Oxymetallation. Part VIII. The stereochemistry of peroxymercuration of cyclohexene, norbornene, but-2-ene, and stilbene; intramolecular co-ordination in β-peroxyalkylmercury trifluoroacetates
Abstract
The configurations of peroxymercurials, RCHA(OOBut)CHB(HgTFA)R, prepared from mercuric trifluoroacetate have been assigned on the basis of vicinal proton–proton coupling constants (JAB). The structures of the cyclohexene and norbornene products are readily assigned from spectral similarity with other oxymercurials and they result from trans- and cis-addition respectively. In the but-2-ene (R = Me) and stilbene (R = Ph) products the assignments depend on comparisons between cis- and trans-derived diastereoisomers. The relative magnitudes of JAB and their behaviour upon addition of pyridine or replacement of trifluoroacetate by bromide indicate that there is intramolecular ButO ⋯ Hg co-ordination in the adducts and that the peroxymercurations involve trans-addition.