Titanocene(III) chloride mediated radical-induced opening of monosubstituted epoxy acetates for the synthesis of primary allylic alcohols

The radical chemistry has become an inevitable tool to the organic chemists now a days for the formation of carbon-carbon bonds. Prolific use of this particular field of chemistry is well established and growing continuously for the synthesis of carbocyclic as well as heterocyclic natural products. High stereo-and regioselectivity and mildness of the radical technique unaffecting various sensitive functional groups makes it a common tool for the synthesis of important organic molecules. Titanocene(III) chloride (Cp2TiCl) mediated selective homolytic epoxide ring opening has established a new era of developing new methodologies for various synthetic strategies eventually leading to numerous biologically active natural products. Radical generated by epoxide ring cleavage takes part in intra-or intermolecular reaction including cascade pathway with an electrophilic radical acceptor depending on either the mode of the reaction or the substrate framework. The commonly used radical acceptors are carbonyl groups or double and triple bonds. But the outcome of this array of reactions is mainly inter or intramolecular addition products, with some rare and isolated examples of elimination reactions. Most of the reported transformations deal either with cyclic epoxy alcohols and acetates in carvone systems or di, tri and tetra substituted epoxy alcohols. However, such type of transformations are yet to be explored for the monosubstituted 2,3-epoxy alcohols and acetates. Herein is reported a mild and simple methodology for the synthesis of primary allylic alcohols by Cp2TiCl mediated epoxide ring opening of monosubstituted epoxy acetates via the acetate elimination reaction as well as the experimental investigation to establish the mechanism of the reaction. Titanocene(III) chloride (Cp2TiCl) was prepared from commercially available Cp2TiCl2 and Zn dust in THF under argon. Some of our results differ from the reported works as may be realized from the following discussion.