Synthesis and characterization of a novel heterocycle: 1‐Substituted‐4‐arylazamethylene‐6‐arylpyrazolo[5,4‐d]‐1,3‐oxazine

Abstract

A series of novel heterocycles 1-aryl-or alkyl-substituted-4-arylazamethylene-6-arylpyrazolo[5,4-d]-1,3-oxazines were synthesized from the acylation of (5-amino-1-substituted-pyrazol-4-yl)-N-carboxamide in 63-89% isolated yields at room temperature within 12 hours. The structure was confirmed by X-ray crystal analysis.

Reaction of 7-phenyl-7H-pyrazolo-[3,4-d][1,2,3]triazin-4-ol with thionyl chloride

“…The reaction progress and the purity of the products were controlled by TLC on Silufol UV-254 plates using a 10:1 CHCl 3 MeOH system. The spectroscopic parameters for compounds 4a and 5 were identical to those given in the literature [9,16]. (2).…”

“…The central bicyclic system N(1-4)C(1-5) was found to be virtually planar, the mean square deviation of the atoms from the plane being only 0.0175 Å. The pyrazole ring N(6,7)C (15)(16)(17) was nearly coplanar with the plane of the central bicyclic system (the dihedral angle being 6.16(8)°), while the phenyl substituent was more twisted (13.50 (8)°). Overall, this heterocyclic system had conventional bond lengths and valence angles.…”

“…The structure of the acid chloride 2 was proved by its conversion to the known 5-amino-1-phenyl-1H-pyrazole-4-carboxylic acid (3) [14,15] and the amides 4a,b, one of which (compound 4a) has been reported in the literature [16] (Tables 1 and 2 Treatment of the acid chloride 2 with triethylamine in acetonitrile at room temperature yielded the ketene C which dimerized to the 6-(5-amino-1-phenyl-1H-pyrazol-4-yl)-1-phenylpyrazolo [3,4-d][1, 2,3]oxazin-4(1H)-one (5) in 89% yield. The latter has been prepared before in 38% yield by heating the pyrazolotriazinol 1 with phosphorus pentoxide [9].…”