Organocatalyzed Enantioselective Protonation of Silyl Enol Ethers: Scope, Limitations, and Application to the Preparation of Enantioenriched Homoisoflavones
In the present work, enantioselective protonation of silylenolethers is reported by means of a variety of chiral nitrogen bases as catalysts, mainly derived from cinchonaalkaloids, in the presence of various protic nucleophiles as proton source. A detailed study of the most relevant reaction parameters is disclosed allowing high enantioselectivities of up to 92% ee with excellent yields to be achieved
Synthesis of Chiral 3-Alkyl-3,4-dihydroisocoumarins by Dynamic Kinetic Resolutions Catalyzed by a Baeyer−Villiger Monooxygenase
作者:Ana Rioz-Martínez、Gonzalo de Gonzalo、Daniel E. Torres Pazmiño、Marco W. Fraaije、Vicente Gotor
DOI:10.1021/jo902519j
日期:2010.3.19
Baeyer−Villigermonooxygenases have been tested in the oxidation of racemic benzofused ketones. When employing a single mutant of phenylacetone monooxygenase (M446G PAMO) under the proper reaction conditions, it was possible to achieve 3-substituted 3,4-dihydroisocoumarins with high yields and optical purities through regioselective dynamic kinetic resolution processes.
Herein is disclosed an efficient catalyticenantioselective protonation of enol acetates by means of a readily implementable transition-metal-free chemical process. By making use of simple hygrogenocarbonates as the proton source and hydroquinine anthraquinone-1,4-diyl diether as the chiral proton shuttle, a series of cyclic enol trifluoroacetates are protonated under mild conditions to yield the corresponding
The asymmetric protonation of silylenolates derived from tetralone, benzosuberone, and cyclohexanone has been successfully achieved by using simple and original betaine catalysts derived from Cinchona alkaloids (quinine and quinidine series) to afford the desired α-substituted ketones in high yields and moderate enantioselectivities. The ease of implementation of this approach along with the easy
Enantioselective Protonation of Alkenyl Trifluoroacetates Catalyzed by Chiral Tin Methoxide
作者:Akira Yanagisawa、Takuya Sugita、Kazuhiro Yoshida
DOI:10.1002/chem.201302975
日期:2013.11.25
Go catalytic! A catalytic enantioselectiveprotonation of alkenyltrifluoroacetates was achieved by using an in situ generated chiraltin bromide methoxide as the chiral catalyst in the presence of methanol (see scheme). Optically active ketones containing a tertiary stereogenic center at the α‐position were obtained with enantioselectivities of up to 94 % ee.