| Project/Area Number |
10208211
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| Research Category |
Grant-in-Aid for Scientific Research on Priority Areas (B)
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| Allocation Type | Single-year Grants |
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| Research Institution | Osaka University |
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Principal Investigator |
HIRAO Toshikazu Osaka University, Professor, 大学院・工学研究科, 教授 (90116088)
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| Project Period (FY) |
1998 – 2001
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| Project Status |
Completed (Fiscal Year 2001)
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| Budget Amount *help |
¥10,900,000 (Direct Cost: ¥10,900,000)
Fiscal Year 2000: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 1999: ¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 1998: ¥3,700,000 (Direct Cost: ¥3,700,000)
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| Keywords | one-electron reduction / catalyst / reversible redox / vanadium catalyst / titanium catalyst / diastereoselectivity / stereo-control / pinacol coupling / 触媒サイクル / バナジウム / 希土類元素 / パナジウム |
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| Research Abstract |
Pinacol coupling provides a versatile method for carbon-carbon bond formation in the synthesis of naturally occurring compounds. Redox process of low-valent early transition metals is synthetically useful in the coupling reaction, but more than stoichiometric amounts of metallic reductants are generally required to accomplish the reduction reaction.
A novel redox system for the vanadium-catalyzed pinacol coupling was achieved in the presence of zinc and a chlorosilane to give the corresponding 1,2-diols in high yields. The co-existence of a chlorosilane is essential for the catalytic coupling reaction. The high diastereoselectivity was attained with PhMe_2SiCl to give the dl isomer.
Catalytic pinacol coupling reaction took place in the presence of an acetylating reagent such as Ac_2O or AcCl. When aromatic aldehydes are treated with 3mol% of VOCl_3, 2 molar amount of Ac_2O, and zinc powder as a co-reductant, vicinal diacetylated diols were obtained with high diastereoselectivity. TiCl_4 could also be utilized as a catalyst with AcCl and metallic aluminum.
A vanadium-catalyzed cyclodimerization of arylidine malononitriles proceeded diastereoselectively with reversible redox between vanadium and zinc in the presnce of chlorotrimethylsilane. In conclusion, an efficient system for catalytic one-electron reduction was developed in reductive coupling reactions.
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