Asymmetric Addition of a Formyl Anion Equivalent to Enoate Surrogates

Significance

An organocatalytic asymmetric conjugate addition of a formyl anion equivalent to enoate surrogates has been developed. Formaldehyde N,N-dialkylhydrazone 2 reacts with β,γ-unsaturated α-keto esters 3 in the presence of thiourea 1 (10 mol%) to give adducts of type 4 in good yields and enantioselectivities. These products (4a) can be transformed into the corresponding nitriles (5a) with preservation of the stereo­chemistry. Furthermore, a transition state to explain the observed absolute configuration is proposed.