Neighboring group participation in solvolysis. III. κΔ solvolysis as the main path in trifluoroacetolysis of 2-arylethyl nosylates with electron-withdrawing substituents
✍ Scribed by Takashi Ando; Nobuaki Shimizu; Sueng-Geon Kim; Yuho Tsuno; Yasuhide Yukawa
- Publisher
- Elsevier Science
- Year
- 1973
- Tongue
- French
- Weight
- 213 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0040-4039
No coin nor oath required. For personal study only.
✦ Synopsis
In recent years solvolysis of 2-arylethyl arenesulfonates has been successfully discussed based on the idea that the reaction proceeds via two discrete and competing paths designated as k, and ks.
2-5 While electrondonating substituents accelerate the reaction mainly or almost exclusively by the anchimerically assisted pathway (kA), solvolysis of 2-arylethyl arenesulfonates having strongly electron-withdrawing substituents has been revealed
to proceed mainly by the solvent-assisted pathway (ks).
Recently, trifluoroacetic acid with its very low nucleophilicity and relatively high ionizing power has become an important solvolyzing solvent which gives rise to ka/ks ratios much higher than formic acid. 6,7
Consequently, it is interesting to investigate the behavior of trifluoroacetolysis of 2-arylethyl arenesulfonates having strongly electron-withdrawing substituents on the 2-aryl group and to determine the per cent fraction of the anchimerically assisted path in the total solvolytic reaction (FkA/kt).
Thompson and Cram reported that trifluoroacetolysis of 3-(p-nitrophenylj-2-butyl tosylate was mainly k,, 8 but the evidences obtained from the stereochemistry of the trifluoroacetates isolated as the minor products are, in our opinion, indirect and only qualitative. We now report the unambiguous and quantitative evidences supporting that trifluoroacetolysis of 2-(m-bromophenyl)ethyl and