Reactions of halonorbornane and oxo-substituted derivatives with different anions by the electron transfer mechanism; redox catalysis in stabilized radicals

Abstract

Reactions of 2-bromo-, 2-chloronorbornane, 3-chloronorbornan-2-one and 3-bromocamphor with Me 3 Sn À , Ph 2 P À or PhS À ions were studied by an S RN 1 mechanism in liquid ammonia or DMSO. The results show that substrates having a carbonyl group facilitate electron transfer reactions, which are impeded in the absence of such a group. However, when the free radical formed is stabilized by conjugation, the coupling reaction decreases, causing a concomitant increase in the reduction product. Theoretical studies explain the observed reactivity on the basis of a mechanism involving reductive cleavage as a function of the p-s interactions.

Reactivity of endo-3-bromocamphor with sulfur-centered nucleophiles by an electron transfer mechanism. Electrophilic behaviour of the 3-camphoryl radical

“…2 Consequently, the oxogroup may enhance the initiation steps by redox catalysis, allowing the formation of radicals. On the other hand, we have described the reactivity of 3-camphoryl radicals with diverse nucleophiles 3 and showed that those conjugated radicals can delay the coupling reactions due to their stability. 3 Other examples involving conjugated radicals have been reported.…”

“…On the other hand, we have described the reactivity of 3-camphoryl radicals with diverse nucleophiles 3 and showed that those conjugated radicals can delay the coupling reactions due to their stability. 3 Other examples involving conjugated radicals have been reported. For instance, p-nitro-1,1-dimethylphenacyl chloride afforded substitution products with 2-nitropropane, diethyl malonate or diethyl methylmalonate anions via the S RN 1 process, whereas classical substitutions were observed when PhSor p-MeC 6 H 4 SO 2 ions were used.…”