Reversibility effects on the stereoselectivity of Pt(II)-mediated cascade poly-ene cyclizations.

ABSTRACT: Cyclization of 1,5-dienes bearing nucleophilic traps with electrophilic trisphosphine pincer ligated Pt(II) complexes results in the formation of a polycyclic Pt-alkyl via a Pt(eta2-alkene) intermediate. With electron-rich triphosphine ligands, an equilibrium between the Pt(eta2-alkene) and Pt-alkyl was observed. The position of the equilibrium was sensitive to ligand basicity, conjugate acid strength, solvent polarity, and ring size. In cases where the ligand was electron poor and did not promote retrocyclization, the kinetic products adhering to the Stork-Eschenmoser postulate were observed (E-alkenes give trans-ring junctions). When retrocyclization was rapid, alternative thermodynamic products resulting from multistep rearrangements were observed (cis-[6,5]-bicycles). Under both kineti

SUBMITTER: Feducia JA 

PROVIDER: S-EPMC2586057 | biostudies-literature | 2008 Jan

REPOSITORIES: biostudies-literature