3-Vinyl-1, 3, 5-hexatriene undergoes an extremely facile thermal electrocyclization to yield 2- vinyl-1, 3-cyclohexadiene. Cyclization is at least thirty times faster than 3-ethyl-1, 3, 5- hexatriene, the saturated analog. Activation parameters indicate that this electrocyclization is one of the most facile yet observed for an acyclic 6π-electron system.
