Thermolysis and CoII-tetraphenylporphyrin-catalysed decomposition of substituted cycloheptatriene endoperoxides: a new synthetic approach to substituted dihydrooxepines

Abstract

Photooxygenation of the carbonyl group-substituted cycloheptatrienes 14–17 affords the corresponding [2+4] cycloaddition products derived from cycloheptatriene and its valence isomer norcaradiene as well as rearranged aromatic compounds. Thermolysis of the cycloheptatriene endoperoxides 19, 22, 23, 26, 27 and 31 at 174 °C gives the corresponding bis-epoxides, no rearranged products being observed. However, treatment of 19, 26 and 31 with cobalt tetraphenylporphyrin provides the ring-opened products 47, 49 and 51 which are easily converted into the substituted 4,5-dihydrooxepine derivatives 48, 50 and 52. The outcome of Co-TPP-catalysed rearrangement is discussed in terms of different conformers.