160833-62-5Relevant articles and documents
Effects of γ-Cyano substituent in allylic bridgehead solvolyses: Evidence for cyano π conjugation in carbocations
Takeuchi, Ken'ichi,Kitagawa, Toshikazu,Ohga, Yasushi,Nakakimura, Akitoshi,Munakata, Motohiro
, p. 8155 - 8164 (1997)
Slightly flexible 4-methylene-3-homoadamantyl mesylate solvolyzes 2 x 105 times faster than rigid 2-methylene-1-adamantyl mesylate. Placement of a cyano substituent on the (E) position of the vinylic carbon of these systems hardly alter the rate ratio (6 x 105). The result suggests fortuitous cancellation of the inductive destabilizing effect of the cyano substituent by its mesomeric stabilizing effect toward the partially conjugated allylic cation. PM3 calculations on simple allylic cations as models supported the experimental results.
A typical example of rate acceleration by F-strain in solvolysis
Takeuchi, K.,Ohga, Y.,Kitagawa, T.
, p. 1631 - 1638 (2007/10/02)
The new bridgehead triflates or mesylates were synthesized for the Z and E forms of the 2-ethylidenebicyclooct-1-yl (3), 2-ethylidene-1-adamantyl (5), and 2-ethylidenebicyclonon-1-yl (7) systems, and their Z/E rate ratios at 25 deg C compared in the solvolysis in ethanol or 2,2,2-trifluoroethanol (TFE).The Z/E rate ratios are 217 for 3-OTf in EtOH and 126 for 5-OMs in TFE, suggesting the marked F-strain in such rigid Z systems.Contrarily, the Z/E rate ratio for rather flexible 7-OMs is O.30, demonstrating the importance of a rigid structure for exerting the F-strain.Molecular mechanics and AM1 calculations supported the rate data.
