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Hydrogen by Deuterium Substitution in an Aldehyde Tunes the Regioselectivity by a Nonheme Manganese(III)–Peroxo Complex
Author(s) -
Barman Prasenjit,
Cantú Reinhard Fabián G.,
Bagha Umesh Kumar,
Kumar Devesh,
Sastri Chivukula V.,
de Visser Sam P.
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201905416
Subject(s) - regioselectivity , chemistry , hydrogen atom abstraction , aldehyde , manganese , density functional theory , reactivity (psychology) , kinetic isotope effect , ligand (biochemistry) , photochemistry , deuterium , cyclohexane , hydrogen atom , hydrogen , medicinal chemistry , computational chemistry , catalysis , organic chemistry , medicine , biochemistry , physics , alternative medicine , receptor , alkyl , pathology , quantum mechanics
Mononuclear nonheme Mn III ‐peroxo complexes are important intermediates in biology, and take part in oxygen activation by photosystem II. Herein, we present work on two isomeric biomimetic side‐on Mn III ‐peroxo intermediates with bispidine ligand system and reactivity patterns with aldehydes. The complexes are characterized with UV/Vis and mass spectrometric techniques and reaction rates with cyclohexane carboxaldehyde (CCA) are measured. The reaction gives an unusual regioselectivity switch from aliphatic to aldehyde hydrogen atom abstraction upon deuteration of the substrate, leading to the corresponding carboxylic acid product for the latter, while the former gives a deformylation reaction. Mechanistic details are established from kinetic isotope effect studies and density functional theory calculations. Thus, replacement of C−H by C−D raises the hydrogen atom abstraction barriers and enables a regioselectivity switch to a competitive pathway that is slightly higher in energy.