Chlorination of carbohydrates and alcohols utilizing a chlorinating reagent selected from triphenylphosphine oxide/thionyl chloride, thiphenylphosphine oxide/phosgene, triphenylphosphine sulfide/thionyl chloride and triphenylphosphine sulfide/phosgene.
The preparation of an alkyl, alkenyl, or alkynyl chloride by the reaction of a corresponding alcohol with phosgene or thionyl chloride in the presence of a phosphine oxide acting as catalyst, wherein the catalyst used is an aliphatic, cycloaliphatic, or cyclic/aliphatic phosphine oxide.
A process for manipulating any polyhydroxy compound bearing two or more primary and secondary hydroxyl groups to expose only the primary hydroxyl groups, while blocking all interfering secondary hydroxyl groups as their methyl or other alkyl ethers. More particularly, the present invention relates to the synthesis of 2,3,3',4,4'-penta-O-methylsucrose by using this method.
Sugars and partly protected sugar derivatives are chlorinated by reaction of unprotected hydroxyl groups with thionyl chloride to form a persulphite followed by decomposition of the sulphite groups to form chlorosulphites, displacement of the chlorosulphite groups and insertion of chlorine atoms at one or more positions, characterised in that formation and displacement of the chlorosulphite groups and insertion of chlorine atoms is effected by reaction with thionyl chloride in an inert solvent in the presence of a quaternary salt of the general formula: wherein R.sup.1, R.sup.2 and R.sup.3, which may be the same or different, each represent a lower alkyl group, and R.sup.4 represents a hydrocarbon group with at least seven carbon atoms; and, when the sugar or partly protected sugar derivative has more than three unprotected hydroxyl groups, the process comprises the following stages: (a) reaction of the sugar or partly protected sugar derivative with thionyl chloride in the presence of pyridine to form a persulphite; (b) isolation of the polysulphite to remove free pyridine; and (c) reaction of the isolated polysulphite with thionyl chloride in an inert solvent or suspension medium in the presence of a quaternary salt of the general formula (I).
The reaction of protected monosaccharides or oligosaccharides or protected monosaccharide and oligosaccharide derivatives containing an anomeric hydroxyl group with secondary .alpha.-haloenamines affords high yields of protected glycosyl halides, which are valuable intermediates for the introduction of sugar groups in the synthesis of oligosaccharides, glycolipids or glycopeptides.
