The preparation of perfluoroalkenyl allenes (trienes) and pentafluorophenyl allenes

Trifluorovinyl- and (Z)-pentafluoropropenylcopper reagents readily react with propargylic halides or tosylates. With primary propargylic substrates, the major product is the alkyne. With secondary propargylic substrates, mixtures of alkyne/allene are obtained; the allene product is the major product. With tertiary propargylic substrates, the allene is regiospecifically and stereospecifically formed in good isolated yields. With pentafluorophenyl copper and primary propargylic substrates, the major product is pentafluorobenzene. With secondary and tertiary propargylic substrates, the allene is regiospecifically formed in good isolated yields.