Site-selective transition-metal-catalyzed mono-deboronative cross-couplings of 1,2-bis-boronic esters are valuable methods for the synthesis of functionalized organoboron compounds.However,such cross-couplings are limited to reaction of the sterically less hindered primary boronic ester.Herein,we report a nickel/photoredox-catalyzed mono-deboronative aryla-tion of 1,2-bis-boronic esters that is selective for coupling of the more sterically hindered secondary/tertiary position.This is achieved by taking advantage of a 1,2-boron shift of primary p-boryl radicals to the thermodynamically favored secondary/tertiary radicals,which are subsequently intercepted by the nickel catalyst to enable arylation.The mild conditions are amenable to a broad range of aryl halides to give β-aryl boronic ester products in good yields and with high regioselectiv-ity.This method also allows stereodivergent coupling of cyclic cis-1,2-bis-boronic esters to give trans-substituted products.
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