Diethyl dithioacetal hydrogenolysis

Occasionally, during hydrogenolysis, a labile substituent is displaced from the position adjacent to the dithioacetal grouping. This behavior was first observed by Wintersteiner and coworkers46 in the reduction of 3-benzamido-2,4,5-tri-0-benzoyl-3,6-dideoxy-D-man-nose diethyl dithioacetal (159) to afford a mixture of 3-benzamido-... 

Treatment of D-galactose diethyl dithioacetal (112) with an aged preparation of Raney nickel or with a limited amount of the fresh reductant affords348 the corresponding 1-S-ethyl-l-thioalditol (163) as the major product the same process occurs for D-gluco, c-arabino, D-manno, and 6-deoxy-L-manno analogues, and complete reduction of 163 to the deoxyalditol 164 was accomplished by further hydrogenolysis. The stepwise conversion of a methanolic solution of 112 into 163 (isolable in 60% yield), and thence into 164 (isolable in fair... 

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