| Project/Area Number |
11650893
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Synthetic chemistry
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| Research Institution | Kyoto Institute of Technology |
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Principal Investigator |
ISHIHARA Takashi Kyoto Institute of Technology, Department of Chemistry and Materials Technology, Associate Professor, 工芸学部, 助教授 (40093182)
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| Project Period (FY) |
1999 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥2,900,000 (Direct Cost: ¥2,900,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥2,100,000 (Direct Cost: ¥2,100,000)
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| Keywords | α-fluoro-β-hydroxy ester / stereoselective synthesis / radical reaction / allylation reaction / chelation control / aluminum Lewis acid / α-フルオロ置換エステル / 立体選択的還元 / 立体選択的アリル化 / トレオ選択性 / 水素化トリプチルスズ / アリルスタナン |
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| Research Abstract |
In this research project directed toward the development of new method (process) for the highly stereoselective synthesis of α-fluoro-β-hydroxy esters, we have explored the radicalic allylation reaction of α-bromo-α-fluoro-β-hydroxy carboxylic acid esters 1 with allylic stannanes.
The starting β-hydroxy esters 1 were readily prepared by the Reformatsky reaction between ethyl dibromofluoroacetate and various aldehydes in the presence of zinc dust and diethylaluminum chloride in THF at -20 ℃ for 1 h. When α-bromo-α-fluoro-β-(t-butyldimethylsilyl) oxy esters, prepared by the siylation of 1 with t-butyldimethylsilyl (TBS) chloride or triflate, were allowed to react with allylic stannanes in the presence of a catalytic amount of triethylborane in toluene or dichloromethane at -78 ℃ for 10 h, the corresponding α-allylated α-fluoro-β-TBS-oxy esters were obtained in good yields with fairly good erythro-selectivities. On the other hand, on treatment of the β-hydroxy esters 1 with trimethylaluminum in dichloromethane at -15 ℃ for 0.5 h, followed by the reaction with allylic stannanes and triethylborane catalyst at -15 ℃ for 6-8 h, the corresponding α-allylated α-fluoro-β-hydroxy esters were given in good yields in a highly threo-selective manner. These results provide us with the first stereoselective synthetic method for an α-fluoro-β-hydroxy carbonyl framework, and are expected to serve as a very significant example in organic synthetic chemistry as well as organofluorine chemistry.
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