The enantioselective addition of trimethylsilyl cyanide to a variety of aldehydes proceeded by the aid of a catalyst prepared in situ from titanium tetraisopropoxide [Ti(O-i-Pr)4] and chiral Schiff bases and gave the corresponding cyanohydrins in high optical yield (up to 96% e.e.). A remarkable rate enhancement was brought about by the addition of the Schiffbase to the titanium alkoxide mediated
Novel enantioselective reaction of diketene with aldehydes promoted by chiral Schiff base–titanium alkoxide complex
作者:Masahiko Hayashi、Tetsuya Inoue、Nobuki Oguni
DOI:10.1039/c39940000341
日期:——
Reaction of a variety of aldehydes with diketene in the presence of chiral Schiff baseâtitanium alkoxide complexes proceeds with high enantioselectivity to afford the corresponding 5-hydroxy-3-oxoesters.
Enantioselective addition Of diketene to aldehydes promoted by chiral schiff base—titanium alkoxide complex. Application to asymmetric synthesis of potential inhibitors of HMG coenzyme reductase
Highly enantioselective addition of diketene to aldehydes was achieved by using novel Schiff base—titanium alkoxide complexes. Up to 92% ee of 5-hydroxy-3-oxoesters was obtained. This procedure provides an efficient method for the asymmetric synthesis of potential inhibitors of HMG coenzyme reductase.
Catalytic Enantioselective Reaction of Diketene with Aldehydes Catalyzed by Chiral Schiff Base-Titanium Alkoxide Complexes
作者:Nobuku Oguni、Kiyoshi Tanaka、Hajime Ishida
DOI:10.1055/s-1998-1744
日期:1998.6
The catalytic enantioselective reaction of diketene with aldehydes was achieved by the use of a catalytic amount (20 mol%) of chiral Schiff base to afford the corresponding 5-hydroxy-3-oxoesters with high enantioselectivity.
Complete reversal of enantioselection using oxazoline-containing Schiff base ligands derived from l-serine in enantioselective addition of diketene to aldehydes
Starting from one stereogenic center (in this case from L-serine), we obtained two chiral Schiff bases possessing oxazoline moieties, each of which recognized a different enantioface of aldehydes with a high enantionteric excess [up to 93% ee (R) and 89% ee (S)] in the addition reaction of diketene to 2-furfural. (c) 2006 Elsevier Ltd. All rights reserved.