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Indazoles
1911 Encyclopedia Britannica
or ENZOPYRAZOLES), organic substances con- /N /CH taming the ring system I I I > NH. The parent substance N/N N indazole, C7H6N2, was obtained by E. Fischer (Ann. 1883, 221, p. 280) by heating ortho-hydrazine cinnamic acid, C 6 H4 CH=CH[[Cooh=C 0 +C, ? Nh]]-NH2 It has also been obtained by heating ortho-diazoaminotoluene with acetic acid and benzene (F. Heusler, Ber., 1891, 24, p. 4161).
C6H4 HN.NHC7H7 = C7H7NH2+C7H6N2.
It crystallizes in needles (from hot water), which melt at 146.5° C. and boil at 269°-270° C. It is readily soluble in hot water, alcohol and dilute hydrochloric acid. Nitrous acid converts it into nitrosoindazole; whilst on heating with the alkyl iodides it is converted into alkyl indazoles.
A series of compounds isomeric with these alkyl derivatives is known, and can be considered as derived from the ring system / NH N. N/NCH7 be prepared by the reduction of the nitroso-ortho-alkylaminoacetophenones with zinc dust and water or acetic acid. The indazoles are weak bases, which crystallize readily. Phenyl indazole, on reduction with sodium and absolute alcohol, gives a dihydro derivative (K. L. Paal, Ber., 1891, 24, p. 963).
For other derivatives, see E. Fischer and J. Tafel, Ann. 1885, 227, p. 314.
These files are public domain.
Chisholm, Hugh, General Editor. Entry for 'Indazoles'. 1911 Encyclopedia Britanica. https://www.studylight.org/encyclopedias/eng/bri/i/indazoles.html. 1910.
