Benzylic C(sp³)−H Bond Oxidation with Ketone Selectivity by a Cobalt(IV)‐Oxo Embedded in a β‐Barrel Protein

Abstract

Artificial metalloenzymes have emerged as biohybrid catalysts that allow to combine the reactivity of a metal catalyst with the flexibility of protein scaffolds. Here, we report the artificial metalloenzymes based on the β‐barrel protein nitrobindin NB4, in which a cofactor [CoIIX(Me3TACD‐Mal)]+X‐ (X = Cl, Br; Me3TACD = N,N´,N´´‐trimethyl‐1,4,7,10‐tetraazacyclododecane, Mal = CH2CH2CH2NC4H2O2) was covalently anchored via a Michael addition reaction. These biohybrid catalysts showed higher efficiency than the free cobalt complexes for the oxidation of benzylic C(sp3)‐H bonds in aqueous media. Using commercially available oxone (2KHSO5·KHSO4·K2SO4) as oxidant, a total turnover number of up to 220 and 97% ketone selectivity were achieved for tetralin. As catalytically active intermediate, a mononuclear terminal cobalt(IV)‐oxo species [Co(IV)=O]2+ was generated by reacting the cobalt(II) cofactor with oxone in aqueous solution and characterized by ESI‐TOF MS.

Engineered Anchor Peptide LCI with a Cobalt Cofactor Enhances Oxidation Efficiency of Polystyrene Microparticles

“…The authors have cited additional references within the Supporting Information (Ref. [50][51][52][53][54][55][56][57][58][59][60][61]). Experimental procedures, spectroscopic characterization, and additional data are available in the Supporting Information.…”

Ein modifiziertes Ankerpeptid LCI mit einem Cobalt‐Cofaktor verbessert die Oxidationseffizienz von Polystyrol‐Mikropartikeln

“…In den Hintergrundinformationen geben die Autoren zusätzliche Literaturstellen an (Lit. [50][51][52][53][54][55][56][57][58][59][60][61]). Experimentelle Versuchsdurchführungen, Angaben zur spektroskopische Charakterisierung und zusätzliche Daten sind in den Hintergrundinformationen enthalten.…”