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Abstract
The preparation of epoxides is efficiently achieved by reaction of alkenes with I2 in aqueous dioxane in the presence of Cu(OAc)2.H2O followed by treatment with KOH in a biphasic system (H2O/ether/pentane).
Notes
We noted that the yield is somewhat reduced if the iodohydrin was left for a long time under reduced pressure. trans-2-Iodocyclohexanol (2a) was reported to sublime under vacuum: Heilbron, M.I. and Bunbury, H.M. ed. “Dictionary of Organic Compounds”, vol II, Oxford University Press, New York, 1943, p. 372.
Our experience showed that all iodohydrins are sufficiently stable to be handled at room temperature for hours, except for 2b which decomposed to iodine and a mixture of unidentified products after being left at room temperature overnight. All iodohydrins could be stored without decomposition in a freezer for at least one month. In this large scale preparation crystallization may occur for some iodohydrins after some time freezer, or just after their preparation.
2e was obtained with 2-iodo-1-hexanol [ca. 10% by HRGC, MS : m/z (%) 55 (100); 83; 101; 126; 171; 228 (M+, 1), HRGC: tR 5.4 min (RTX-5)].