Silver-catalyzed [4 + 3] cycloaddition of 1,3-dienes with alkenyl-N-triftosylhydrazones: a practical approach to 1,4-cycloheptadienes

Abstract

The first formal [4 + 3] cycloaddition of 1,3-dienes with alkenyl-N-sulfonylhydrazones has been achieved employing easily decomposable alkenyl-N-triftosylhydrazones in the presence of a silver catalyst. A series of acyclic and cyclic 1,3-dienes reacted effectively with silver(I) non-acceptor vinyl carbenes, including challenging alkyl- and alkenyl-substituted substrates, producing a broad spectrum of 1,4-cycloheptadienes with high yields and predictable stereochemistry. The products resulting from the transformation described herein include bridged and fused polycyclic systems, as well as the natural product dictyopterene C′ and its isomer ectocarpene. The reaction mechanism and the origin of stereoselectivity were investigated via experimental work and density functional theory calculations.