15 (アレーン)クロム錯体を用いたアトロプ異性体の立体選択的合成(口頭発表の部)

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Biphenyl or binaphtyl compounds with an axial chirality are attractive compounds not only as the chiral ligands in asymmeric reactions but also for the synthesis of the biological active natural products. There is a considerable current interest in the development of efficient methodologies for the synthesis of the biphenyl or binapthyl compounds with atropisomers in an optically active form. The cross-coupling reaction of (2,6-disubstituted-1-bromobenzene)chromium complexes 1 with o-substituted phenylboronic acids 2 in the presence of palladium(0) gave mono Cr(CO)_3-complexed biphenyl compounds, whose axial stereochemistry is depending upon the nature of ortho-substituents; phenylboronic acids with ortho alkyl sbustituents 2a〜2c gave kinetically controlled biphenyl mono-Cr(CO)_3 complexes 3, while o-formylphenylboronic acid 2d gave the corresponding axially isomeric coupling products 4. Furthermore, the kinetically controlled coupling products 3 isomerize under thermal condition to the thermodynamically more stable Cr(CO)_3 complexes 4 with central bond rotation. This atropisomerization combined with the diastereoselective cross-coupling reaction provides a promising approach to the formation of the optically pure biphenyl compounds 12 and 14 with axial chirality in both enantiomeric forms from a single chiral arene chromium complex 9. This diastereoselective cross-coupling reaction of the (η^6-arene)Cr(CO)_3 complexes with the arylboronic acids can be applied for the synthesis of steganacinan and korupensamines. We are currently investigating total synthesis of steganacin and korupensamines utilizing enantiomerically pure (arene)chromium complexes 16 and 25.
天然有機化合物討論会の論文
1995-09-01

15 (アレーン)クロム錯体を用いたアトロプ異性体の立体選択的合成(口頭発表の部)

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