Making carboxylic acids from organometallics and carbon dioxide
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
ص190-191
2025-05-08
815
Carbon dioxide reacts with organolithiums and Grignard reagents to give carboxylate salts. Protonating the salt with acid gives a carboxylic acid with one more carbon atom than the starting organometallic. The reaction is usually done by adding solid CO2 to a solution of the organolithium in THF or ether, but it can also be done using a stream of dry CO2 gas.
The example belows shows the three stages of the reaction: (1) forming the organometallic, (2) reaction with the electrophile (CO2), and (3) the acidic work-up or quench, which protonates the product and destroys any unreacted organometallic. The three stages of the reaction have to be monitored carefully to make sure that each is finished before the next is begun. In particular it is absolutely essential that there is no water present during either of the first two stages—water must be added only at the end of the reaction, after the organo metallic has all been consumed by reaction with the electrophile. You may occasionally see schemes written out without the quenching step included, but it is nonetheless always needed.
carboxylic acids from organometallics
This next example shows that even very hindered chlorides can be used successfully. The significance of this will be clearer when you reach Chapter 15.
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