NEW DIPHOSPHINE LIGANDS BASED ON HETEROCYCLIC AROMATICS INDUCING VERY HIGH REGIOSELECTIVITY IN RHODIUM-CATALYZED HYDROFORMYLATION - EFFECT OF THE BITE ANGLE
NEW DIPHOSPHINE LIGANDS BASED ON HETEROCYCLIC AROMATICS INDUCING VERY HIGH REGIOSELECTIVITY IN RHODIUM-CATALYZED HYDROFORMYLATION - EFFECT OF THE BITE ANGLE
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DOI：
10.1021/om00006a057
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发表时间：
1995-06-01
期刊：
影响因子：
2.8
通讯作者：
FRAANJE, J
中科院分区：
文献类型：
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作者：
KRANENBURG, M;VANDERBURGT, YEM;FRAANJE, J
以一系列双齿双膦配体为配体，研究了咬合角对催化氢甲酰化反应区域选择性的影响。这些配体的咬合角通过配体主干的细微变化进行微调。当X的10位桥(X)发生变化时，由分子力学计算的咬合角从102度逐步增加到131度，而下列配体的空间体积效应和电子效应几乎没有变化：双(2-(二苯基膦)苯基)醚(DPEphos，1)，X=H，H；4，6-bis(diphenylphosphino)-10，10-dimethylphenoxasilin(Sixantphos，2)，X=Si(CH3)(2)；2，8-dimethyl-4，6-bis(diphenylphosphino)phenoxathiin(Thixantphos，3)，X=S；9，9-dimethyl-4，6-bis(diphenylphosphino)xanthene(Xantphos，4)，X=C(CH3)(2)；4，6-双(二苯基膦)二苯并呋喃(DBFphos，5)，X=键。在1-辛烯的氢甲酰化反应中，区域选择性增加。随着咬合角的增加有规律地增加：在40℃时，Xantphos可以得到98.3%的正醛，没有1-辛烯的异构化或加氢。DBFphos不形成络合物，因此没有观察到更高的选择性。温度升高到80℃时，催化剂的选择性几乎不受影响，具有较高的转化率(TOF)和恒定的选择性：97.7%的正醛，0.5%的异构化，TOF值为800mol(Mel Of Rh)(-1)h(-1)。到目前为止，在1-烯烃的氢甲酰化反应中，Xantphos对双膦化合物生成直链醛的选择性是最高的。合成了(双膦)Rh(H)(CO)(PPh(3))和(双膦)Rh(H)(CO)(2)，并用H-1，P-31和C-13核磁共振谱进行了确证。苯乙烯对直链醛的选择性也有所提高(70%的正醛与黄磷反应，而三苯基膦的选择性为11%)。报道了Xantphos配体的X-射线晶体结构(正交晶系，空间群Pbnm，a=8.7678(8)Angstrom，b=18.967(1)Angstrom，c=19.181(1)Angstrom，V=19.181(4)Angstrom(3)，Z=4)。
The effect of the bite angle on regioselectivity in the rhodium-catalyzed hydroformylation reaction was studied with a series of bidentate diphosphines based on xanthene-like backbones as ligands. The bite angles of these ligands are fine-tuned by subtle alterations of the backbone of the ligands. When the bridge (X) in the 10-position of xanthene is varied, the bite angle as calculated from molecular mechanics increases stepwise from 102 to 131 degrees, whereas the changes in steric bulk and electronic effects are virtually absent for the following ligands: bis(2-(diphenylphosphino)phenyl) ether (DPEphos, 1), X = H, H; 4,6-bis(diphenylphosphino)-10,10-dimethylphenoxasilin (Sixantphos, 2), X = Si(CH3)(2); 2,8-dimethyl-4,6-bis(diphenylphosphino)phenoxathiin (Thixantphos, 3), X = S; 9,9-dimethyl-4,6-bis(diphenylphosphino)xanthene (Xantphos, 4), X = C(CH3)(2); 4,6-bis(diphenylphosphino)dibenzofuran (DBFphos, 5), X = bond. In the hydroformylation of 1-octene the regioselectivity increased. regularly with increasing bite angle: at 40 degrees C up to 98.3% n-aldehyde was obtained with Xantphos, without isomerization or hydrogenation of 1-octene. DBFphos does not form chelates, and consequently no increased selectivity was observed. The selectivity of the catalyst was almost unaffected by raising of the temperature to 80 degrees C, resulting in a higher turnover frequency (tof) with a constant selectivity: 97.7% n-aldehyde, 0.5% isomerization, and a tof value of 800 mol (mel of Rh)(-1) h(-1). Xantphos induces the highest selectivity for the formation of the linear aldehyde reported for diphosphines in the hydroformylation of 1-alkenes until now. The complexes (diphosphine)Rh(H)(CO)(PPh(3)) and (diphosphine)Rh(H)(CO)(2) were prepared and identified with H-1, P-31, and C-13 NMR. The enhanced selectivity to the linear aldehyde was also observed for styrene (70% n-aldehyde with xantphos compared to 11% with triphenylphosphine). An X-ray crystal structure of the Xantphos ligand is presented (orthorhombic, space group Pbnm, with a = 8.7678(8) Angstrom, b = 18.967(1) Angstrom, c = 19.181(1) Angstrom, V = 3189.8(4) Angstrom(3), and Z = 4).