Y. Masuyama et al., ULTRASOUND-PROMOTED PALLADIUM-CATALYZED CARBONYL ALLYLATION BY ALLYLIC ALCOHOLS WITH TIN(II) CHLORIDE IN NONPOLAR-SOLVENTS, Inorganica Chimica Acta, 220(1-2), 1994, pp. 155-159
Heterogeneous ultrasound-promoted palladium-catalyzed carbonyl allylat
ion by gamma-substituted allylic alcohols with tin(II) chloride in non
-polar solvents such as diethyl ether, diisopropyl ether and toluene w
as carried out stepwise (first, the formation of allylic tin intermedi
ates by ultrasonication, followed by the allylation of aldehydes by th
e intermediates) to produce 1,4-disubstituted 3-buten-1-ols regioselec
tively in moderate yields. The regioselectivity (alpha-selection) in t
he ultrasound-promoted reaction is the inverse of that (gamma-selectio
n) in the homogeneous palladium-catalyzed carbonyl allylation in polar
solvents such as 1,3-dimethyl-2-imidazolidinone, DMF, DMSO and ethyle
ne glycol. The more bulky the gamma-substituent, the higher is the alp
ha-regioselectivity.