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Synlett 2011(15): 2171-2176  
DOI: 10.1055/s-0030-1261205
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Cationic Ir(I)-Catalyzed sp³ C-H Bond Alkenylation of Ureas with Alkynes for the Synthesis of 2,3-Disubstituted Indoles

Takanori Shibata*a, Hiroyuki Hirashimaa, Mitsugu Kasagawaa, Kyoji Tsuchikamaa, Kohei Endob
a Department of Chemistry and Biochemistry, School of Advanced Science and Engineering, Waseda University, Okubo, Shinjuku, Tokyo 169-8555, Japan
Fax: +81(3)52868098; e-Mail: tshibata@waseda.jp;
b Waseda Institute for Advanced Study, Shinjuku, Tokyo 169-8050, Japan
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Publication History

Received 27 June 2011
Publication Date:
30 August 2011 (online)

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Abstract

Secondary sp³ C-H bond activation of ureas was achieved by a cationic Ir(I)-JOSIPHOS catalyst. Regioselective C-H bond cleavage adjacent to the nitrogen atom in N-benzylureas and an N-allyl urea possessing a 2-alkynylphenyl group, and subsequent intramolecular reaction with an alkyne along with double-bond isomerization provided 2,3-disubstituted indoles.

Key words

C-H bond activation - directing group - indoles - iridium - ureas

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8

When a methoxy group was installed at the para position, the reaction gave a complex mixture.

9

Dehydrogenation from diethylurea group is a possible hydrogen source.