Novel pathway to 1-aminopyrroles and other nitrogen heterocycles from glyoxal monohydrazones and acylated active methylene compounds in solvent-free reactions under microwave irradiation

• Published in: Tetrahedron 1998-04, Vol.54 (18), p.4561-4578
• Main Authors: Jolivet-Fouchet, Sandrine, Hamelin, Jack, Texier-Boullet, Françoise, Toupet, Loïc, Jacquault, Patrick
• Format: Article
• Language: English
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/S0040-4020(98)00159-8

Heterobicyclic compounds 5 obtained by ring closure of glyoxal monophenylhydrazones 1a with acyl active methylene compounds 2 (R 3COCH 2CO 2R 4), in solvent-free reaction catalyzed by piperidine, give after acidic treatment functionalized N-anilino 6 which may also be readily obtained in a one-pot reaction starting from 1 and 2 in the presence of piperidine followed by the acidic treatment. When R 3 is an isopropyl 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 bears two acyl groups 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-pyrrolidinones 11. Graphic