Carbon Participation in the Solvolysis of 6‐endo‐Substituted 2‐exo‐Norbornyl Toluenesulfonates. Norbornanes part 6

Abstract

The solvolysis rate constants k for the 6-endo-substituted 2-exo-norbornyl toluenesulfonates 7 have been determined. Values of log k correlate well with the respective inductive constants of the substituents except when the latter are nucleophilic and therefore lead to endo-cyclization, or when they are n-electron donors and cause concerted fragmentation. In general 6-endo-substituted tosylates 7 react somewhat more slowly than their 6-exo-epimers.Identical or different mixtures were obtained from the C(6)-epimers 7 and 1 depending on whether the substituent was an electron donor or acceptor. It is concluded that donor substituents at C (6) enhance 1,3-bridging in the intermediate epimeric cations and lead to their rapid and complete equilibration, and that electron acceptors reduce bridging and hence their equilibration rates.Corresponding author. 2,Norbornanes, Part 5: [l].

Carbon Participation in the Solvolysis of 6‐ and 7‐Substituted 2‐Norbornyl p‐Toluenesulfonates. Norbornanes, Part 11

“…This indicates that C(6)-C(2)-bridging occurs in the incipient ion pair 18 from 12. But not being directly attached to C (6), the 7-anti-substituents have less effect on rates, as the lower p,value shows. Bridging in the intermediate cations 18 is confirmed by the exclusive formation of the 2-exo-norbornanols 19 with retention of configuration.…”

“…Finally, reversible Wagner-Meerwein rearrangements of the cations 3 and 4 were fast relative to their capture by solvent when R was a donor, but slow when R was an acceptor, as in 5 and 6 [6], a sign that bridging and rearrangement are related.…”

The reactions of norbornyl-type cations derived from the reaction of silver toluene-4-sulphonate with 3-substituted 5-iodonorbornane-2,6-lactones

“…C14H1402 requires C, 79.2; H, 5.773, v, , , . (CHzC12) 1 770 (s, CO), and 1 600 cm-' (m, aromatic); 6(250 MHz; CDC13) 1.97br (t, 7-anti-, 7-syn-H), 2.12 (dd, 5-H), 2.29 (dm, 4-H), 2.76br (s, 1-H), 3.09 (d, 2-H), 4.91 (t, 6-H), 7.30 (m, aromatic); J(1, 2) 2.2, (1, 6) 2.5, (4, 5) 5, (5,6) -A solution of the S-lactone (14b) (0.2 g, 0.57 mmol) in anhydrous acetonitrile (4 ml) was added dropwise to a well stirred solution of silver toluene-4-sulphonate (0.3 g, 1.1 mmol) in anhydrous acetonitrile (10 ml) cooled in an ice-water-bath. The reaction was performed under nitrogen and with protection from light.…”