ULTRASOUND-PROMOTED PALLADIUM-CATALYZED CARBONYL ALLYLATION BY ALLYLIC ALCOHOLS WITH TIN(II) CHLORIDE IN NONPOLAR-SOLVENTS

Heterogeneous ultrasound-promoted palladium-catalyzed carbonyl allylation by gamma-substituted allylic alcohols with tin(II) chloride in non-polar solvents such as diethyl ether, diisopropyl ether and toluene was carried out stepwise (first, the formation of allylic tin intermediates by ultrasonication, followed by the allylation of aldehydes by the intermediates) to produce 1,4-disubstituted 3-buten-1-ols regioselectively in moderate yields. The regioselectivity (alpha-selection) in the ultrasound-promoted reaction is the inverse of that (gamma-selection) in the homogeneous palladium-catalyzed carbonyl allylation in polar solvents such as 1,3-dimethyl-2-imidazolidinone, DMF, DMSO and ethylene glycol. The more bulky the gamma-substituent, the higher is the alpha-regioselectivity.