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

TY - JOUR

T1 - 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

AU - Fairlamb, Ian J. S.

AU - Grant, Stephanie

AU - Tommasi, Simona

AU - Lynam, Jason M.

AU - Bandini, Marco

AU - Dong, Hao

AU - Lin, Zhenyang

AU - Whitwood, Adrian C.

PY - 2006/11/27

Y1 - 2006/11/27

N2 - 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.

AB - 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.

KW - anion effects

KW - C-C bond formation

KW - cyclization

KW - isomerization

KW - palladium

KW - PALLADIUM-CATALYZED CYCLOISOMERIZATION

KW - CLOSING OLEFIN METATHESIS

KW - ACID-PROMOTED CYCLIZATION

KW - HYDRIDE DONOR ABILITIES

KW - ASYMMETRIC HYDROGENATION

KW - HETEROCYCLIC-COMPOUNDS

KW - COUPLING REACTIONS

KW - BOND FORMATION

KW - COMPLEXES M

KW - C-C

U2 - 10.1002/adsc.200600346

DO - 10.1002/adsc.200600346

M3 - Article

SN - 1615-4150

VL - 348

SP - 2515

EP - 2530

JO - Advanced Synthesis and Catalysis

JF - Advanced Synthesis and Catalysis

IS - 16-17

ER -