Photorearrangement of 2-cyanobicyclohept-2-ene. Observation of 1,2- and 1,3-sigmatropic shifts

Article abstract of DOI:10.1139/v82-226

Irradiation of 2-cyanobicyclo<2.2.1>hept-2-ene (2-cyanonorbornene, 4) in hexane, with the full arc of a mercury vapour lamp, gives the rearrangement products 1-cyanobicyclo<4.1.0>hept-2-ene 5 and 7-cyanotricyclo<4.1.0.0^3,7>heptane 6 in the ratio 20:1.These products were separated by preparative vpc.The structure of the major product 5 was determined by single crystal X-ray analysis.Reduction of 5 with lithium aluminum hydride gave the corresponding primary amine, which was converted to the p-bomobenzenesulfonamide 9, mp 150-151 deg C, which gave single crystals from ethanol-water.The crystal and molecular structures are described.The minor product 6 was hydrogenated to give 7-cyanobicyclo<2.2.1>heptane.Formation of 5 and 6 may involve concerted ?_2s + ?_2s and ?_2a + ?_2a processes respectively, which are photochemically allowed.