Stereoselective Intramolecular [2+2] Trapping of 1,2‐Cyclohexadienes: a Route to Rigid, Angularly Fused Tricyclic Scaffolds

Abstract

Abstract1,2‐Cyclohexadienes generated under mild fluoride‐mediated desilylative conditions undergo efficient intramolecular [2+2] trapping, providing tricyclic alkylidene cyclobutanes with complete diastereoselectivity for the cis‐fused products. Pendent styrenes or electron‐deficient olefins can trap simple 1,2‐cyclohexadienes or their oxygenated counterparts, with 14 substrates being disclosed. Reactions proceed at ambient temperature using just cesium fluoride in up to 91 % yield, and the necessary precursors are easily accessed from substituted 2‐bromocyclohexenones. Multiple synthetic routes have been developed to install the appropriate functional groups required for [2+2] trapping.