| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 1998: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1997: ¥2,300,000 (Direct Cost: ¥2,300,000)
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| Research Abstract |
Although the enantioselective synthesis of optically active amines by nucleophilic addition of organometallic reagents is a topic of current interest, the enantioselective addition of allylmetals to C=N double bond is quite underdeveloped in comparison to the effort on record in the area of asymmetric addition to carbonyl compounds. This research project aimed at design of asymmeric allylat ion reaction of imines, We have found that N-metallo imines such as N-silyl, N-aluminum, and N-borylimines were allylated with allylboron reagents to give the corresponding homoallylamines in good yield. Removal of N-substituents from the homoallylamines were quite easy. This approach is thus a novel efficient method for the synthesis of optically active primary homoallylamines. For example, N-silylimines were enantioselectively allylated with chirally modified allylboron reagent to give the homoallylamines in almost quantitative yield with high enantioselectivity (> 90% ee). To our knowledge, this
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is the first report of high level of asymmetric induction realized in the enantioselective addition of allylboron reagent to imines. Although N-silylimines derived from enolizable aldehydes resulted in the formation of complexed mixture as the product of allylat ion, N-alumino imines having alpha-proton could be allylated to give the homoallylamine. In the cases of the enantioselective allylation of N-alumino imines and N-boryl imines afforded the enantioenriched homoallylamines in good yield with high selectviity. It is noteworthy that high enantioselectivty (>80% ee) was attained even at room temperature when these imines were allylated.
Polymer-supported chiral reagents and catalysts are of interest in the field of asymmetric synthesis, since the chiral reagents can be recycled many times. In some cases, continuous flow system is possible by using polymer-suppored chiral catalyst. We have prepared polymer- supported chirally modified allylboron reagents. Asymmetric allylation of N-metallo imines described above with the polymer-supported reagents have been investigated. Polymer- supported N-sulfonylaminoalcohols derived from D-camphor or norephedrine were quite suitable chiral ligands for the allylation of imines. In spite of heterogeneous reaction using such polymers, sufficient reactivity and high enantioselelctivity was attained. This is also the first finding of the enantioselective allylation of imines using polymeric reagent. Less
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