Epoxidation using dioxiranes

2012-09-27T12:00:16Z (GMT) by Lesley Walton
Chapter 1 contains a brief review of the historical background of dioxiranes and an outline of their more recent chemistry. The preparation of homochiral 2-fluoro-2-substituted-1-tetralones and ethyl 2-fluoro-1-indanone-2-carboxylate is described in Chapter 2 and the X-ray crystal structure of (1' R,2' R,5' R)-( -)-menthyl 2S-fluoro-1-tetralone-2- carboxylate presented. The synthesis of racemic 2,5,7 -trifluoro-1-indanone-2- carboxylate is also discussed. The dioxirane derivatives of the above ketones have been prepared in situ and have been shown to epoxidise trans-stilbene, trans-β-methylstyrene and 6-chloro-2,2-dimethyl-2H-1-benzopyran, but not enantioselectively. The individual results of these epoxidations are given in Chapter 3. The incorporation of fluorine into the aromatic ring of aryl alkyl ketones is shown to increase dioxirane reactivity. Chapter 4 briefly describes the reactions carried out in order to ascertain the optimum conditions for the epoxidation of alkenes by in situ derived dioxiranes. The rate of this oxidation was shown to be highly dependent on the concentration of the dioxirane in the organic phase. Described in Chapter 5 are the procedures used for the isolation of the dioxirane derivatives of dimethyldioxirane, 1,1, 1-trifluoroacetone, 2,2,2- trifluoroacetophenone, hexafluoroacetone and cyclohexanone, in solutions of the corresponding ketone with or without dichloromethane.