Vinylcyanoacetylene (C₂H₃C₃N or H₂C=CH–C≡C–C≡N) was detected toward TMC-1 by Lee and co-workers, as reported in 2021. The observations were made with the 100m GBT and relied in part on experimental data from Thorwirth and co-workers. The detection has not yet been confirmed with subsequent observations.

Vinylcyanoacetylene is more properly named 4-penten-2-ynenitrile because there are five (penta) carbon atoms, including a nitrile (–C≡N) group. There is a triple bond between carbon atoms 2 and 3 (the "2-yne" part of the name) and a double bond between carbon atoms 4 and 5 [the "4-penten(e)" part of the name].

As a nitrile, vinylcyanoacetylene is a member of the extensive list of known cyano-, isocyano-, and cyanide-containing astromolecules.