A new synthesis of substituted [1]benzopyrano[3,4-d]imidazol-4(3H)-ones, starting from 3-nitrocoumarin N-functionalized amidines 3, has been developed. When the 3-nitro-amidines 3 were treated with NaBH4 in the presence of 10% palladium on charcoal, 2-substituted [1]benzopyrano[3,4-d]imidazol-4(3H)-ones 4 were produced. Structure elucidation of compounds 4 revealed that they exist as one of the three possible tautomeric structures (i.e., 4dα). Alkylation of 4d to give 6, as well as NOE experiments on 6 and energy calculations allowed the most favoured structure of the 4 derivatives to be identified. Alternatively, the reduction of the 3-nitro-amidines 3 by triethyl phosphite, through a nitrene intermediate, cyclization and a [1.5] sigmatropic shift, yielded 2-morpholino-3-alkyl-[1]benzopyranol 3,4-d]imidazol-4(3H)-ones 7.
3-Nitrocoumarin Amidines: A New Synthetic Strategy for Substituted [1]Benzopyrano[3,4-d]imidazol-4(3H)-ones / E.M. Beccalli, A. Contini, P. Trimarco. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - 2003:20(2003), pp. 3976-3984.
Titolo: | 3-Nitrocoumarin Amidines: A New Synthetic Strategy for Substituted [1]Benzopyrano[3,4-d]imidazol-4(3H)-ones |
Autori: | BECCALLI, EGLE MARIA (Primo) CONTINI, ALESSANDRO (Secondo) TRIMARCO, PASQUALINA (Ultimo) |
Settore Scientifico Disciplinare: | Settore CHIM/06 - Chimica Organica |
Data di pubblicazione: | 2003 |
Rivista: | |
Tipologia: | Article (author) |
Digital Object Identifier (DOI): | http://dx.doi.org/10.1002/ejoc.200300109 |
Appare nelle tipologie: | 01 - Articolo su periodico |