Tunable and Highly Regio- and Diastereoselective Vinylogous Mannich-Type Reaction of Dioxinone-Derived Silyl Dienolate

A tunable and highly regio- and diastereoselective vinylogous Mannich-type reaction of dioxinone-derived silyl dienolate (1) with chiral N-tert-butanesulfinyl imino ester (2) was developed. By appropriate choice of Lewis acid catalyst, two diastereomers of the γ-product were obtained, respectively, with dr up to 95:5. The procedure for the Ag(I)-catalyzed vinylogous Mannich-type reaction also provided facile access to the α-regioisomer with excellent diastereoselectivities (up to >99:1 dr) by changing the counterion of the Ag(I) salt.