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.
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 beta-ketoiminato complexes to afford highly enantio-enriched 4-hydroxy-2,3-epoxy-ketones are also presented.
Greatrex
Ben W
BW
Department of Chemistry, The University of Adelaide, South Australia 5004.
Jenkins
Natalie F
NF
Taylor
Dennis K
DK
Tiekink
Edward R T
ER