Mechanistic Scientific studies on the Epoxidation of Alkenes by Macrocyclic Manganese Porphyrin Catalysts

Mechanistic Studies on the Epoxidation of Alkenes by Macrocyclic Manganese Porphyrin Catalysts

Ion mobility mass spectrometry reveals that a manganese (III) porphyrin cage reacts with the oxidant iodosylbenzene to type an inside of iodosylbenzene advanced, which is transformed into a manganese(V)oxo complex in which the oxo group is positioned within the cage (still left). It reacts within just the cage with alkenes to variety epoxides. When the cage is blocked by methyl teams the response with iodosylbenzene and the development of the manganese(V)oxo intricate takes place at the outdoors of the cage (correct). Subsequent reaction with alkenes usually takes put at the outdoors.

Abstract

Macrocyclic metal porphyrin complexes can act as form-selective catalysts mimicking the action of enzymes. To realize enzyme-like reactivity, a mechanistic knowledge of the reaction at the molecular degree is required. We report a mechanistic review of alkene epoxidation by the oxidant iodosylbenzene, mediated by an achiral and a chiral manganese(V)oxo porphyrin cage intricate. Each complexes change a good wide variety of alkenes into epoxides in yields varying concerning 20–88 %. We monitored the process of the formation of the manganese(V)oxo complexes by oxygen transfer from iodosylbenzene to manganese(III) complexes and their reactivity by ion mobility mass spectrometry. The effects display that in the case of the achiral cage elaborate the preliminary iodosylbenzene adduct is fashioned on the inside of the cage and in the circumstance of the chiral one on the outside of the cage. Its decomposition sales opportunities to a manganese intricate with the oxo ligand on possibly the inside or outside of the cage. These experimental outcomes are confirmed by DFT calculations. The oxo ligand on the outside the house of the cage reacts faster with a substrate molecule than the oxo ligand on the within. The outcomes indicate how the catalytic exercise of the macrocyclic porphyrin complicated can be tuned and make clear why the chiral porphyrin complicated does not catalyze the enantioselective epoxidation of alkenes.


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