DO FLUORINE-ATOMS ATTACHED TO SP(2)-HYBRIDIZED CARBON-ATOMS HINDER ELECTROPHILIC ADDITION TO THE C=C BOND

Interaction of mercuric trifluoroacetate with 2,3-difluorobicyclo[2.2. 1]hepta-2,5-diene (I) in a non-polar medium leads to adduct IIa, forme d as a result of exo-cis-addition of the salt to the FC=CF bonds of tw o diene molecules. Under the action of mercuric acetate in acetic acid , diene I gives an exo-cis-adduct to the FC=CF bond (IIb) as well as o ne to the HC=CH (IIc) in a 3:2 ratio. Adduct IIb reacts with excess Hg (OCOCH3)(2) and isomerizes to the tricyclic exo,exo-adduct IId. Diene IV, i.e. ,4a,5,8,8a-hexahydro-1,4,5,8-dimethanonaphthalene, reacts wit h anhydrous CF3COOH adding two molecules of the acid non-stereospecifi cally to both double bonds, and giving a mixture of isomeric bis-adduc ts V. A mixture of the monoadducts to the FC=CF and HC=CH bonds is for med in a 1:1.7 ratio when IV interacts with CF3COOH in CH2Cl2. It is n otable that addition to the FC=CF bond leads to the euo-trifluoroaceta te VIa whereas reaction with the HC=CH bond gives a mixture of exo- an d endo-trifluoroacetate, VIb and VIc. The relative activities of the d ouble bonds in I and IV are discussed.