Fenton-like Chemistry by a Copper(I) Complex and H2O2 Relevant to Enzyme Peroxygenase C–H Hydroxylation

Lytic polysaccharide monooxygenases have received significant attention as catalytic convertors of biomass to biofuel. Recent studies suggest that its peroxygenase activity (i.e., using H₂O₂ as an oxidant) is more important than its monooxygenase functionality. Here, we describe new insights into peroxygenase activity, with a copper(I) complex reacting with H₂O₂ leading to site-specific ligand-substrate C-H hydroxylation. [Cu^I(TMG₃tren)]⁺ (1) (TMG₃tren = 1,1,1-Tris{2-[N²-(1,1,3,3-tetramethylguanidino)]ethyl}amine) and a dry source of hydrogen peroxide, (o-Tol₃P═O·H₂O₂)₂ react in the stoichiometry, [Cu^I(TMG₃tren)]⁺ + H₂O₂ → [Cu^I(TMG₃tren-OH)]⁺ + H₂O, wherein a ligand N-methyl group undergoes hydroxylation giving TMG₃tren-OH. Furthermore, Fenton-type chemistry (Cu^I + H₂O₂ → Cu^II-OH + ·OH) is displayed, in which (i) a Cu(II)-OH complex could be detected during the reaction and it could be separately isolated and characterized crystallographically and (ii) hydroxyl radical (·OH) scavengers either quenched the ligand hydroxylation reaction and/or (iii) captured the ·OH produced.