摘要：

Beckmann rearrangement of 4,9-methano[11]annulenone oxime with tosyl chloride in pyridine and subsequent direct methanolysis leads to azaannulene 5 in 90% yield. The oxime of 3,8-methano[11]annulenone rearranges only with difficulty to give β-lactam 13. The valence isomeric lactam 14 cannot be detected at temperatures up to 110°. The contrasting behavior of 8 and 13 and the question of heavy thermodynamic weighting in the direction of the bridged cycloheptatriene form are discussed. It is concluded that planar bridged cycloheptatriene derivatives are more stable because of lessened strain and electronic delocalization of the neutral homoaromatic type. The electrochemical reduction of 5 reveals that multielectron (2ε) discharge occurs, but that the resulting dianion is highly reactive or unstable (cyclic voltammetry data). Alkali metal reductions performed in liquid ammonia support the surprising instability of dianion 18. Dihydro products 19 and 20 were formed upon quenching.

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