Iodoacetamide-fluoride reaction

The anomalous iodoacetamide-fluoride reaction violates this rule, in that a less stable -halonium complex (18) must be involved, which then opens to (19) in the Markownikoff sense. This has been rationalized in the following way estimates of nonbonded destabilizing interactions in the possible products suggest that the actual product (16) is more stable than the alternative 6)5-fluoro-5a-iodo compound, so the reaction may be subject to a measure of thermodynamic control in the final attack of fluoride ion on the iodonium intermediate. To permit this, the a- and -iodonium complexes would have to exist in equilibrium with the original olefin, product formation being determined by a relatively high rate of attack upon the minor proportion of the less stable )9-iodonium ion. 

Iodoacetamide-fluoride reaction, 458 2a-Iodoandrost-4-ene-3,17-dione, 202 3/3-Iodocholest-5-ene, 443 19-Iodocholesterol acetate, 202 Iodofluorides, 457... 

---