Base- and Co(II)-Catalyzed Ring-Opening Reactions of Perhydrooxireno[2,3-d][1,2]dioxines: An Efficient Route to 4-Hydroxy-2,3-epoxy-ketones

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Abstract
A series of 3,4,6-substituted 3,6-dihydro-1,2-dioxines were epoxidized with m-chloroperbenzoic acid to furnish perhydrooxireno[2,3-d][1,2]dioxines (epoxy-1,2-dioxines) in yields ranging from 51% to 93% with de's from 26% to 100%. Unsymmetrical epoxy-1,2-dioxines were ring-opened using triethylamine to yield 4-hydroxy-2,3-epoxy-ketones quantitatively, and meso-epoxy-1,2-dioxines were ring-opened using Co(II) salen complexes to afford 4-hydroxy-2,3-epoxy-ketones in 77−98% yield. The first reported examples of the catalytic asymmetric ring-opening of meso-epoxy-1,2-dioxines using a range of chiral Co(II) salen and β-ketoiminato complexes to afford highly enantio-enriched 4-hydroxy-2,3-epoxy-ketones are also presented.