Synthesis and biological evaluation of new bicyclic fluorinated uracils through ring-closing metathesis

Two families of bicyclic fluorinated uracils are prepared starting from a gem-difluorinated unsaturated nitrile by means of a ring-closing metathesis reaction to form the new ring, which is fused at the C-5/C-6 or N-1/C-6 positions of the uracil moiety. The selective formation of olefin regioisomers in the metathesis process could be controlled according to the reaction conditions.