ChemInform Abstract: SYNTHESIS AND SCREENING OF SOME SUBSTITUTED 3,5‐DIOXOPYRAZOLIDINES

Abstract

Die Malonsäurediäthylester (I) werden mit Hydrazin bzw. Phenylhydrazin (II) zu den Dioxopyrazolidinen (III) umgesetzt und anschließend mit den p‐substituierten Benzoy1= chloriden (IV) substituiert.

Tetrazolo[1,5-a]pyridines and furazano[4,5-b]pyridine 1-oxides

“…The same conversion may be achieved by cautiously heating 2d/3d alone to 120 °C, or more conveniently by heating in toluene for 30 min in the dark under reflux until the gas evolution is completed. In a similar fashion the parent furazano [4,[5][6]]pyridine 1-oxide (pyridofuroxan) (6b) may be prepared by heating a toluene solution of 3b under reflux, providing some evidence that the latter compound is also in equilibrium with the corresponding azido isomer, at least at elevated temperatures.…”

“…1969, 12, 505. (5) Hardy, W. B.; Parent, R. A. French Patent 1 395 886, 1965, American Cyanamid Co.; Chem. Abstr.…”

“…haps the most satisfactory method, however, has been the thermolysis of o-nitrophenyl azides.11 A recent report has described a one-pot synthesis of benzofuroxans from ochloronitrobenzenes, involving nucleophilic displacement of the chlorine by azide ion followed by in situ cyclization under solid-liquid phase-transfer catalysis conditions.12 (10) Boulton, A, J. Middleton, D. J. (Investigations in these laboratories suggest that phasetransfer catalysis may be unnecessary.13) As an extension of our interest in benzofuroxans, we chose to examine the synthesis and chemistry of tetrazolo [ 1,5-a]pyridines and furazano [4,[5][6]]pyridine 1-oxides (pyridofuroxans).…”

“…In the case of the unsubstituted compound, the equilibrium is far to the right. No trace of the azido compound 2a can be detected in the infrared or NMR spectra, although the loss of 28 mass units provides the base peak of the mass spectrum and the generation of the pyridine-2-nitrene (5) has been cited in the pyrolysis of tetrazolopyridine.15 Similarly 4-nitrotetrazolo[ 1,5-a]pyridine (3b) appears to be free of the azido isomer 2b, with no trace of the latter being visible in the infrared and NMR spectra. Once again, however, the mass spectrum of 3b showed a prominent peak at 137 attributed to the loss of molecular nitrogen.…”

“…Thus in chloroform-d the azido form 2d is present at 100% to the exclusion of 3d, while in DMSO-d6 2d is present to only 9%, the tetrazolopyridine dominating at 91%. [4,[5][6] ]pyridine The equilibrium between 4,6-dinitrotetrazolo[l,5-a]pyridine and 2-azido-3,5-dinitropyridine is further complicated by the fact that 2-azido-3,5-dinitropyridine undergoes reaction in solution at ambient temperature. The nature of the reaction in acetone-and DMSO-d6 is still uncertain, but in chloroform-d, benzene-d6, and acetonitrile-da the azido compound loses molecular nitrogen and recyclizes to form 6-nitrofurazano [4,[5][6]]pyridine 1-oxide (6-nitropyridofuroxan) (6d) (Scheme III).…”