Efficient Trapping of 1,2-Cyclohexadienes with 1,3-Dipoles

1,2‐Cyclohexadienes are transient intermediates that undergo rapid dimerization and intermolecular trapping with activated olefins and heteroatomic nucleophiles. Fluoride‐mediated desilylative elimination of readily accessible 6‐silylcyclohexene‐1‐triflates allows the mild, chemoselective, and functional‐group tolerant generation of cyclic allene intermediates, which undergo efficient trapping reactions with stable 1,3‐dipoles. The reactions proceed with high levels of both regio‐ and diastereoselectivity. The reaction of cyclic allenes with azides is accompanied by the facile loss of dinitrogen, resulting in the formation of tetrahydroindoles or polycylic aziridines depending on the azide employed. It′s a trap! 1,2‐Cyclohexadienes, strained, highly reactive, short‐lived intermediates, are readily generated from silyl triflate precursors. These species undergo efficient reactions with several classes of 1,3‐dipoles to afford polycyclic products with high regio‐ and stereoselectivity (see scheme). In the case of azide traps, unusual new products are formed by the loss of dinitrogen.