Uncatalysed olefin metathesis reaction
Abstract
The 1,1,2,2-tetracyanodispiro[3.0.2.x]alkanes (7a and b) manifest two modes of thermal cleavage (180°C) of the 4-membered ring, giving rise to the respective 4-dicyanomethylene-spiro [2.x]alkanes (9a and b) with extrusion of vinylidenecyanide, and the respective intramolecular [3 + 4] cycloaddition products (11a and b) in a ratio depending on the solvent used; the formation of the respective olefin metathesis product (3) from the reaction of TCNE with (1) in MeNO2 is explained in terms of an initial formation of the thermally unstable cyclobutane (2), undergoing ring-fusion to yield the products.