Synthesis of 2,3-Disubstituted Benzo[b]selenophenes via Electrophilic
Cyclization
Tanay Kesharwani, Shilpa A. Worlikar, and Richard C. Larock*
Department of Chemistry, Iowa State UniVersity, Ames, Iowa 50011
ReceiVed NoVember 23, 2005
2,3-Disubstituted benzo[b]selenophenes have been prepared by the electrophilic cyclization of various
1-(1-alkynyl)-2-(methylseleno)arenes by Br2, NBS, I2, ICl, PhSeCl, PhSeBr, and Hg(OAc)2. This method
tolerates a wide variety of functional groups, including alcohol, ester, nitrile, nitro, and silyl groups, and
proceeds under exceptionally mild reaction conditions.
Introduction
Similar cyclizations have also been reported using transition-
metal catalysts.11 However, some of these transition-metal
approaches are either incompatible with functionality or lack
regioselectivity. Chalcogens, like sulfur, selenium, and tellurium,
have seldom been employed in such transition-metal-catalyzed
cyclizations as a result of their strong affinity for transition
metals.
Benzo[b]selenophenes have received little attention as po-
tential drugs, although their potent biological activity and
synthetic utility have been discussed in the literature.12 Recently,
Otsubo and co-workers have shown that high performance
The electrophilic cyclization of alkynes having a nucleophile
in close proximity to the triple bond has proven to be an efficient
way of constructing a wide array of carbocycles and hetero-
cycles.1 Recently, our group and others have successfully
utilized this approach to synthesize benzo[b]thiophenes,2 ben-
zofurans,3 furans,4 thiophenes,5 indoles,3c,6 isoquinolines,7 quin-
olines,8 isocoumarins,9 and polycyclic aromatic hydrocarbons.10
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10.1021/jo0524268 CCC: $33.50 © 2006 American Chemical Society
Published on Web 02/17/2006
J. Org. Chem. 2006, 71, 2307-2312
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