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. 2022 May 23;61(22):e202112101.
doi: 10.1002/anie.202112101. Epub 2022 Mar 29.

Hydrazone and Oxime Olefination via Ruthenium Alkylidenes

Daniel J Nasrallah  1 , Troy E Zehnder  1 , Jacob R Ludwig  1 , Daniel C Steigerwald  1 , John J Kiernicki  1   2 , Nathaniel K Szymczak  1 , Corinna S Schindler  1
Affiliations

Hydrazone and Oxime Olefination via Ruthenium Alkylidenes

Daniel J Nasrallah et al. Angew Chem Int Ed Engl. .

Abstract

We describe the development of an efficient method for the olefination of hydrazones and oximes. The key design approach that enables this transformation is tuning of the energy/polarity of C=N π-bonds by employing heteroatom functionalities (NR2 , OR). The resulting hydrazones or oximes facilitate olefination with ruthenium alkylidenes. Through this approach, we show that air-stable, commercially available ruthenium alkylidenes provide access to functionalized alkenes (20 examples) in ring-closing reactions with yields up to 88 %.

Keywords: Alkylidenes; Hydrazones; Olefination; Oximes; Ruthenium.

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Conflict of interest statement

Conflicts of Interest

The authors declare no conflicts of interest.

Figures

Figure 1.
Figure 1.
A. Alkene formation via metal alkylidenes. B. Literature precedent for imine-alkylidene cross metathesis. C. Ruthenium-mediated olefination of hydrazones and oximes developed herein.
Figure 2.
Figure 2.
Design rationale for imine-olefin metathesis based on literature precedent in carbonyl-olefin metathesis relying on metal alkylidenes.
Figure 3.
Figure 3.
Robustness of the ruthenium-mediated olefination of hydrazones and oximes.
Figure 4.
Figure 4.
Divergent reactivity of carbonyls and oximes with Schrock’s complex (73), HG-2 (20), and Tebbe’s reagent (74) to enable selective carbonyl-olefin metathesis, oxime olefination, and carbonyl olefination. [a] Yield determined by 1H-NMR using phenyltrimethylsilane as internal standard. [b] Yield relative to equivalents of HG-2 (20) used. [c] Isolated as mixture of alkene isomers.
Figure 5.
Figure 5.
Isolation of a ruthenium derivative formed.
See this image and copyright information in PMC

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