T-Butylmagnesium chloride

The actual mechanism by which a particular reaction proceeds strongly depends on the nature of the organomagnesium reagent. For instance benzophenone reacts with methylmagnesium bromide by a polar mechanism, while the reaction with t-butylmagnesium chloride proceeds for steric reasons by a SET-mechanism. 

Polarization also occurs in coupling and disproportionation reactions of Grignard reagents with alkyl halides. The vinyl protons of isobutene produced in the reaction of t-butylmagnesium chloride with t-butyl bromide show A/E polarization as do the methyl protons of isobutane (Ward et al., 1970). Similar results arise in the reaction of diethyl-magnesium with organic halides (Kasukhin et al., 1972). 

Mikolajczyk and coworkers have summarized other methods which lead to the desired sulfmate esters These are asymmetric oxidation of sulfenamides, kinetic resolution of racemic sulfmates in transesterification with chiral alcohols, kinetic resolution of racemic sulfinates upon treatment with chiral Grignard reagents, optical resolution via cyclodextrin complexes, and esterification of sulfinyl chlorides with chiral alcohols in the presence of optically active amines. None of these methods is very satisfactory since the esters produced are of low enantiomeric purity. However, the reaction of dialkyl sulfites (33) with t-butylmagnesium chloride in the presence of quinine gave the corresponding methyl, ethyl, n-propyl, isopropyl and n-butyl 2,2-dimethylpropane-l-yl sulfinates (34) of 43 to 73% enantiomeric purity in 50 to 84% yield. This made available sulfinate esters for the synthesis of t-butyl sulfoxides (35). 

Figure 1. Isotactic, heterotactic, and syndiotactic triad frequencies (i, h, and s) in poly(methyl methacrylate) polymerized and initiated at 225 by t-butylmagnesium bromide fleft), t-butylmagnesium chloride fright,), and di-t-butylmagnesium (top) with initial mole fraction of monomer a = 0.10.

Di-t-butylbenzo[c ]furan (454) was postulated as an intermediate in the base catalyzed dehydrobromination of (453) to yield the diketone (455) (69TL5215). However, (457) has been prepared by treatment of 1-phenylphthalide (456) with t-butylmagnesium chloride and subsequent dehydration with p-toluenesulfonic acid. 

Yields are variable, but in favourable cases can be very high for example, phenyl cyanate and t-butylmagnesium chloride gave pivalonitrile (92%) and phenol (87%). 

Variable yields of azo compounds were also obtained from reactions of Grignard reagents with diazonium salts, but benzenediazonium tetrafluoroborate gave acceptable yields from arylmagnesium bromides or t-butylmagnesium chloride in THF [19] ... 

Bromo-2-chloro-3-hexylthiophene (0.0355 mol) was added over a period of 30 minutes to a mixture consisting of 75 ml of 2-methyltetrahydrofuran, magnesium (0.0355 mol), and 0.15 ml of IM t-butylmagnesium chloride solution in THF at 60°C to 70°C. The mixture was stirred for 90 minutes at 70°C. It was then cooled to 60°C and treated with a suspension of l,2-bis(diphenylphosphino)ethane nickel(II) chloride (0.177 mmol) in 12.5 ml of 2-methyltetrahydrofuran for over 30 minutes. The mixture was stirred an additional 3 hours at 80°C and further treated with triethylphosphite (3 mmol) and stirred for 30 minutes at 80°C. The mixture was then concentrated and the residue dissolved in 10 ml of toluene. This solution was poured into 100 ml of EtOAc, which created a suspension, and the suspension was stirred for 30 minutes at 80°C. The cooled suspension was filtered, the residue washed twice with 20 ml of EtOAc, and the product isolated in 81% yield having a Mn of 19,543 daltons with a of 224°C. 

Grignard reagents have been used directly in mono-and diketone formation. More recently, it has been found that a catalytic quantity of cuprous chloride greatly increases the yields." An example is the formation of hexamethylacetone in 70-80% yield from t-butylmagnesium chloride and trimethylacetyl chloride. Diketones have... 

Six a-isopropoxy acids have been made in 20-80% yield by the hydro-genolysis of dioxolones by t-butylmagnesium chloride. The Grignard reagent is oxidized to isobutylene. An improved procedure for preparing the dioxolones from a-hydroxy acids and acetone is described. ... 

Preparation of Chiral Sulfinates. Optically active sulfinates can be prepared by reaction of a symmetrical sulfite with t-Butylmagnesium Chloride in the presence of an optically active amino alcohol. The best enantioselectivity has been observed using quinine as the optically active amine (eq 2)3 An alternative approach to this new enantioselective asymmetric synthesis of alkyl t-butylsulfinates would be reaction of a racemic sulfinate with r-butylmagnesium chloride complexed by optically active alkaloids (eq 3). In this case, kinetic resolution of the racemic sulfinate leads to an optically active sulfinate and an optically active sulfoxide. 

At the high T needed for addition, such elimination from t-butylmagnesium chloride (to form isobutene) and from other organomagnesiums with jS-hydrogens can compete with their additions to alkenes. 

Reactions which have rale-determining FT have transition slates with charge development and should be accelerated in the more polar solvent THF. Since the various coordination equilibria existing in the reaction mixtures are seriously shifted, reactivity changes have to be carefully analysed. Although the FT reaction with azobenzene is accelerated in Till, the F.T reaction between t-butylmagnesium chloride and di-r-hulylperoxide is extremely slow in THF 1441... 

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