What Can You Add To A Grignard Reagent

Haloalkanes and Alcohols

Robert J. Ouellette , J. David Rawn , in Organic Chemistry, 2014

Grignard Reagents

Haloalkanes and other compounds with the element of group vii atom bonded to either sp³-hybridized or sp^two-hybridized carbon atoms (aryl and vinyl halides) react with magnesium metal to yield organomagnesium halides called Grignard reagents . Grignard reagents are usually prepared in diethyl ether (CH₃CH_iiO─CH₂CH_three). An ether solvent is essential for the reaction. The French chemist Victor Grignard discovered this reaction in 1900, and it has been studied and used extensively e'er since.

Grignard reagents class hands from one°, 2°, and 3° alkyl halides, although their reactivities differ. Aryl and vinyl halides react somewhat more slowly, and the cyclic ether tetrahydrofuran (THF) is required to prepare Grignard reagents of these compounds. The higher boiling point of the cyclic ether provides more vigorous reaction weather, but the rate of the reaction also increases because THF solvates the Grignard reagent better than diethyl ether.

Molecular model of a complex of methyl-magnesium chloride, a Grignard reagent, in which two molecules of tetrahydrofuran, THF, are leap to magnesium. The model is based on the crystal structure.

The order of reactivity of the halogens in haloalkanes is I > Br > CI > > F. Organofluorides are and so unreactive that they are never used to ready Grignard reagents. Organohalogen compounds containing bromine and chlorine are readily available, and are commonly used to fix Grignard reagents. Grignard reagents are used synthetically to form new carbon–carbon bonds. A Grignard reagent has a very polar carbon–magnesium bond in which the carbon atom has a partial negative accuse and the metal a partial positive charge.

The polarity of the carbon–magnesium bond is opposite that of the carbon–element of group vii bond of haloalkanes. Because the carbon atom in a Grignard reagent has a partial negative charge, it resembles a carbanion, and it reacts with electrophilic centers such as the carbonyl carbon cantlet of aldehydes, ketones, and esters. Nosotros volition discuss this chemistry extensively in subsequently chapters.

Grignard reagents react rapidly with acidic hydrogen atoms in molecules such as alcohols and water. When a Grignard reagent reacts with water, a proton replaces the halogen, and the product is an alkane. The Grignard reagent therefore provides a pathway for converting a haloalkane to an alkane in two steps.

Trouble 9.7

Devise a synthesis of CH₃CH₂CHDCH₃ starting from ane-butene and heavy water (D_twoO).

Sample Solution

Reaction of a Grignard reagent, RMgBr, with D ₂O volition yield R─D. The necessary Grignard reagent is obtained from the respective bromoalkane, RBr.

The required ii-bromobutane can be prepared from 1-butene past adding HBr. This reaction occurs according to Markovnikov'southward rule, and a hydrogen atom adds to the less substituted carbon cantlet of the double bond.

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Alcohols

Robert J. Ouellette , J. David Rawn , in Organic Chemistry, 2014

15.10 Alcohol Synthesis Using Grignard Reagents

Haloalkanes and aryl and vinyl halides react with magnesium metal to yield organomagnesium halides chosen Grignard reagents . An ether solvent, usually diethyl ether, is required for preparation of Grignard reagents. The French chemist Victor Grignard discovered this reaction over a century agone in 1900. Grignard reagents are powerful tools for the synthesis of alcohols.

A Grignard reagent has a very polar carbon–magnesium bond in which the carbon atom has a partial negative charge and magnesium has a partial positive charge. Considering the carbon atom in a Grignard reagent has a partial negative charge, it resembles a carbanion, and information technology reacts with electrophilic centers such as the carbonyl carbon atom of aldehydes, ketones, and esters. We will discuss this chemistry in the next section.

Grignard reagents form easily from 1°, 2°, and 3° alkyl halides. Aryl and vinyl halides react somewhat more than slowly, and the circadian ether tetrahydrofuran (THF) is oft used to prepare Grignard reagents of these compounds. The higher boiling indicate of the circadian ether provides more than vigorous reaction conditions, just the rate of the reaction is also increased because THF solvates the Grignard reagent better than diethyl ether. The solvent, either diethyl ether or THF, is an essential component of the reaction.

Grignard reagents react rapidly with acidic hydrogen atoms in molecules such as alcohols and h2o. When a Grignard reagent reacts with water, a proton replaces the element of group vii, and the product is an alkane. The Grignard reagent therefore provides a pathway for converting a haloalkane to an methane series in 2 steps. If the second step of this procedure is carried out in D_twoO, deuterium is introduced into the compound at the position initially occupied by the halogen.

Synthesis of Alcohols Using Grignard Reagents

Grignard reagents add to carbonyl compounds to give primary, secondary, and tertiary alcohols. A primary alcohol is synthesized by reacting the Grignard reagent, R′─MgX, with formaldehyde.

Reacting a Grignard reagent with an aldehyde gives a secondary alcohol.

Reacting a Grignard reagent with a ketone gives a tertiary booze.

Limitations of the Grignard Reaction

We call back that Grignard reagents cannot be made if acidic functional groups are also present in the halogen compound. The Grignard reagent is destroyed past reaction with acidic hydrogen atoms of water, alcohols, phenols, or carboxylic acid groups.

For the same reason, we must consider the structure of the carbonyl compound selected for reaction with a Grignard reagent. If the carbonyl chemical compound too contains a hydroxyl group, the fastest reaction will exist the devastation of the added Grignard reagent by protonation.

Alcohol Protecting Groups

Many ways have been devised to protect acidic groups, such as an hydroxyl group, that would interfere with Grignard reactions. I of the simplest is conversion of an alcohol to a silyl ether.

To foreclose the production of HCl, the reaction is carried out along with an amine catalyst, which is converted to an ammonium table salt.

After the alcohol has been protected, a Grignard reaction is possible. In the second footstep of the reaction, when the magnesium salt is hydrolyzed, the silyl ether is hydrolyzed too.

Acetylenic Alcohols

Alkynide ions react with carbonyl groups in much the same way as Grignard reagents do. We remember that these ions are effective nucleophiles that will readapt a halide ion from an alkyl halide to requite an alkylated alkyne. The alkynides are prepared in an acid–base reaction with acetylene or a concluding alkyne using sodium amide in ammonia. If a carbonyl compound is so added to the reagent, an alcohol forms after acid work-up. If the alkynide is derived from acetylene, an acetylenic alcohol forms.

We can likewise produce alkynides without using liquid ammonia. Nosotros recall that alkynes are more acidic than alkanes. Therefore, the acid–base reaction of an alkyne with a readily available Grignard reagent gives a Grignard reagent of the alkyne. This alkynide ion of the Grignard reagent reacts with carbonyl compounds.

Trouble 15.twenty

The European bark beetle produces a pheromone that causes beetles to congregate. Depict two ways that the compound could be synthesized by a Grignard reagent.

Problem fifteen.21

Write the structures of the two products obtained by reaction of iv-tert-buty1cyclohexanone with sodium acetylide. Predict which one is obtained in the larger amount.

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Ethers and Epoxides

Robert J. Ouellette , J. David Rawn , in Principles of Organic Chemical science, 2015

nine.4 The Grignard Reagent and Ethers

Ethers such as diethyl ether or tetrahydrofuran are excellent solvents for certain reagents that would otherwise react with protons supplied by protic solvents. 1 such example is the Grignard reagent , represented as R—Mg—Ten, which can be prepared from haloalkanes besides every bit from aryl halides.

The oxygen cantlet of diethyl ether (or THF) forms a complex with the magnesium atom of the Grignard reagent. These reagents in ether solution are very usefUl in organic synthesis.

The French pharmacist Victor Grignard received the Nobel Prize in 1912 for developing the methods to fix these organomagnesium compounds. In a Grignard reagent, the R group may exist a 1°, ii°, or 3° alkyl group also as a vinyl or aryl group. The halogen may be Cl, Br, or I. Fluorine compounds do not form Grignard reagents.

A Grignard reagent has a very polar carbon-magnesium bond in which the carbon atom has a partial negative accuse and the metallic a partial positive accuse.

This bond polarity is opposite that of the carbon-halogen bond of haloalkanes. Because the carbon atom in a Grignard reagent has a partial negative charge, it resembles a carbanion, and it reacts with electrophiles. Grignard reagents are very reactive reactants that are used synthetically to course new carbon-carbon bonds. We will discuss these reactions in Section ten.6.

Grignard reagents react quickly with acidic hydrogen atoms in molecules such as alcohols and h2o to produce alkanes. Thus, formation of the Grignard reagent followed by reaction with water provides a way to convert a haloalkane to an alkane in two steps.

Problem 9.3

Devise a synthesis of CH₃CH₂CHDCH₃ starting from 1-butene and "heavy water" (D₂O).

Solution

Reaction of a Grignard reagent R—MgBr with D _iiO yields R—D. The necessary Grignard reagent is obtained from the respective bromoalkane R—Br.

The required ii-bromobutane can exist prepared from 1-butene by adding HBr. This reaction occurs according to Markovnikov'south rule; that is, a hydrogen atom adds to the less substituted carbon atom of the double bail.

Problem 9.4

Devise a synthesis of the following compound starting from benzene.

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Synthesis: Carbon with Two Heteroatoms, Each Fastened by a Single Bond

Christopher G. Barber , in Comprehensive Organic Functional Group Transformations, 1995

4.14.two.one.1.(iii).(b) By add-on of a Grignard reagent to a vinylsilane

Grignard reagents will add to vinyl silanes to generate the corresponding α-magnesiosilyl alkanes ( Equation (85)). Equally with the preparation of α-lithiosilyl alkanes above, the reaction is sensitive to the reagents used. Good yields for addition to the vinyl group were just accomplished with either chloro or alkoxide groups on silicon single bond presumably every bit a event of reducing the electron density of the double bond. Displacement of the halide or alkoxy group on silicon simply became significant when either a primary Grignard reagent was used or more than one halide or alkoxy group was present <70JA7424>. Amino groups on silicon take also been shown to facilitate the Grignard reagent improver <84TL1905>. The add-on of Grignard reagents to trimethyl(vinyl)silane has been reported when forcing weather condition were used <84CB383>.

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Intramolecular addition of a Grignard reagent to a vinyl silane gave a highly diastereoselective synthesis of the cyclopentane ( 289 ) which could be quenched in loftier yield with an electrophile (Equation (86)) <85TL2101>.

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The addition of an organomagnesium reagent to the silylated α,β-amidate anion of ( 290 ) resulted in the generation of an α-magnesio-α-silylamide (Scheme 60). The normal i,2-improver of the Grignard reagent to the carbonyl grouping was suppressed past the α-anion generated during the reaction. As with the addition of organolithium reagents described higher up, the reaction was sensitive to exchange on the β-carbon of the vinylic grouping <93JOC7474>.

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Synthesis: Carbon with No Attached Heteroatoms

Alan Armstrong , in Comprehensive Organic Functional Grouping Transformations, 1995

one.07.3.2.3.(ii) Organomagnesiums

Grignard reagents usually undergo ane,2-improver to α,β-unsaturated carbonyl compounds, but there are examples where particular structural features of the substrate, particularly steric hindrance in the region of the carbonyl grouping, crusade sectional i,4-addition. North,North-Disubstituted cinnamides were reported as long agone as 1905 to react with Grignards in this way <05MI 107-01>. An interesting instance of this, highlighting likewise the differing reactivity of Grignard reagents compared with organocuprates, is seen in the addition to amide ( xx ) (Scheme 23) <83TL5089>.

A major accelerate in the history of cohabit addition was the study by Kharasch and Tawney that the addition of catalytic amounts of copper(I) salts caused Grignard reagents to undergo i,4-addition to isophorone (Equation (41)) <41JA2308>. While this process was widely used for many years, it was ofttimes unreliable, and has largely been superseded by the apply of stoichiometric organocopper reagents.

(41)

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Synthesis: Carbon with Two Heteroatoms, Each Attached by a Single Bond

David T. Macpherson , Harshad Thou. Rami , in Comprehensive Organic Functional Grouping Transformations, 1995

four.04.3.two.2.(i) With organometallic reagents

Grignard reagents react with orthoformates to provide aldehyde acetals by displacement of an alkoxy group ( Equation (73)). Alkyl, aryl, alkynyl, vinyl and heterocyclic Grignard reagents have all been employed, and the reaction is generally carried out in refluxing diethyl ether with yields ranging from fair to good <B-70MI 404-03>. The mixed ortho ester ( 76 ) prepared from triethyl orthoformate and phenol <70CB643> reacts with a wide diversity of Grignard reagents at room temperature and in higher yields than standard ortho esters <81JCR(M)4016>. Treatment of ( 76 ) with acetylenic Grignard reagents in dichloromethane allowed the training of some sensitive acetals (Equation (74)), <84JOC2031>. Allyl and propargyl aluminum reagents react with orthoformates or trimethyl orthoacetate at −80 °C to form unsaturated acetals <86CB1725>. Organocuprates <84TL3075> and allylsilanes <89S128> also react readily with ortho esters in the presence of Lewis acids. The reaction of alkynes with ortho esters catalysed past zinc salts <58JA4607, 63OSC(iv)801> is an alternative to Equations (73) and (74) for the training of acetylenic acetals (Equation (75)). Although this method allows access to ketone acetals, it requires a force per unit area vessel for the reaction of volatile alkynes.

(73)

(74)

(75)

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Alkaline metal Earth Organometallics☆

T.P. Hanusa , in Reference Module in Chemistry, Molecular Sciences and Chemic Engineering science, 2014

Chiral Grignard reagents

Grignard reagents that are chiral at the metal should requite strong asymmetric induction, and if their chirality is controlled, they could have great potential in stereoselective syntheses. At that place are likewise possibilities for studying single-electron transfer (SET) in the reaction of Grignard reagents, in which the metallic-bearing carbon is the only stereogenic center. In order to avoid the complimentary-radical reactions that would thwart the synthesis of such species, the α-chloro- and α-bromoalkyl Grignard reagents (R)-BrMgCHXCH ₂Ph (X = Cl, Br), with > 97% ee were generated past a sulfoxide Mg exchange reaction from the enantiomerically and diastereomerically pure sulfoxides, p-ClC_half-dozenH₄S(O)CHCXCH₂Ph. These Grignard reagents are configurationally stable at − 78 °C, but racemization occurs ≥ − threescore °C, especially when the solution contains bromide ions. In the absenteeism of halide ions, the configurational stability extends to − twenty °C. ¹¹² A review ¹¹³ documents how the asymmetric synthesis of the related Grignard reagent ((S)-one-benzylpropylmagnesium chloride) (eqn [nine]) was used as a probe to examine the extent to which Set is involved in reactions of organomagnesium reagents, including amination, ¹¹⁴ allylation, ¹¹⁵ ^, ¹¹⁶ oxidation, ¹¹⁷ and transmetallation. ¹¹⁸

[ix]

The Grignard reagent (Due south)-PhCH_iiCH(MgCl)CH₂CH_iii, in which the magnesium-begetting carbon cantlet is the sole stereogenic heart, adds to CO₂, PhNCO, PhNCS, and sure aldehydes with full retention of configuration. In contrast, reaction with benzophenone, electron-deficient aldehydes, and several allyl halides proceeds with partial or complete racemization. The findings reflect a competition between concerted polar and stepwise SET reaction pathways. ¹¹⁵ 3-Iodoenoates are converted into the corresponding alkenylmagnesium species with consummate retention of configuration of the double bail; both straight reaction and copper(i)-mediated reactions (via CuCN(2LiCl)) with various electrophiles (e.k., PhCOCl, Me₃SnCl, ethyl 2-(bromomethyl)prop-2-enoate) provide polyfunctional enoates. ¹¹⁹

The majority of Grignard reagents are iv-coordinate, but the cis-isomers of octahedral complexes would exist useful in the study of stereoselective synthesis. Half dozen-coordinate octahedral Grignard reagents, (thienyl)MgBr(dme)₂ and (vinyl)MgBr(dme)_ii, were prepared every bit racemic mixtures of d- and l-cis-isomers and characterized with X-ray crystallography. They are stereochemically rigid in toluene solution, simply were not enantiomerically resolved. ¹²⁰ The absolute asymmetric syntheses of the d and l enantiomers for both cis-[MgBr(4-MeC_{half dozen}H_iv)(dme)₂] and cis-[MgMe(dme)_ii(THF)]I take been accomplished. Subsequent reaction with RCHO (R = Prⁱ or Ph) yields the corresponding alcohol in upwards to 22% ee. The enantiomeric Grignard reagents crystallize separately but racemize in solution; at − 60 °C, the racemic species crystallize. ¹²¹ Iii chiral species cis-[MgBr(R)(dme)_two] (R = Pr^north, Prⁱ, allyl) accept been prepared and characterized with X-ray diffraction; all are racemic. The isolation of trans-[MgBr_two(tmen)₂] and cis-[MgBr₂(dme)₂] indicates that bidentate tertiary amine bases are less suitable for the preparation of cis-octahedral compounds, merely the structures of cis-[MgBr₂(triglyme)] and [Mg_two(μ-Br)₂(triglyme)_two][Mg₂(μ-Me)₂Br_four] propose that triglyme may exist well suited for this purpose. ¹²²

Optical activity retention is observed in the course of the germination of the Grignard reagent from optically active (+)-R-1-chloro-ane-phenylethane and Mg in Et₂O. ¹²³ Treatment of the latter with Mg in Et₂O and then with Me₃COD gives 88% (+)-S-PhCHDMe in 6.2% optical yield. ¹²³

Later quenching with D₂O or Bu^tOD, analysis of the products from the Grignard reagents formed from PhCHXMe (X = Cl, Br, I) in the optically active solvent –(R)-ii-methoxypentane leads to the conclusion that Grignard reagent formation occurs on the Mg surface within a solvent cage by a ane-electron transfer mechanism. ¹²⁴

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Principal-Group Elements, Including Noble Gases

T.P. Hanusa , ... North.R. Rightmire , in Comprehensive Inorganic Chemistry II (2nd Edition), 2013

1.37.4.2.2.1.2 Grignard reagents and related complexes

Grignard reagents are normally represented past the uncomplicated formula RMgX (R = organic group, 10 = halogen), although solvation, dismutation, aggregation, and deviations from this stoichiometry are mutual. Despite extensive work in the area, equally documented in previous reviews, ^310–313 the mechanisms of Grignard reagent formation are still under study. The many variables involved, including the identity of the substrates, the nature of the solvents used, and the physical course of the magnesium, profoundly complicate the research. Both radical and anionic pathways have been implicated in Grignard formation. ³¹⁴ Grignard germination is found to exist dramatically affected by the presence of magnesium halides ³¹⁵ and fe(II) chloride. ³¹⁶ Several books and reviews on Grignard reagents, stressing applications in organic synthesis, ^317–319 and the chemistry of highly functionalized organomagnesium reagents ³²⁰ have been published.

Schlenk equilibrium ³²¹ (eqn [16]) occurs normally with many Grignard reagents, particularly in ethereal solvents, simply deliberate manipulation of the equilibrium can affect the progress of reactions and the production distribution. Di- or polyfunctionalized Grignard reagents remain comparatively rare, although they can offering enhanced reactivity relative to their monofunctional counterparts RMgX; their chemistry has been reviewed elsewhere. ³²²

[16]

For over a century after the initial reports of Grignard chemistry, it was uncritically assumed that the high reactivity of the magnesium–carbon bond mandated the use of anhydrous experimental conditions. This assumption was disproved in the case of Barbier–Grignard allylation of aldehydes (eqn [17]). ³²³ In dry THF, the reaction between benzaldehyde, allyl bromide, and Mg proceeds quantitatively, only when the water content in THF reaches 7%, the reaction stops. When neat water is the solvent, even so, the allyl halide is plain confined to the magnesium surface because of hydrophobic interactions, shielding the metal from the h2o. The allylation reaction and so proceeds, but with depression conversion. The reaction of allyl bromide or iodide with benzaldehyde and Mg in 0.1 North aqueous HCl or NH₄Cl once again produces quantitative conversion of the aldehyde to allylation and pinacol coupling products. Such aqueous systems have received additional investigation, ^324, ³²⁵ as aqueous Grignard chemistry is attractive for its utilise of an environmentally benign solvent; information technology has been the subject of several reviews. ^326–330

[17]

Grignard reagents that are chiral at the metal should give strong asymmetric consecration, and if the chirality were controlled, they could take corking potential in stereoselective syntheses. In that location are also possibilities for studying single-electron transfer (Gear up) in the reaction of Grignard reagents, in which the metal-begetting carbon is the only stereogenic centre. Reactions in which Set is involved include amination, ³³¹ allylation, ^332, ³³³ oxidation, ³³⁴ and transmetallation. ³³⁵ This chemical science has been reviewed elsewhere. ³³⁶

The bulk of Grignard reagents are four-coordinate, but the cis isomers of octahedral complexes would exist useful in the study of stereoselective synthesis. A variety of such systems are known ^337, ³³⁸ ; as an instance, the accented disproportionate synthesis of the d and l enantiomers for both cis-[MgBr(4-MeC_{half dozen}H_four)(dme)₂] and cis-[MgMe(dme)₂(thf)]I has been achieved. Subsequent reaction with RCHO (R = (i-Pr) or Ph) yields the corresponding booze in up to 22% enantiomeric backlog. ³³⁹

Determination of the structures of Grignard reagents continues to be of interest, and reviews on this subject have been published. ^340, ³⁴¹ Most of the structure authentications are done on crystalline materials, although solution studies performed with extended 10-ray absorption fine structure (EXAFS) spectroscopy are also bachelor. Halide-bridged structures are common ^342, ³⁴³ ; for example, the Grignard compounds MeMgBr and EtMgBr were establish to be dimers in (northward-Bu)₂O at both room temperature and − 85 °C. ³⁴⁴

The traditional uses of Grignard reagents in organic synthesis are documented in many references outside this chapter. ^317–319 There are numerous cases in which a Grignard reagent is used as a source of magnesium or equally a ligand transfer reagent. In many reactions, the products are not organometallic species (east.g., phosphoranes, ³⁴⁵ alkoxides ³⁴⁶ ) and are not detailed here.

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Horizons in Sustainable Industrial Chemistry and Catalysis

Matilde V. Solmi , ... Walter Leitner , in Studies in Surface Scientific discipline and Catalysis, 2019

2.1.1 Grignard Reagents

Grignard reagents (RMgX, X = element of group vii, R = alkyl or aryl) are highly active nucleophiles. They were reported to actuate CO₂ to carboxylic acids already in the 1900s, by Grignard [45]. Unfortunately, their high reactivity limits the possibility of using substrates with functional groups (electrophiles), which would react faster with the Grignard nucleophile leading to a low chemo-selectivity in the desired carboxylic acid. Nevertheless, their high activity allows their transformation in carboxylic acids under mild weather condition such as i bar of CO₂ and room temperature [46] and the development of a continuous catamenia processes [47]. Dowson reported an analysis from which information technology was ended that the synthesis of acetic acid starting from CH_iiiMgX and captured CO_two was estimated to be economically feasible, with costs comparable to those of well-established processes [48]. Nevertheless, the Grignard reagents should exist regenerated past electrolysis of MgX_two salts obtained as by-products of the reaction, requiring extremely high amounts of free energy to be obtained from renewable resources at depression price. Furthermore, the treatment of Grignard reagents on the calibration of bulk chemicals is prohibitive with current technologies for prophylactic reasons. Therefore, such a process would non follow the Green Chemistry principles, despite the utilise of CO_two as feedstock.

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Synthesis: Carbon with Two Heteroatoms, Each Attached by a Unmarried Bond

Max J. Gough , John Steele , in Comprehensive Organic Functional Group Transformations, 1995

4.08.two.2.2 Beryllium or magnesium

Grignard reagent analogues derived from sulfones accept been known since the 1930s, and tin be synthesized by the reaction of a sulfone with a Grignard reagent. For example, Field treated methyl phenyl sulfone with ethylmagnesium bromide, and obtained the magnesio derivative in approximately 90% yield ( Equation (85)) <52JA3919>. Simpkin's book contains a useful summary of this chemistry <B-93MI 408-01>. The first report of an α-sulfenyl alkylmagnesium reagent was past Normant and Castro, who prepared benzylthiomethylmagnesium chloride from the corresponding chloromethyl sulfide in THF in 50% yield <64CR(259)830>. Later, Sakurai and co-workers obtained a Grignard reagent from chloromethyl methyl sulfide by treatment with magnesium activated with iodine and dibromoethene <67CC889>. A blackness solution was obtained which reacted with TMS-Cl to requite ( 127 ) in 33% yield (Scheme 49). The procedure was optimistically hailed by the authors as a useful constructed method. Much afterward, Ogura and co-workers modified the reaction conditions (substantially past controlling the temperature between 10 °C and twenty °C) of Sakurai's experiment, and obtained the same Grignard reagent in yields to a higher place xc% (by titration) <82CL1697>.

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Seebach and co-workers have described what amounts formally to an α-thio magnesium species. They transmetallated the thioacrolein dianion, originally prepared from thioacrolein with two equivalents of n-butyllithium (see Section 4.08.1.ii.1.i), with magnesium bromide, whereupon subsequent reactions with electrophiles were confined to the α over the γ position <76AG(Due east)437>.

The but report of an α-thio glucinium species is past Yamamoto <87BCJ1189>, who obtained ( 128 ) in 89% yield upon mixing the ylide ( 129 ) with beryllium chloride in THF (Equation (86)).

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