Reaction of halogenated carbohydrates with sodium cobalt tetracarbonyl and carbon monoxide. A new novel synthesis of unsaturated sugars

Abstract

Methyl tri-O-acetyl 2-deoxy-2-iodo-β-D-glucopyranoside reacted at room temperature with sodium cobalt tetracarbonyl and carbon monoxide in ether to give in high yield methyl 4,6-di-O-acetyl-2,3-dideoxy-β-D-erythro-hex-2-enoside (5). Under the same reaction conditions the corresponding 2-iodo-α-D-mannopyranoside failed to react, but at 100 ° it was smoothly converted into the anomeric α-D-erythro-hex-2-enoside (7). When methanol was used in place of ether no appreciable ester formation took place but elimination of iodine and an acetoxy group occurred, accompanied by complete deacetylation of the remaining ester groups.