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- orendo-Envelope) in the Bicyclic Ligand Scaffold
作者:Ian J. S. Fairlamb、Stephanie Grant、Simona Tommasi、Jason M. Lynam、Marco Bandini、Hao Dong、Zhenyang Lin、Adrian C. Whitwood
DOI:10.1002/adsc.200600346
日期:2006.11
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
双齿配体结构的变化显着影响单阳离子Pd(II)催化的1,6-二烯环异构化过程中的催化活性,从而得到环戊烯产物。双环[3.2.0]庚基二亚膦酸酯配体(B [3.2.0] DPO,3)是第一个能够促进区域选择性的1,6-二烯环异构化的磷基双齿配体。痕量的水对于催化活性至关重要,正如1,6-二烯,Pd(II)前催化剂和添加剂混合的精确顺序一样。配体主链的构象变化似乎对于稳定活性催化剂物质(假定是阳离子Pd(II)氢化物物质)很重要。DFT计算支持阳离子Pd(II)氢化物物种的咬合角从大约90°(顺式)到170°(反式); 在后一种几何结构中,双环系统的C4内氢与Pd(II)的有害相互作用稳定了阳离子金属中心。这种独特的配体性质可以在其他过渡金属催化的过程中得到利用。