THE USE OF NAFION(R)-H TO PROMOTE EPOXIDE CYCLIZATIONS

Nafion(R)-H is shown to be an effective promoter of epoxide cyclizatio ns to aromatic positions. The reactions can be done by passing a solut ion of the epoxide through a column packed with Nafion(R)-H, or by sti rring a mixture of the compound with the acidic promoter and then filt ering off the solid and washing it with the appropriate solvent. The s olvent mixture that gave the highest yields had a fluorine-containing solvent, and trifluoroethanol in 3-10% amounts seems to be particularl y good at maximizing yields. In general, yields are comparable to the same reactions that have been promoted by Lewis acids such as SnCl3 an d BF3. OEt2, but the workup is significantly easier. Because of the co nvenience of workup and the fast rates of reaction with this super-aci d catalyst, many reactions can be done in a short time period. The rea ction mixtures show almost no side products. A biomimetic cyclization was also investigated using the described protocol.