Synthesis of novel cinchona-amino acid hybrid organocatalysts for asymmetric catalysis
作者:Pedro Barrulas、Maurizio Benaglia、Anthony J. Burke
DOI:10.1016/j.tetasy.2014.05.003
日期:2014.6
Three novel subclasses of cinchonidine derivatives coupled to diverse amino acids were prepared in very good overall yield and tested in a benchmark organocatalytic aldol reaction, betweenacetone and aromatic aldehydes. These subclasses are a family of amino acid-cinchonidine (subclass A), N-formamides-cinchonidine (subclass B) and dipeptide-cinchonidine (subclass C) hybrids. Our main goal, besides
Synthesis of Chiral Organocatalysts derived from Aziridines: Application in Asymmetric Aldol Reaction
作者:Shikha Gandhi、Vinod K. Singh
DOI:10.1021/jo8019863
日期:2008.12.5
We report the synthesis of a new series of highly efficient chiral organocatalysts derived via the regio- and stereoselective ring opening of chiral aziridines with azide anions. The catalysts have proved to be very efficient for a direct asymmetric aldolreaction, both with cyclic as well as acyclic ketones in brine with 2 mol % of catalyst loading, and afforded the products in excellent yields (up
Highly Efficient Small Organic Molecules for Enantioselective Direct Aldol Reaction in Organic and Aqueous Media
作者:Monika Raj Vishnumaya、Vinod K. Singh
DOI:10.1021/jo900548f
日期:2009.6.5
A series of highly efficient organocatalysts have been derivedfrom naturally available amino acids for carrying out enantioselectivedirectaldolreaction in both organic and aqueous medium. The aldol products were obtained in high diastereoselectivities (up to 99:1) and enantioselectivities (up to >99% ee) for a broader range of substrates using 1 mol % of a catalyst. The results demonstrate that
Highly Enantioselective Organocatalytic Direct Aldol Reaction in an Aqueous Medium
作者:Vishnu Maya、Monika Raj、Vinod K. Singh
DOI:10.1021/ol071013l
日期:2007.6.1
We have demonstrated that small organic molecules 1 and 2 catalyzed the directaldolreaction of both acyclic and cyclic ketones with different aldehydes in an excess of water/brine. Excellent enantioselectivities up to >99% and diastereoselectivities up to 99% with very good yields were obtained by using much lower catalyst loadings (0.5 mol %).
Highly Enantioselective Direct Aldol Reaction Catalyzed by Organic Molecules
作者:Monika Raj、Vishnumaya、Sandeep K. Ginotra、Vinod K. Singh
DOI:10.1021/ol0616081
日期:2006.8.1
compounds catalyzed the directaldolreaction between aldehydes and acetone to provide beta-hydroxy ketones in good yields. The reaction is efficient, and 5-10 mol % of the catalyst and excellent enantioselectivities (97-99% ee) were obtained in both aromatic and aliphatic aldehydes. The presence of a gem-diphenyl group at the beta-carbon is necessary for high enantioselectivity.