Photoinduced reactions of Cr(CO)3-coordinated N-cyanoazepine: [6 + 4] cycloaddition with conjugated dienes

The tricarbonyl(N-cyanoazepine)chromium(0) complex (2) is formed when (MeCN)₃Cr(CO)₃ is treated photochemically with N-cyanoazepine (1). U.v photolysis of Cr(CO)₃( ⁶-N-cyanoazepine)chromium(0) (2) and conjugated dienes [1,3-butadiene (3), trans-1,3-pentadiene (4), trans,trans-2,4-hexadiene (5)] in PhMe give the [6 + 4]cycloadducts, tricarbonyl{ ^4:2-11-N-cyano-11-azabicyclo[4.4.1]-undeca-2,4,8-triene}chromium(0) complexes (6–8). The -complex (2) and these new bicyclic compounds (6–8) were purified by chromatography, recrystallized, isolated as analytically pure crystalline solids in moderate yields and characterized by mass, i.r. and n.m.r. spectroscopy. The heterobicyclotrienes, 11-N-cyano-11-azabicyclo[4.4.1]undeca-2,4,8-triene (9–11), were isolated from the complexes (6–8) by heating in PhMe, and their structures were assigned by the same spectroscopic methods.