Toward Safer Methodologies for the Synthesis of Polyheterocyclic Systems: Intramolecular Arylation of Arenes under Mizoroki−Heck Reaction Conditions

Abstract

[reaction: see text] A straightforward synthesis of ibudilast-related pyrazolo[1,5-f]phenanthridines is accomplished by a tandem amine-exchange/heterocyclization of arylenaminones followed by an intramolecular biaryl coupling of the so-formed diarylpyrazoles. The direct, environmentally convenient ring-closure of the latter pyrazole intermediates, which show a close resemblance to the antiinflammatory drug celecoxib, is efficiently performed under Mizoroki-Heck reaction conditions.