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

Abstract

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‐3 H ‐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. magnified image