Hybrid Organometallic and Enzymatic Tandem Catalysis for Oxyfunctionalisation Reactions

Abstract

Unspecific peroxygenases (UPOs) are promising biocatalysts for oxyfunctionalisation reactions, owing to their simplicity of handling, stability and robustness. A limitation of using UPOs on a large scale is their deactivation in the presence of even rather modest concentrations of H2O2, requiring a constant and controlled supply of low amount of H2O2. Herein, we report an organometallic complex [Cp*Ir(pica)NO3] {pica=picolinamidate=κ2-pyridine-2-carboxamide ion (−1)} 1 capable of efficiently regenerating FMNH2 from FMN (TOF=350 h−1, 298 K), driven by NaHCOO; FMNH2, in turn, spontaneously reacts with O2 leading to H2O2. After having studied the compatibility of 1 with the UPO from Agrocybe aegerita (rAaeUPO PaDa-I) and individuated the best experimental conditions, we applied such a hybrid catalytic tandem in some hydroxylation, epoxidation and sulfoxidation reactions. Best performances were obtained by using a 1/rAaeUPO molar ratio of 50. TONs for the biocatalyst of up to 18933 were obtained for the transformation of ethylbenzene derivatives into (R)-1-phenylethanols (ee>99 %). 1/rAaeUPO was found to oxidise also cis-methyl styrene (TON=13488), leading exclusively (1R,2S)-cis-methyl styrene oxide (ee>99 %), cyclohexane (TON=1634) and thioanisole (TON=1369).