Helvetica Chimica Acta p. 2298 - 2311 (1981)
Update date:2022-07-30
Topics:
Fischer, Walter
Grob, Cyril A.
Hanreich, Reinhard
Sprecher, Georg von
Waldner, Adrian
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.
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Doi:10.1007/BF02758943
(1892)Doi:10.1016/S0957-4166(97)00052-9
(1997)Doi:10.1016/S0040-4020(97)00211-1
(1997)Doi:10.1016/S0040-4039(01)98737-4
(1968)Doi:10.1021/jo00056a029
(1993)Doi:10.1016/S0022-328X(96)06659-4
(1997)