CATALYZED ASYMMETRIC 1,3-DIPOLAR CYCLOADDITION REACTIONS

本项目研究的中心目的是建立催化不对称1，3-偶极环加成反应方法学，为杂环化合物的立体选择性合成提供了一个重要的入口。将烯丙醇底物应用于硝酮和氧化腈的环加成反应中，得到了以下发现：1.在镁离子存在下，苯腈与烯丙醇的环加成反应可以被加速。含α-手性中心的烯丙醇在镁离子催化下的反应具有较高的合成选择性。镁离子催化的含伽马取代烯丙醇的反应具有较高的区域选择性。在取代较多的烯丙醇底物的镁离子催化反应中，观察到较高的速率加速。在伽马位置有两个甲基取代基的底物比未取代的底物快16000倍。在镁离子催化的氧化甲腈与烯丙醇的反应中，最大催化循环数为34。在上述反应中，化学计量的(R，R)-1，2-二苯基-1，2-乙二醇双(二苯甲基硅基)醚的存在不会引起任何对映体选择性。其他手性配体如(R，R)-1，2-二苯基-1，2-乙二醇双(二苯甲基)醚和(R，R)-1，2-二苯基-1，2-乙二醇的双(三苯甲基)醚也被用于不对称反应，但效果不佳。在上述手性配体存在的情况下，在镁离子催化的反应中使用巴豆醇而不是烯丙醇会抑制反应。在DBFOX修饰的镁离子存在下，3-丙烯酰基-2-恶唑烷酮与硝酮的环加成反应具有很高的对映选择性，但氧化腈的环加成反应也没有发现速率加速的现象。

The central purpose of the present project research is the establishment of catalyzed asymmetric 1,3-dipolar cycloaddition methodology, which provides an important entry to stereoselectivesynthesis of heterocyclic compounds. A llylic alcohol substrates have been employed in nitrone and nitrile oxide cycloadditions to give the following findings :1. Benzonitrile oxide cycloadditions with allylic alcohols can be accelerated in the presence of magnesium ions.2. High syn selectivity is observed in the magnesium ion catalyzed reactions of allylic alcohols bearing an alpha-chiral center.3. High regioselectivity is observed in the magnesium ion catalyzed reactions of allylic alcohols bearing gamma-substituents.4. Higher rate acceleration is observed in the magnesium ion caralyzed reactions of more substiituted allylic alcohol substrates. The substrate having two methyl substituents at the gamma-position is 16000 times faster than the unsubstituted one.5. The maximum catalytic cycle of 34 has been recorded in the magnesium ion catalyzed reactions between mesitonitrile oxide and allyl alcohol.6. The presence of a stoichiometric amount of bis (diphenylmethylsilyl) ether of (R,R)-1,2-diphenyl-1,2-ethanediol in the above reaction did not induce any enantioselectivity.7. Other chiral ligands such as bis (diphenylmethyl) ether and bis (triphenylmethyl) ether of (R,R)-1,2-diphenyl-1,2-ethanediol have been employed in the asymmetric reactions to give poor results.8. Use of crotyl alcohol, instead of allyl alcohol, in the magnesium ion catalyzed reactions in the presence of the above chiral ligands result in the inhibition of reaction.9. The nitrone cycloadditions using 3-acryloyl-2-oxazolidinone in the presence of DBFOX-modified magnesium ion are highly enantioselective, but the nitrile oxide cycloadditions can not find rate acceleration either.