75305-52-1Relevant academic research and scientific papers
POLAR AND ANCHIMERIC EFFECTS IN THE SOLVOLYSIS OF 6-endo-SUBSTITUTED 2-NORBORNYL-p-TOLUENE-SULFONATES
Grob, Cyril A.,Guenther, Bettina,Hanreich, Reinhard
, p. 1211 - 1214 (1981)
A study of the influence of 6-endo substituents on the reactivity of 2-exo- and 2-endo-norbornyl p-toluenesulfonates 3 and 4, respectively, confirms that polar rather than steric effects control relative rates.
Synthese und Hydrolyse von 6endo-substituierten p-Toluolsulfonsaeure-estern.
Grob, Cyril A.,Guenther, Bettina,Hanreich, Reinhard
, p. 2288 - 2298 (2007/10/02)
The Synthesis and Hydrolysis of 6endo-Substituted 2endo-Norbornyl p-Toluenesulfonates; The hydrolysis products of the p-toluenesulfonates of several hitherto unknown 6endo-substituted 2endo-norbornanols have been determined.
Polar versus Steric Effects in the Solvolysis of 6endo-substituted 2endo-Norbornyl p-Toluenesulfonates
Grob, Cyril A.,Guenther, Bettina,Hanreich, Reinhard
, p. 2110 - 2117 (2007/10/02)
The solvolysis rates and products of the 6endo-R-substituted 2endo-norbornyl toluenesulfonates 6a-6i have been determined.The rates of 6a-6g correlate with the inductive constants ?qI of the 6endo-substituents and are not related to the size of the latter.It is therefore concluded that polar rather than steric effects control the exo/endo-rate ratios of norbornyl sulfonates.Products are derived mainly from rearranged 6exo-R-norbornyl cations when the substituent is an electron donor and from unrearranged 6endo-R-substituted cations when the substituent is an electron acceptor.
Carbon Participation in the Solvolysis of 6-exo-substituted 2-exo- and 2-endo-Norbornyl p-Toluenesulfonates. Norbornanes Part 5
Fischer, Walter,Grob, Cyril A.,Hanreich, Reinhard,Sprecher, Georg von,Waldner, Adrian
, p. 2298 - 2311 (2007/10/02)
The solvolysis rates and products of the 6-exo-substituted 2-exo- 1a-1u, and 2-endo-norbornyl p-toluenesulfonates 2a-2u, have been determined.In general, the rate constants for 1 and 2 (log k) correlate well with the inductive constants ?qI of the substituents at C(6); however, their sensitivity to ?qI is much larger in the 2-exo-series 1 than in the 2-endo-series 2.This differential transmission of polar effects is the cause of decreasing 2-exo/2-endo rate ratios from 2388 for R=t-C4H9 to 0.37 for R=Br, i.e., with increasing electron attraction by the substituent.The high sensitivity of the rate constants for the 2-exo-p-toluenesulfonates 1 to ?qI indicates an unusually strong inductive interaction between C(6) and the incipient cationic center at C(2).This interaction is ascribed to the participation of the pentacoordinate C(6)-atom, i.e. to 1,3-bridging, a consequence of steric hindrance of nucleophilic solvent participation in norbornanes.Donor substituents enhanche 1,3-bridging, lead to faster reactions and to the formation of 2-exo substitution products.Conversely, acceptor substituents reduce 1,3-bridging, decrease rates and facilitate the formation of 2-endo substitution products.Graded 1,3-bridging is discussed in the light of Winstein's nonclassical ion concept.
Carbon Participation in the Solvolysis of 6-endo-substituted 2-exo-Norbornyl Toluenesulfonates. Norbornanes Part 6
Grob, Cyril A.,Guenther, Bettina,Hanreich, Reinhard
, p. 2312 - 2321 (2007/10/02)
The solvolysis rate constants k for the 6-endo-substituted 2-exo-norbornyl toluenesulfonates 7 have been determined.Values of logk 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.
Die Hydrolyse von 6exo-substituierten 2exo- und 2endo-Norbornylestern der p-Toluolsulfonsaeure
Fischer, Walter,Grob, Cyril A.,Sprecher, Georg von,Waldner, Adrian
, p. 928 - 937 (2007/10/02)
Hydrolysis of the 6exo-substituted 2exo- and 2endo-norbornyl p-toluenesulfonates 1b-l and 2b-l, respectively, in 70percent dioxane led to different amounts of the following products: Unrearranged 2exo-norbornanols 3 and norbornenes 5, accompained in somes cases by small amounts of the rearranged Rendo-epimers 4 and 6 and by nortricyclenes 7.When the 6exo-substituent was a nucleophile group as in 1e-l and 2e-l, various amounts of tricyclic products were also formed by endo-cyclozation.These results show that the 2exo- and 2endo-esters 1 and 2, respectively, react by way of different intermediates.In cases where the 6exo-substituent was an n-electron donor, as in 1m-r and 2m-r, quantitative fragmentation to (3-cyclopentenyl)acetaldehyde (13) occurred.
