Controlled ring-opening of [1.1.1]propellane with aryl catecholato boronates to form monomeric and dimeric methylenecyclobutanes

Abstract [1.1.1]propellane (TCP) is a highly strained molecule characterized by two inverted bridgehead carbons. While considerable attention has been given to the 1,3-difunctionalization of TCP for synthesizing bicyclo[1.1.1]pentane (BCP), its ring-opening to form methylenecyclobutane (MCB) remains underexplored. In this study, we introduce an unexpected and efficient method for the ring-opening of TCP to selectively produce the dimeric MCB using aryl catecholato boronates (ArBcat). Comprehensive mechanism studies, including both experimental studies and theoretical calculations, have been conducted to elucidate the origin of the dimeric selectivity. This method is notable for being catalyst-free, highly efficient, and exhibiting distinct dimer selectivity. The resulting dimeric cyclobutanes serve as valuable precursors in the synthesis of bioisosteres of meta-substituted benzene. Importantly, the monomeric intermediate can be strategically intercepted via oxygen oxidation, yielding the monomeric butanol.