Stereoselective Pinacol Coupling of Planar Chiral (arene) chromium Complexes ; Synthesis of Optically Pure 1,2-Dihetero Compounds

手性纯1，2-二醇和二胺类化合物是不对称反应中重要的手性配体或辅助化合物。羰基化合物的还原偶联，频那醇偶联，是合成1，2-二醇的最直接方法。虽然用稀土金属或低价过渡金属可以高产率地实现这一反应，但在传统的还原偶联方法下，1，2-二醇的高立体选择性是有问题的。基于平面手性，(芳烃)铬络合物可以以两种对映体形式存在。我们研究了苯甲醛和苯甲醛的平面手性铬配合物的片呐酚偶联反应。在四氢呋喃中，用二碘化钐分别处理对映体纯的(邻位取代苯甲醛)铬(CO)_3配合物和(邻位取代苯甲醛)铬(CO)_3配合物，得到立体选择性的纯铬配合物苏二醇和二胺。这些与铬配位的二醇和二胺被氧化，得到无铬的1，2-二醇和二胺，具有对映体纯净的形式。同样，平面手性(二烯)Fe(CO)_3和α-取代二茂铁甲醛高产率地合成了相应的对映体纯的1，2-二醇。此外，在相同的反应条件下，具有二羰基、二亚胺和亚胺基官能团的轴向手性联苯对映体纯铬配合物在分子内偶联，分别得到反式1，2-二醇、二胺和氨基醇。

Enantiomerically pure 1, 2-diols and diamines are important compounds as chiral ligand or auxiliary in asymmetric reaction. The reductive coupling of carbonyl compounds, pinacol coupling, is the most direct way to synthesize 1, 2-diols. Although this reaction can be achieved in high yield by lanthanoid metals or low valent transition metals, highly stereoselective formation of 1, 2-diols is problematic under conventional reductive coupling methods. (Arene)chromium complex can exist in two enantiomeric forms based on the planar chirality. We have investigated the pinacol coupling of planar chiral chromium complexes of benzaldehydes and benzaldiminesEnantiomerically pure (o-substituted benzaldehyde)Cr(CO)_3 complexes and (o-substituted benzaldimine)Cr(CO)_3 complexes were treated with samarium diiodide in THF to produce stereoselectively optically pure chromium-complexed threo-diols and diamines, respectively. These chromium-complexed threo-diols and diamines were oxidized to give the chromium free 1, 2-diols and diamines in enantiomerically pure form. Similarly, planar chiral (diene)Fe(CO)_3 and alpha-substituted ferrocencarboxaldehydes produced the corresponding enantiomerically pure 1, 2-diols in high yield.Furthermore, an intramolecular pinacol coupling of enantiomerically pure chromium complexes of axially chiral biphenyls having dicarbonyl, diimine and iminokarbonyl function afforded to trans 1,2-diols, diamines and aminoalcohols, respectively, under the same reaction conditions.