Pyrano azepines

In a new reaction of the pyrano[2,3-c]azepines 40 with hydrazine hydrate, the first derivatives of the pyridazino[4,3-c]azepine system 42 (for example R1 = R2 = Me) have been described (Scheme 10). The rearrangement probably involves initial ring opening to the intermediate 41. Aromatisation of this system was achieved by further oxidation with thallium (III) nitrate or copper(II) acetate . 

In other somewhat related work, the synthesis of pyrano[2,3-c]azepines (and pyrido[2,3-c]azepines has been described. Reaction of hydrazoic with iV-(5,6,7.8-tetrahydro-2,5-dioxo-2W-l-benzopyran-3-yl)benzamide (or 8-hydrazono) derivatives afforded pyrano[2,3-c]azepines, which in turn can be transformed to pyrido[2,3-c]azepines <00H(53)1111>. 

A mechanistically novel reaction of pyrano[3,2-f]azepines 228 and hydrazine was used to prepare pyridazino[4,3-f]-azepines such as 229. Further oxidation of 229 yielded fused pyridazine derivatives (e.g., 230 Scheme 27) <2000SL254>. Mechanistic insight was provided for this transformation and is shown in Scheme 28. 

A variety of other ring fused azepines and azepinones have been described. Kocevar et al. have reported the first syntheses of the pyrano azepinediones 70 and 71 from 69 via the Schmidt reaction at -15 °C to 0 °C (in CHCh or CH2CI2) the products 70 are favoured, while at 32 °C to 35 °C the percentage of the isomers 71 increased overall yields were high... 

The reactions of 3-formylchromones, e.g. (186), with various ort/io-substituted anilines (Y = S, O, or NH) provide a high-yielding route to the fused benzo-pyrano-compounds (187)." Various substituted 2,3-dihydro-l,4-benzox-azepin-5(4H )-one-7-acetic acid esters were prepared by the Schmidt reactions of chromanone derivatives." ... 

Reaction with Cyclic Enones. Conjugate addition of azide ion to cyclic enones in water using sodium azide in the presence of Lewis base resulted in the formation of 8-azido carbonyl compounds (eq 55). The Schmidt reaction of benzopyranones with sodium azide led to pyrano[3,2-b]azepines in reasonable yields (eq 56). 

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