RESUMEN
Selective transformations at the more sterically hindered sites of organic molecules represent a frontier in the ability to precisely modify molecules. The lack of effective synthetic methods stands in stark contrast to the large number of encumbered sites encountered in molecules of interest. Here, we demonstrate that 1,2-bis(boronates) undergo selective alkynylation and alkenylation at the more sterically hindered C-B bond. Our preliminary mechanistic studies disclosed that this reaction can proceed through two convergent pathways involving direct coupling of sterically encumbered site versus 1,2-boron migratory coupling. Notably, this method facilitated convenient access to alkenyl and alkynyl boron products, which can be diversified by an array of transformations.
RESUMEN
Asymmetric cross-couplings based on 1,2-carbon migration from B-ate complexes have been developed efficiently to access valuable organoboronates. However, enantioselective reactions triggered by 1,2-boron shift have remained to be unaddressed synthetic challenge. Here, Ir-catalyzed asymmetric allylic alkylation enabled by 1,2-boron shift was developed. In this reaction, we disclosed that excellent enantioselectivities were achieved through an interesting dynamic kinetic resolution (DKR) process of allylic carbonates at the elevated temperature. Notably, the highly valuable (bis-boryl)alkenes have enabled an array of diversifications to access versatile molecules. Extensive experimental and computational studies were conducted to elucidate the reaction mechanism of DKR process and clarify the origin of excellent enantioselectivities.
