Substituted 4,5-dihydroazepines

Substituted 4,5-dihydroazepines 321 (e.g., R1 = Bn, R2 = R3 = H, R4 = M e 82% yield) may be prepared in high yield by a rhodium-mediated hetero-[5+2]-cycloaddition of the cyclopropyl imines derived from 318 on reaction with the primary amines 319, with dimethyl acetylenedicarboxylate 320 (Equation 48) <2002JA15154>. 

A concise approach to substituted dihydroazepines 3 has been described involving the reaction of ylides, generated in situ from styryldiazoacetates (e.g. 1), with imines 2. In the case of 1 and the imine 2 (Ar = Ph, R = Me) the yield of the corresponding azepine 3 was 73% [01OL3741],... 

A lithium-induced cyclization of the imine-diene 267, followed by N-alkylation (e.g., with EX = EtBr) or iV-acylation (e.g. with EX = PhCOCl), to form the 4,5-dihydroazepines 268 in poor to fair yields has been reported (Equation 36) <1995TL7065>. By using the different imine-dienes 269 but the same conditions as for 267 to form the anionic intermediate for the 1,7-electrocyclization, the N-substituted 2,3-dihydroazepines 270 were obtained (Equation 37) <1996T14801>. NMR spectroscopy was used to monitor the progress of these reactions. 

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