Studies on tertiary amine oxides. LXXI. Some electrophilic reactions of 1-hydroxy-2-phenylindole.

Abstract

1-Hydroxy-2-phenylindole (1) reacts with tosyl chloride and p-nitrobenzenesulfonyl chloride in DMF-pyridine to give the corresponding 2-phenyl-3-sulfonyloxyindole (2 and 4). Benzoyl chloride is less reactive, and 1-benzoyloxy-2-phenylindole (5) or 3-benzoyloxy-2-phenylindole (6) is formed, depending upon the reaction conditions. 3-Acetoxy-2-phenylindole (7) is also obtained by refluxing 1 with acetic anhydride or with acetyl chloride in DMF-pyridine. Treatment of 1 with tosyl chloride and then with 1-morpholinocyclohexene (9), ethyl acetoacetate (17) and ethyl cyanoacetate (20) in DMF-pyridine at room temperature affords 3-(2-oxocyclohexyl)-2-phenylindole (10), ethyl α-(2-phenyl-3-indolyl) acetoacetate (18) and ethyl α-(2-phenyl-3-indolyl) cyanoacetatc (21) in 23.2, 41 and 61% yields, respectively.