Highly Enantioselective Cyanoformylation of Aldehydes Catalyzed by a Mononuclear Salen‐Ti(O<i>i</i>Pr)₄ Complex Produced In Situ

Abstract

Abstract An efficient enantioselective cyanoformylation of aldehydes with ethyl cyanoformate, catalyzed by a salen‐Ti(O i Pr) 4 complex generated in situ, has been developed. Studies of nonlinear effects indicated that the mononuclear salen‐titanium complex, and not a heterochiral complex, played a key role in the stereodiscriminating step of the reaction. During the preparation of the catalyst, the addition of isopropyl alcohol was shown to avoid the formation of a heterochiral complex. In the presence of 5 mol‐% catalyst, the reaction can be carried out in excellent yields (up to 99 %) and with high enantioselectivities (up to 91 % ee ). From preliminary studies, a transition state to explain the origin of the asymmetric induction has been proposed. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2007)