Organocatalytic Asymmetric Cyclization Reaction of 2‐Alkynyl‐3,3‐Difluoro‐3H‐Indoles and 2‐Mercaptoimidazoles: Access to gem‐Difluorinated C2‐Spiro Indolines

We reported a cupreidine catalyzed enantioselective cascade cyclization reaction of 2‐alkynyl‐3,3‐difluoro‐3H‐indole and 2‐mercaptoimidazole under simple and mild conditions. The corresponding chiral gem‐difluorinated C2‐spiro indolines were obtained in moderate to good yields and enantioselectivities, which could be interesting compounds from synthetic and medicinal chemistry points of view. This work represents the first catalytic enantioselective example of utilizing 2‐alkynyl‐3,3‐difluoro‐3H‐indoles as the bis‐electrophiles in a cyclization reaction.