Organolithium reagents, reaction with carbon dioxide

Carboxylic acid groups can also be installed in molecules using the reaction of an organometallic compound with carbon dioxide. This is a reductive method since the carbon dioxide is reduced to a carboxylic acid by formation of a new carbon-carbon bond. Both Grignard reagents and organolithium compounds work well in this reaction. 

The reactions of carbon dioxide and carbon disulfide with organoUthium reagents have attracted much attention and have been applied in various organic synthesis. Reaction of carbon dioxide with organolithium compounds normally affords carboxylic acids after hydrolysis [50]. The formation of unsymmetrical ketones was reported from the reaction of CO2 and two organolithium compounds via an intermolecular reaction pathway [51]. When 1,4-dilithio-l,3-dienes 1 was treated with CO2, cyclopentadienone derivatives 20 with various substituents could be prepared in high yields in one-pot within several minutes via cleavage of one of the C=0 double bonds (Scheme 10) [52]. The experimental results indicate that this intermolecular reaction pattern affords cyclopentadienones in the reaction mixture before hydrolysis. 

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