A series of oxometallic species and metal acetylacetonates (acac) was examined as catalysts for oxidative carbonylation of styrene with benzaldehyde using t-butylhydroperoxide as the co-oxidant in warm acetonitrile. Among them, VO((acac)2 and vanadyl(IV) chloride were found to be the only catalyst class to achieve cross-coupling processes by judiciously tuning the ligand electronic attributes, leading to β-hydroxylation- and β-peroxidation-carbonylation of styrene, respectively, in a complementary manner. Mechanistic studies indicated that vanadyl-associated acyl radicals generated by t-butoxy radical-assisted, homolytic cleavage of the aldehyde C-H bond were involved in tandem processes with an exclusive syn diastereoselectivity in the case of β-methylstyrene.
Vanadyl Species-Catalyzed Complementary -Oxidative Carbonylation of Styrene Derivatives with Aldehydes. -The oxidative coupling of styrenes with aldehydes using tBuOOH as the oxidant is studied. In the presence of VO(acac) 2 as the catalyst -hydroxyketones (III) and (V) are isolated whereas VOCl2 as the catalyst produces -peroxy ketones (VIII), (IX), and (XI) in good yields. -(YANG, W.-C.; WENG, S.-S.; RAMASAMY, A.; RAJESHWAREN, G.; LIAO, Y.-Y.; CHEN*, C.-T.; Org. Biomol. Chem. 13 (2015) 8, 2385-2392, http://dx.
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