Diastereoselective addition of trimethylsilyl cyanide to chiral O ‐, S ‐ and N ‐heterocyclic aldimines

Systematic investigation of asymmetric trimethylsilylcyanation of heterocyclic azomethines has been realized. The addition of trimethylsilyl cyanide to optically active furan, thiophene and pyridine aldimines, derived from ( R )‐ and ( S )‐1‐phenylethylamine, was studied in the presence of Lewis acids, and a series of the corresponding α ‐amino nitriles was obtained in fair to good yields (up to 91%). Unsaturated nitriles were also formed from pyridine imines. The sense of asymmetric induction and the degree of diastereoselectivity in the synthesis of α ‐amino nitriles were determined by means of 1 H NMR. The stereochemical outcome is a result of the same sense of asymmetric induction: Re face attack to the ( S )‐imines and Si face addition to the ( R )‐imines took place. The ( R,R )‐ (up to 81%) or ( S,S )‐ (up to 87%) α ‐amino nitriles predominated in the products obtained from the all furan, thiophene and pyridine ( R )‐ or ( S )‐imines respectively. Copyright © 2002 John Wiley & Sons, Ltd.