No abstract

Communications to the EditorOn the Intermediacy of Tetracyclo[3.2.0.02'7.04'6]hept-l(7)-ene, a Highly Strained Bridgehead Olefin Sir:Recently evidence has been accumulated that tricyclo[4.1.0.02'7]hept-l(7)-ene and related bicyclo[1.1.0]but-1 (3)-ene derivatives are formed as fleeting intermediates, when the corresponding bridgehead-halogen-substituted bicyclo[1.1.0]butanes are treated with a strong base.1 We now report our preliminary results on the quadricyclane2 system which indicate that the title compound might be a short-lived species, generated by the base treatment of 1-chloroquadricyclane (lc). Scheme I 1cThe synthesis of lc was achieved by metalating quadricyclane (la)3 with the «-butyllithium-tetramethylethylenediamine complex to lb (in «-hexane, 24 h at 20 °C) and chlorinating lb with /i-toluenesulfonyl chloride4 (yield 44%). Structure proof for lc rests on its 13C NMR spectrum ((CDC13) 14.04 (d), 23.65 (d), 24.92 (d), 26.97 (d), 31.23 (t), 31.73 (d), 45.77 (s)), its mass spectrum (m/e 126, 128 (M+)), and its facile conversion to 2-chloronorbornadiene,5 either thermally at 140 °C (in C(X>e, sealed NMR tube), or by catalysis with a trace of silver trifluoromethylsulfonate at 20 °C.

Bei der Lithiierung des Kohlenwasserstoffs (I) entsteht die Li‐Verbindung (II), die mit den Verbindungen (III) zu den Substitutionsprodukten (IV) führt.

Das Chlorid (I) ergibt mit überschüssigem Butyl‐Li in Äther in nahezu augenblicklicher Reaktion das Alkylderivat (IIa).

Bei der Behandlung des Chlorquadricyclans (I) mit BuLi entsteht über das Olefin (II) das Butylquadricyclan (III).