Formation of dihydroxyselenides from allylic alcohols and their conversion to β-hydroxy epoxides via substitution of a phenylselenonyl group

Hydroxyselenation of allylic alcohols occurs with high regio- and stereoselectivity to give β,β′-dihydroxyphenylselanyl adducts in high yields. An exception is the reaction of the terminal alcohol, 2-methylprop-2-en-1-ol, which forms only a 1,2-diol product. Generally, the addition is Markovnikov in orientation, but the fact that one anti-Markovnikov addition is observed and that addition to 1,2-disubstituted alkenes shows a strong preference for one regioisomer suggests that an interaction of the allylic alcohol with the selenium atom of the reaction intermediate (which weakens the Cβ–Se bond in the intermediate) is also an important factor in determining the preference for addition of the phenylselanyl group to the double bond carbon nearest the allylic alcohol. The hydroxyselenated adducts of allylic alcohols can be readily converted to β-hydroxy epoxides in good yields via oxidation with m-chloroperbenzoic acid to a selenone and subsequent treatment with base. Hydroxyselenation of crotyl acetate and 3-acetoxycyclohexene is more regiocatholic than hydroxyselenation of the corresponding allylic alcohols. It appears that the known selectivity of additions of phenylselanyl chloride to these acetates in organic solvents is lost when water or a Lewis acid complexes to the acetate group.