Cinnolinones tautomerism

Although there is little doubt that 4(1//)- (1) and 3(2//)-cinnolinone exist predominantly as such rather than as the tautomeric 4- and 3-cinnolinols, respectively, this issue has received further theoretical, nuclear quadrupole reso-... 

Tautomeric Cinnolinones Alkaline hydrolysis has also been used. " ... 

The conversion of tautomeric cinnolinones into halogenocinnolines has been covered in Section 3.1. Other reactions are discussed in the subsections that follow. 

Tautomeric cinnolinones usually undergo A -alkylation to afford regular N-alkylcinnolinones, zwitteiionic Al-alkylcinnoliniumolates, or a mixture of both 0-alkylation to afford alkoxycinnolines is rare but not unknown. These possibilities are illustrated in the following classified examples. 

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

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

Note The formation of these ethers by primary synthesis Chapter 1), by alcoholysis or phenolysis of halogenocinnolines (Section 3.2), and by alkylation of tautomeric cinnolinones (Section 4.1.2.1) has been covered already. Other routes appear to be unrepresented. 

Note Examples of alkanelysis (Section 2.2.1) and conversion into tautomeric cinnolinones (Section 4.1.1) have been given already. 

Note A few such products have been made by primary synthesis (see Chapter 1) but most, by alkylation of tautomeric cinnolinones (see Section 4.1.2.1). Minor routes are exemplified here. 

Note A few tautomeric cinnolinethiones have been made by the thiolysis of halogenocinnolines (see Section 3.2) and both tautomeric and nontautomeric cinnolinethiones, by thiation of cinnolinones (see Sections 4.1.2.2 and 4.2). 

Note-. These acylcinnolines have been made by primary synthesis (see Chapter 1), Reissert-type addition to cinnoline (Section 2.1.3), oxidation of alkylcin-nolines (Section 2.2.2), displacement of halogeno substituents (Section 3.2), hydrolysis of dihalogenomethylcinnolines (Section 3.2), N-acylation of tautomeric cinnolinones (Section 4.1.2.2), oxidation of extranuclear hydro-xycinnolines (Section 4.2), or as illustrated here. 

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