Origins of stereoselectivity in radical additions: Reactions of alkenes and radicals bearing oxazolidine and thiazolidine amide groups

Article abstract of DOI:10.1021/ja00046a010

Single-crystal X-ray analysis of four alkenes that undergo stereoselective radical addition reactions are reported. The facial selectivity of radical additions to these alkenes is understood based upon their solid-state conformations. Alkenes which have a conformation placing a group at a position in space sterically protecting one of the faces from addition undergo radical addition with diastereofacial selectivity. The structures of the alkenes are analyzed by the polar coordinates of groups relative to the alkene center undergoing addition. The analysis of conformations of alkenes also provides a rationale for stereoselectivity in the reactions of radicals derived from the alkenes. Factors which influence the conformation of the alkene also apparently influence the conformation of analogous radicals. Several products of addition were also subjected to X-ray cryslallographic analysis, and the steric factors which influence the conformation of the reactant alkene are also observed to affect the conformation of the radical addition products.