Orthoesters hydrogenolysis

Hydrogenolysis of cyclic orthoesters with diborane (a method using lithium aluminum hydride-aluminum chloride had been described for 1,2-orthoesters37) has been shown to be a route to cyclic acetals38 thus, a mixture of the endo and exo isomers of methyl 3,4-0-(ethoxy-ethylidene)-/3-L-arabinopyranoside led to methyl endo-3,4-0-ethy]i-dene-/3-L-arabinopyranoside (yield 66%). 

Summarizing, it may be concluded that the ease of hydrogenolysis is (1) cyclic orthoester > isopropylidene acetal, cyclohexylidene acetal > benzylidene acetal > ethylidene acetal > methylene acetal, and (2) 5,6-O-linked and 3,5-O-linked > 1,2-0-linked acetals. 

S. S. Battacharjee and P. A. J. Gorin, Hydrogenolysis of cyclic and acyclic orthoesters of carbohydrates with lithium aluminium hydride-aluminium trichloride, Carbohydr. Res. 72 57 (1970). 

Bhattachaijee SS, Gorin PAJ (1969) Hydrogenolysis of carbohydrate acetals, ketals, and cyclic orthoesters with lithium aluminum hydride — aluminum trichloride. Can J Chem 47 1195-1206... 

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