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). Full circle: A chiral cationic indium phosphate complex was identified that enables unprecedented [4+2] annulation between β,γ‐unsaturated α‐keto esters and non‐activated allenes. The reaction affords C3‐selective adducts in good yields and with high enantioselectivity.