Bromomagnesium

An accurate control of the reaction temperature in the hydrolysis step is crucial in obtaining high yields of the cis-isomer. ( )-(2-Nitroethenyl)benzene gave a 50 50 mixture of the two diastereomers with bromomagnesium diethyl-bis(2-propenyl)aluminate. 

Figure 7.11 Selective ortho coupling reaction using bromomagnesium salts.

Figure 14 The structure of 9-bromo-9-[(bromomagnesium)methylene]fluorene 30. 

Substituted cyclopropanols were also obtained, albeit in moderate yields, upon reaction of esters such as methyl pentanoate with l,4-bis(bromomagnesium)butane (38) in the presence of titanium tetraisopropoxide. This corroborates the formation of a titanacy-clopropane—ethylene complex 40 from an initially formed titanacyclopentane derivative 39 (Scheme 11.12) [103], Apparently, an ester molecule readily displaces the ethylene ligand from 40, and a subsequent insertion of the carbonyl group into the Ti—C bond, a formal [2S + 2J cycloaddition, leads to the oxatitanacyclopentane 42, the precursor to 1-butylcyclopropanol (43). 

The methods previously used to obtain single aldol products (or their dehydrated derivatives) from reactants where several aldol products are possible8 include the reaction of bromozinc enolates, from a-bromo-ketones, with aldehydes 9 the reaction of bromomagnesium enolates, from either a-bromoketones or from ketones and bromomagnesium... 

Optimum reaction conditions were achieved with the bromomagnesium cuprate, and explored in several examples. 

Another reagent, sodium bis 2-methoxyethoxy)aluminum hydride (Vitride), was used to reduce nonanoic acid to 1-nonanol in refluxing benzene in 92% yield [969]. The same reagent converts sodium or bromomagnesium salts of acids to alcohols sodium stearate to 1-octadecanol at 80° in 96% yield, and bromomagnesium octanoate to 1-octanol at 80° in 85% yield [970]. 

Among other reagents which effect epoxide ring opening are diethylaluminum 2,2,6,6-tetramethylpiperidide and bromomagnesium /V-cyclohcxyl-A-(2-propyl)amide. 

The structures of three monomeric organomagnesium bromides in which the magnesium center is penta-coordinate have been established in the solid state. These compounds are MeMgBr(THF)(TMEDA) (156) , 9-bromo-9-[(bromomagnesium)methylene]fluorene tris-THF complex (157) and MeMgBr(THF)3 (158) . 

The action of magnesium on a-halo ketone has been used by Malmgren, for the synthesis of bromomagnesium enolate 2 derived from 3-bromocamphor 1 (equation 1) . 

Felhnann and Dubois have described the structure of the enolate 29 derived from the reaction of f-butyl acetate with (MeO)2Mg. The NMR spectrum reveals two O-metallated species, which should be symmetric enolates as proposed by Pinkus and Wu for the bromomagnesium enolate of methyhnesityl ketone (metal is tricoordinated). ... 

BMDA or DAMgBr (chloromagnesium (bromomagnesium drisopropylamide) diisopropylamide)... 

Krafft and Holton have found that bromomagnesium diisopropylamide (BMDA) in an ethereal solution may be used in conjunction with the system TMSCl/EtsN/HMPA to prepare thermodynamic silylenol ethers. Reaction times of 8-12 h at 25 °C are required for the complete conversion to trimethylsilyl enolates (equation 67). 

Enol alkylation of cyclohexanone by oxetane has been achieved by the reaction of oxetane with an enamine salt, bromomagnesium Af-cyclohexyliminocyclohexane, in THF. An 80%... 

Chloroethyl benzoate has been prepared from benzoyl chloride and ethylene chlorohydrin from benzoic acid, ethylene glycol, and hydrogen chloride at 100° from ethylene oxide and benzoyl chloride from benzoyl chloride and dioxane in the presence of titanium tetrachloride from benzoic acid, ethylene, and chlorine in the presence of various catalysts. It has also been obtained by hydrolysis of 2-chloroethyl benzimidate " by the action of bromomagnesium benzoate on 2-chloroethyl -toluene-sulfonate and by the action of sodium benzoate on bis-(2-chloroethyl) sulfate. ... 

When the sodium or bromomagnesium salts of these anions are treated with transition metal halides (FeCU) (78JOM(156)C33, 81IC3252) or carbonyls, e.g. Mn2(CO)10, very interesting 175 67r-phosphole transition metal complexes (89) and (90) are formed (equations 51 and 52) <79JCS(D)1552, 80JA994). 

G. Casiraghi, M. Cornia, G. Rassu, L. Zetta, G. G. Fava, and M. F. Belicchi, Stereoselective arylation of pyranoid glycals using bromomagnesium phenolates an entry to 2,3-unsaturated C-a-glycopyranosylarenes, Carbohydr. Res., 191 (1989) 243-251. 

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