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Let's take the conjugated alkyne chain (e) below, taken from Wikipedia:

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How would one typically go about synthesising such a conjugated chain with a series of alkyne functions?

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A carbenoid Fritsch-Buttenberg-Wiechell (FBW) rearrangement of a substituted dibromoolefinic precursor is used to generate a lithium acetylide, and subsequent trapping with carbon-based electrophiles provides a wide range of di- and triynes. The lithium acetylide formed from the FBW reaction can also undergo transmetalation to provide zinc, copper, tin, or platinum acetylides [1]. The paper described the preparation of poly-ynes of up to 6 triple bond units.

FBW reaction

Image source: organic-chemistry.org

References

  1. Luu, T.; Morisaki, Y.; Cunningham, N.; Tykwinski, R. R. One-Pot Formation and Derivatization of Di- and Triynes Based on the Fritsch−Buttenberg−Wiechell Rearrangement. J. Org. Chem. 2007, 72 (25), 9622–9629. https://doi.org/10.1021/jo701810g .
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Waylander
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    Limiting the target to diynes I mention the earlier still valuable oxidative coupling of terminal alkynes, copper catalysed, in air. – Alchimista Jul 02 '19 at 09:12