Benzyl magnesium bromide

By the action of carbon dioxide on benzyl magnesium bromide. Ivanov, Bull. soc. chim. (4) 37, 287 (1925). 

To a mixture of vinyl bromide (40 mmol) and the catalyst dichloro-[(R)-Af,N-dimethyl-l-[(.S)-2-(diphenylphosphino)ferrocenyl]ethylamine]-palladium(n) (0.2 mmol) was added an ethereal solution of [a-(trimethyl-silyl)benzyl]magnesium bromide (0.6-1 m, 80 mmol) at —78 °C. The mixture was stirred at 30 °C for 4 days, and then cooled to 0 °C and hydrolysed with dilute aqueous HC1 (3 m). The organic layer was separated, and the aqueous layer was re-extracted with ether. The combined organic extracts were washed with saturated sodium hydrogen carbonate solution and water, and dried. Concentration and distillation gave the chiral allylsilane (79%, 66% ee), b.p. 55°C/0.4mmHg. 

The reaction is carried out under a dry nitrogen atmosphere. To a mixture of 7.32 g (40 mmol) of ( )-bromophenylethcnc and 0.20 mmol of the palladium complex are added 100 mL (80 mmol) of a 0.8 M solution of [a-(trimethylsilyl)benzyl]magnesium bromide in diethyl ether at —78 °C. The mixture is allowed to warm and stirred at 0 "C for 2 d and then hydrolyzed with 10% HCI at 0 C. The organic layer and ether extracts from the aqueous layer are combined, washed with aq NaHCG3 and then water, and dried over anhyd MgS04. The solvent is evaporated and the product isolated by distillation yield 10.1 g (93% ) bp 135-139 JC/0.9 Torr [a]p° —43.9 (c = 1.0, benzene) 95% op (determined by hydrogenation and direct comparison with an authentic sample prepared via asymmetric hydrosilylation and correlated with 1,3-diphenyl-t -propanol). 

Another synthetic route starts with the condensation of N-methoxyamide (x) with 4-(methylsulfanyl) benzyl-magnesium bromide to give 1-(6-methylpyridin-3-yl)-2-(4-(methylsulfanyl)phenyl)ethanone (xiii), which is finally oxidized with the wolframate to ketosulfone (ix). 

Benzotelluropyrylium salts react with a variety of nucleophiles via distinct mechanistic pathways. 2-Benzotelluropyrylium salts 30 react with common Grignard reagents to afford products of reductive dimerization 31 (Equation 6) <1998J(P1)2123>. Under similar conditions, the reactions of the 2-benzotelluropyrylium salts with benzyl magnesium bromide take a completely different course leading to addition of the benzyl group to the... 

In the second approach, benzyl bromide is converted to benzyl magnesium bromide (a Grignard reagent), which serves as a nucleophile in a subsequent reaction with carbon dioxide. The resulting carboxylate ion is then protonated with to produce the desired carboxylic acid. 

Alternatively, the carboxylic acid can be prepared via a Grignard reaction between benzyl magnesium bromide and carbon dioxide, followed by acid work-up, as shown ... 

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