Copper-free synthesis of skipped diynes via cross-coupling reactions of alkynylalanes with propargylic electrophiles.

Alkynylalanes provide a new, copper-free route to skipped diynes when combined with propargylic electrophiles bearing an aluminum-complexing leaving group. The reaction is mild, efficient, and, in contrast to copper-mediated methods, highly regioselective. [reaction: see text]

New method based on 1-(trimethysilyl)alk-1-yne to prepare 1,4-skipped diynes.

[reaction: see text] We have developed a novel reaction between a terminal TMS-alkyne and a propargyl halide in the presence of a fluoride source and a catalytic amount of copper iodide to prepare 1,4-skipped diynes with good yields and in mild conditions. We have shown that this reaction also works very well with germanium and tin derivatives as an alternative to silicon. This new method can be useful for the synthesis of polyunsaturated fatty acids.