Indazolinone synthesis

Boulton <86JCS(P1)1249> has described the synthesis of 3-methoxyindazole from indazolinone and Aran <93JCS(P1)1119> has reported the transformation of sp/ro-indazolylio oxides into dimeric macrocycles (l-alkyl-3-alkyloxy-bisindazoles). 

Carbon monoxide insertion is another widely observed reaction. The following carbon monoxide insertion into an azobenzene palladium complex is typical lu). Azobenzene-palladium chloride complex has a carbon-palladium bond at the ortho-position, the carbonylation of which gives indazolinones by carbon monoxide insertion. Further carbonylation of indazolinone catalyzed by Co2(CO)8 produces quinazolinedione, hydolysis of which gives aniline and anthranilic acid 172). Thus this method is useful for the synthesis of substituted anthranilic acid. 

In 1967, Takahashi and Tsuji [61] reported that carbonylation of substituted azobenzene in protic solvents such as alcohols or water proceeded smoothly under mild conditions to afford 2-aryl-3-indazolinones with separation of metallic palladium in a high yield, as shown in Eq. (7.33). Hence, the reactions are a very good synthetic method for the synthesis of substituted 2-aryl-3-indazolinones 7.39. 

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