Oxidation of Cyclic Ethers with Sodium Bromite in the Presence of Organoslicon Catalys

Abstract

Oxidation of cyclic ethers with sodium bromite (NaBrO2) in the presence of a catalytic amount of chlorotrimethylsilane (Me3SiC1) afforded coresponding lactones. The oxidizing system was shown to be useful for the preparation of rbutyrolactone from tetrahydrofuran (THF). Further, cyclic vinyl ethers were also oxidized readily and gave bromo substituted lactones in good yields. The oxidations of 6 and 7 membered cyclic eyhers to the lactones proceeded, but with less satisfactory results. In such cases, the use of hydrochloric acid as a co-catalyst led to an increase in the yields. On the other hand, tributylchlorostann ane (Bu3SnC1) and copper(II) sulfate, which presented a facile technuque for the activation of NaBrO2 as an oxidizing agent, were not effective in those reactions. As to the co-catalyst, the organic acids such as acetic, p-toluenesulfonic, and m-chlorobenzoic acid did not enhance the formation of lactones from THF. The oxidation reaction employing a catalytic amount of Me3SiC1a nd hydr ochloric acid with NaBrO2 was demonstrated to be usable as a convenient procedure for the one-pot transfor mation of cyclic ethers to lactones underjmild conditions.