Perfluorovinyl and Perfluoroaryl Zinc and Cadmium Reagents

Abstract

F-Vinyl iodides and bromides react directly with cadmium or zinc metal to stereospecifically produce the corresponding F-vinyl cadmium and zinc reagents. These vinyl cadmium and zinc reagents exhibit excellent thermal stability (> 100°C) and do not couple with F-vinyl halides. Metathesis with Cu(I) salts gives the analogous F-vinyl copper reagents. The F-vinyl copper reagents readily undergo stereospecific alkylation, coupling and acylation reactions. They also add stereospecifically syn to F-2-butyne to produce F-dienyl copper reagents. Acylation of the dienyl copper reagent gives a dienyl ketone which spontaneously undergoes electrocyclization to a pyran derivative. The F-vinyl zinc reagents couple to aryl iodides in the presence of Pd° and provide useful stereoselective routes to α,β,β- trifluorostyrenes and 1-arylperfluoropropenes. Similar Pd° catalyzed coupling of the F-vinyl zinc reagent with 1-iodoperfluoroolefins provides a stereospecific route to F-dienes. Reaction of bromopentafluorobenzene with cadmium metal gives the analogous F-aryl cadmium reagent, which readily undergoes metathesis with Cu(I) salts to give the F-aryl copper reagent essentially quantitatively. The F-aryl copper reagent also adds stereospecifically syn to F-2-butyne to give a vinyl copper reagent which is easily alkylated, arylated or acylated.