Preparation of 3,2'-Annelated 2-Phenylpyridines and Their Cyclopalladation Chemistry

Article abstract of DOI:10.1021/jo00377a013

A series of 3,2'-polymethylene-bridged derivatives of 2-phenylpyridine has been prepared by thermolysis of O-allyloximes of 2,3-benzocycloalkanones.The electronic absorption and NMR spectra of these molecules may be related to the degree of nonplanarity of the system resulting from polymethylene bridging.These molecules react with palladium bis(acetylacetonate) and its hexafluoro derivative to give soluble, monomeric cyclopalladated products.Rates of cyclopalladation were measured for these systems as well as for 2-(phenyl-d5)pyridine, and the results indicate the liklihood that for the less planar substrates the deprotonation step may show increasing importance over the electrophilic attack of palladium on the phenyl ring.The possible oxidative addition of palladium to a phenyl C-H bond cannot be ruled out.