Preparation of Cinnolinecarboxylic Acids

This chapter deals with nuclear and extranuclear cinnolinecarboxylic acids and the corresponding carboxylic esters, acyl halides, carboxamides, carbohydrazides, carbonitriles, and carbaldehydes, and the ketonic acylketones. To avoid repetition, the interconversion of these cinnoline derivatives are discussed only at the first opportunity for example, the esterification of cinnolinecarboxylic acids is covered as a reaction of cinnolinecarboxylic acids rather than as a preparative route to carboxylic esters, simply because the section on acids precedes that on esters. To avoid any confusion, appropriate cross-references have been included. 

The formation of cinnolinecarboxylic acids by primary synthesis (see Chapter 1) and by hydrolysis of trihalogenomethylcinnolines (see Section 3.2) have been covered already the oxidative routes from alkylcinnolines, hydroxyalkylcinnolines, or cinnolinecarbaldehydes appear to be unrepresented in the 1972-2004 literature the remaining approaches are illustrated in the following classified examples. 

4-Chlorocinnoline (1) gave its 2-lithio derivative (2) [LLNPij (made in situ), THF, substrate], —75°C] and thence, by carbonation of the reaction mixture. 

Cinnolines and Phthalazines Supplement II, The Chemistry of Heterocyclic Compounds, Volume 64, by D.J. Brown Copyright 2005 John Wiley Sons, Inc. 

4-chloro-3-cinnolinecarboxylic acid (3) (solid C02i, —75°C, 2h 57% overall). °  

---