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Selective photocatalytic hydroxylation and epoxidation reactions by an iron complex using water as the oxygen source

2017; Royal Society of Chemistry; Volume: 8; Issue: 11 Linguagem: Inglês

10.1039/c7sc02780j

2041-6539

Bittu Chandra, Kundan K. Singh, Sayam Sen Gupta,

Photosynthetic Processes and Mechanisms

The iron complex [(bTAML)FeIII-OH2]- (1) selectively catalyses the photocatalytic hydroxylation and epoxidation reactions of alkanes and alkenes, respectively, using water as the oxygen-atom source. Upon the oxidation of unactivated alkanes, which included several substrates including natural products, hydroxylation was observed mostly at the 3° C-H bonds with 3° : 2° selectivity up to ∼100 : 1. When alkenes were used as the substrates, epoxides were predominantly formed with high yields. In the presence of H218O, more than 90% of the 18O-labelled oxygen atoms were incorporated into the hydroxylated and epoxide product indicating that water was the primary oxygen source. Mechanistic studies indicate the formation of an active [{(bTAML)FeIV}2-μ-oxo]2- (2) dimer from the starting complex 1via PCET. The subsequent disproportionation of 2 upon addition of substrate, leading to the formation of FeV(O), renders the high selectivity observed in these reactions.