SYNTHETIC REACTIONS AND STRUCTURAL STUDIES OF HETEROCYCLIC CONTAININGNITROGEN .14. DEHYDRATION OF 2-(2-ARYLETHYL)-2-HYDROXY-4-OXOPENTANOICACIDS AND THEIR HYDRAZONES TO FORM HETEROCYCLES

Dehydration of 2-(2-arylethyl)-2-hydroxy-4-oxopentanoic acids 1 with h ydrochloric acid/acetic acid, affords 3-(2-arylethyl)-5-hydroxy-5-meth yl-2(5H)-furanones 4. Compounds of type 1 and 4 represent suitable pre cursors for the formation of pyridazin-3-ones 7 as they smoothly react with hydrazine. A new series of s-triazolo[4,3-b]pyridazin-3-ones 12 and tetrazolo[1,5-b]pyridazines 15 are obtained from the 3-chloropyrid azines 11 upon treatment with semicarbazide and sodium azide, respecti vely. Reaction of 11 with phenyl- acetyl-hydrazine provides 3-benzyl-6 -phenyl-8-(2-phenyl-ethyl)-s-triazolo [4,3-b]pyridazine 13 via dehydra tive cyclization of the intermediate 14 which was clarified to exhibit tautomeric equilibria between enol-hydrazine form A and keto-hydrazin e form B by means of H-1 and C-13 NMR spectroscopy. Attempts to synthe size 3-alloxy-pyridazines 18 by reacting 11 with sodium alloxide affor d N-allyl compounds 17.