A Facile Synthesis of Vicinal Diamines Promoted by Low-Valent Niobium: Preparation of Chiral Octahydrobiisoquinolines and Their Application to Catalytic Asymmetric Synthesis
作者:Shigeru Arai、Satoshi Takita、Atsushi Nishida
DOI:10.1002/ejoc.200500301
日期:2005.12
homocoupling of imines to give vicinaldiaminespromoted by low-valentniobium, generated by treatment of NbCl5 with zinc powder, is described. The desired products were obtained in good to excellent yields. Dihydroisoquinoline derivatives also gave the coupling products with good diastereoselectivities (D,L/meso). Optical resolution of the racemic octahydrobiisoquinolines was achieved and their complexes
Electroorganic chemistry. 129. Electroreductive synthesis of chiral piperazines and enantioselective addition of diethylzinc to aldehydes in the presence of the chiral piperazines
Electroreduction of diimines, prepared from 1,2-diamines and aromatic aldehydes, in acidic media gave intramolecularly coupled products, 2,3-diarylpiperazines, stereoselectively. Chiral tri- and tetrasubstituted piperazines were synthesized effectively from chiral 1,2-diamines by the same electroreductive method. Chiral piperazines, prepared from 1(R),2(R)-diaminocyclohexane were effective chiral ligands of catalysts for the enantioselective addition of diethylzinc to aldehydes.