Using Bicyclo[4.1.0] Heptane As A Radical Probe To Study The Radical Mechanism Of The Lyons System

The oxidation of a variety of hydrocarbons catalyzed by metalloporphyrin usingO2as the oxidant, Lyons system, is analogous to the catalytic cycle of CYP450systems except that it does not require reductants or photochemical andelectrochemical technical assistance has received much attention in recent decades.In this paper, we studied the hydroxylation process in the Lyons system usingbicyclo [4.1.0] heptane as a radical and carbocation probe based on the Lyons systemmechanism proposed by our group and others.Firstly, we reviewed the mechanism of oxidation of a variety of hydrocarbonscatalyzed by metalloporphyrin using O2as the oxidant; Overview of the developmentradical probe and the meanings of our research topic.Secondly, we established a GC quantitative analysis method of the products ofbicyclo [4.1.0] heptane according to the demanding of our research.Thirdly, we studed the oxidation of bicyclo[4.1.0] heptane catalyzed bymetalloporphyrin using O2as the oxidant using different catalysts andsolvents.Hydroxylation by metalloporphyrin occurs through a two-stepprocess:hydrogen atom abstraction to generate a shortlived carbon centered radicaland subsequent recombination to afford an unrearrangement product.Hydrogenabstraction from norcarane generates carboncentered radicals with significantlifetimes that allow substrate rearrangement afford a rearrangement product.With aknown rearrangement rate and the observed ratio of unrearranged to rearrangedproducts (U/R) for norcarane, we calculated the recombination rate(Kreb) and radicallifetime (τ).Fourthly, heavy oxygen water (H182O) and heavy water ([2H]2O) were used asprobes for exploring high-valent metala-oxo species and porphyrin Fe-OOHintermediates. The GC-MS analysis of the products showed that18O incorporates intothe2a and2c, no2H incorporates into the products. The study show that high-valentiron-xo species is a potent oxidizing agent,but does not appear Porphyrin Fe-OOHintermediate or porphyrin Fe-OOH intermediate is not active intermediate.Fifthly, Under the existing conditions in the laboratory, we attempt to takeadvantage of a free radical trapping(DMPO/PBN) and GC-MS to detecte radicalintermediates in the cyclohexane oxidation catalyzed by metalloporphyrin. During the experiment to prevent the radical adduct is decomposed at high temperature incapillary column,we silylanized the free adduct with BSTFA. But did not achieve thedesired results,it may be due to the radical adduct too little beyond the detection limitof the GC-MS. And finally we proposed the mechanism of the oxidation ofbicyclo[4.1.0] heptane catalyzed by metalloporphyrin.