An Alkyl-Aluminium Promoted Stereospecific Addition to Vinyl Olefins

The reaction of tris-crotyl-boron with vinylic olefins in the presence of triethyl-aluminium, results in the addition of an α-methylallyl group and an aluminium atom to the double bond, as indicated by the hydrolysis products. The stereochemical aspect of the reaction is discussed and a mechanism is proposed to explain the preferential formation of one diastereoisomer.