Pyrrolopyridines tautomerism

Pyrrolo[3,2-c]pyridine, 4-hydroxy-tautomerism, 4, 500 Pyrrolo[3,2-c]pyridine, 2,3,3-trimethyl-methylation, 4, 513 Pyrrolo[3,4-6]pyridine, 2-methyl-UV spectra, 4, 501 Pyrrolo[3,4-c]pyridine, 2-methyl-UV spectra, 4, 501 Pyrrolopyridines acylation, 4, 504 bromination, 4, 505 diazo coupling, 4, 506 NMR, 4, 498... 

The pyrrolopyridines contain one nitrogen heteroatom in the five-membered pyrrole ring and one nitrogen atom in the six-membered pyridine ring. A more common name is azaindoles, with 7-azaindole (l//-pyrrolo[2,3-6]pyridine (1)) being the most widely studied isomer of the series. Twelve isomers of pyrrolopyridines are listed in the Chemical Abstracts Ring Formula Index. Table 1 lists the pyrrolopyridines with their Chemical Abstracts Registry Numbers. The 1//-pyrrolopyridines (l)-(6) are the most frequently prepared, but some work has also been carried out on the isomers (7), (8), and (10). Isomers (8), (9), (11), and (12) are tautomeric structures which are considered later (see Section 7.06.4.4). 

Prototropic tautomerism is observed in the pyrrolopyridines. As a consequence, the endocyclic bond angle centered on the five-membered ring nitrogen closes while the endocyclic bond angle... 

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