Synthesis of diarylamines in the benzo[ b]thiophene series bearing electron donating or withdrawing groups by Buchwald–Hartwig C–N coupling

Abstract

Diarylamines in the benzo[ b]thiophene series bearing electron donating or withdrawing groups, were prepared by Buchwald–Hartwig C–N coupling in moderate to high yields. The conditions used were Pd(OAc) 2 (3 mol%), BINAP as ligand (4 mol%) and Cs 2CO 3 as base (1.4 equiv.), in toluene at 100°C, being 6-bromo or amino benzo[ b]thiophenes coupled, respectively, with substituted anilines or phenylbromides. The 6-aminobenzo[ b]thiophene derivatives were also prepared by palladium catalyzed C–N coupling of the corresponding 6-bromo compounds with benzophenone imine, followed by acidic hydrolysis of the imino derivatives. When 4-nitrobromobenzene and 4-bromobenzonitrile were used as coupling components, triarylamines were also isolated in small amounts. The presence of a fluorine atom on the phenylbromide highly increases the diarylamine yields.