The use of polymer supports in organic synthesis. V. The preparation of monoacetates of symmetrical diols

Abstract

A 2% cross-linked divinylbenzene–styrene copolymer was directly lithiated with n-butyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine. The lithiated polymer on reaction with a benzophenone gave an insoluble polymer-bound trityl alcohol. Further reaction with acetyl chloride gave a polymer-bound trityl chloride which, on treatment with the primary symmetrical diols 1,10-decanediol, 1,7-heptanediol, and 1,4-butanediol, gave mostly symmetrical diols monoblocked by insoluble polymer-bound trityl groups. Acetylation followed by acid cleavage from the polymer gave the monoacetates of 1,10-decanediol, 1,7-heptanediol, and 1,4-butanediol and some recovered diols. The recovered polymer can be efficiently recycled. The quantity of recovered diol was related to the problem of 'double-binding' of the symmetrical diols to the polymer-bound trityl groups. The extent of 'double-binding' could be greatly reduced by the use of polymer-bound trityl chloride prepared via the lithiated polymer and methyl benzoate or phosgene.