Chemistry Of Azepines And Their Derivatives

1.0 Introduction

1.1 Background of the Study

Azepines and their benz-fused derivatives have commanded a considerable amount of synthetic interest. This is particularly true of the latter systems because of their continuing pharmacological significance. Ring synthesis by ring construction is the dominant general approach, although a number of new ring transformation strategies have been developed. Amongst the ring construction strategies a flowering of methods based on ring closing metathesis is evident for type c and type d processes. There is scope also for extension of this methodology to type b processes. A novel zirconium-mediated approach to substituted azepanes has been described and this reaction has considerable further synthetic potential. The synthetic power of sequential reactions has also been demonstrated, for example in the synthesis of tetrahydro-1H-1-benzazepine derivatives. A single crystal X-ray structure of the first reported 2-azatropone is also a significant development.

1.2 Statement Problem

The azepine ring system has continued to attract considerable attention since the publication of CHEC-II(1996). Several reviews of this system have also appeared and an account of an efficient ring construction strategy for seven-membered rings, including dihydroazepines, has been published. A reference series has also reviewed seven-membered heterocycles including azepines and benzazepines, while annual synopses of these systems are covered in the series Progress in Heterocyclic Chemistry.

Most of the chemistry has centered on reduced or oxidized forms of the ring system, since the parent 1H-azepine 1 is not stable, although N-substituted derivatives are known. Considerable chemistry has been described for benz-fused azepines and other fused derivatives. Chemical aspects of the former, of which the parents are 1H-1-benzazepine 2, 1H-2-benzazepine 3, and 3H-3-benzazepine 4, and their tautomers, are also covered in this seminar.

1.3 Research Objective

The objective of this study was to evaluate the chemistry of azepines and their derivatives.

4.0 Conclusion And Recommendation

4.1 Recommendations

A Beckmann rearrangement-reduction sequence has been used to access a number of substituted 1H-1-benzaze- pine derivatives, with the required substituted α-tetralone precursors being prepared by a xanthate-based free radical cyclization process. Further 1,4-disubstituted 1-benzazepin-2-one derivatives have been evaluated as blockers of a voltage-gated sodium channel; one compound in this series showed highly potent activity and, encouragingly, was also active in a rat model of neuropathic pain after oral administration. A range of compounds based on a 4,4- difluoro-1-benzazepine core system, and with substituents at positions 1 and 5, have been synthesized and evaluated as selective antagonists of the arginine vasopressin V1A receptor. Potent and selective dopamine D3-receptor antagonists have also been reported based on 1H-1-benzazepin-2-one (and analogous 2,5-dione) derivatives. Detailed structure-activity relationships have been developed for a series of 5-, 6-, and 7-methyl substituted azepan-3-ones with cathepsin K inhibitory activity.

New pyridobenzazepine and pyridobenzothiepine derivatives were synthesized using a methodology for Pd-catalyzed formation of C–N and C–S bonds.9 Additionally, the successful transformations of thiepine 31 to tetrahydro and biphenyl derivatives opened up new possibilities for the preparation of structurally diverse substituted derivatives. All newly and previously synthesized compounds were evaluated for their in vitro antimicrobial activity against eight bacterial and three fungal pathogenic strains. All pyridobenzazepine derivatives showed better antibacterial and antifungal activity than the corresponding dipyridoazepine analogues. Among the synthesized azepines, derivative 8 was the most active and showed a broad spectrum of antibacterial activity (MIC ranged 39–78 µg mL–1). The synthesized thiepine derivatives exhibited weak antibacterial activity but, on the other hand, with the exception of 31, all thiepines showed pronounced antifungal activity.

4.2 Conclusion

A series of new pyridobenzazepine and pyridobenzothiepine derivatives was synthesized by Pd-catalyzed formation of C–N and C–S bonds. All synthesized compounds were tested for their in vitro antimicrobial activity. The pyridobenzazepine derivatives showed better antibacterial and antifungal activity than the corresponding dipyridoazepine analogue. Among the synthesized azepines, derivative 8 displayed potent activity against the tested bacteria (MIC ranged 39–78 µg mL-1), while azepine 12 showed promising antifungal activity (MIC ranged 156–313 µg mL-1). The synthesized thiepine derivatives exhibited weak antibacterial activity, but showed pronounced antifungal activity.