5-Pyrazolone, 3-methyl-1-phenyl-, ring

Phenyl hydrazine undergoes condensation with /3-diketones and /3-ketone-acid-esters with the formation of ring compounds contain- Ing nitrogen — the so-called pyrazoles and pyrazolones- The phenyl methyl pyrazolone formed from acetacetic ester and phenyl hydrazine is of importance ... 

When ethyl acetoacetate is warmed with an equivalent quantity of phenyl-hydrazine, the compound (I), which is not a true hydrazone, is first formed this undergoes ring formation (II) with loss of ethyl alcohol upon further heating. The product (II) is N or l-phenyl-3-methyl-5-pyrazolone. 

The methylene group may be part of a ring structure as in coumarine and indoxyl, or may be part of a heterocyclic ring altached to a phenyl group as in l-phcnylO-methyl-S-pyrazolone. 

Diazo Components With Cycloammonium Groups. Polynuclear N heterocycles that carry an amino group in the carbocyclic aromatic ring can be diazotized and then joined to azo dyes by using aromatic or heterocyclic coupling components. Quatemization at the heterocyclic nitrogen atom may occur before or after coupling. The azo dye 43, from 2-methyl-5-aminobenzimidazole and l-phenyl-3-methyl-5-pyrazolone, used in the form of its hydrochloride, dyes paper and leather in clear yellow shades [130],... 

In what may foreshadow a versatile and general route to heavily functionalized 1,2-diazocines, as well as to many other larger-ring heterocyclic compounds, oxidative cleavage by periodate of the carbon-carbon double bond of a bicyclic pyrazolone was reported to yield 1,2,6,7-tetrahydro-l-methyl-2-phenyl-l,2-diazocin-3,4,8(5. -trione (29) (85%) (Equation (4)) cleavage of larger-ring... 

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