Aerobic Dialkoxylation of Styrenes: A Profound Influence of an o-Phenol

Significance

A new palladium(II)-catalyzed dia­stereoselective dialkoxylation of styrene derivatives is reported. The use of o-phenol derivatives proved critical for preventing β-hydride elimination. The use of a catalytic amount of copper and an oxygen balloon were necessary to avert catalyst decomposition. The reaction did prove to be very sensitive to substrate electronics and sterics, with certain substrates requiring the addition of Cs₂CO₃ for increased yield, or, in some cases, the lowering of temperature to increase diastereoselectivity. The importance of the phenolic proton was seen when it was protected with a methyl group and the resulting product was that of a typical Wacker-type oxidation.