide; this nucleophilic radical has been successfully used in the carbamoylation of heteroaromatic bases.
- Minisci, Francesco,Recupero, Francesco,Punta, Carlo,Gambarotti, Cristian,Antonietti, Fabrizio,Fontana, Francesca,Pedulli, Gian Franco
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- Substrate-Specific Heterogeneous Catalysis of CeO2 by Entropic Effects via Multiple Interactions
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Achieving complete substrate specificity through multiple interactions like an enzyme is one of the ultimate goals in catalytic studies. Herein, we demonstrate that multiple interactions between the CeO2 surface and substrates are the origin of substrate-specific hydration of nitriles in water by CeO2, which is exclusively applicable to the nitriles with a heteroatom (N or O) adjacent to the α-carbon of the CN group but is not applicable to the other nitriles. Kinetic studies reveal that CeO2 reduces the entropic barrier (TΔS?) for the reaction of the former reactive substrate, leading to 107-fold rate enhancement compared with the latter substrate. Density functional theory (DFT) calculations confirmed multiple interaction of the reactive substrate with CeO2, as well as preferable approximation and alignment of the nitrile group of the substrate to the active OH group on CeO2 surface. This can lead to the reduction of the entropic barrier. This is the first example of an entropy-driven substrate-specific catalysis of a nonporous metal oxide surface, which will provide a new design strategy for enzyme-inspired synthetic catalysts.
- Tamura, Masazumi,Sawabe, Kyoichi,Tomishige, Keiichi,Satsuma, Atsushi,Shimizu, Ken-Ichi
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- Direct Oxidative Amination of the Methyl C-H Bond in N-Heterocycles over Metal-Free Mesoporous Carbon
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Direct oxidative amination of the sp3C-H bond is an attractive synthesis route to obtain amides. Conventional catalytic systems for this transformation are based on transition metals and complicated synthesis processes. Herein, direct and efficient oxidative amination of the methyl C-H bond in a wide range of N-heterocycles to access the corresponding amides over metal-free porous carbon is successfully developed. To understand the fundamental structure-activity relationships of carbon catalysts, the surface functional groups and the graphitization degree of porous carbon have been purposefully tailored through doping with nitrogen or phosphorus. The results of characterization, kinetic studies, liquid-phase adsorption experiments, and theoretical calculations indicate that the high activity of the carbon catalyst is attributed to the synergistic effect of surface acidic functional groups (hydroxyl/carboxylic acid/phosphate) and more graphene edge structures exposed on the surface of carbon materials with a high graphitization degree, in which the role of acidic functional groups is to adsorb the substrate molecule and the role of the graphene edge structure is to activate O2
- Long, Xiangdong,Wang, Jia,Gao, Guang,Nie, Chao,Sun, Peng,Xi, Yongjie,Li, Fuwei
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p. 10902 - 10912
(2021/09/08)
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- Highly Regioselective Carbamoylation of Electron-Deficient Nitrogen Heteroarenes with Hydrazinecarboxamides
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The use of hydrazinecarboxamides as a new class of carbamoylating agents has been established through the dehydrazinative Minisci reaction of electron-deficient nitrogen heteroarenes. A wide range of electron-deficient nitrogen heteroarenes, including isoquinoline, quinoline, pyridine, phenanthridine, quinoxaline, and phthalazine, underwent copper/acid-catalyzed oxidative carbamoylation with hydrazinecarboxamide hydrochlorides to afford structurally diverse nitrogen-heteroaryl carboxamides as single regioisomers in moderate to excellent yields. The functional group tolerance was substantially demonstrated in the direct carbamoylation of quinine obviating multistep sequences involving protecting groups and prefunctionalization of the heterocycle.
- He, Zeng-Yang,Huang, Chao-Fan,Tian, Shi-Kai
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supporting information
p. 4850 - 4853
(2017/09/23)
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- Mild and selective heterogeneous catalytic hydration of nitriles to amides by flowing through manganese dioxide
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A sustainable flow chemistry process for the hydration of nitriles, whereby an aqueous solution of the nitrile is passed through a column containing commercially available amorphous manganese dioxide, has been developed. The product is obtained simply by concentration of the output stream without any other workup steps. The protocol described is rapid, robust, reliable, and scalable, and it has been applied to a broad range of substrates, showing a high level of chemical tolerance.
- Battilocchio, Claudio,Hawkins, Joel M.,Ley, Steven V.
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supporting information
p. 1060 - 1063
(2016/10/17)
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- An in-depth study of the biotransformation of nitriles into amides and/or acids using Rhodococcus rhodochrous AJ270
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A variety of aliphatic, aromatic and heterocyclic nitriles have been readily hydrolysed into the corresponding amides and/or acids under very mild conditions using Rhodococcus sp. AJ270. The nitrile hydratase involved in this novel nitrile-hydrolysing microorganism efficiently hydrates most nitriles tested, irrespective of the electronic and steric effects of the substituents, to form the amides. Conversion of amides into acids catalysed by the associated amidase is rapid and efficient in most cases. Substrates bearing an adjacent substituent (which may be an ortho substituent on an aromatic nitrile, an adjacent heteroatom in a heterocyclic ring or a geminal substituent in an α,β-unsaturated nitrile) undergo slow hydrolysis of the amides allowing efficient amide isolation. The scope, limitations and reaction mechanism of this enzymatic process have been systematically studied. A molecular size of >7 A diameter and the presence of functions capable of metal complexation near to the nitrile inhibit hydrolysis.
- Meth-Cohn, Otto,Wang, Mei-Xiang
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p. 1099 - 1104
(2007/10/03)
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- A Powerful New Nitrile Hydratase For Organic Synthesis-Aromatic And Heteroaromatic Nitrile Hydrolyses- A Rationalisation
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A powerful new nitrile hydratase organism, Rhodococcus rhodocrous AJ270 has been isolated that efficiently hydrolyses all kinds of nitriles to amides and/or acids.This paper shows that aromatic and heterocyclic nitriles are readily hydrolysed to acids but, that those bearing an adjacent-substituent (which may be an ortho substituent or an adjacent heteroatom in the ring) give amides in good yield but only slowly proceed to acids.
- Meth-Cohn, Otto,Wang, Mei-Xiang
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p. 9561 - 9564
(2007/10/02)
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- PHOTOINDUCED FRAGMENTATION OF PYRIDO-as-TRIAZINIUM-4-OLATE AS ITS BENZOLOGUE. A CONTRIBUTION TO THE MECHANISM OF CURTIUS REARRANGEMENT.
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The zwitterionic pyrido-as-triazinum-4-olates (1a-b) and as-triazinoisoquinolinium-1-olate (10) were photolysed to give acid amides (5) and (11), respectively.Formation of 5 through acylnitrene (4) was supported in separate experiment.
- Batori, Sandor,Messmer, Andras,Timpe, Hens-Joachim
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p. 649 - 654
(2007/10/02)
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- Tetrahydrofolate Coenzyme Models: Synthesis of Tetrahydroimidazoisoquinolines and Tetrahydroimidazoquinolines
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The new dihydroimidazoles 3-methyl-1,5,6,10b-tetrahydroimidazoisoquinoline and 1-methyl-3,3a,4,5-tetrahydroimidazoquinoline are efficiently and conveniently prepared from isoquinoline and quinoline, via 1-aminomethyl-1,2,3,4-tetrahydroisoquinoline and 2-aminomethyl-1,2,3,4-tetrahydroquinoline, respectively.Deprotonation of the fused dihydroimidazoles at the methyl substituent leads to homologation via C-alkylation, C-acylation, or C-phosphonylation-condensation.The properties of the tetrahydroimidazoisoquinolines and tetrahydroimidazoquinolines towards reducing agents mirror those of monocyclic dihydroimidazoles, affording aminomethyl-isoquinolines and -quinolines, respectively.
- Jones, Raymond C. F.,Smallridge, Mark J.,Chapleo, Christopher B.
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p. 385 - 391
(2007/10/02)
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