Modified Guanidines as Potential Chiral Superbases. 1. Preparation of 1,3-Disubstituted 2-Iminoimidazolidines and the Related Guanidines through Chloroamidine Derivatives
作者:Toshio Isobe、Keiko Fukuda、Tsutomu Ishikawa
DOI:10.1021/jo000744v
日期:2000.11.1
Modified guanidines were explored as potential chiral superbases. Thus, chiral 1,3-dimethyl-2-iminoimidazolidines with or without 4,5-diphenyl groups, their guanidinium salts, and the 2-iminoimidazolidines with (S)-1-phenylethyl groups on the ring nitrogens were prepared by treatment of 2-chloroimidazolinium chlorides with appropriate amines. Bicyclic guanidines were also prepared from a prolinamide using a similar procedure.
Guanidinium Ylide Mediated Aziridination from Arylaldehydes: Scope and Limitations in the Formation of Unactivated 3-Arylaziridine-2-carboxylates
Abstract The scope and limitations of guanidiniumylide mediated aziridinations from arylaldehydes yielding unactivated 3-arylaziridine-2-carboxylates, applicable to asymmetric synthesis, are discussed. The scope and limitations of guanidiniumylide mediated aziridinations from arylaldehydes yielding unactivated 3-arylaziridine-2-carboxylates, applicable to asymmetric synthesis, are discussed.
Enantiopure Guanidine Bases for Enantioselective Enone Epoxidations: 2, Cyclic Guanidines
作者:Richard J. Taylor、Julie C. McManus、Thorsten Genski、John S. Carey
DOI:10.1055/s-2003-37107
日期:——
A range of structurally and functionally varied enantiopure cyclic and bicyclic guanidines has been prepared and evaluated in the enantioselective epoxidation of 3-tert-butoxycarbonylamino-4,4-dimethoxycyclohexa-2,5-dien-1-one 1 using tert-butylhydroperoxide. Encouraging enantiomeric excesses were observed (up to 60%). Low enantiomeric excesses were also observed with 2-methylnaphthoquinone and trans-chalcone.