Olefins Kharasch-Sosnovsky reactions

Recently, iron catalysis gained general importance. Its catalytic chemistry has been summarized ([2] recent reviews [3, 4]). Iron(II) and iron(III) salts have a long history in radical chemistry. The former are moderately active in atom-transfer reactions as well as initiators for the Fenton reaction with hydrogen peroxide or hydroperoxides (reviews [5-12]). Important applications of this principle are the Kharasch-Sosnovsky reaction (the allylic oxidation of olefins) [13], which often... 

Fig. 4.40 The Kharasch-Sosnovsky reaction for allylic oxidation of olefins.

Allylic Oxidation. The Kharasch-Sosnovsky reaction involves oxidation of the allylic position while the olefin remains intact. In the presence of catalytic copper (II) salts, treatment of olefins with peresters affords acylated allylic alcohols. When (S)-(—)-4-(2-methylpropyl)-2-(2-pyridyl)-2-oxazoline was involved, (R)-cyclohexenyl benzoate was isolated in 57% yield and 28% ee (eq 6). ... 

Scheme 8. Kharasch-Sosnovsky reaction of terminal olefins...

Scheme 14. Asymmetrization of racemic olefins by the Kharasch-Sosnovsky reaction...

The Pfaltz group developed a chiral boron-bridged bisoxazoline ligand (5,5)-L36 and tested its Cu complex in the Kharasch-Sosnovsky reaction of cyclic olefins. The enantioselectivity of the reaction (79% ee) was comparable with the previously reported best ones obtained using the BOX ligands. ... 

Although the asymmetric Kharasch-Sosnovsky reaction of cyclic olefins has been developed with high enantioselectivity, the results for acyclic olefins are unsatisfied in terms of the enantioselectivity and regioselectivity. For examples, in the recent work of the oxidation of allylbenzene reported by Ginotra and Singh (Scheme 5.69), only 60% yield of a mixture of benzoates (b l = 47 53) was obtained. The enantiomerie excess of branched product was only 40%. 1-Octene also gave a poor yield of branched and linear products in a ratio of 3 2 and low enantioselectivity (27% ee). ... 

Reaction with unsaturated compounds (reviews Kharasch,Sosnovsky,andYang reported that, in the presence of a catalytic amount of a copper or cobalt salt, t-butyl perbenzoate reacts with an olefin to give an allylic benzoate with no allylic rearrangement with a terminal olefin the only product isolated was the allylic ester with a terminal double bond. A further example is the reaction with 1-methylene-4-f-butylcyclohexane. However, in contrast to these early reports, Kochi found by o... 

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