Magnesium-catalyzed hydrosilylation of α,β-unsaturated esters

Lampland, Nicole L.; Pindwal, Aradhana; Neal, Steven R.; Schlauderaff, Shealyn; Ellern, Arkady; Sadow, Aaron D.

doi:10.1039/c5sc02435h

Cited by 51 publications

(36 citation statements)

References 66 publications

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“…The stability of complexes 3 a and 3 b in solution is limited as they are very sensitive towards moisture. Thus, 1 H NMR spectra of 3 a or 3 b , respectively, in the presence of H 2 O, show a new set of 1 H NMR signals, which can be attributed to HL H 2 , the protonated ligand with a reduced C=N moiety, underscoring the reactivity of the hydridoborate anion . Infrared spectroscopy of 3 a and 3 b revealed no assignable Mo=O stretch.…”

Section: Resultssupporting

confidence: 82%

Heterolytic Si−H Bond Cleavage at a Molybdenum‐Oxido‐Based Lewis Pair

Zwettler

Walg

Belaj

et al. 2018

Chemistry A European J

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The reaction of a molybdenum(VI) oxido imido complex with the strong Lewis acid B(C6F5)3 gave access to the Lewis adduct [Mo{OB(C6F5)3}(NtBu)L2] featuring reversible B−O bonding in solution. The resulting frustrated Lewis pair (FLP)‐like reactivity is reflected by the compound's ability to heterolytically cleave Si−H bonds, leading to a clean formation of the novel cationic MoVI species 3 a (R=Et) and 3 b (R=Ph) of the general formula [Mo(OSiR3)(NtBu)L2][HB(C6F5)3]. These compounds possess properties highly unusual for molybdenum d0 species such as an intensive, charge‐transfer‐based color as well as a reversible redox couple at very low potentials, both dependent on the silane used. Single‐crystal X‐ray diffraction analyses of 2 and 4 b, a derivative of 3 b featuring the [FB(C6F5)3]− anion, picture the stepwise elongation of the Mo=O bond, leading to a large increase in the electrophilicity of the metal center. The reaction of 3 a and 3 b with benzaldehyde allowed for the regeneration of compound 2 by hydrosilylation of the benzaldehyde. NMR spectroscopy suggested an unusual mechanism for the transformation, involving a substrate insertion in the B−H bond of the borohydride anion.

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Section: Resultssupporting

confidence: 82%

Heterolytic Si−H Bond Cleavage at a Molybdenum‐Oxido‐Based Lewis Pair

Zwettler

Walg

Belaj

et al. 2018

Chemistry A European J

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“…Encouraged by these promising results, we investigated catalytic reductions of these ketones by a silane as the hydride source(Table ) . To the best of our knowledge, only one example of a magnesium‐catalysed hydrosilylation has been reported to date, which is the 1,4‐addition of Ph 2 SiH 2 to α,β‐unsaturated esters in the presence of a sterically demanding magnesium hydridoborate . Thus, we attempted the hydrosilylation of our previous two substrates with PhSiH 3 in varying stoichiometries in the presence of catalytic amounts of 5 .…”

Section: Resultsmentioning

confidence: 99%

Ring‐Shaped Phosphinoamido‐Magnesium‐Hydride Complexes: Syntheses, Structures, Reactivity, and Catalysis

Fohlmeister

Stasch

2016

Chemistry A European J

114

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A series of magnesium(II) complexes bearing the sterically demanding phosphinoamide ligand, L(-) =Ph2 PNDip(-) , Dip=2,6-diisopropylphenyl, including heteroleptic magnesium alkyl and hydride complexes are described. The ligand geometry enforces various novel ring and cluster geometries for the heteroleptic compounds. We have studied the stoichiometric reactivity of [(LMgH)4 ] towards unsaturated substrates, and investigated catalytic hydroborations and hydrosilylations of ketones and pyridines. We found that hydroborations of two ketones with pinacolborane using various Mg precatalysts is very rapid at room temperature with very low catalyst loadings, and ketone hydrosilylation using phenylsilane is rapid at 70 °C. Our studies point to an insertion/σ-bond metathesis catalytic cycle of an in situ formed "MgH2 " active species.

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“…[25] a,b-Unsaturated esters were reduced efficientlyw ith silanes catalyzed by magnesium hydridoborate complex 5b,w hich is similart ot he Hill complex 1e.C atalyst 5b was prepared by the reactiono f5a with phenylsilane and B(C 6 F 5 ) 3 (Scheme14). [25] a,b-Unsaturated esters were reduced efficientlyw ith silanes catalyzed by magnesium hydridoborate complex 5b,w hich is similart ot he Hill complex 1e.C atalyst 5b was prepared by the reactiono f5a with phenylsilane and B(C 6 F 5 ) 3 (Scheme14).…”

Section: Hydrosilylationmentioning

confidence: 96%

“…Proposed mechanism for the hydroboration of isonitriles with pinacolb orane with magnesium hydride 1c as key species. [25] Scheme15. The Hill catalyst 1e and its application in the reduction of CO 2 .…”

Section: Hydrosilylationmentioning

confidence: 99%

Recent Developments in Homogeneous Organomagnesium Catalysis

et al. 2015

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Stoichiometric organomagnesium chemistry has continually progressed since its initiation by Victor Grignard over one century ago. Other than acting as a Lewis acid, however, homogeneous magnesium catalysis is a rare topic in the literature. Magnesium catalysts that govern reactions within the coordination sphere of magnesium have only recently begun to appear. This Concept covers recent progress in this young but potentially powerful new chapter of magnesium chemistry.

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Magnesium-catalyzed hydrosilylation of α,β-unsaturated esters

Abstract: A magnesium hydridoborate compound catalyzes the 1,4-hydrosilylation of α,β-unsaturated esters to give silyl ketene acetals.

Cited by 51 publications

References 66 publications

Heterolytic Si−H Bond Cleavage at a Molybdenum‐Oxido‐Based Lewis Pair

Heterolytic Si−H Bond Cleavage at a Molybdenum‐Oxido‐Based Lewis Pair

Ring‐Shaped Phosphinoamido‐Magnesium‐Hydride Complexes: Syntheses, Structures, Reactivity, and Catalysis

Recent Developments in Homogeneous Organomagnesium Catalysis

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