Two highly enantioselective methods for hydrocyanation of aldehydes were developed by using chiral alkoxytitanium reagents. Treatment of benzaldehyde with cyanotrimethylsilane in the presence of a chiral alkoxytitanium affords mandelonitrile in good chemical and optical yields. By the use of the chiral cyanotitanium reagent generated in situ from the chiral alkoxytitanium and cyanotrimethylsilane, aliphatic aldehydes are converted into the corresponding cyanohydrins in a highly enantioselective manner.
The asymmetric hydrocyanation of aldehydes with cyanotrimethylsilane proceeds by the use of a chiral alkoxy titanium(IV) to give the corresponding cyanohydrins with good enantioselectivity.
Asymmetric synthesis via chiral acetal templates. 7. Further studies on the cyanation reaction. The use of acetals derived from diols with one chiral center
作者:Vanessa M.F. Choi、John D. Elliott、William S. Johnson
DOI:10.1016/s0040-4039(00)99946-5
日期:1984.1
New examples of the cyanation reaction are described, including one that affords the cyanochydrin 8, an intermediate for synthesizing pyrethroid insecticides. Also tile reaction with acetals derived from S-1,3-butanediol has been examined.
The enzyme catalyzed synthesis of aliphatic (S)-cyanohydrins has been accomplished for the first time by application of a hydroxynitrile lyase from leaves of Hevea brasiliensis. The optical purities of (S)-cyanohydrins are in a range between 60-97%.