Generation and Utility of Cyclic Dienyl Gold Carbene Intermediates
Cheng Zhang, Kemiao Hong, Shanliang Dong, Mengting Liu, Matthias Rudolph, Martin C. Dietl, Jian Yin, A. Stephen K. Hashmi, Xinfang Xu
Abstract
Exploration of intermediates that enable chemo- and stereoselective cycloaddition reactions for the expeditious construction of fused- and bridged-ring systems continues to draw a great deal of interest from the synthetic community. Vinylcarbene intermediates, which serve as 1- or 3-carbon building blocks, have been frequently used for the construction of cyclic frameworks through the successive formation of multiple carbon–carbon or/and carbon–heteroatom bonds. Here, we present a concise strategy for the catalytic generation of cyclic dienyl gold carbene species (Au-CDC) via a selective gold-promoted diazo-enyne carbocyclization process. Following cycloadditions of these in situ formed carbene intermediates with different types of dipolarophiles are disclosed, producing a diverse array of fused and bridged skeletons with high chemo- and stereoselectivity. This method provides a tool resulting in straightforward access to ring systems with structural complexity and diversity, and is a substantial complementary protocol to existing methods relying on using open-chained vinylcarbene species. The subsequent exploration of these generated cyclopentadiene motifs with dipolarophiles in accessing targets of polycyclic structures can further increase this rings-per-operation count, leading conceptually to the Au-CDC as a key bridge capable of connecting back-to-back cycloadditions.