Organocatalytic Synthesis of gem‐Difluorinated C2‐Spiro Indolines and Pyrimido[1,2‐a]benzimidazoles from 2‐Alkynyl‐3,3‐Difluoro‐3H‐Indoles.

Abstract: In this communication, we report a substrate‐controlled product diversity in the 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD)‐catalyzed cascade cyclization of 2‐alkynyl‐3,3‐difluoro‐3H‐indoles with N,N‐ or N,S‐bis‐nucleophiles. The products represent two important heterocyclic compounds, C2‐spiro indoline, and pyrimido[1,2‐a]benzimidazole, featuring a versatile gem‐difluoromethylene group on the framework. In these cascade processes, two new C−N bonds, or one C−S and one C−N bond, are consecutively formed in a single step. The present protocol is characterized with high regioselectivity, high yield, broad substrate scope, good functional group tolerance, facile scalability and mild reaction conditions. [ABSTRACT FROM AUTHOR]