Synthesis and isolation of bromo-beta-carbolines obtained by bromination of beta-carboline alkaloids

Citation
Ma. Ponce et R. Erra-balsells, Synthesis and isolation of bromo-beta-carbolines obtained by bromination of beta-carboline alkaloids, J HETERO CH, 38(5), 2001, pp. 1087-1095
Citations number
29
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF HETEROCYCLIC CHEMISTRY
ISSN journal
0022-152X → ACNP
Volume
38
Issue
5
Year of publication
2001
Pages
1087 - 1095
Database
ISI
SICI code
0022-152X(200109/10)38:5<1087:SAIOBO>2.0.ZU;2-0
Abstract
beta -Carbolines (1-5) undergo electrophilic aromatic substitution with N-b romosuccinimide under different experimental conditions. Although 6-bromo-n or-harinane (1a) obtained by bromination of nor-harmane (1) was isolated an d fully characterized sometime ago, the other bromoderivatives of nor-harma ne (lb-le) and harmane (2a-2e) were partially described as part of the reac tion mixtures, The preparation and subsequent isolation, purification and f ull characterization of 1b, 1c, Id, le, 2a, 2b, 2c, 2d, 2e are reported (mp , Rf, IH-nmr, C-13-nmr and ms) together with the preparation, isolation and charaterization, for the first time, of the bromoderivatives obtained from harmine (3a-3e), harmol (4a, 4b) and 7-acetylharmol (5a-5c). As brominatin g reagent N-bromosuccinimide and N-bromosuccinimide-silica get in dichlorom ethane and in chloroform as well as the beta -carboline - N-bomosuccinimide solid mixture have been used and their uses have been compared. Semiempiri cal AMI and PM3 calculations have been performed in order to predict reacti vity in terms of the energies of HOMO, HOMO-LUMO difference and in terms of the charge density of beta -carbolines (1-5) and bromo-beta -carbolines (l a-le, 2a-2e, 3a-3e, 4a, 4b, 5a, 5b and 5c) (Scheme 1). Theoretical and expe rimental results are discussed briefly.