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A kinetic study of the tin(II) chloride catalyzed reaction of diazodiphenylmethane with ethylene glycol in dimethoxyethane is reported. The preparation and characterization of ethylene glycol monodiphenylmethyl ether, the main product from this reaction, is also reported as well as the preparation of the two diphenylmethyl monoethers of methyl 4,6-O-benzylidene-alpha-D-glucopyranoside. An unexpected relationship between the concentration of ethylene glycol and the pseudo first-order rate constant, k', was observed in these reactions. For low concentrations of ethylene glycol (below 0.06 M), k' increases with increasing concentration of the diol. This trend is reversed for high concentrations of ethylene glycol (from about 0.06 to about 0.2 M). The apparent rate constant was also inversely related to the initial concentration of diazodiphenylmethane for the concentrations investigated. These results make the previously proposed involvement of a 1,3,2-dioxastannolane intermediate very unlikely [Petursson, S.; Webber, J.M. Carbohydr. Res. 1982, 103, 41-52]. The results suggest that more likely intermediates for these reactions involve tin(II) chloride complexes in a dynamic equilibrium with the diol.

The paper reports selective mono-etherification of the 2-, and 3-hydroxyl groups of methyl 4,6-O-isopropylidene-α-d-mannopyranoside using tin(II) chloride catalysed reactions of diaryldiazomethanes. By the use of different diazo compounds and the variation of the tin(II) chloride concentration the ether formation can be shifted from over 90% 3-selectivity to over 90% 2-selectivity.

A tentative mechanism for complexation, and a possible model of a tin(II)chloride—methyl glycoside intermediate complex, have been established largely from analysis of methyl ethers formed on methylation of methyl α- l -rhamnopyranoside and its monomethyl ethers by diazomethane in the presence of a catalytic amount of tin(II) chloride in selected solvents. The complex is mainly formed through displacement of molecules of the donor solvent coordinated to a tin(II) atom by the favorably cis -disposed, hydroxyl groups of the sugar moiety. The spatial arrangement of the hydroxyl groups plus the distribution of atomic charges at the individual oxygen atoms of hydroxyl groups of the methyl glycoside were found to be the main factors responsible for the selectivity observed. The effect of selected solvents on the stability and/or ability to participate in the formation of the foregoing intermediate complex could not be satisfactorily clarified.

Highly regioselective monoalkylations of the cis -2,3-diol group in mannopyranosides can be achieved with diaryldiazoalkanes in the presence of catalytic amounts of tin(II) chloride. With diazo(diphenyl)methane ( 1 ), its 4,4′-dimethyl ( 2 ) and 4,4′-dichloro ( 3 ) derivatives, and 9-diazofluorene ( 5 ), methyl 4,6- O -benzylidene- α - d -mannopyranoside gave high yields of the respective 3-diarylmethyl ethers. By contrast, methyl 4,6- O -isopropylidene- α - d -mannopyranoside ( 11 ) gave mainly the 3-[bis(4-methylphenyl)methyl] derivative with 2 , approximately equal amounts of the 2- and 3-ethers with 1 and 3 , and mainly the 2-ether with 5 . With diazo[bis(4-methoxyphenyl)]methane, 11 gave only the 3-ether (61%).