Titanium as a regio- and stereo-selective control element in the reaction of α-alkoxyallylic phosphine oxide anions with carbonyl compounds

Abstract

A general method is described for directing the condensation of α-methoxyallylphosphine oxide anions (2) with aldehydes, preferentially at the α-position of the allyl system. The procedure, which employs the formation of the titanium ate complex, yields pure diastereoisomers with high stereoselectivity, and these can be used in Horner-Wittig reactions to provide an efficient and convenient synthesis of conjugated methoxydienes of defined geometry. Under the same conditions, acyl halides yield γ-adducts.