Ruthenium-Catalyzed E-Selective Alkyne Semihydrogenation with Alcohols as Hydrogen Donors

Andreas Ekebergh,Romain Begon,Nina Kann

doi:10.1021/acs.joc.9b02721

Andreas Ekebergh, Romain Begon + Show 1 more

Open Access

https://doi.org/10.1021/acs.joc.9b02721

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Abstract

Selective direct ruthenium-catalyzed semihydrogenation of diaryl alkynes to the corresponding E-alkenes has been achieved using alcohols as the hydrogen source. The method employs a simple ruthenium catalyst, does not require external ligands, and affords the desired products in > 99% NMR yield in most cases (up to 93% isolated yield). Best results were obtained using benzyl alcohol as the hydrogen donor, although biorenewable alcohols such as furfuryl alcohol could also be applied. In addition, tandem semihydrogenation–alkylation reactions were demonstrated, with potential applications in the synthesis of resveratrol derivatives.

Highlights

The alkene motif is present in a variety of important molecules, including natural products, pharmaceuticals, and fragrances (Figure 1).1 Stereoselective installation of this functionality system in the latter case
While benzyl alcohol gave the most favorable E-selectivity and conversion, renewable alcohols such as furfuryl alcohol could be applied as hydrogen donors with good results
Reactions were monitored by thin-layer chromatography carried out on 0.25 mm E

Summary

Introduction

The alkene motif is present in a variety of important molecules, including natural products, pharmaceuticals, and fragrances (Figure 1). Stereoselective installation of this functionality system in the latter case. The alkene motif is present in a variety of important molecules, including natural products, pharmaceuticals, and fragrances (Figure 1).. The alkene motif is present in a variety of important molecules, including natural products, pharmaceuticals, and fragrances (Figure 1).1 Stereoselective installation of this functionality system in the latter case. An inexpensive and sustainable alcohol (ethanol) is used as the hydrogen source. A few accounts of direct ruthenium-based E-selective semihydrogenations of alkynes have been published in the past decade (Scheme 1).. Ruthenium-Catalyzed Methods for Alkyne Semihydrogenation to E-Alkenes

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Results

Conclusion