Enantioselective Synthesis of α-Amino Nitriles from <i>N</i>-Benzhydryl Imines and HCN with a Chiral Bicyclic Guanidine as Catalyst
作者:E. J. Corey、Michael J. Grogan
DOI:10.1021/ol990623l
日期:1999.7.1
[formula: see text] A novel catalytic enantioselective Strecker synthesis of chiral alpha-amino nitriles and alpha-amino acids is described and analyzed with regard to the possible mechanistic basis for stereoselectivity. Key features of the enantioselective process include (1) the use of the chiral bicyclicguanidine 1 as catalyst and (2) the use of the N-benzhydryl substituent on the imine substrate
evaluated as ligands for catalytic asymmetric Streckerreactions. N-Benzhydrylaldimines derived from aromatic and aliphatic aldehydes reacted with TMSCN in the presence of 10 mol% of Ti-1 complex to give the Strecker products in excellent yields and in up to >98% ee. The presence of a protic additive is essential to ensure good conversion and reaction rate. The reaction conditions are simple and the stereochemical
In the pursuit of a credible mechanism for the abiotic synthesis of α-amino acids, solid-state asymmetric Strecker/retro-Strecker reactions have been demonstrated. Asymmetric addition of cyanide to enantiomorphic crystals of achiral imines proceeded to produce enantioenriched aminonitriles. Moreover, dehydrocyanation of enantioenriched aminonitriles gave chiral crystals of achiral imines stereoselectively
An enantioselective Strecker-type reaction of imines with Et2AlCN in the presence of chiral additives has been examined. The enantioselectivity varied depending on the substituents of the imino group as well as the chiral additives used. Thus, alpha-aminonitriles were obtained in good yields with good en antioselectivities in the reaction of N-benzylidenebenzhydrylamine with Et2AlCN and BINOL. The reaction with excess BINOL gave the aminonitrile with reversed configuration. (C) 2004 Published by Elsevier Ltd.