NOVEL PATHWAY TO 1-AMINOPYRROLES AND OTHER NITROGEN-HETEROCYCLES FROMGLYOXAL MONOHYDRAZONES AND ACYLATED ACTIVE METHYLENE-COMPOUNDS IN SOLVENT-FREE REACTIONS UNDER MICROWAVE IRRADIATION

Heterobicyclic compounds 5 obtained by ring closure of glyoxal monophe nylhydrazones 1a with acyl active methylene compounds 2 ((RCOCH2CO2R4) -C-3), in solvent-free reaction catalyzed by piperidine, give after ac idic treatment functionalized N-anilinopyrroles 6 which may also be re adily obtained in a one-pot reaction starting from 1 and 2 in the pres ence of piperidine followed by the acidic treatment. When R-3 is an is opropyl group, the reaction follows a different course leading to new nitrogen fused heterocycles 7 and 8. Microwave irradiation converts 5 into the isomeric N-anilinopyrroles 12 except when 5 hears two acyl gr oups which then leads to 6. Starting from glyoxal N-dimethylhydrazones 1b, N,N-dimethylamino pyrroles 9 can be prepared at room temperature or under microwaves in the presence of catalytic amounts of piperidine . Microwave irradiation converts cyclohexanones 10 into benzo-pyrrolid inones 11. (C) 1998 Elsevier Science Ltd. All rights reserved.