Synthesis of unsymmetrically disubstituted ethynes by the palladium/copper(I)-cocatalyzed sila-Sonogashira-Hagihara coupling reactions of alkynylsilanes with aryl iodides, bromides, and chlorides through a direct activation of a carbon-silicon bond

Yasushi Nishihara, Eiji Inoue, Shintaro Noyori, Daisuke Ogawa, Yoshiaki Okada, Masayuki Iwasaki, Kentaro Takagi

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22 Citations (Scopus)

Abstract

In this paper, we explore the copper/palladium-cocatalyzed cross-coupling reactions of 1-aryl-2-trimethylsilylethynes with aryl iodides, bromides, and chlorides as coupling partners, to furnish unsymmetrically disubstituted ethynes in moderate to excellent yields. Various aryl iodides were subjected to reaction under the optimized conditions with 5 mol % of Pd(PPh 3) 2 and 50 mol % of CuCl. The steric properties of the aryl iodide proved more influential to the outcome of the cross-coupling reaction than electronic factors. In addition, we succeeded in synthesizing unsymmetrical diarylethynes using two different aryl iodides in one-pot. Furthermore, under the same reaction conditions with 10 mol % of PdCl 2, 40 mol % of P(4-FC 6H 4) 3, and 50 mol % of CuCl as catalyst, we succeeded in synthesizing unsymmetrical diarylethynes from various aryl bromides. Finally, we explored reactions with aryl chlorides and duly discovered that unsymmetrical diarylethynes were obtainable in moderate to good yields when 10 mol % of Pd(OAc) 2, 10 mol % of (-)-DIOP, and 10 mol % of CuCl were used. These reactions proceed through a direct activation of a carbon-silicon bond in alkynylsilanes by CuCl to generate the corresponding alkynylcopper species via transmetalation from silicon to copper. Mechanistic investigations on the reaction of alkynylsilanes with aryl bromides confirmed that the trimethylsilyl bromide generated in situ retarded both transmetalation steps between CuCl and alkynylsilane, and between palladium(II) species formed by oxidative addition and alkynylcopper species.

Original languageEnglish
Pages (from-to)4869-4881
Number of pages13
JournalTetrahedron
Volume68
Issue number24
DOIs
Publication statusPublished - Jun 17 2012

Fingerprint

Acetylene
Palladium
Iodides
Silicon
Bromides
Chlorides
Copper
Carbon
Chemical activation
Cross Reactions
Catalysts

Keywords

  • Alkynylsilanes
  • C-Si bond activation
  • Copper
  • Palladium
  • Sonogashira-Hagihara coupling

ASJC Scopus subject areas

  • Biochemistry
  • Organic Chemistry
  • Drug Discovery

Cite this

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title = "Synthesis of unsymmetrically disubstituted ethynes by the palladium/copper(I)-cocatalyzed sila-Sonogashira-Hagihara coupling reactions of alkynylsilanes with aryl iodides, bromides, and chlorides through a direct activation of a carbon-silicon bond",
abstract = "In this paper, we explore the copper/palladium-cocatalyzed cross-coupling reactions of 1-aryl-2-trimethylsilylethynes with aryl iodides, bromides, and chlorides as coupling partners, to furnish unsymmetrically disubstituted ethynes in moderate to excellent yields. Various aryl iodides were subjected to reaction under the optimized conditions with 5 mol {\%} of Pd(PPh 3) 2 and 50 mol {\%} of CuCl. The steric properties of the aryl iodide proved more influential to the outcome of the cross-coupling reaction than electronic factors. In addition, we succeeded in synthesizing unsymmetrical diarylethynes using two different aryl iodides in one-pot. Furthermore, under the same reaction conditions with 10 mol {\%} of PdCl 2, 40 mol {\%} of P(4-FC 6H 4) 3, and 50 mol {\%} of CuCl as catalyst, we succeeded in synthesizing unsymmetrical diarylethynes from various aryl bromides. Finally, we explored reactions with aryl chlorides and duly discovered that unsymmetrical diarylethynes were obtainable in moderate to good yields when 10 mol {\%} of Pd(OAc) 2, 10 mol {\%} of (-)-DIOP, and 10 mol {\%} of CuCl were used. These reactions proceed through a direct activation of a carbon-silicon bond in alkynylsilanes by CuCl to generate the corresponding alkynylcopper species via transmetalation from silicon to copper. Mechanistic investigations on the reaction of alkynylsilanes with aryl bromides confirmed that the trimethylsilyl bromide generated in situ retarded both transmetalation steps between CuCl and alkynylsilane, and between palladium(II) species formed by oxidative addition and alkynylcopper species.",
keywords = "Alkynylsilanes, C-Si bond activation, Copper, Palladium, Sonogashira-Hagihara coupling",
author = "Yasushi Nishihara and Eiji Inoue and Shintaro Noyori and Daisuke Ogawa and Yoshiaki Okada and Masayuki Iwasaki and Kentaro Takagi",
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T1 - Synthesis of unsymmetrically disubstituted ethynes by the palladium/copper(I)-cocatalyzed sila-Sonogashira-Hagihara coupling reactions of alkynylsilanes with aryl iodides, bromides, and chlorides through a direct activation of a carbon-silicon bond

AU - Nishihara, Yasushi

AU - Inoue, Eiji

AU - Noyori, Shintaro

AU - Ogawa, Daisuke

AU - Okada, Yoshiaki

AU - Iwasaki, Masayuki

AU - Takagi, Kentaro

PY - 2012/6/17

Y1 - 2012/6/17

N2 - In this paper, we explore the copper/palladium-cocatalyzed cross-coupling reactions of 1-aryl-2-trimethylsilylethynes with aryl iodides, bromides, and chlorides as coupling partners, to furnish unsymmetrically disubstituted ethynes in moderate to excellent yields. Various aryl iodides were subjected to reaction under the optimized conditions with 5 mol % of Pd(PPh 3) 2 and 50 mol % of CuCl. The steric properties of the aryl iodide proved more influential to the outcome of the cross-coupling reaction than electronic factors. In addition, we succeeded in synthesizing unsymmetrical diarylethynes using two different aryl iodides in one-pot. Furthermore, under the same reaction conditions with 10 mol % of PdCl 2, 40 mol % of P(4-FC 6H 4) 3, and 50 mol % of CuCl as catalyst, we succeeded in synthesizing unsymmetrical diarylethynes from various aryl bromides. Finally, we explored reactions with aryl chlorides and duly discovered that unsymmetrical diarylethynes were obtainable in moderate to good yields when 10 mol % of Pd(OAc) 2, 10 mol % of (-)-DIOP, and 10 mol % of CuCl were used. These reactions proceed through a direct activation of a carbon-silicon bond in alkynylsilanes by CuCl to generate the corresponding alkynylcopper species via transmetalation from silicon to copper. Mechanistic investigations on the reaction of alkynylsilanes with aryl bromides confirmed that the trimethylsilyl bromide generated in situ retarded both transmetalation steps between CuCl and alkynylsilane, and between palladium(II) species formed by oxidative addition and alkynylcopper species.

AB - In this paper, we explore the copper/palladium-cocatalyzed cross-coupling reactions of 1-aryl-2-trimethylsilylethynes with aryl iodides, bromides, and chlorides as coupling partners, to furnish unsymmetrically disubstituted ethynes in moderate to excellent yields. Various aryl iodides were subjected to reaction under the optimized conditions with 5 mol % of Pd(PPh 3) 2 and 50 mol % of CuCl. The steric properties of the aryl iodide proved more influential to the outcome of the cross-coupling reaction than electronic factors. In addition, we succeeded in synthesizing unsymmetrical diarylethynes using two different aryl iodides in one-pot. Furthermore, under the same reaction conditions with 10 mol % of PdCl 2, 40 mol % of P(4-FC 6H 4) 3, and 50 mol % of CuCl as catalyst, we succeeded in synthesizing unsymmetrical diarylethynes from various aryl bromides. Finally, we explored reactions with aryl chlorides and duly discovered that unsymmetrical diarylethynes were obtainable in moderate to good yields when 10 mol % of Pd(OAc) 2, 10 mol % of (-)-DIOP, and 10 mol % of CuCl were used. These reactions proceed through a direct activation of a carbon-silicon bond in alkynylsilanes by CuCl to generate the corresponding alkynylcopper species via transmetalation from silicon to copper. Mechanistic investigations on the reaction of alkynylsilanes with aryl bromides confirmed that the trimethylsilyl bromide generated in situ retarded both transmetalation steps between CuCl and alkynylsilane, and between palladium(II) species formed by oxidative addition and alkynylcopper species.

KW - Alkynylsilanes

KW - C-Si bond activation

KW - Copper

KW - Palladium

KW - Sonogashira-Hagihara coupling

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