Microwave Assisted Synthesis of Mono- and Bis-Phenylhydrazones of L-Threo- and D-Erythro-2,3- Hexodiulosono-1,4-Lactones for the Synthesis of an Array of Heterocyclic Compounds

Microwave assisted organic synthesis (MAOS) and organic reaction enhancement (MORE) for the conversion L-ascorbic acid (1) and D-isoascorbic acid (2) to various heterocyclic compounds via their monophenylhydrazones 3 and 4 and bis(phenylhydrazones) 7 and 8 have been achieved. Acetic anhydride converted 3 and 4 to the olefinic compound 6 and their oximes 11 and 12 to 4-(L-threo-2,3-diacetoxy-(1-hydroxypropyl-2-phenyl-1,2,3-triazole-5-carboxylic acid lactone (14). Treatment of 7 and 8 with alcoholic cupric chloride gave 15 which can be acetylated to 5-O-acetyl-3,6-anhydro-3-phenylazo-L-xylo-2-hexulosono-1,4-lactone phenylhydra- zone (16) and degraded to 1-(2-phenylhydrazide)-2-(2-phenylhydrazone) mesoxalic acid (17). They were transformed to 1-phenyl-3-(L-threo or D-erythro-glycerol-1-yl)-pyrazoline-4,5-dione phenylhydrazone 18 and 19 whose degradation afforded 3-carboxaldehyde-1-phenyl pyrazoline- 4,5-dione 4-phenylhydrazone (22). All the reactions using MW gave cleaner, faster and similar or higher yields of products.