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.