Difunctionalization of N-alkyl cyclobutyl and cyclopropyl amines via photoredox catalysis

by Wang, Qile; Zheng, Nan

To drive the unfavorable ring opening of N-alkyl cyclopropyl- and cyclobutyl-amines, we developed a new strategy of employing TMSCN as an iminium trap to drive the ring opening. This novel mode of activation allowed us to overcome the constraint of requiring N-aryl amines in the [3+2] and [4+2] annulation reactions. Furthermore, rather than the formation of aniline-substituted five-membered or six-membered carbocycles, acyclic 1,3 or 1,4 difunctionalized products with saturated carbon backbones were produced. Both transformations are generally difficult to be achieved. Finally, this difunctionalization process via photoredox catalysis greatly increased the scope of cyclopropyl- and cyclobutyl-amines, including primary, secondary and tertiary amines as well as N-alkyl and N-aryl amines. Rapid increase of the mol. complexity and late stage modification with great functional group tolerance can be achieved with ease.