Catalytic Access to Bridged Sila-N-heterocycles from Piperidines via Cascade sp(3) and sp(2) C-Si Bond Formation

Described herein is the development of an unprecedented route to bridged sila-N-heterocycles via B(C6F5)(3)-catalyzed cascade silylation of N-aryl piperidines with hydrosilanes. Mechanistic studies indicated that an outer-sphere ionic path is operative to involve three sequential catalytic steps having N-silyl piperidinium borohydride as a resting species: (i) dehydrogenation of the piperidine ring, (ii) beta-selective hydrosilylation of a resultant enamine intermediate, and (iii) intramolecular dehydrogenative sp(2) C-H silylation.