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[摘要]：Nafion(R)-H is shown to be an effective promoter of epoxide cyclizations to aromatic positions. The reactions can be done by passing a solution of the epoxide through a column packed with Nafion(R)-H, or by stirring a mixture of the compound with the acidic promoter and then filtering off the solid and washing it with the appropriate solvent. The solvent mixture that gave the highest yields had a fluorine-containing solvent, and trifluoroethanol in 3-10% amounts seems to be particularly good at maximizing yields. In general, yields are comparable to the same reactions that have been promoted by Lewis acids such as SnCl3 and BF3. OEt2, but the workup is significantly easier. Because of the convenience of workup and the fast rates of reaction with this super-acid catalyst, many reactions can be done in a short time period. The reaction mixtures show almost no side products. A biomimetic cyclization was also investigated using the described protocol. |
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