55] - Oxidation of Carbohydrates by the Sulfoxide–Carbodiimide and Related Methods: Oxidation with Dicyclohexylcarbodiimide-DMSO, Diisopropylcarbodiimide-DMSO, Acetic Anhydride-DMSO, and Phosphorus Pentaoxide-DMSO

Abstract

Publisher Summary This chapter discusses the oxidation of carbohydrates by the sulfoxide-carbodiimide and other related methods. In sulfoxide-carbodiimide method, oxidations are achieved by treatment of the alcohol with three molar equivalents of a suitable carbodiimide, namely, dicyclohexylcarbodiimide (DCC) and 0.5 molar equivalents of an appropriate acid in dimethyl sulfoxide (DMSO) or a mixture of DMSO and an inert solvent such as benzene or ethyl acetate. These optimal conditions have been determined by studies on model alcohols and the greatest flexibility in the method lies in the choice of the acid. In general, acids of intermediate strength such as anhydrous orthophosphoric and dichloroacetic acids are most suitable while weak acids such as acetic acid or very strong acids such as trifluoroacetic acid or mineral acids are unsatisfactory. In the DMSO–sulfur trioxide method, the alcohol is treated at ∼ 25° with 3 molar equivalents of the sulfur trioxide-pyridine complex and 7–16 molar equivalents of triethylamine in DMSO solution.