Cinnolines, amino-, tautomerism

Cinnoline, 4-alkylamino-3-phenyl-tautomerism, 3, 5 Cinnoline, 4-amino-biological aaivity, 3, 56 nitration, 3, 21 tautomerism, 3, 5 Cinnoline, dihydro-... 

Cinnoline, 4-alkylamino-3-phenyl-tautomerism, 3, 5 Cinnoline, 4-amino-biological aaivity, 3, 56 nitration, 3, 21 tautomerism, 3, 5 Cinnoline, dihydro-N-aminoindoles from, 4, 361 Cinnoline, 3,4-diphenyl-synthesis, 3, 42 Cinnoline, 3-hydroxy-synthesis, 2, 92 tautomerism, 3, 4 Cinnoline, 4-hydroxy-tautomerism, 3, 4 Cinnoline, 4-methyl-nitration, 3, 21... 

Tautomerism, particularly keto-enol, thione-thiol and amino-imino, was discussed in CHEC-I <84CHEC-l(3B)l>. In general, hydroxy substituents at all positions of the heterocyclic ring of pyridazines, phthalazines, and cinnolines exist in the keto form, with the exception (noted in CHEC-I) of the 3- and 5-hydroxy derivatives of pyridazine 1-oxide. In cases where two hydroxy or thiol substituents are present, the normal situation is for only one to be in the keto or thione form. In contrast, amino derivatives usually exist as such. 

Chemical reactivity, as method to study tautomerism, 321 Chromone, 2-hydroxy-, 346 Chromonediols, 363 Cinchonie acids, 2-thienyl-, 99 Cinnoline 4-amino-, 415... 

The tautomerism of the rarely assayed OH-, SH-, and NH2 cinnolines (46) was reinvestigated in DMSO-d, solution (Scheme 5.37). Multinuclear NMR studies, especially N N M R spectra, proved the presence of both the hydroxy and mercapto compounds (46, X = O, S) in the -one(thione) form, while aminocinnohne prefers the amino form 46b [86]. 

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