Co‐Catalyzed Peroxidation of Cyclic β‐Dicarbonyls

The reactivity of cyclic β-dicarbonyls (cyclic β-diketones, 4-hydroxy-2(5H)-furanones, and Meldrum‘s acids) towards metal/hydroperoxide system was disclosed. An efficient method for the peroxidation of 4-hydroxy-2(5H)-furanones and Meldrum's acids with TBHP has been developed using Co²⁺ salt as a catalyst. Cycle cleavage, expected from previous reports for cyclic β-dicarbonyls, was observed only for cyclic 1,3-diketones. Overall, this work extends the understanding of metal-catalyzed peroxidation towards different structural motifs.

Abstract

A Co-catalyzed peroxidation of cyclic β-dicarbonyls (cyclic 1,3-diketones, 4-hydroxy-2(5H)-furanones and Meldrum's acids) with TBHP has been disclosed. A series of the alkylperoxy derivatives of 4-hydroxy-2(5H)-furanones and Meldrum's acids were synthesized in moderate to good yields (13–86 %). The functionalization of 4-hydroxy-2(5H)-furanones by the ^t BuOO group was performed with high selectivity in the presence of the cocktail of reactive oxidizing species, including metal and radical intermediates. The key species in the peroxidation process are probably the tert-butylperoxy radical or its Co(III) complex, which are generated from the Co(II)/TBHP system. Cycle cleavage, which would be expected for cyclic β-dicarbonyls based on previous reports, was observed to a large extent only for cyclic 1,3-diketones.

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