3H-Azepines and related systems. Part 5. Photo-induced ring expansions of o-Azidobenzonitriles to 3-Cyano- and 7-Cyano-3H- azepin-2(1H)-ones

Synthesis of Benzotriazine and Aryltriazene Derivatives Starting from 2‐Azidobenzonitrile Derivatives

“…The calculations were performed with the Gaussian 03 package. [37] 2-Azidobenzonitrile (4a): [20,38] 2-Aminobenzonitrile (6a; 10.0 g, 84.6 mmol) was dissolved by heating in concentrated hydrochloric acid (75 mL) and water (25 mL). The solution obtained was then cooled to 0°C and diazotized over 0.5 h at 0-5°C with sodium nitrite (6.54 g, 94.8 mmol) dissolved in a minimum volume of water.…”

“…[20] This compound was prepared from 2-amino-5-methylbenzonitrile (6c; [28] 3.40 g, 25.5 mmol) according to the procedure given for compound 4a. The product was obtained as a yellow solid (3.65 g, 91 %), m.p.…”

“…The product was obtained after extraction with EtOAc (3 ϫ 20 mL) followed by evaporation which resulted in a yellow oil (0.92 g, 91 % 2-Azido-5-chlorobenzonitrile (4e): [20] This compound was prepared from 2-amino-5-chlorobenzonitrile (6e; [30] 2.85 g, 18.7 mmol) according to the procedure given for compound 4a. The product was obtained as a yellow solid (2.40 g, 72 %), m.p.…”

“…86-88°C (ref. [20] 85°C 2-Azido-3,5-dibromobenzonitrile (4g): [32] This compound was prepared from 2-amino-3,5-dibromobenzonitrile (6g; [33] 4.50 g, 16.4 mmol) according to ref. [32] The product was obtained as a pale-yellow solid (4.70 g, 95 %), m.p.…”

“…[20] Exposure of 2-azidobenzonitrile (4) to methylmagnesium bromide in THF or diethyl ether at room temperature gave, after work-up, a white solid material in 78 % yield, the LC-MS data of which indicated the same mass as 3-methylindazole. However, because NMR and IR analysis did not give clear-cut information about the structure, the molecule was subjected to an X-ray analysis which gave conclusive evidence for 3,4-dihydro-4-imino-3-methyl-1,2,3-benzotriazine (7a; Scheme 2, Table 1, entry 1).…”