Hydrometallation of alkenes and alkynes with magnesium hydride

Ashby, E. C.; Smith, T. N.

doi:10.1039/c3978000030b

Cited by 39 publications

(11 citation statements)

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“…[140] The hydromagnesiation reaction of olefins 267 can be an attractive alternative to standard methods for the synthesis of Grignard reagents 268 if the required alkyl or vinyl halides are not readily synthesised or if they contain functional groups incompatible with Grignard reagent formation. The reaction of MgH 2 with alkenes is inefficient, [141] and although titanium and zirconium salts can be used to catalyse this reaction, [142] the most common approach is to use a Grignard reagent 269 bearing b-hydrogen atoms as a superficial source of "HÀMgX" (Scheme 59 A). An equivalent of alkene 270 is produced as a by-product, and thus the reaction is generally reversible and thermodynamically driven.…”

Section: Hydromagnesiationmentioning

confidence: 99%

Iron‐Catalysed Hydrofunctionalisation of Alkenes and Alkynes

2014

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The metal‐catalysed hydrofunctionalisation of alkenes and alkynes provides a convenient and atom‐economic route to diversely functionalised products with control of regio‐, chemo‐ and stereoselectivity. As one of the most abundant elements on earth, iron offers a level of sustainable and long‐term availability that is uncommon for most transition metals. Although iron is commonly found in the oxidation states of +2 and +3, the use of redox‐active ligands has allowed the synthesis and application of low oxidation state iron complexes in catalysis. A broad range of hydrofunctionalisation reactions have been developed by using iron catalysts in a wide variety of oxidation states. Intense development over the past decade has resulted in the development of iron‐catalysed hydroamination, hydroalkoxylation, hydrocarboxylation, hydrothiolation, hydrovinylation, hydrosilylation, hydroboration, hydrophosphination, hydromagnesiation and carbonylation reactions, amongst others. With the field still in its infancy, there is great potential for further developments in the mechanistic understanding and synthetic and industrial applicability of these processes.

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Section: Hydromagnesiationmentioning

confidence: 99%

Iron‐Catalysed Hydrofunctionalisation of Alkenes and Alkynes

2014

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“…Magnesium hydride, generated in situ from metallic magnesium Mg and H 2 , adds to ethene, isobutene and 1 -octene to give the corresponding magnesium dialkyls in yields of 4 -13%. Meanwhile, the reaction of α -and 1,1 -(or l,2) -disubstituted alkenes with MgH 2 in the presence of catalytic amounts of Cp 2 TiCl 2 in THF, molar ratio alkene : MgH 2 : [Ti] of 2 : 3: 0.05, under mild conditions (from 20 to 60 ° C) was found to afford the magnesium alkyl derivatives in high yields [185] . The system CrCl 3 · [Mg -anthracene] (1 : 1) in THF has been recommended as a promoter for the synthesis of magnesium hydride complexes (HMgCl · MgH 2 or 2HMgCl · MgH 2 ) [186,187] .…”

Section: Catalytic Hydromagnesiation 473mentioning

confidence: 99%

“…The direction and selectivity of this reaction depend on the nature of the catalyst, the structure of the starting alkyne and the hydromagnesiation reagent used. Hydromagnesiation of disubstituted acetylenes with MgH 2 [185] , MgH 2 · CuI, MgH 2 · CuO -t -Bu [212] or i -BuMgHal [171,213] in the presence of catalytic amounts of Cp 2 TiCl 2 was found to yield alkenylmagnesium compounds (78) or (79) with E -double bonds (Scheme 18.81 ).…”

Section: Alkynesmentioning

confidence: 99%

“…Vinylic OMCs synthesized by the hydromagnesiation of disubstituted acetylenes were used in the selective synthesis of ( Z ) - [185,222,223] and ( E ) -alkenes [224] , terpenoids [225] , ( E ) -allylic alcohols [226,227] , ( Z ) -α , β -unsaturated ketones [228] , substituted furans [229,230] , biologically active compounds and fragrances (Scheme 18.84 ) [215, 231 -234] .…”

Section: Catalytic Hydromagnesiation 479mentioning

confidence: 99%

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Hydrometallation of Unsaturated Compounds

Джемилев

Ибрагимов

2008

Modern Reduction Methods

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18 IntroductionTo the number of signifi cant hydrometallating reagents that have been introduced into organic synthesis should be added the stable hydrides of transition metals (Zr) and nontransition metals (B, Al, Mg).Today, hydrides of the these metals and their derivatives are widely used in the reduction of alkenes, dienes, alkynes, allenes, heteroolefi ns and carbonyl compounds as well as for the production of the corresponding organometallic compounds and selective alkene functionalization via the synthesis of compounds containing polar metal -carbon (M − C) bonds. These may be involved in reactions with electrophilic or nucleophilic reagents affording functional derivatives.Generally, the thermal additions of the above hydrides to alkenes proceed via the four -center transition state (1) , with subsequent cleavage of the M − H bond and metal addition. In this case the corresponding organometallic compounds are formed according to Scheme 18.1 .The use of metal complex catalysts in organic and metalloorganic chemistry allows the chemo -, regio -and stereoselective hydroalumination of unsaturated compounds under mild conditions with high yields.The role of a transition metal catalyst in these reactions is determined by its ability to activate the starting substrate by coordination to the metal center forming the intermediate hydride complex (2) . The latter, being a more active hydrometallating reagent, attacks alkenes under mild conditions with subsequent transmetallation of the starting hydride affording the target organic compound (3) according to Scheme 18.2 .To date, a large number of reports have appeared in the literature on the application of hydride reagents in both thermal and catalytic hydrometallation of unsaturated compounds. Hydroboration, hydroalumination, hydrozirconation and hydromagnesiation of unsaturated compounds such as alkenes, dienes or alkynes are considered the most effective reactions for producing the related metalloorganic compounds. It is not possible to consider all these reactions within the

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“…2 The successful hydridomagnesiation of alkenes, therefore, would present an attractive but, as yet, underexploited route to Mg-C bond formation, particularly in cases when the use of ether solvents or the presence of residual halide is disadvantageous. Although the transition metal promoted addition of alkenes to MgH 2 has been described, [3][4][5][6][7][8][9] and a signicant number of well-dened Mg-H bonded species have now been reported, 10 the rst fully authenticated example of the direct insertion of an olen into the Mg-H bond of any molecular compound was only provided by Parkin and coworkers in 2017. 11 In this case, reaction of the terminal magnesium hydride derivative, [Tism i-PrBenz ]MgH (1, Tism i-…”

Section: Introductionmentioning

confidence: 99%