ON THE TAUTOMERISM OF CINNOLIN-4-OL,CINNOLINE-4-THIOL,AND CINNOLIN-4-AMINE

摘要

Detailed NMR spectroscopic investigations(~1H,~(13)C,~(15)N)with cinnolin-4-ol(1)reveal this compound to exist exclusively in the cinnolin-4(1H)-one form in deuteriodimethyl sulfoxide solution.This finding is confirmed by comparison of the NMR spectroscopic data of 1 with those of the corresponding 'fixed' O-methyl and N-methyl derivatives,i.e.4-methoxycinnoline(3)and l-methylcinnolin-4(1H)-one(5).Similarly,cinnoline-4-thiol(4)is present in the thione form in deuteriodimethyl sulfoxide,whereas cinnolin-4-amine(7)exists in the amino form.In addition,in-depth analyses of the NMR spectra of some simple 4-substituted cinnolines are provided.