Aromatic and vinylic cyclometallations with palladium II

Abstract

This thesis is concerned with the formation of palladium-carbon sigma bonds by an intramolecular cyclometallation reaction. 1-Tetralone oximes metallate to form dimeric chlorine-bridged complexes. Palladation fails when an isopropyl group is adjacent to the aromatic carbon to be metallated. The progress of reaction between 1-tetralone oximes and palladium II can be followed by n.m.r. spectroscopy. The mechanism may be explained by initial nitrogen co-ordination, followed by formation of a π-species which then appears to form the sigma-bonded complex by an irreversible process. The cyclometallation reaction can be extended to oxime derivatives of the N.Z. naturally occurring compound, Podocarpic Acid. The oximes of 1-benzalcyclohexanone and 1-acetylcyclohexene metallate by an intramolecular process, but straight chain α,β-unsaturated oximes do not. Successful reactions of palladium-carbon bonds to form substituted organic compounds appear to involve an insertion process. A high yield route to 12-methoxynorpodocarpatetraenes gives an alkene mixture which may be isomerised to predominantly one isomer. Steroidal analogues may be synthesised from the different alkenes. The stereochemistry at C10 prevents the formation of C19-ethynyl carbinol derivatives of Podocarpic Acid.