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Synlett 2011(7): 911-914  
DOI: 10.1055/s-0030-1259699
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Palladium-Catalyzed, One-Pot, Three-Component Approach to α-Alkynyl Indoles from o-Bromo-(2,2-dibromovinyl)benzenes, Terminal Alkynes and Arylamines

Yun Lianga,b, Tianhao Menga, Hui-Jun Zhanga, Zhenfeng Xi*a,c
a Beijing National Laboratory for Molecular Sciences (BNLMS), Key Laboratory of Bioorganic Chemistry and Molecular Engineering of Ministry of Education, College of Chemistry, Peking University, Beijing 100871, P. R. of China
Fax: +86(10)62759728; e-Mail: zfxi@pku.edu.cn;
b Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research, Ministry of Education, Hunan Normal University, Changsha, Hunan 410081, P. R. of China
c State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, P. R. of China
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Publication History

Received 11 October 2010
Publication Date:
08 March 2011 (online)

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Abstract

α-Alkynyl indoles were efficiently synthesized in one pot from o-bromo-(2,2-dibromovinyl)benzenes, terminal alkynes, and arylamines via a palladium-catalyzed three-component coupling process.

Key words

multi-component coupling - o-halo-(2,2-dihalovinyl)-benzene - alkyne - arylamine - indole - palladium-catalyzed reaction

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Typical Procedure for the preparation of α-alkynyl-indole 4a: Under the protection of nitrogen, Pd(OAc)2 (5 mol%) and Xantphos (10 mol%) were added to NMP (2 mL). The reaction mixture was stirred at r.t. for 15 min, then o-bromo-2-(2,2-dibromovinyl)benzene (0.4 mmol), phenylacetylene (0.4 mmol), and aniline (0.3 mmol) were added and the reaction mixture was stirred at 120 ˚C for 5 h. The reaction mixture was quenched with water and extracted with Et2O. The organic extract was washed with brine and dried over MgSO4. The solvent was then evaporated in vacuo and the residue was purified by using a SiO2 column (petroleum ether-ethyl acetate, 100:1) to afford 1-phenyl-2-(phenylethynyl)-1H-indole (4a) as a colorless solid (80%, 70 mg). ¹H NMR (400 MHz, CDCl3): δ = 6.99 (s, 1 H), 7.12-7.16 (m, 1 H), 7.17-7.22 (m, 4 H), 7.27-7.30 (m, 3 H), 7.38 (t, J = 8.0 Hz, 1 H), 7.46-7.54 (m, 4 H), 7.62 (d, J = 7.2 Hz, 1 H); ¹³C NMR (100 MHz, CDCl3): δ = 81.78, 95.25, 109.35, 110.48, 120.89, 120.95, 121.88, 122.64, 123.63, 127.25, 127.49, 127.56, 128.25, 128.30, 128.95, 131.04, 137.47, 137.56; HRMS (ESI): m/z calcd for C22H16N+: 294.1277; found: 294.1274