A series of in situ formed alkenyl diboronate complexes from alkenyl Grignard reagents (commercially available or prepared from alkenyl bromides and Mg) with B2Pin2 (bis(pinacolato)diboron) react with diverse alkyl halides by a Ru photocatalyst to give various gem-bis(boryl)alkanes. Alkyl radicals add efficiently to the alkenyl diboronate complexes, and the adduct radical anions undergo radical-polar crossover, specifically, a 1,2-boryl-anion shift from boron to the α-carbon sp2 center. This transformation shows good functional-group compatibility and can serve as a powerful synthetic tool for late-stage functionalization in complex compounds. Measurements of the quantum yield reveal that a radical-chain mechanism is operative in which the alkenyl diboronates acts as reductive quencher for the excited state of the photocatalyst.
An Olefinic 1,2-Boryl-Migration Enabled by Radical Addition: Construction of gem-Bis(boryl)alkanes / Zhao B.; Li Z.; Wu Y.; Wang Y.; Qian J.; Yuan Y.; Shi Z.. - In: ANGEWANDTE CHEMIE. INTERNATIONAL EDITION. - ISSN 1433-7851. - STAMPA. - 58:28(2019), pp. 9448-9452. [10.1002/anie.201903721]
An Olefinic 1,2-Boryl-Migration Enabled by Radical Addition: Construction of gem-Bis(boryl)alkanes
Zhao B.;Shi Z.
2019
Abstract
A series of in situ formed alkenyl diboronate complexes from alkenyl Grignard reagents (commercially available or prepared from alkenyl bromides and Mg) with B2Pin2 (bis(pinacolato)diboron) react with diverse alkyl halides by a Ru photocatalyst to give various gem-bis(boryl)alkanes. Alkyl radicals add efficiently to the alkenyl diboronate complexes, and the adduct radical anions undergo radical-polar crossover, specifically, a 1,2-boryl-anion shift from boron to the α-carbon sp2 center. This transformation shows good functional-group compatibility and can serve as a powerful synthetic tool for late-stage functionalization in complex compounds. Measurements of the quantum yield reveal that a radical-chain mechanism is operative in which the alkenyl diboronates acts as reductive quencher for the excited state of the photocatalyst.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.