Hydrogen by Deuterium Substitution in an Aldehyde Tunes the Regioselectivity by a Nonheme Manganese(III)–Peroxo Complex. Issue 31 (13th June 2019)

• Record Type: Journal Article
• Authors: Barman, Prasenjit; Cantú Reinhard, Fabián G.; Bagha, Umesh Kumar; Kumar, Devesh; Sastri, Chivukula V.; de Visser, Sam P.
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 31(2019)
• Page Start: 10639
• Page End: 10643
• Publication Date: 2019-06-13
• Subjects: biomimetic models -- density functional theory -- hydrogen atom abstraction -- kinetic isotope effects -- oxidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201905416
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: 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. Abstract : Regioselective hydrogen‐atom abstraction : A combined experimental and computational study gives evidence of electrophilic reactivity of a side‐on manganese(III)–peroxo complex. Furthermore, isotopic substitution of the substrate changes the regioselectivity of the reaction and the product distributions.