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Phosphinite ligand effects in palladium(II)-Catalysed cycloisomerisation of 1,6-dienes: Bicyclo[3.2.0]heptanyl diphosphinite (B[3.2.0]DPO) ligands exhibit flexible bite angles, an effect derived from conformational changes (exo- or endo-envelope) in the bicyclic ligand scaffold

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JournalAdvanced Synthesis and Catalysis
DatePublished - 27 Nov 2006
Issue number16-17
Volume348
Number of pages16
Pages (from-to)2515-2530
Original languageEnglish

Abstract

Changes in bidentate ligand structure significantly affect catalytic activity in mono-cationic Pd(II)-catalysed 1,6-diene cycloisomerisation processes to give cyclopentene products. A bicyclo[3.2.0]heptanyl diphosphinite ligand (B[3.2.0]DPO, 3) is the first phosphorus-based bidentate ligand capable of promoting regioselective 1,6-diene cycloisomerisation. Trace quantities of water are essential for catalytic activity, as is the precise order of mixing of 1,6-diene, Pd(II) pro-catalyst and additives. Conformational changes in the ligand backbone seem to be important in stabilising the active catalyst species, assumed to be a cationic Pd(II) hydride species. DFT calculations support a change in bite angle on the cationic Pd(II) hydride species from circa 90 degrees (cis) to 170 degrees (trans); in the latter geometry an agostic interaction of the C4 endo hydrogen of the bicyclic ring-system with Pd(II) stabilises the cationic metal centre. This unique ligand property could be exploited in other transition metal catalysed processes.

    Research areas

  • anion effects, C-C bond formation, cyclization, isomerization, palladium, PALLADIUM-CATALYZED CYCLOISOMERIZATION, CLOSING OLEFIN METATHESIS, ACID-PROMOTED CYCLIZATION, HYDRIDE DONOR ABILITIES, ASYMMETRIC HYDROGENATION, HETEROCYCLIC-COMPOUNDS, COUPLING REACTIONS, BOND FORMATION, COMPLEXES M, C-C

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