RING-CLOSURE ISOMERIZATIONS FOR 1-ISOCYANO-2-PHENYL-NAPHTHALENE, 1-(2-ISOCYANO-PHENYL)-NAPHTHALENE AND 2-(2-ISOCYANOPHENYL)-NAPHTHALENE

Benzo[g]cyclohept[b]indole (7) and benzo[e]naphth[1,8-cd]azepine (8) were produced from 1-isocyano-2-phenylnaphthalene (4) and 1-(2-isocyanophenyl) naphthalene (5), respectively, upon irradiation at 254 nm in cyclohexane. Benzo[c]phenanthridine (10), the heterocycle (8), and benzo[i]phenanthridine (11) were produced from the isocyanides (4), (5), and 2-(2-isocyanophenyl) naphthalene (6), respectively, upon irradiation at 300 nm in methanol. Thermolysis isomerised each isocyanide into the corresponding aryl cyanide and the isocyanide (4) into the heterocycles (7) and (10). Solvent (tetradecane) participation accounted for the formation of 6-tetradecylbenzo[c]phenanthridines (12) and 5-tetradecylbenzo[i]phenanthridines (13) from the isocyanides (4) and (6), respectively. Irradiation slowly consumed 1-isothiocyanato-2- phenylnaphthalene and 2-(2-isothiocyanatophenyl) naphthalene but desulphurisation into an isocyanide was not detected.