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Synthesis 2002(1): 0083-0086
DOI: 10.1055/s-2002-19314
PAPER
© Georg Thieme Verlag Stuttgart · New York

Bromination of Isoquinoline, Quinoline, Quinazoline and Quinoxaline in Strong Acid

William Dalby Browna, Alex Haahr Gouliaev*b
a Department of Chemistry, University of Copenhagen, Copenhagen, 2100, Denmark
b Nuevolution A/S, Copenhagen, 2100, Denmark
Fax: +4570200986; e-Mail: ahg@nuevolution.com;
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Publication History

Received 10 September 2001
Publication Date:
04 August 2004 (online)

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Abstract

Bromination of benzazines and benzodiazines most often gives a mixture of products. In this paper, we show that isoquinoline (1) may be regioselectively monobrominated in concentrated H2SO4 using NBS or in CF3SO3H using N,N’-dibromoisocyanuric acid (DBI) to give 5-bromoisoquinoline (2). The bromination was found to be highly sensitive to the choice of brominating agent, acid, temperature and concentration. Quinoline, quinazoline and quinoxaline may be brominated likewise, although with the strong regioselectivity reserved to isoquinoline.

Key words

bromination - electrophilic aromatic substitution - regioselective - benzazines - benzodiazines

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This expected doublet of doublet was observed as a triplet with the given coupling constant.