A mild procedure for the regiospecific benzylation and allylation of polyhydroxy-compounds via their stannylene derivatives in non-polar solvents

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Abstract
The reactions of benzyl and allyl bromides on the stannylene derivatives of polyhydroxy-compounds, which normally proceed only at insignificant speed in refluxing benzene solution, are greatly accelerated in the presence of quaternary ammonium halides. These conditions were tested on benzyl β-D-galactopyranoside (1) and ten derivatives, (2)–(11), which were benzylated, allylated, or acetalated. In such a collection may be found all the possible arrangements, except one, of two, three, or four hydroxy-groups on a β-D-galactopyranoside ring. Regiospecific substitution in good yield was observed on nine of the starting polyols. Benzylation in this way of benzyl 2,3-di-O-benzyl-α-D-glucopyranoside only gave the 6-O-benzyl ether in 80% yield, a great improvement over the reaction in NN-dimethylformamide, which has no preparative value. The same new method allows a smooth preparation of the monomethoxymethyl ethers of glycols. The preparations and synthetic uses of the stannylene derivatives of γ-and ε-glycols are reported for the first time.

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