Wiley InterScience Backfile Collection 1832-2000
Chemistry and Pharmacology
Mechanism of the Reaction of Trifluoromethanesulfonic Anhydride with Ketones: Reaction with CamphorReaction of camphor (1) with trifluoromethanesulfonic anhydride (Tf2O) in the absence of base yields a mixture of 2,2-bis(trifluoromethylsulfonyloxy)camphane (9), 1,2-bis(trifluoromethylsulfonyloxy)-endo-isocamphane (10), and 2,4-bis(trifluoromethylsulfonyloxy)-endo-isocamphane (11). The ratio of these compounds depends on the reaction temperature. 9, 10, and 11 could not be isolated because, during the final aqueous treatment, they undergo hydrolysis leading to 1, 1-camphenyl triflate (2), and 4-camphenyl triflate (3). In the presence of 2,6-di-tert-butyl-4-methylpyridine (DTBMP) 2 is the main reaction product. The reaction rate is independent of the base concentration. It can be inferred that the base only neutralized the trifluoromethanesulfonic acid (TfOH), without reaction with Tf2O. - Reaction of 2 with TfOH in dichloromethane takes place with addition and Nametkin rearrangement. The ratio of these reactions depends on the reaction temperature. No rearrangement products are obtained in the reaction of 1 with TfOH. The reaction paths for the reaction of 1 with Tf2O are compared with those for other ketones, and some conclusions on the electronic requirements of the Nametkin rearrangement are inferred.
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