The Stille cross-coupling of the bromoallenes 3 with the stannylalkynes 6 or distannylalkyne 8 provided a convenient route for the synthesis of the conjugated yne-allenes 7 or the diastereomeric yne-diallenes, meso-9 and (R,R)/(S,S)-9. Analogously to 7, the phosphorylyne-allenes 14 were also prepared under Stille conditions, starting from the phosphorylallenes 12 and propargylstannane 6a. Alternatively, yne-allenes 17 and 18 were obtained from hexadiynol 16 with orthoester 2b or diethoxychlorophosphane 13a by [3.3]- and [2.3]-sigmatropic rearrangements.
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Saalfrank et al. (1999) studied this question.