Synthetic studies on anion and radical induced olefin cyclizations

Abstract

Anion Cyclizations The synthesis of cis-methyl-11-bromoundec-6-enoate and the attempted synthesis of trans-methyl-11-broinoundec-6-enoate, model compounds for anion cyclization, are presented. These compounds contain a terminal ester group which under suitable conditions provides the ester enolate, which acting as a nucleophile, could attack through the olefin bond on the terminal alkyl bromide. Isolation and identification of the cyclization products would provide a means of determining: the degree of stereospecificity. The attempted cyclization of cis-methyl-11- bromoundec-6-enoate by treatment with the lithium salt of cyclohexylisopropylamine is described. Radical Cyclizations Free radical reactions of 1,10-dichloro-5-decyne and cis-1,10-dichloro-5-decene have been studied. The reactions were performed in dilute solutions in order to minimize intermolecular reactions and were initiated with tri-n-butyltin hydride from the dichlorides. The products were separated and collected by preparative gas chromatography, and consisted of a series of mono-, bi-, and acyclic compounds. The structure of the individual products was established by spectroscopic analyses (nmr, gc-ms). A radical mechanism is indicated by the nature of these products.