Catalytic Regio- and Enantioselective [4+2] Annulation Reactions of Non-activated Allenes by a Chiral Cationic Indium Complex.

Regio- and enantioselective [4+2] annulation between β,γ-unsaturated α-keto esters and non-activated allenes was achieved by using a chiral cationic indium(III)/phosphate catalyst. The reaction affords the corresponding C3-selective dihydropyrans in good yields and with high enantioselectivity (up to 99 % ee).