Enantioselective sulfoxidation catalyzed by polymer-supported chiral Schiff base–VO(acac)2 complexes
摘要:
The preparation of a series of polymer supported chiral Schiff bases derived from salicylic aldehydes and optically active amino alcohols is reported. These heterogeneous ligands have been complexed with VO(acac)(2) and employed to catalyze the enantioselective oxidation of sulfides to sulfoxides with hydrogen peroxide as an environmentally acceptable oxidant. The procedure affords the sulfoxides in good yield and selectivity and with ee values comparable to those obtained with the homogeneous counterparts. The catalyst can be used for at least four cycles without any significant decrease in both efficiency or enantioselectivity. (C) 2004 Elsevier Ltd. All rights reserved.
Enantioselective sulfoxidation catalyzed by polymer-supported chiral Schiff base–VO(acac)2 complexes
摘要:
The preparation of a series of polymer supported chiral Schiff bases derived from salicylic aldehydes and optically active amino alcohols is reported. These heterogeneous ligands have been complexed with VO(acac)(2) and employed to catalyze the enantioselective oxidation of sulfides to sulfoxides with hydrogen peroxide as an environmentally acceptable oxidant. The procedure affords the sulfoxides in good yield and selectivity and with ee values comparable to those obtained with the homogeneous counterparts. The catalyst can be used for at least four cycles without any significant decrease in both efficiency or enantioselectivity. (C) 2004 Elsevier Ltd. All rights reserved.
New chloramphenicol Schiff base ligands for the titanium-mediated asymmetric aldol reaction of α,β-unsaturated aldehydes with diketene: a short synthesis of atorvastatin calcium
Several novel chiral Schiff base ligands were prepared from a commercially available chloramphenicol base and applied to the titanium-mediated asymmetricaldolreaction of diketene with various α,β-unsaturated aldehydes. This reaction proceeded in good yield with high enantioselectivity. The synthetic utility of this methodology was demonstrated in the short synthesis of atorvastatin calcium.