Fluorine-containing 1,1-dicyanoethylenes: their preparation, diels-alder reactions, and derived norbornenes and norbornanes

Abstract

Several new 1,1-dicyanoethylenes, which are potent dienophiles, were prepared in two or more steps by the condensation of fluorocarbonyl compounds with malononitrile. These include (NC) 2CC(Cl)R f (R f is CF 3, C 2F 5, and C 3F 7) obtained from perfluorocarboxylic acid esters, KCH(CN) 2 and PCl 5, and CF 3 (CF 2Cl)CC(CN) 2 from CF 3COCF 2Cl and malononitrile. Reaction of cyclopentadiene with these new dienophiles, and also with the known (CF 3) 2CC(CN) 2, ClHCC(CN) 2, and Cl 2CC(CN) 2, gave dicyanonorbornenes. Addition of chlorine, bromine, or hydrogen to the norbornenes gave norbornanes. Many of these compounds are exceptionally toxic. For example, 2,2-dicyano-5,6-dichloro-3,3-bis(trifluoromethyl)norbornane has an approximate lethal dose for rats of only 0.2 mg/kg, indicating it to be one of the most potent synthetic oral toxins known.