29125-24-4Relevant articles and documents
Aromatic cation activation: Nucleophilic substitution of alcohols and carboxylic acids
Nguyen, Thanh V.,Bekensir, Alp
supporting information, p. 1720 - 1723 (2014/04/17)
A new method for the nucleophilic substitution of alcohols and carboxylic acids using aromatic tropylium cation activation has been developed. This article reports the use of chloro tropylium chloride for the rapid generation of alkyl halides and acyl chlorides under very mild reaction conditions. It demonstrates, for the first time, the synthetic potential of tropylium cations in promoting chemical transformations.
Nitrile hydratase activity of a recombinant nitrilase
Fernandes, Bruno C. M.,Mateo, Cesar,Kiziak, Christoph,Chmura, Andrzej,Wacker, Jan,Van Rantwijk, Fred,Stolz, Andreas,Sheldon, Roger A.
, p. 2597 - 2603 (2007/10/03)
Appreciable amounts of amide are formed in the course of nitrile hydrolysis in the presence of recombinant nitrilase from Pseudomonas fluorescens EBC 191, depending on the α-substituent and the reaction conditions. The ratio of the nitrilase and nitrile hydratase activities of the enzyme is profoundly influenced by the electronic and steric properties of the reactant. In general, amide formation increased when the α-substituent was electron-deficient; 2-chloro-2-phenylacetonitrile, for example, afforded 89% amide. We found, moreover, that (R)-mandelo-nitrile was hydrolysed with 11% of amide formation whereas 55% amide was formed from the (S)-enantiomer; a similar effect was found for the O-acetyl derivatives. A mechanism that accomodates our results is proposed.
Enantioselective protonation of silyl enol ethers and ketene disilyl acetals with Lewis acid-assisted chiral Bronsted acids: Reaction scope and mechanistic insights
Nakamura, Shingo,Kaneeda, Masanobu,Ishihara, Kazuaki,Yamamoto, Hisashi
, p. 8120 - 8130 (2007/10/03)
Enantioselective protonation is a potent and efficient way to construct chiral carbons. Here we report details of the reaction using Lewis acid-assisted chiral Bronsted acids (chiral LBAs). The 1:1 coordinate complex of tin tetrachloride and optically active binaphthol ((R)- or (S)-BINOL) can directly protonate various silyl enol ethers and ketene disilyl acetals to give the corresponding α-aryl ketones and α-arylcarboxylic acids, respectively, with high enantiomeric excesses (up to 98% ee). A catalytic version of enantioselective protonation has also been achieved using stoichiometric amounts of 2,6-dimethylphenol and catalytic amounts of monomethyl ether of optically active BINOL in the presence of tin tetrachloride. This protonation is also effective for producing α-halocarbonyl compounds (up to 91% ee). DFT calculations on the B3LYP/LANL2DZ level show that the conformational structure of the chiral LBA and the orientation of activated proton on (R)-BINOLs are important for understanding the absolute stereochemistry of the products.