Formation of dialkoxyphosphinylalkylidene derivatives of galactitol by transacetalation reactions

Abstract Transacetalation reactions of galactitol with 2,2-dialkoxyethylphosphonates gave the expected 1,3:4,6-diacetal as the minor product, but the major product was 1,3:4,5 derivative. With a 3,3-diethoxypropylphosphonate, the 1,3:4,6-diacetal became the major product. The influence of the dialkoxyphosphinyl substituent on the acetal linkage is shown to be stereoelectronic.