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Catalytic Hydrogenation of Trivinyl Orthoacetate: Mechanisms Elucidated by Parahydrogen Induced Polarization
Author(s) -
Pravdivtsev Andrey N.,
Brahms Arne,
Kienitz Stephan,
Sönnichsen Frank D.,
Hövener JanBernd,
Herges Rainer
Publication year - 2021
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.202000957
Subject(s) - spin isomers of hydrogen , hyperpolarization (physics) , chemistry , molecule , geminal , catalysis , methylene , polarization (electrochemistry) , induced polarization , photochemistry , nuclear magnetic resonance spectroscopy , hydrogen , stereochemistry , medicinal chemistry , organic chemistry , engineering , electrical engineering , electrical resistivity and conductivity
Abstract Parahydrogen ( p H 2 ) induced polarization (PHIP) is a unique method that is used in analytical chemistry to elucidate catalytic hydrogenation pathways and to increase the signal of small metabolites in MRI and NMR. PHIP is based on adding or exchanging at least one p H 2 molecule with a target molecule. Thus, the spin order available for hyperpolarization is often limited to that of one p H 2 molecule. To break this limit, we investigated the addition of multiple p H 2 molecules to one precursor. We studied the feasibility of the simultaneous hydrogenation of three arms of trivinyl orthoacetate (TVOA) intending to obtain hyperpolarized acetate. It was found that semihydrogenated TVOA underwent a fast decomposition accompanied by several minor reactions including an exchange of geminal methylene protons of a vinyl ester with p H 2 . The study shows that multiple vinyl ester groups are not suitable for a fast and clean (without any side products) hydrogenation and hyperpolarization that is desired in biochemical applications.