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| 苯甲醛和苯胺反应生成亚胺，亚胺和二氢吡喃在GdCl3的催化下反应生成中间体exo(3)、endo(4)产物的收率应该相当。但中间体1、2的稀土原子仍然存在空的配位点，在无溶剂或溶剂的配位能力和极性不是太大时，GdCl3除了与亚胺上的氮原子络合外，还可以与另一个反应底物二氢吡喃上的氧原子配位，活化双键，进而生成endo（4）生成了顺式的产物。而在像CH3CN这种体积小配位能力和极性强的溶剂中GdCl3已经被溶剂分子包围，没有空的配位点与二氢吡喃的氧原子配位所以形成了exo(3)，生成了以反式为主的产物。在像HMPA,Py这种配位能力非常强的溶剂中GdCl3被溶剂完全配位以至于无法与亚胺的氮原子配位使反应无法进行。 |
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yuyong050725(金币+6,VIP+0):多谢 11-9 22:01
yuyong050725(金币+6,VIP+0):多谢 11-9 22:01
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The reaction of benzaldehyde and aniline returns to imine.In the catalytic reaction of GdCl3，the reaction yield of imine and dihydro-pyran, exo (3), endo (4) would be comparable. But the intermediate 1,2-rare earth atoms still have empty collocation points, in the absence of solvent or low coordination capability and polarity of solvent, GdCl3 not only additions to the nitrogen atom on the imine complex, but also can coordinate with the other reaction substrate dihydropyrano oxygen atoms on the ligand, activating double bond, thereby generating cis-endo (4). In such a small size as the CH3CN，whose ligand capacity and polarity is strong，GdCl3 has been surrounded by solvent molecules, and there is no empty coordination point to coordinate with the oxygen of dihydropyrano，so forming exo (3) and mainly generating trans-oriented product. In these solvents such as HMPA, Py，whose coordination capacity is very strong ，GdCl3 has been completely coordinated by the solvent ，so that it can not coordinate with the nitrogen atoms of imine |
4楼2009-11-08 21:45:49
| Benzaldehyde and aniline reaction, and with two hydrogen in the GdCl3 pyranoid catalytic reaction exo intermediates endo (3), (4) the product yield should be fairly. But the intermediate 1 and 2, rare earth atoms remains empty, without solvent with sites in the coordination ability or solvents and polarity is not too big, GdCl3 except with the imine nitrogen atoms, and complexation another response substrates dihydrogen pyranoid on oxygen activation, coordination, et cetera endo (4) and the product of a generation. And in like CH3CN this small coordination ability and strong polarity solvent GdCl3 solvent molecules has been surrounded, no empty matchs with two hydrogen atom coordination of pyranoid so formed exo (3), produced by the product mainly trans. In this, like HMPA coordination ability Py very strong solvents GdCl3 by solvent that cannot completely coordination of nitrogen atom can make reaction. |
6楼2009-11-15 12:22:37
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yuyong050725(金币+4,VIP+0): 11-16 10:55
yuyong050725(金币+4,VIP+0): 11-16 10:55
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The reaction of benzaldehyde and aniline imine, imine, and dihydro-pyran in the catalytic reaction GdCl3 intermediate exo (3), endo (4) product yield would be comparable. But the intermediate 1,2-rare earth atoms is still empty collocation points, in the absence of solvent or solvent coordination capability and polarity are not too large, GdCl3 addition to the nitrogen atom on the imine complex, but also with The other reaction substrate dihydropyrano oxygen atoms on the ligand, activated double bond, thereby generating endo (4) generates cis-product. In such a small size as the CH3CN ligand capacity and polarity of the solvent GdCl3 has been surrounded by solvent molecules, Coordination is not an empty point dihydropyrano coordination of oxygen atoms so formed exo (3), generated by trans-oriented product. In such as HMPA, Py coordination capacity of this very strong solvent was solvent GdCl3 that they can not fully coordinate with the imine nitrogen atoms coordinated the reaction can not proceed.: |
7楼2009-11-15 12:57:20
★ ★ ★ ★ ★
yuyong050725(金币+5,VIP+0): 11-16 10:55
yuyong050725(金币+5,VIP+0): 11-16 10:55
| The reaction of benzaldehyde and aniline imine, imine, and dihydro-pyran in the catalytic reaction GdCl3 intermediate exo (3), endo (4) product yield would be comparable. But the intermediate 1,2-rare earth atoms is still empty collocation points, in the absence of solvent or solvent coordination capability and polarity are not too large, GdCl3 addition to the nitrogen atom on the imine complex, but also with The other reaction substrate dihydropyrano oxygen atoms on the ligand, activated double bond, thereby generating endo (4) generates cis-product. In such a small size as the CH3CN ligand capacity and polarity of the solvent GdCl3 has been surrounded by solvent molecules, there is no empty coordination point dihydropyrano coordination of oxygen atoms so formed exo (3), generating in order to trans-oriented product. In such as HMPA, Py coordination capacity of this very strong solvent was solvent GdCl3 that they can not fully coordinate with the imine nitrogen atoms coordinated the reaction can not proceed. |
8楼2009-11-15 18:20:00
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