Epimeric 2-norbornyl cations in the solvolysis of 6-exo- and 6-endo-substituted 2-exo-norbornyl p-toluenesulfonates

ChemInform Abstract: NORBORNANES. PART 10. SOLVOLYSIS OF THE STEREOISOMERIC 6‐CYANO‐2‐NORBORNYL P‐TOLUENESULFONATES. A CORRECTION

“…These findings are in accordance with the view that nucleophilic attack on bridged norbornyl cations occurs predominantly on the unbridged exo-side of C (2), whereas attack can occur on both sides of C (2) in unbridged or weakly bridged norbornyl cations [ 11 [2]. In contradiction to this view no endo-alcohol 9 (R=CN) was detected among the solvolysis products of the cyano p-toluenesulfonates 1-3 (R= CN) [ 11 [2], although the cyano group (a?= 3.05) is considerably more electron-attracting than the fluorine atom (a?= 2.57). Instead, large amounts of the 'nortricyclenecarbonitrile' 15 were reported beside the 2exo-norbornanols 10 and 11, the olefins 12 and 13 and small amounts of the lactone 14.…”

“…The Table also reveals that only small amounts of the lactone 14 and traces of the 'nortricyclenecarbonitrile' 15 were formed. Furthermore, less than 8% of the products are derived from a Wagner-Meerwein rearrangement of the type 5 -6 or 6 4 5 which confirms that -I substituents hinder 1,3-bridging and hence also rearrangement [2].…”

“…k l / k 2 and k3/k4) and of the solvolysis products caused by varying the substituent R, in that 2exo-norbornanols only were obtained when R was an electron donor, whereas 2exo-and 2endo-substitution products resulted when R was an acceptor. Thus, due to the electron-attracting fluorine substituent, 1-3 (R = F) yielded 57, 7 and 4%, respectively, of 6exo-fluoro-2endo-norbornanol (9; R = F) beside the corresponding 2exo-alcohol when reacted in dioxane/water 7 : 3 (w/w) [ 11 [2]. Furthermore, considerable endo-cyclization took place when R was a nucleophilic substituent such as COOH, COOCH3 or CH20H.…”

“…Earlier kinetic studies have shown that the logarithms of the rate constants for the 6-substituted 2-norbornyl p-toluenesulfonates 1-3 correlate well with the inductive substituent constant of R except when the latter is a F-atom in the series 1 and 2 and the cyano group in the series 1 [ l ] [2]. In these cases solvolysis rates were faster by factors of 3 to 8 than calculated from the inductive regression line.…”