Oxidative carbonylation is a class of reactions that use
carbon monoxide
Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the si ...
in combination with an oxidant to generate
ester
In chemistry, an ester is a compound derived from an acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...
s and
carbonate esters. These transformations utilize transition metal complexes as
homogeneous catalysts.
Many of these reactions employ palladium catalysts. Mechanistically, these reactions resemble the
Wacker process.
Illustrative oxidative carbonylations
Oxidative carbonylation, using palladium-based catalysts, allows certain alkenes to be converted into homologated esters:
:2 RCH=CH
2 + 2 CO + O
2 + 2 MeOH → 2 RCH=CHCO
2Me + 2 H
2O
Such reactions are assumed to proceed by the insertion of the alkene into the Pd(II)-CO
2Me bond of a
metallacarboxylic ester followed by
beta-hydride elimination (Me = CH
3).
Arylboronic acids react with Pd(II) compounds to give Pd(II)-aryl species, which undergo carbonylation to give Pd(II)-C(O)aryl. These benzyl-Pd intermediates are intercepted by alkenes, which insert. Subsequent beta-hydride elimination gives the arylketone.
[
The conversion of methanol to dimethylcarbonate by oxidative carbonylation is economically competitive with phosgenation. This reaction is practiced commercially using Cu(I) catalysts:]dimethyl oxalate
Dimethyl oxalate is an organic compound with the formula or . It is the dimethyl ester of oxalic acid. Dimethyl oxalate is a colorless or white solid that is soluble in water.
Production
Dimethyl oxalate can be obtained by esterification of oxa ...
by oxidative carbonylation has also attracted commercial interest. It requires only C1 precursors:[Hans-Jürgen Arpe: ''Industrielle Organische Chemie: Bedeutende Vor- und Zwischenprodukte'', S. 168; {{ISBN, 978-3-527-31540-6.]
:4 CO + O2 + 4 MeOH → 2 (MeO2C)2 + 2 H2O
References
Chemical reactions
Carbon monoxide