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Hydrogen Atom Transfer Induced Boron Retaining Coupling of Organoboronic Esters and Organolithium Reagents.

ABSTRACT: ?-Functionalization of alkyl boronic esters and homologation of aryl boronic esters by regioselective radical C(sp³)-H activation in boron-ate complexes is reported. Reaction of commercial or readily accessed aryl boronic acid pinacol esters with alkyl lithium reagents provides boron-ate complexes. Selective ?-C-H abstraction by in situ generated trifluoromethyl radicals leads to radical anions that undergo electron transfer oxidation followed by 1,2-aryl/alkyl migration from boron to carbon to give the ?-arylated/alkylated alkyl boronic esters. The valuable boronic ester functionality remains in the products and the cheap trifluoromethyl iodide acts as the oxidant in these C-C couplings. The 1,2-alkyl migration from boron to carbon is highly stereospecific allowing access to stereoisomerically pure boronic esters.

SUBMITTER: Wang D

PROVIDER: S-EPMC6756585 | biostudies-literature | 2019 Sep

REPOSITORIES: biostudies-literature

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Hydrogen Atom Transfer Induced Boron Retaining Coupling of Organoboronic Esters and Organolithium Reagents.

Wang Dinghai D Mück-Lichtenfeld Christian C Studer Armido A

Journal of the American Chemical Society 20190829 36

α-Functionalization of alkyl boronic esters and homologation of aryl boronic esters by regioselective radical C(sp3)-H activation in boron-ate complexes is reported. Reaction of commercial or readily accessed aryl boronic acid pinacol esters with alkyl lithium reagents provides boron-ate complexes. Selective α-C-H abstraction by in situ generated trifluoromethyl radicals leads to radical anions that undergo electron transfer oxidation followed by 1,2-aryl/alkyl migration ...[more]

PMID: 31454481

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