SACCHARIDE (2,4-DICHLOROPHENOXY)ACETYLHYDRAZONES, THE MECHANISM OF HETEROCYCLIZATION UNDER ACETYLATIVE CONDITIONS

Article abstract of DOI:10.1016/0008-6215(83)88242-1

The synthesis of the (2,4-dichlorophenoxy)acetylhydrazones of a number of monosaccharides is described.The reaction of the corresponding D-galactose derivative with acetic anhydride in pyridine was investigated.Penta-O-acetyl-aldehydo-D-galactose (2,4-dichlorophenoxy)acetylhydrazone was prepared by reaction of the hydrazine with penta-O-acetyl-aldehydo-D-galactose, and its 1H-n.m.r. spectrum indicated its existence as two geometric isomers.Reaction of the pentaacetate with boiling acetic anhydride caused its acetylative heterocyclization into 3-acetyl-5-<(2,4-dichlorophenoxy)methylene>-2-(1,2,3,4,5-penta-O-acetyl-D-galacto-pentinol-1-yl)-1,3,4-oxadiazoline.A generalized mechanism for the heterocylization , based on "soft" and "hard" acids and bases, is discussed.D-arabino-Hexos-2-ulose 2-(2,4-dichlorophenoxy)acetylhydrazone 1-phenylhydrazone was also prepared.