Discovery of A Novel Palladium Catalyst for the Preparation of Enynes with a Copper- and Ligand-Free Sonogashira Reaction

Xia Mi; Mengmeng Huang; Yujian Feng; Yangjie Wu

doi:10.1055/s-0031-1290938

Synlett, Inhaltsverzeichnis

Synlett 2012; 23(8): 1257-1261
DOI: 10.1055/s-0031-1290938

letter

Discovery of A Novel Palladium Catalyst for the Preparation of Enynes with a Copper- and Ligand-Free Sonogashira Reaction

Autor*innen

Xia Mi

Chemistry Department, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, P. R. of China, Fax: +86(371)67979408 eMail: wyj@zzu.edu.cn eMail: hmm@zzu.edu.cn
Mengmeng Huang*

Chemistry Department, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, P. R. of China, Fax: +86(371)67979408 eMail: wyj@zzu.edu.cn eMail: hmm@zzu.edu.cn
Yujian Feng

Chemistry Department, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, P. R. of China, Fax: +86(371)67979408 eMail: wyj@zzu.edu.cn eMail: hmm@zzu.edu.cn
Yangjie Wu*

Chemistry Department, Henan Key Laboratory of Chemical Biology and Organic Chemistry, Key Laboratory of Applied Chemistry of Henan Universities, Zhengzhou University, Zhengzhou 450052, P. R. of China, Fax: +86(371)67979408 eMail: wyj@zzu.edu.cn eMail: hmm@zzu.edu.cn

Abstract

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Abstract

A new palladium(II) complex based on N,N-dimethylethanolamine, (SP-4-1′)-bis[N,N-dimethylaminoethoxy-kN,O]palladium(II) which coordinates with two moles of AcOH, has been synthesized. The structure of the complex has been established by X-ray diffraction analysis. Using this complex as a catalyst, a series of conjugated enynes were successfully synthesized by Sonogashira cross-coupling reaction in the absence of co-catalyst CuX and any ligand at room temperature during 20 hours affording the corresponding products in moderate to excellent yields. The optimized catalytic systems are tolerant in the presence of a broad variety of functional groups in the substrates. The catalytic system was found to be ineffective for vinyl chloride. Moreover, it was found that (Z)-β-bromostyrene reacts with terminal alkynes with retention of the steric configuration and the transformation of most of the Z-isomer did not occur in this reaction.

Key words

N,N-dimethylethanolamine - copper-free - ligand-free - Sonogashira reaction - enyne - β-bromostyrene - stereochemistry

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Referenzen

References

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17 Synthesis of (Me₂NCH₂CH₂O)₂Pd⋅2AcOH: A solution of Me₂NCH₂CH₂OH (0.24 g, 2.68 mmol) in toluene (10 mL) was add to a stirred solution of Pd(OAc)₂ (0.3 g, 1.34 mmol) in toluene (10 mL), and the mixture was stirred at r.t. After 2 d all volatiles were removed under reduced pressure to give 2 as a yellow crystalline solid. Yield: 0.54 g (80%); mp 93–95 °C. ¹H NMR (400 MHz, C₆D₆): δ = 1.92–2.00 (m, 4 H, CH₂N), 2.01 (s, 6 H, CH ₃COOH), 2.17 (s, 12 H, CH₃N), 3.37–3.75 (m, 4 H, CH₂O), 11.00–11.15 (br s, 2 H, CH₃COOH). ¹³C NMR (100 MHz, C₆H₆): δ = 22.08 (CH₃COOH), 49.63 (CH₃N), 63.87 (CH₂N), 68.50 (CH₂O), 174.27 (C=O). Anal. Calcd for C₈H₂₀N₂O₂Pd⋅2AcOH: C, 35.78; H, 7.01; N, 6.96. Found: C, 35.20; H, 6.79; N, 6.88
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