Naphthyridines physical properties

The physical properties of four of the six possible naphthyridines have been examined in some detail, and hydration could not be demonstrated in the neutral species and cations of 1,5-, 1,6-, 1,7-, and... 

During the past 20 years several groups of workers19-28 have carried out quantum mechanical calculations on the naphthyridines and have correlated the results with various chemical and physical properties. 

This chapter covers information on the preparation, physical properties, and reactions of 1,5-naphyhyridine and its C-alkyl, C-aryl, /V-alkyl, and /V-aryl derivatives as well as their respective ring-reduced analogs. In addition, it includes methods for introducing alkyl or aryl groups (substituted or otherwise) into 1,5-naphthyridines already bearing substituents and the reactions specific to the alkyl or aryl groups in such compounds. For simplicity, the term alkyl-l,5-naphthyridine in this chapter is intended to include alkyl-, alkenyl-, alkynyl-, aralkyl-, and cycloalkyl-1,5-naphthyridines likewise, aryl-l,5-naphthyridine includes both aryl-and heteroaryl-1,5-naphthyridines. 

The bald physical properties of 1,8-naphthyridine may be found from its entry in Table A4. More extensive information or studies, usually involving comparisons with related systems and/or alkyl derivatives, are referenced here. 

Despite a general paucity of information on 2,6-naphthyridines, the system has been included in several reviews 50-52 57 58 61,265,436,1357 1430 1432 4-methyl-2,6-naphthyridine has been found to occur naturally in several Antirrhina species,226 241 267 and physical properties of the parent heterocycle (1) have been quite extensively studied, usually for comparison with those of the other unsubstituted naphthyridines (see Section 29.2.2). 

Papers that report studies of the various physical properties of 2,6-naphthyridine are referenced here. 

These six tables are reasonably comprehensive lists of 1,5- (Table Al), 1,6- (Table A2), 1,7- (Table A3), 1,8- (Table A4), 2,6- (Table A5), and 2,7-naphthyridines (Table A6) described before 2007. For each compund are recorded (1) melting and/or boiling point(s) (2) an indication of any reported spectra or other physical properties (3) any reported salts or simple derivatives, especially when the parent compund was characterized poorly or not at all and (4) direct references to the original literature. 

In this book, the respective volumes of reported data have led to treatment of the first four of the other naphthyridines in seven chapters each, whereas each-naphthyridine system is covered in a single rather long chapter. The appendix tables aim to list all simple naphthyridines, along with an indication of their physical properties, that have been reported before 2006. 

The chemistry and physical properties of 1,7-naphthyridines (3) <82H(19)363> and of heterocycles (l)-(6) <83AHC(33)147) have been reviewed. The reactions of heterocycles (l)-(6) with nitrogen nucleophiles have also been reviewed <83AHC(33)95>. Reviews covering pyranopyridines (87AKZ104) and pyranopyrans <75MI 715-01) have been published. 

Tire purpose of this chapter is to review the chemistry of the nitro-1,5-, -1,6-, -1,7-, and -1,8-naphthyridines (1) [nitro-2,6- and nitro-2,7-naph-thyridines (2) are unknown], with special attention to the results obtained in the laboratories of both authors. Tliis article mainly refers to the synthesis and reactivity of the nitronaphthyridines their physical and spectroscopic properties and biological activity are only covered briefly. For the convenience of the reader a table listing melting points of (di-)nitronaph-thyridines and some derivatives is included (Table III). Tire literature to about 1998 has been covered. 

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