Halogenation of carbohydrates by triphenylphosphine complex reagents in highly concentrated solution under microwave activation or conventional heating

Halogenation of carbohydrates with triphenylphosphine and carbon tetrachloride, hexachloroethane or 1,2-dibromotetrachloroethane was shown to be very efficient in highly concentrated solutions of nonpolar solvents such as toluene or 1,2-dichloroethane, with, in some cases, addition of potassium chloride, potassium bromide, and/or pyridine. The reactions were very fast under microwave irradiation (2 to 30 min) as well as by classical heating (2 to 45 min) at 80–120 °C. Most often, the yields were better under microwave irradiation and the reaction product distribution was sometimes different from that obtained with classical methods with, in all experiments, the amount of solvent strongly reduced.