Organic photochemical reactions-VI. Photochemical and thermal ring contractions of 2-methoxy- and 2-amino-3-acyl-3H-azepines

Article abstract of DOI:10.1016/0040-4020(69)80042-6

Photolysis of 3-benzoyl-2-methoxy-3H-azepine (IIa) in methanol led to 7-benzoyl-2-methoxy-3-azabicyclo[2.1.0]hepta-2,4-diene (IVa), 2-methoxy-3-phenacylpyridine (Va) and 2-phenylfuro[2.3-b]-pyridine (VIa). This reaction was extended to 3-benzoyl-5-chloro- and -6-chloro-2-methoxy-3H-azepines (IIb, c) and 3-acetonyl-2-methoxy-3H-azepine (IId) which underwent analogous conversion into the corresponding pyridine derivatives (Vb-d and VIb), respectively. Pyrolysis of IIa-c gave similar pyridine derivatives. Thermal rearrangement of 2-amino-3-acyl-3H-azepines (IIIa-c) gave pyrrolo[2.3-b]pyridine derivatives (XIa-c) or 2-diethylamino-3-phenacylpyridines (XIIa, b). A tentative mechanism of these ring contractions is presented.