著者

金政 修司 大平落 洋二

出版者

The Society of Synthetic Organic Chemistry, Japan

雑誌

有機合成化学協会誌 (ISSN:00379980)

巻号頁・発行日

vol.56, no.5, pp.368-376, 1998-05-01 (Released:2010-01-28)

参考文献数

16

被引用文献数

11 12

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Cationic aqua complexes of a trans-chelating tridentate ligand, (R, R) -4, 6-dibenzofurandiyl-2, 2' -bis (4-phenyloxazoline), and transition metal (II) perchlorates are effective catalysts in the cyclopentadiene Diels-Alder reactions, nitrone cycloadditions, and diazomethane cycloadditions with 3-alkenoyl- 2-oxazolidinones to show excellent enantioselectivities. The active catalyst complex prepared from nickel (II) perchlorate hexahydrate has an octahedral structure with three aqua ligands, and it can be isolated and stored for months without loss of catalytic activity. The aqua complex prepared from Ni (II) or Zn (II) perchlorate results in highly effective chiral amplification in the Diels-Alder reaction. Two mechanisms for amplification are involved for this remarkable chiral amplification : (1) precipitation of S4-symmetric meso-2 : 1 complex between DBFOX/Ph and Ni (II) ion, and (2) associative formation of 1 : 1 heterochiral complexes by the aid of hydrogen bonds based on aqua ligands to produce stable meso oligomers.