The formation of 5,6,7,8-Tetrahydronaphthalene-1,3-dicarbonitrile by thermal rearrangement of Cyclohex-1-enyl(prop-2-ynyl)malononitrile

Abstract

Cyclohex-1-enyl(prop-2-ynyl)malononitrile (1), heated neat at 200°, forms 5,6,7,8-tetrahydronaphthalene-1,3-dicarbonitrile (2) and much polymer. Two probable intermediates (4) and (5) have been isolated from rearrangements at lower temperatures and in hydrocarbon solvents. A reaction pathway is proposed which includes Cope rearrangement, apparent [1,3]H shift, electrocyclic reaction, [1,5]CN shift, and dehydrogenation. An o-quinonoid imine (10) has been trapped with N- phenylmaleimide and other dienophiles. Dehydrogenation of the adduct (11) with Pd/C in boiling Ph₂O proceeds with hydrogenolysis of a cyano group to a methyl group.