Asymmetric synthesis of O-acetylcyanohydrins by reaction of aldehydes with NaCN/KCN catalyzed by recyclable chiral dimeric titanium(IV)/vanadium(V) salen complexes

摘要

The efficient catalytic asymmetric addition of an inexpensive and nonvolatile cyanide source such as NaCN or KCN and acetic anhydride to various aldehydes was catalyzed by recyclable dimeric Ti-IV and V-V chiral salen complexes at -20 degrees C. High chiral induction (96% ee) in the O-acetylcyanohydrin was obtained in the case of 2-fluorobenzaldehyde, and the results achieved with sodium cyanide are quite comparable to those with potassiurn cyanide. The chiral V-V salen complex Was found to be the most efficient recyclable catalyst reported so far in the literature, and was better than the Ti-IV salen system. Both the catalysts were recovered after the first use and recycled effectively four times. (c) Wiley-VCH Verlag GmbH & Co.