Diastereoselective synthesis of polycyclic indolines dearomative [4 + 2] cycloaddition of 3-nitroindoles with -aminophenyl -quinone methides.

A formal [4 + 2] cycloaddition of 3-nitroindoles with -aminophenyl -quinone methides a dearomatization process was developed. This method provides a facile approach for preparing tetrahydro-5-indolo[2,3-]quinolones with good results. With the bifunctional alkaloid-squaramide as the catalyst, the asymmetric version of the reaction successfully afforded the corresponding chiral products with moderate to good enantioselectivities. This work represents the first dearomative cycloaddition of electron-deficient heteroarenes triggered by aza-Michael addition from -QMs.