Thermische, nichtkatalysierte Cycloadditionen der Acrylverbindungen an Cycloheptatrien

The cycloaddition reactions of cycloheptatriene with acrylonitrile and methyl acrylate have been investigated in some detail. The exo ( 1 ) and endo ( 2 ) adducts resulting from the [2+2+2]‐cycloaddition of acrylic components to the 2,5‐positions of cycloheptatriene have been separated and the structures have been elucidated by NMR. The by‐products are 7‐ endo ‐substitued derivatives of bicyclo[4,2,1]nona‐2,4‐diene ( 3 ), resulting from the formal [6+2]‐cycloaddition to the 1,6‐positions of cycloheptatriene. The mechanism of their formation is discussed. Irradiation (λ = 253,7 nm) of 3 in various solvents gave an almost quantitativ yield of [2+2]‐cyclodimers of the 14 type. No intramolecular photocyclization of 3 to cyclobutenes 13a and/or 13b was observed.