David Brevet

New efficient electrochemical synthesis of 1,5-dithioxylopyranosides in the presence of a sacrificial anode.

Electroreduction of the disulfide derivative RSSR (5, R= [bond]C(6)H(4)[bond]CO[bond]C(6)H(4)[bond]CN) on a mercury pool or a carbon gauze electrode in the presence of 2,3,4-tri-O-acetyl-5-thio-D-xylopyranosyl bromide (1), using a sacrificial zinc anode gave an alpha,beta anomeric mixture of [4-(4-cyanobenzoylphenyl)] 2,3,4-tri-O-acetyl-1,5-dithio-D-xylopyranoside (6) in 40-70% yield, according to the experimental conditions used (nature of solvent, electrolyte salt, and temperature). High selectivity favouring the alpha anomer of 6 is observed starting from the alpha anomer of 1. Mechanistic aspects are discussed.

Efficient electrochemical synthesis of thioxylal

Reduction elimination of acetylated thioxylopyranosyl bromide or acetylated thioxylopyranosyl chloride affording thioxylal is easily performed by direct electroreduction or using niobocene dichloride as catalyst.