258345-33-4Relevant academic research and scientific papers
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.
Die Synthese von 6exo-substituierten p-Toluolsulfonsaeure-estern
Fischer, Walter,Grob, Cyril A.,Sprecher, Georg von,Waldner, Adrian
, p. 816 - 823 (2007/10/02)
The preparation of hitherto unknown p-toluenesulfonates of 6exo-substituted 2endo-norbornanols is described.
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.
ACTION DU N-BROMOSUCCINIMIDE SUR LES DIOXOLANNES EN SERIE BICYCLOHEPTANIQUE. LIMITATION DES TRANSPOSITIONS DE WAGNER-MEERWEIN
Bazbouz, Akram,Christol, Henri,Coste, Jacques,Plenat, Francoise
, p. 2745 - 2755 (2007/10/02)
Vicinal benzoyloxy-trans-bicycloheptanic bromhydrins, otherwise difficult to obtain are formed from N-bromosuccinimide and norbornanes bearing a 2-aryl-1,3 dioxolane skeleton.The greater stability of the intermediate dioxolenium ion reduces the tendency towards both Wagner-Meerwein rearrangement and neighbouring group participation by chlorine, processes usually observed when a less stable intermediate is involved.Nevertheless, methoxycarbonyl neighbouring group participation and Wagner-Meerwein rearrangement occur in methoxycarbonylbicycloheptane and in a bornanic compound respectively.
Die Synthese von 6exo-substituierten p-Toluolsulfonsaeure-estern
Fischer, Walter von,Grob, Cyril A.,Sprecher, Georg von
, p. 806 - 815 (2007/10/02)
A number of hitherto unknown 6exo-substituted 2exo-norbornanols and their p-toluenesulfonates have been prepared by functionalization of intermediate norbornenes.
