Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
作者:Ewelina Błocka、Mariusz J. Bosiak、Mirosław Wełniak、Agnieszka Ludwiczak、Andrzej Wojtczak
DOI:10.1016/j.tetasy.2014.03.001
日期:2014.4
Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes have been studied with NMR techniques. Among them the complex with the Schiffbase obtained from 2-hydroxy-3-isopropylbenzaldehyde, is the most selective
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
Zr(OBut)4 As an effective promoter for the Meerwein–Ponndorf–Verley alkynylation and cyanation of aldehydes: development of new asymmetric cyanohydrin synthesis
Zr(OBut)4 Can serve as an effective promoter for the Meerwein–Ponndorf–Verley alkynylation of aldehydes and also facilitate MPV type cyanide transfer to aldehyde carbonyls with commercially available acetone cyanohydrin under mild conditions. Based on this finding, a new procedure for asymmetric cyanohydrin synthesis has been developed employing (4R,5R)-2,2-dimethyl-α,α,α′,α′-tetraphenyl-1,3-dioxolane-4
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.
Enzymatic kinetic resolution of racemic cyanohydrins via enantioselective acylation
作者:Qing Xu、Yongli Xie、Xiaohong Geng、Peiran Chen
DOI:10.1016/j.tet.2009.11.074
日期:2010.1
Enzymatickineticresolution of a series of aromatic and aliphatic cyanohydrins in organic media has been investigated. The behavior of potential lipases, molecular sieves, acyl reagent, reaction temperature, and organic solvents on the kineticresolution was studied. The influence of substrate structure, steric, and electronic nature and position of the aryl substituent on the enantioselectivity was