Differential bridging in the solvolysis of 6- and 7-substituted 2-exo and 2-endo-norbornyl p-toluenesulfonates

✍ Scribed by Peter Flury; Cyril A. Grob

• Publisher: Elsevier Science
• Year: 1983
• Tongue: French
• Weight: 204 KB
• Volume: 24
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)88133-2

✦ Synopsis

The large difference between the reaction constants p, for the solvolysis of the 6-exo-and 7-anti-substituted norbornyl tosylates 3 and 1, respectively, is further proof for the hypothesis that 2-norbornyl cations are anisotropic with regard to the transmission of polar effects and that through space induction involves graded bridging.

Evidence was recently presented that the ionization rates of bicyclic sulfonates in protic solvents are strongly affected by the bridging of the cationic center to a pentacoordinate R-carbon atom, as in 1 i. It was also suggested that the differences between the rates of epimeric sulfonates are due mainly to differential bridging strain in the respective transition states 2 and that effective 1,3-bridging requires that the back lobe of the R-C@ orbital overlap strongly with the incipient p-orbital of the cationic center, 3 as illustrated in 2 .