Sucrochemistry. Part 33. The selective pivaloylation of sucrose

Abstract

The pivaloylation of sucrose by pivaloyl chloride (2,2-dimethylpropanoyl chloride) has been studied under a variety of conditions and shown to be selective for certain hydroxy groups. There exists two principal, but divergent, reaction pathways lying between sucrose and its octapivalate in which the orders of acylation of the eight hydroxy groups are as follows (a) 6,6′-OH > 1′-OH > 4′-OH > 2-OH > 4-OH > 3′-OH > 3-OH; (b) 6,6′-OH > 1′-OH > 3′-OH > 3-OH > 4′-OH > 2-OH and 4-OH. With the exception of the 1′,3′,6,6′-tetra- and the 1′,2,3′,4,4′,6,6′-hepta-pivalate, all of the intermediary esters in these two reaction pathways have been isolated in yields in the range 30–52% depending upon the conditions employed.