Thiol Additions to Bicyclo[l.l.O]butane Systems')The additions of thiols to bicycle[ 1.l.Olbutanes leading to cyclobutyl thioethers proceed via a radical chain mechanism. The intermediate thiyl radical opens the central bond of the strained ring system with inversion of configuration at the attacked carbon atom. The results of the thiol additions to a series of 1-substituted tricycl0[4.1.0.0~~~]heptanes 6 show that the thiyl radical regiospecifically approaches the sterically less hindered bridge-head position C-7 forming the more stable of the two possible cyclobutyl radicals (7 and not 10). The outcome of the thiophenol addition to the 1,3-disubstituted bicyclobutane 25 indicates that the orientation in the adduct depends more on steric factors in the bicyclobutane unit than on the energy content of the intermediate cyclobutyl radical. -A convenient route to norpinane is described.

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The rel. rate constants for the addition of the phenylthiyl radical to the C-t/C-3 bond of bicyclo-[ 1.1 .O]butanes, determined by competition experiments, revealed steric and electronic influences by the substituents. Electron acceptor substituents in the 1-position of the bicyclus slowed down the rate of the thiyl radical attack, whereas donor substituents enhanced this rate. In the series of 1-substituted tricyclo[4.1.0.02"]heptanes a reasonable correlation between the 1'' ionization potential and the log (kre,,) of the phenylthiyl radical addition was found.Uber stereo-und regiochemische Aspekte der Thiylradikal-Addition an die Zentralbindung des Bicyclol l.

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

Die Addition des Titelradikals an sterisch nahezu unveränderte Bicyclobutansysteme wie z.B. (I) zeigt, daß elektronenliefernde Brückenkopfsubstituenten die Reaktion beschleunigen, elektronenanziehende sie verzögern.