Alkoxy-2,7-naphthyridines

Bismuth(lll) chloride catalyzes the intramolecular hetero-Diels-Alder reaction of aldimines, generated in situ from aromatic amines and the A -allyl derivative of o-aminobenzaldehyde, in acetonitrile at reflux to generate [l,6]naphthyridine derivatives <2002TL1573>. The hetero-Diels-Alder reaction of 3-aryl-2-benzoyl-2-propeneni-triles and enol ethers yields 2-alkoxy, 6-diaryl-3,4-dihydro-2//-pyran-5-carbonitriles (Scheme 29) <1997M1157>. 

Although alkoxy ion is a more powerful nucleophile than aryloxy ion, both types react vigorously with activated halogeno-l,5-naphthyridines and even (albeit sluggishly) with 3(7)-halogeno-l,5-naphthyridines. In the absence of kinetic data, the following preparative examples illustrate the practicalities of such displacement reactions. 

The term oxy-1,5-naphthyridine includes the tautomeric and nontautomeric 1,5-naphthyridinones, extranuclear hydroxy-l,5-naphthyridines, alkoxy-and aryloxy-... 

Note. All known alkoxy-l,5-naphthyridines have been made by primary synthesis (see Chapter 1), by alcoholysis of halogeno-l,5-naphthyridines (see Section 3.2.1), or by alkylation of 1,5-naphthyridinones (see Section 4.1.2). 

This chapter summarizes what has been reported on the 1,7-naphthyridinones, the alkoxy- or acyloxy-l,7-naphthyridines, and the 1,7-naphthyridine /V-oxides. 

This chapter includes the 1,8-naphthyridinones, alkoxy- and aryloxy-1,8-naphthyridines, and 1,8-naphthyridine N-oxides. Much of the available material in these areas was stimulated by a search for analogs of nalidixic acid (1) with improved antimicrobial and other bioactivities. Some of the resulting compounds (usually bearing halogeno substituents) have been mentioned at the beginning of Chapter 24 others are included in numerous papers and reviews, mainly covering their bioactivities t51-159-171-192-212-219-227-228-235-238-242-248-294-295-313-342-347-370-373-380-... 

Note The hydrolysis of alkoxy-l,8-naphthyridines to 1,8-naphthyridinones has been exemplified in Section 25.1.1. No other reactions appear to have been reported. 

Almost every reported aspect of 3,6-naphthyridinones, alkoxy-2,6-naphthyri-dines, and 2,6-naphthyridine N-oxides has been covered already. 

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