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Reaction Mechanism of Pd‐Catalyzed “CO‐Free” Carbonylation Reaction Uncovered by In Situ Spectroscopy: The Formyl Mechanism
Author(s) -
Geitner Robert,
Gurinov Andrei,
Huang Tianbai,
Kupfer Stephan,
Gräfe Stefanie,
Weckhuysen Bert M.
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202011152
Subject(s) - carbonylation , chemistry , catalysis , reaction mechanism , methyl formate , formic acid , reaction intermediate , carbon monoxide , formate , photochemistry , molecule , nuclear magnetic resonance spectroscopy , hydride , organic chemistry , metal
“CO‐free” carbonylation reactions, where synthesis gas (CO/H 2 ) is substituted by C1 surrogate molecules like formaldehyde or formic acid, have received widespread attention in homogeneous catalysis lately. Although a broad range of organics is available via this method, still relatively little is known about the precise reaction mechanism. In this work, we used in situ nuclear magnetic resonance (NMR) spectroscopy to unravel the mechanism of the alkoxycarbonylation of alkenes using different surrogate molecules. In contrast to previous hypotheses no carbon monoxide could be found during the reaction. Instead the reaction proceeds via the C−H activation of in situ generated methyl formate. On the basis of quantitative NMR experiments, a kinetic model involving all major intermediates is built which enables the knowledge‐driven optimization of the reaction. Finally, a new reaction mechanism is proposed on the basis of in situ observed Pd‐hydride, Pd‐formyl and Pd‐acyl species.