Other Reactions of Tautomeric Cinnolinones

Several other important reactions of tautomeric cinnolinones are represented in the more recent literature, as illustrated in the following classified examples. 

Ethyl 4-0X0-l,4-dUiydro-3-cinnohnecarboxylate (41, R = C02Et) gave ethyl 4-thioxo-l,4-dihydro-3-cinnolinecarboxylate (42, R = C02Et) (P2S5, trace 

Note Unlike alkylation, acylation of a tautomeric cinnolinone usually affords an acyloxycinnoline rather than an A-acylated cinnolinone. 

4-Oxo-l,4-dihydro-3-cinnolinecarbonitrile (48) gave 4-acetoxy-3-cinnoline-carbonitrile (49) (neat AcaO, 95°C, 30 min 70%) several analogs likewise.  

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