Cyclobutene is an organic compound with the chemical formula C4H6.

A modern synthesis involves the 2-step dehydration of cyclobutanol.

[1] The compound was first prepared by thermolysis of the ammonium salt [C4H7N(CH3)3]OH (cyclobutyltrimethylammonium hydroxide).

This strongly exothermic reaction reflects the dominance of ring strain.

In contrast, the corresponding equilibrium for hexafluorocyclobutene disfavors hexafluorobutadiene.