Prior to the development of the petroleum industry, coal was the promary source of organic chemicals. Acetylene can be synthesized from the carbon in coal, but it takes a couple of steps:
Synthesis of Calcium carbide: CaO (from roasting of limestone) reacts with carbon (coke, from coal) to make CaC2.
Calcium carbide is a diacetylide, and a ready source of the acetylide anion synthon. We've seen it used to make long chain alkynes, and reaction with water forms acetylene and Ca(OH)2.
In the 1940s, German chemist Walter Reppe discovered a really neat catalytic way to make 1,3,5,7-cyclooctatetraene. This had previously only been prepared via a very laborious 13-step synthesis in the early 1900s. The mechanism is thought to involve cyclization of two acetylenes on a nickel center to form a "metallacyclopentadiene," and that two of these sequentially link ends to first make a C8 chain, and then the carbocycle:
A catalyst formed from Ni salts and calcium carbide reacts with acetylene to form benzene (which is more cheaply isolated from petroleum) and cyclooctatetraene.
(Fun fact: Dr. Gable did his Ph. D. thesis studying the catalyst and found evidence that it's a complex organic framework assembled from the acetylides that supports a number of reduced Ni atoms. See paper in Organometallics.

One application was discovered in the 1990s. Another metal-catalyzed process called "olefin metathesis" essentially switches ends of two molecules with double bonds. When this is done with cyclooctatetraene, the rings open up and link together, resulting eventually in a high polymer. This "Ring-Opening Metathesis Polymerization" or "ROMP" results in a long chain of conjugated double bonds. This is conductive, and its discovery was awarded the Nobel Prize in 2000.
A ruthenium catalyst performs ROMP on cyclooctatetraene to form a long chain of conjugated double bonds. The color changes from yellow, to orange, to red, to black, to silver (reflective) as the chain length grows.
A paper with a picture of a sample of conductive polyacetylene: https://iopscience.iop.org/article/10.1088/1757-899X/54/1/012019/pdf