Substitution vs. addition. Regioselective electrobromination of benzofuran

Citation
H. Tanaka et al., Substitution vs. addition. Regioselective electrobromination of benzofuran, HETEROCYCLE, 54(2), 2001, pp. 825
Citations number
7
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
HETEROCYCLES
ISSN journal
0385-5414 → ACNP
Volume
54
Issue
2
Year of publication
2001
Database
ISI
SICI code
0385-5414(20010201)54:2<825:SVAREO>2.0.ZU;2-P
Abstract
Regioselective electro-bromination of benzofuran (2) was achieved successfu lly by an adequate choice of solvents and bromide salts to afford 5-bromobe nzofuran (1), 5,7-dibromobenzofuran (3), and 2,3-dibromo-2,3-dihydrobenzofu ran (4), respectively. Upon electrolysis of benzofuran (2) in AcOH/H2O (100 /1) containing NH4Br, substitution at the C(5)-position of benzofuran (2) p roceeded smoothly to afford 5-bromobenzofuran (1). After passage of totally 4 F/mol of electricity in a similar medium, 5,7-dibromobenzofuran (3) was obtained as a sole product. On the other hand, electrolysis of benzofuran ( 2) in CH2Cl2/H2O (1/1) and/or AcOH/H2O (10/1) in the presence of either NaB r or NH4Br afforded 2,3-dibromo-2,3-dihydrobenzofuran (4), exclusively.