Azirines 3- benzazepines

The aldehyde functionality present in 3-phenyl-2H-azirine-2-carbox-aldehyde reacts selectively with amines and with Qrignard and Wittig reagents to give a variety of substituted azirines. These azirines have been used, in turn, to prepare a wide assortment of heterocyclic rings such as oxazoles, imidazoles, pyrazoles, pyrroles, and benzazepins. ... 

By analogy with the formation of3//-azepines by cycloaddition of 2//-azirines withcyclopenta-dienones, l,3-diphenyl-2//-inden-2-one (58) and its dibenzo analog 60 enter into [4 + 2] cycloadditions with 27/-azirines to give 3//-2-benzazepines 59 and phenanthro[9,10-e]azepincs 61, respectively.96... 

Photolysis of (Z)-3-phenyl-2-(2-phenylvinyl)-2//-azirine (1) in benzene solution yields 1-phenyl-3//-2-benzazepine (2) in excellent yield.39 However, the stereochemistry of the alkenyl side chain and the solvent used are important in determining the outcome of the reaction. For example, the E-isomer of the 2//-azirine 1 on photolysis in benzene solution yields 2,3-diphenyl-pyrrole as the major product (85 %) the pyrrole is also obtained on heating the Z- or E-isomer in benzene solution. In contrast, irradiation of the Z-isomer in methanol yields only acyclic products. 

Reports of pericyclic cyloadditions to other azepine systems are rare. Addition to the diene system of 6,7-dihydro-l//-azepines occurs readily with DMAD (72CPB1740) and with N-phenylmaleimide (73JA7320). The 5,5a-dihydro-3-benzazepin-2-one (157), a suspected but non-isolable intermediate in the formation of l,2,4,5-tetrahydro-3//-3-benzazepine-2,4-diones by photoaddition of diphenylketen to amino-2//-azirines, has been trapped in the photolysate by N-phenyl-1,3,4-triazoline-2,4-dione as the [4+2]tt adduct (158). Its structure was confirmed by X-ray analysis (80JOC2951). 

Isobenzofuran and 2//-azirines yield the stable adducts, e.g. (239). However, on treatment with neutral alumina these adducts undergo rapid and efficient isomerization to the novel 4,5-epoxy-4,5-dihydro-3//-2-benzazepines (240) (74JOC2031). 3-Benzazepin-2-ones are one of the products from the addition of diphenylketen to 3-dimethylamino-2//-azirines (80JOC2951). 

On irradiation, (Z)-2-styryl-2//-azirines, e.g. (249), undergo analogous ring fission, followed by intramolecular 1,7-dipolar cycloadditions of the resulting nitrile ylide to give 1 -phenyl-3//-2-benzazepines in high yield (80%) (75JA4682). Naphthoazepines have been prepared similarly. 

Padwa and Smolanoff470 irradiated E and Z 3-phenyl-2-styryl-2if-azirines (22) in benzene and isolated high yields of the benzazepine 23 this with DMAD gave 24. 

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