Synthesis of 1(3H)-Imino-2-benzothiophene and 1-Imino-1H-2-benzothiopyran Derivatives by Reactions of Secondaryo-(Vinyl)thiobenzamide Derivatives with Iodine
Synthesis of 1(3H)-Imino-2-benzothiophene and 1-Imino-1H-2-benzothiopyran Derivatives by Reactions of Secondaryo-(Vinyl)thiobenzamide Derivatives with Iodine
Synthesis of 1(3<i>H</i>)-Imino-2-benzothiophene and 1-Imino-1<i>H</i>-2-benzothiopyran Derivatives by Reactions of Secondary<i>o</i>-(Vinyl)thiobenzamide Derivatives with Iodine
Efficient methods have been developed for the preparation of 1(3H)-imino-2-benzothiophene and 1-imino-1H-2-benzothiopyran derivatives. Treatment of secondary o-(vinyl)thiobenzamide derivatives with iodine in the presence of sodium hydrogencarbonate in acetonitrile at 0 °C gave the former derivatives. Similar treatment at reflux gave the latter derivatives.
Secondary 2-(vinyl)thiobenzamide derivatives, easily prepared by reacting 2-lithiostyrene derivatives with various isothiocyanates, undergo intramolecular cyclization on treatment with concentrated hydriodic acid to produce 1(3H)-iminobenzo[c]thiophene derivatives in fair-to-good yields. Some of them have been hydrolyzed under acidic conditions to afford benzo[c]thiophen-1(3H)-one derivatives in good yields.