Pyranopyrazoles. II. Synthesis and reactions of 1H,6H-pyrano[2,3-c]pyrazol-6-ones

Various 1H,6H-pyrano2,3-c]pyrazol-6-ones (III-XXIII) were obtained from β-keto esters and 1H-pyrazol-5-ones or hydrazines. Nitrations, chlorinations and brominations of these pyranopyrazoles were also carried out giving the corresponding derivatives (XXIV-LXIV). The pyrone ring is the more reactive one in these reactions and the preferred position of attack is the 5-position. The substitution products are formed by the addition-elimination route.