3-Indazolone

The facile insertion of CO takes place. The 2-aryl-3-indazolone 484 is obtained in high yields from the azobenzene complex 463 in alcohol or waterf442]. For unsymmetrically substituted 4-methyl, 4-chloro-, and 4-meth-... 

Baiocchi Synthesis, properties and reactions of indazolones 78S633... 

Two double bonds. This is the most important class which includes the aromatic compounds pyrazole (3), indazole (4) and isoindazole (5), their non-aromatic isomers, pyrazolenines (or 3iL-pyrazoles 6), isopyrazoles (or 4JT-pyrazoles 7) and 3JT-indazoles (8), and the carbonyl derivatives of pyrazolines with the endocyclic double bond in positions 1, 2 or 3, i.e. (9), (10) and (11), respectively. The indazolones (12) and the pyrazolidinediones (13) and (14) also belong to this group. 

Substituted indazolones exist in the OH form (143b) and 2-substituted indazolones exist in the NH form (144a), whereas the structure of AC-unsubstituted indazolones varies with the physical state. This difference of behaviour, depending on the position of the A -R substituent, corresponds to the aromatic structure of the indazole derivatives compared with the quinonoid structure of isoindazoles. 

From the results quoted in Section 4.04.2.1.3(x) the stability of acetyl derivatives of indazolone decreases in the order Af(l)-acetyl >A (2)-acetyl > 0(3)-acetyl. The reactivity of 3-hydroxypyrazoles is covered by Dorn s comprehensive review (80CHE1). Amongst the results reported there are the Claisen rearrangement of allyloxypyrazoles (475a) (475b)... 

Recently (82CC450) the conversion of aromatic hydrazides into indazolones in good yield when treated with three equivalents of n-butyllithium has been described. For example, benzoylhydrazine afforded indazolone in an 80% yield (Scheme 51). 

Indazoles can also be prepared by the [CCC + NN] method. For instance indazolones have been obtained rather simply by the action of hydrazine hydrate on 2-halobenzoic esters (78S633). 

Some of these indazoles showed analgesic activity greater than that of aspirin and several possessed significant antiinflammatory action. Both properties were the most striking and characteristic ones of the series. In a few cases the authors isolated the corresponding indazolones (705) which were less active than (704) in terms of analgesic and antiinflammatory properties. 

No definite experiments have been carried out with regard to the relative stability of the tautomers of 2-substituted indazolones 111. On the basis of basicity arguments, (he hydroxy tautomer 111a was considered to be preferred [96JCS(P2)2263],... 

Only the appearance of the rearranged product is significant for benzocyclopropenone intermediacy, since the indazolone 168 was detected and trapped by tetra-cyclone via 170 in the oxidation of 167, which was shown to yield only unrearranged ester 169 by nucleophilic cleavage by the solvent thus 168 cannot be a precursor of benzocyclopropenone 171. 

Reaction of 3-Lithiomethyl-2-methyl-l-phenylpyrazolin-5-one with 6 A New General Method for the Synthesis of 1,2-Disubstituted Indazolones and Their Condensed Analogs (Type III, 3a Model)... 

Azo compounds are reactive dienophiles. Indeed, one of the very first Diels-Alder reactions was the addition of diethyl azodicarboxylate to cyclopentadiene (equation 134)128 129. Other early examples of the reaction are the formation of tetrahydropyridazines from indazolone 252 and phthalazinedione 253 (equations 135 and 136)130. 

Dienophilic cyclic a-carbonylazo compounds (triazoline diones, indazolone, phthalazine dione) prepared in a flow cell, by anodic oxidation of the corresponding hydrazino compounds in acidic methanol or acetonitrile, react with dienes (Scheme 50) [72, 73]. 

Falbe and co-workers have studied carbonylation of unsaturated amides to give imides (34), unsaturated amines to give lactams (37), and unsaturated alcohols to give lactones (38). Rosenthal and co-workers studied carbonylation of aromatic ketoximes, (127), phenylhydrazones (131), semicarbazones (129), azines (129), and nitriles (128) to produce phthalimidines. Horiie (65) has described the carbonylation of azobenzenes to give indazolones or 2,4-dioxo-l,2,3,4-tetrahydroquinazolines. Pritchard (121) and Murahashi et al. (103) have described the carbonylation of Schiff s bases to yield substituted phthalimidines. 

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