ISOPROPYLIDENATION OF D-MANNITOL UNDER NEUTRAL CONDITIONS

Article abstract of DOI:10.1016/S0008-6215(00)85208-8

Isopropylidenation of D-mannitol (2) under neutral conditions, by treatment with 2,2-dimethoxypropane in 1,2-dimethoxyethane, is described. 1,2:5,6-Di-O-isopropylidene-D-mannitol is the main equilibrium product, which does not undergo further substitution under the conditions used. 1,2:3,4:5,6-Tri-O-isopropylidene-D-mannitol, the other major product, was shown to be derived mainly from initial 3,4-substitution of 2.The presence of a difunctional ether, of suitable geometry, is a necessary requirement for the reaction.Some mechanistic aspects of the reaction are discussed.