Preparation of 1,8-Naphthyridinecarboxylic Acids

These carboxylic acids have been made by primary synthesis (see Chapter 8), oxidation of alkyl-1,6-naphthyridines (see Section 9.2.2), or the routes illustrated in the following classified examples. 

Note The choice between acidic or alkaline hydrolysis may depend on the other substituents present in the molecule. 

Ethyl 7-chloro-1 -cyclopropyl-8-fluoro-4-oxo-1,4-dihydro-1,6-naphthyridine-3-carboxylate (1, R = Et) gave 7-chloro-l-cyclopropyl-8-fluoro-4-oxo-l,4-dihydro-l,6-naphthyridine-3-carboxylic acid (1, R = H) (HC1, H20, EtOH, reflux, 9h 81%) 1175 analogs likewise.648 

The Naphthyridines The Chemistry of Heterocyclic Compounds, Volume 63, by D.J. Brown Copyright 2008 John Wiley Sons, Inc. 

A brief review of antibacterial naphthyridinecarboxylic acids has appeared.542 

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