Carbon monoxide incorporation extends the carbon chain
المؤلف:
Jonathan Clayden , Nick Greeves , Stuart Warren
المصدر:
ORGANIC CHEMISTRY
الجزء والصفحة:
1077
2025-08-07
500
Carbon monoxide incorporation extends the carbon chain
Carbonylation (the addition of carbon monoxide to organic molecules) is an important industrial process as carbon monoxide is a convenient one-carbon feedstock and the resulting metal–acyl complexes can be converted into aldehydes, acids, and their derivatives. The OXO process is the hydroformylation of alkenes such as propene and uses two migratory insertions to make higher value aldehydes. Although a mixture is formed, this is acceptable from very cheap and abundant starting materials. Here the metal complex is a catalyst, not a stoichiometric reagent.
A catalytic cycle (going clockwise from the top) shows the various stages of alkene coordination, hydrometallation (migratory insertion) to produce an alkyl metal species, coordination of carbon monoxide followed by another migratory insertion, and finally reductive cleavage with hydrogen to produce the metal–hydride intermediate, which is then ready for another cycle. The steps leading to the other regioisomeric aldehyde and the ligands on the metal are omitted for clarity.
The mechanisms of the two key migratory insertion steps are worth discussion. Hydrometallation occurs by initial π complex formation followed by addition of the metal to one end of the alkene and hydrogen to the other. Both of the possible regioisomers are formed. The carbonyl insertion reaction is another migration from the metal to the carbon atom of a CO ligand.
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