B(C₆F₅)₃/CPA‐Catalyzed Aza‐Diels‐Alder Reaction of 3,3‐Difluoro‐2‐Aryl‐3H‐indoles and Unactivated Dienes

Abstract

Here we report B(C6F5)3/CPA‐catalyzed enantioselective aza‐Diels–Alder reaction of 3,3‐difluoro‐2‐Aryl‐3H‐indoles with unactivated dienes to access chiral 10,10‐difluoro‐tetrahydropyrido[1,2‐a]indoles. This protocol allows the formation of pyrazole‐based C2‐quaternary indolin‐3‐ones with high enantioselectivities and regioselectivities. Moreover, gram‐scale synthesis of the 10,10‐difluoro‐tetrahydropyrido[1,2‐a]indole skeleton was successfully achieved without any reduction in both yield and enantioselectivity.