HFIP-Catalyzed Mannich Reaction: Divergent Synthesis of Difluoro-Substituted 3,4-Dihydroquinoxalin-2(1H)-ones and Monofluoroquinoxalin-2(1H)-ones

Hexafluoroisopropanol (HFIP) has been extensively applied in organic synthesis as a versatile reaction media. However, the application of HFIP as an catalyst in organic synthesis has been rarely studied. Presented here, is the example of HFIP-catalyzed Mannich-type reaction between quinoxalin-2(1H)-ones and difluoroenoxysilanes. The developed protocol tolerates various substituents under mild reaction conditions, providing a divergent approach to the construction of difluoro-substituted 3,4-dihydroquinoxalin-2(1H)-ones and monofluoroquinoxalin-2(1H)-ones in 51-92% yields.