Cobalt-catalyzed deoxygenative triborylation of carboxylic esters to access 1,1,2-triborylalkanes

Abstract

Multiborylated compounds are of significant value in the synthesis of value-added building blocks by enabling sequential transformations of multiple C–B bonds. However, traditional catalytic polyborylation methods are typically limited to the construction of vicinal or geminal diborylalkanes and 1,1,1-triborylalkanes. 1,1,2-Triborylalkanes possess diverse boryl interrelationships between their various boron groups, which may provide more opportunities in the area of C–B diversifications. However, the lack of practical synthetic approaches for 1,1,2-triborylalkanes, especially from readily available materials, starkly contrasts with their substantial synthetic potential. Herein, we present a cobalt-catalyzed deoxygenative triborylation of carboxylic esters, enabling the efficient synthesis of 1,1,2-triborylalkanes with a broad substrate scope and high functional group tolerance. Gram-scale reactions and further product derivatizations highlight its practicality. Preliminary mechanistic studies reveal an iterative deoxygenation, deoxyborylation, and diborylation process.