Utilization of the N-silyl enamine intermediate from N-heteroarene: Synthesis of cyclic amidines and bicyclic pyrazolidinone derivatives

초록

Regioselective dearomatization of the readily available N-heteroarenes is an emerging strategy to obtain complex molecules. Especially, B(C6F5)3 catalyzed dearomative hydrosilylation of the N-heteroarenes has been studied actively. However, due to the intrinsic unstability of the N?Si bond, the utility of the partially reduced N-silyl enamine intermediate from the mono-hydrosilylation of the N-heteroarene has been rarely reported. In this context, our group recently developed a methodology to synthesize the cyclic amidine by using in situ utilization of the N-silyl enamine with organic azide. [3 + 2] cycloaddition and rearrangement involving hydride shift resulted in (Z)-selective cyclic amidine. The substrate scope has been widely expanded from quinolines to isoquinolines and pyridines with various class of electron withdrawing organic azides. Furthermore, we recently discovered a reactivity of the Nsilyl enamine toward azomethine imine which could achieve novel bicyclic pyrazolidine skeleton.