Regiochemistry, Stereochemistry, and Mechanism of Addition of Trifluoroacetic Acid to (Z)-Cyclooctene

Article abstract of DOI:10.1021/ja00317a039

The regiochemistry and stereochemistry of addition of CF3CO2D to cyclooctene have been established by 2H NMR analysis of the cyclooctanol derived from the trifluoroacetate product.A complex mixture dominated by (Z)-cyclootanol-2-d (4-OH) and (Z)-cyclooctanol-4-d (8-OH) was obtained after 99percent reaction of the olefin essentially under kinetic control.Determination of the product composition as a function of time and extrapolation to zero, however, established that the trifluoroacetates of 4-OH and 8-OH are the exclusive primary adducts.These and complementary results indicate that the reaction proceeds entirely by stereospecific formation of a 1,5-hydride-bridged carbonium ion which is partitioned between nucleophilic solvent attack and, to a lesser extent, reversion to olefin by nearly completely anti vicinal deprotonation or dedeuterionation.