A. Baumstark, F. Kovač, P. Vásquez,
2002
Citations
0
Influential Citations
3
Citations
Journal
Heterocyclic Communications
Abstract
Kinetic data (k2's, LFER and activation parameters) for the oxidation of a series of acetals by dimethyldioxirane to the corresponding esters in dried acetone are reported; the results are consistent with either a Η-atom abstraction or direct insertion mechanism. Introduction Dioxiranes are powerful, versatile oxidants for the mild oxidation of a great variety of organic substrates. Dimethyldioxirane is often the reagent of choice rather than the more reactive methyl(trifluoromethyl)dioxirane because of its inexpensive, facile preparation. Dimethyldioxirane has been shown to be useful in epoxidation, heteroatom oxidation and C-H oxidation. Specifically, extensive CH bond oxidation studies have been carried out on saturated hydrocarbons, phenyl-substituted hydrocarbons, aldehydes, alcohols and ethers. Several reports have appeared on the reactions of acetals with either dimethyldioxirane or methyl(trifluoromethyl)dioxirane. We report here a kinetic study of the oxidation of a series of acetals by dimethyldioxirane in dried acetone. Results The reaction of dimethyldioxirane 1 [isolated; -0.1 Μ in dried acetone] with substituted benzaldehyde dimethyl acetals (2a-c), 2-aryl-1,3-dioxolanes (3a-g), 2-methyl-1,3-dioxolane (4) and 2phenyl-1,3-dioxane (5) produced the corresponding esters in good to excellent yields (reaction 1). A threefold excess of 1 was employed to achieve efficient conversion. Product studies in the dark under inert X p-R1 R Ο ς Η O R t k2 acetone Ο Λ ο + II R C O R i (1) 1 2 Rj = Rj = Me 3,4 R1( Rj = .CH2CH25 R1( Rj = -CH2CH2CH2· (N2) atmosphere, yielded results essentially identical to those obtained when carried out under normal conditions (Table 1). The yields for oxidation of 2a and 3c are essentially identical to those previously