Xi-kui Jiang, Chengxue Zhao, Y. Gong
1991
Citations
0
Influential Citations
14
Citations
Journal
Journal of Physical Organic Chemistry
Abstract
In the reactions of 2,5-di-tert-butyl-1,4-dimethoxybezene (1) with different oxidants, the radical cation 1+. is always detectable by EPR. However, the observed reactivity of 1+. depends greatly on the oxidation systems employed. In S2OCu2+HOAc and Ce4+HOAc systems (HOAc = acetic acid), 1+. appears to have long lifetimes and does not undergo fragmentation spontaneously. In contrast, in (RFCO2)2CF2CICFCI2 (F113) systems, the readily formed 1+. is short-lived, and large amounts of de-tert-butylation products have been isolated. Experimental results imply that the CC bond cleavage involved in de-tert-butylation could be a consequence of an attack by perfluoroacyloxy radical on 1+. in their original solvent cage. The fact that addition of methanol to the reaction mixture leads to the formation of a large amount of tBuOCH3 (46%) and other evidence suggest that the tert-butyl group leaves as a carbocation. On the basis of these results, we conclude that the reactions of 1 with (RFCO2)2 are initiated by electron transfer and followed by a fast coupling of various radical species, namely, 1+. with RFCO2 or with RF in the solvent cage, to form σ-complexes which collapse or react with nucleophiles to yield the final products.