Highly regio- and enantioselective γ-alkylation of linear α,β-unsaturated aldehydes

Asymmetric alkylation is one of the most useful carbon–carbon bond-forming reactions in synthetic organic chemistry. Chiral-amine-catalyzed alkylation reactions often lack regioselectivity owing to multiple reactive centers. In particular, the alkylation of linear 2-enals through dienamine catalysis produces a mixture of regioisomers owing to reactive α-and γ-positions. A few attempts have been made to mask the α-reactive center to achieve γ-selectivity. Controlling the enantioselectivity at the remote γ-position has also been found to be quite challenging. Herein, we achieved the highly regioselective γ-alkylation of linear α,β-unsaturated aldehydes by using trifluoroethanol (TFE) as a cosolvent. Further, we demonstrated in situ kinetic resolution for enantioenrichment of the γ-alkylated products. This method brings together the activation of an electrophile facilitated by TFE and in situ kinetic resolution to achieve excellent selectivity in dienamine catalysis.