Bromobenzene Grignard reagent from

Bromobenzene is a colourless liquid of b.p. 156°, and d, 1 50 it has a faint agreeable odour. The bromine atom, being directly joined to the benzene ring, is very inert, and the only common reactions in which it is split off from the ring are the Fittig reaction (p. 288) and the Grignard reagent (pp. 280-284). 

To the Grignard reagent prepared from 0.59 part of magnesium, 3.95 parts of bromobenzene... 

Bromobenzaldehyde from aluminum chloride catalyzed bromination of benzaldehyde, 40, 9 Bromobenzene, conversion to Grignard reagent, 41, 91... 

The Grignard reagent—magnesium phenyl bromide—is prepared as described in Preparation 21 from 1-2 gms. (1 mol.) of dry magnesium and 8 gms. (1 mol.) of dry bromobenzene. 6-8 gms. (1 mol.) of dry methyl benzoate dissolved in 25 gms. of sodium-dried ether are added to the cold solution, slowly and with constant shaking. The liquid is then heated on a water bath until no further change takes place. Ice and dilute sulphuric acid are added to the cold reaction mixture, which, when the precipitate has dissolved, is steam distilled. The triphenyl carbinol which remains is recrystallised from benzene. 

In each part of this problem in which there is a change in the carbon skeleton, disconnect the phenyl group of the product to reveal the aldehyde or ketone precursor that reacts with the Grignard reagent derived from bromobenzene. Recall that reaction of a Grignard reagent with formaldehyde (H2C=0) yields a primary alcohol, reaction with an aldehyde (other than formaldehyde) yields a secondary alcohol, and reaction with a ketone yields a tertiary alcohol. 

Treatment of TV-methyl-4-piperidone with the Grignard reagent derived from bromobenzene gives a tertiary alcohol that can be dehydrated to an alkene. Hydrogenation of the alkene completes the synthesis. 

To the Grignard reagent prepared from 0.59 part of magnesium, 3.95 parts of bromobenzene and 50 parts of ether there are added 7.5 parts of 4-( 5-dimethylaminoethoxy)-a-ethyldesoxybenzoin in 50 parts of ether. After heating under reflux for 3 hours, the mixture is decomposed by the addition of a solution of 60 parts of ammonium chloride in 150 parts of water. The mixture is separated, and the ethereal layer is dried with anhydrous sodium sulfate, and the ether is evaporated. The residue is crystallized from methanol. There is thus obtained l-(p-p-dimethylaminoethoxyphenyl)-l,2-diphenylbutan-l-ol, melting point 120°C to 121°C. 

Phenylmagnesium bromide is prepared in the usual manner [Org. Syntheses Coll. Vol. 1, 226 (1941)] from 24 g. (1.0 gram atom) of magnesium and 157 g. (1.0 mole) of bromobenzene. To the ethereal solution of the Grignard reagent is added slowly 79 g. (1.0 gram atom) of selenium. The mixture is heated to reflux for 30 minutes and hydrolyzed with excess dilute hydrochloric acid. The ether layer is separated and the aqueous layer extracted with ether. The com-... 

Organophosphorus compounds find wide use in the chemical industry as catalysts, intermediates, complexes, and end-use products. Arylphosphines and phosphine oxides are often produced by the reaction of a preformed Grignard reagent with a halophosphine or phosphine oxide. Yields are reduced by the production of unwanted side-reaction products such as biaryls. These unwanted products are reduced when the reaction is conducted under Barbier conditions. When alkyl and aryl halides are reacted with magnesium metal, a trihalophosphine or phosphine oxide, a metal halide or amine catalyst, in THE benzene mixtures, at reflux, good yields of phosphines or phosphine oxides are obtained [74]. For example, triphenylphosphine can be prepared in a 97.2% yield from the reaction of bromobenzene, trichlorophosphine, magnesium metal, aluminum chloride, and sodium chloride in THF-benzene at 70 80 C. 

The reaction of 3-bromo-l-(phenylsulfonyl)prop-l-ene with Grignard reagents derived from allyl bromide, 2-propynyl bromide, bromobenzene, benzyl bromide or l-bromo-3-methylbut-2-ene affords 2-substituted cyclopropyl phenyl sulfones. On the other hand, alkylmagnesium bromides give the corresponding y-substituted allyl derivatives (Table 20, entries 6-8). 

---