Fairlamb, I.J.S., Grant, S., Tommasi, S., Lynam, J.M., Bandini, M., Dong, H., Lin, Z. and Whitwood, A.C. (2006) 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. Advanced Synthesis & Catalysis, 348 (16-17). pp. 2515-2530. ISSN 1615-4150Full text not available from this repository.
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° (cis) to 170° (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.
|Keywords:||anion effects • CC bond formation • cyclization • isomerization • palladium|
|Institution:||The University of York|
|Academic Units:||The University of York > Chemistry (York)|
|Depositing User:||York RAE Import|
|Date Deposited:||28 Aug 2009 10:55|
|Last Modified:||28 Aug 2009 10:55|
|Publisher:||John Wiley & Sons|