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Synlett 2011(16): 2420-2424  
DOI: 10.1055/s-0030-1261229
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

A NHC-Involved, Cascade, Metal-Free, and Three-Component Synthesis of 2,3-Diarylated Fully Substituted Furans under Solvent-Free Conditions

Chenxia Yua, Jun Lua, Tuanjie Lia, Donglin Wanga, Binbin Qina, Honghong Zhanga, Changsheng Yao*b
a School of Chemistry and Engineering, Jiangsu Key Laboratory of Green Synthetic Chemistry for Functional Materials, Xuzhou Normal University, Xuzhou, Jiangsu 221116, P. R. of China
b School of Chemistry and Engineering, Key Laboratory of Biotechnology for Medicial Plant, Xuzhou Normal University, Xuzhou, Jiangsu 221116, P. R. of China
Fax: +86(516)83500365; e-Mail: csyao@xznu.edu.cn;
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Publication History

Received 14 July 2011
Publication Date:
08 September 2011 (online)

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Abstract

An efficient synthesis of 2,3-diarylated fully substituted furans was performed through the sequential reactions of Knoevenagel reaction, Stetter reaction catalyzed by NHC, and intramolecular cyclization under solvent-free conditions. The protocol has the advantages of easy workup, high yields, and an environmental benign procedure compared with the reported methods.

Key words

NHC - fully substituted furans - umpolung - solvent-free synthesis - multicomponent reaction

    Primary data for this article are available online and can be cited using the following DOI: 10.4125/pd0016th:
  • Primary Data
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General Procedure for the Synthesis of 5 Aryl aldehyde 1 (1 mmol), DBU (0.35 mmol), and malononitrile 2 (1 mmol) were triturated together in an agate mortar with a pestle for 5 min. Then the mixture was kept at 55 ˚C for a certain time (monitored by TLC). After addition of another aryl aldehyde (1 mmol), sulfamethiazole salt (0.15 mmol) was added and mixed thoroughly by grinding at 55 ˚C. The reaction mixture was mixed by grinding every half an hour with a pestle and mortar during 1-5 h reaction time (monitored by TLC). The resultant mixture was cooled to r.t., purified through column chromatography using acetone and PE (1:5) as the eluent, to give pure product 5a-o.

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Characterization Data of Representative Compounds 5a
Yield 90%, white solid, mp 205-206 ˚C (reported 204-206 ˚C). IR (KBr): νmax = 3467, 3443, 2216, 1653, 1455, 1067, 763, 694 cm-¹. ¹H NMR (400 MHz, DMSO-d 6): δ = 7.17-7.27 (m, 5 H, ArH), 7.38-7.47 (m, 5 H, ArH). 7.75 (s, 2 H, NH2) ppm. ¹³C NMR (100 MHz, DMSO-d 6): δ = 163.5, 136.6, 131.2, 129.4, 129.0, 128.8, 128.6, 128.3, 126.9, 124.2, 121.8, 115.5, 69.2 ppm. ESI-HRMS: m/z calcd for C17H11N2O [M - H]-: 259.0871; found: 259.0871.