HIGHLY REGIOSELECTIVE ALLYLATION OF ALPHA-ENONES AND EPOXIDES WITH LITHIUM TETRAALLYLLANTHANOID ATE COMPLEX

Tetraallyllanthanoid ate complex (1), which was readily prepared in situ from tetraallyltin, lanthanoid trichloride, and butyllithium in tetrahydrofuran (THF), reacts smoothly with alpha-enones (3-11) with a high degree of 1,2-regioselectivity (1,2: 1,4=>99: 1) to give 1,5-diene-3-ols in good to excellent yields. The mechanistic study with 4,4-(ethylenedioxy)-2,6-dimethyl-2,5-cyclohexadienone (29) as a probe suggests that single electron transfer (SET) may be involved in this carbonyl allylation reaction with 1. Allylative ring opening of styrene oxide with 1 occurs at the more subsituted carbon (alpha-attack) in higher selectivity (alpha: beta=85: 15) than with allyllithium and allylmagnesium bromide in diethyl ether. The complex 1 reacts with 3,4-epoxy-1-butene (35) in diethyl ether predominantly at the most substituted carbon of the oxirane to give 3-hydroxymethyl-1,5-hexadiene (36) together with 1,6-heptadien-3-ol (37), (E) and (Z)-2,6-heptadienols (38) (36: 37:38=87: 9:4)