Allyl cobaloximes

Our first choice of alkene was allyltributyltin which had been previously studied by our group (see above). By employing the chloro(pyridine)cobaloxime(III)/magnesium redox couple in which chloro(pyridine)cobaloxime(III) was used in the catalytic amount, we were now able to synthesize the same allylated PCTFE (Eq. 4) with a higher degree of functionalization of approximately 50%. 

In 1979, Johnson reported the first reactions of cobaloximes with carbon-centered radicals (Scheme 27) [71]. These reactions provide the allylated products in generally... 

When RX is easily reduced, as in the case of allyl iodides and benzyl bromides, the competing further reduction of the intermediate radical is suppressed and radical reactions such as dimerization, addition to double bonds and aromatic compounds or reaction with anions can be favored. The radical pathway can be also promoted by catalysis with reduced forms of vitamin Bn, cobaloximes or nickel complexes. These react with the alkyl halide by oxidative addition and release the alkyl radical by homolytic cleavage. 

Sh2 and Sh2 reactions have been devised to prepare sulfides or sulfones. The former ones are limited to highly strained carbocyclic compounds [6d-e, 76]. The latter ones are more common, and various vinylic or allylic derivatives including stan-nanes and cobaloximes are known to react with sulfur-centered radicals [77]. A representative example is shown in Eq. (32), where the three-membered ring in IH-cyclopropabenzene opens upon attack by various thiyl radicals to give the corresponding ort/zo-substituted toluenes. 

An Example of a Change in Mechanism in a Solvolysis Reaction Studied Using cr" 452 A Swain-Lupton Correlation for Tungsten-Bipyridine-Catalyzed Allylic Alkylation 453 Using Taft Parameters to Understand the Structures of Cobaloximes Vitamin 612 Mimics 455 The Use of the Schleyer Method to Determine the Extent of Nucleophilic Assistance in the Solvolysis of Aryl vinyl Tosylates 459... 

In a temperature-dependent n.m.r. study of alkyl cobaloximes it has been established that two differwt dynamic processes may occur, [equations (4) and (5)]. Both processes interchange the two possible allyl structures, (differentiated... 

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