Lewis Acid-Catalyzed 1,3-Dipolar Cycloaddition Reaction

首次实现了路易斯酸催化的1，3偶极环加成反应的立体和区域控制。主要结果如下：1)由(亚烷氨基)乙酸酯衍生的Z-烯醇酸锂在与α，β-不饱和羰基化合物的反应中充当1，3-偶极，以高度立体选择性的方式得到吡咯烷-2-羧酸酯；2)由大体积醛或酮衍生的(烷亚氨基)乙酸酯与α，β-不饱和羰基化合物发生反选择性的Michael加成反应；3)以甘氨酸的樟脑亚胺为给体的Michael加成反应，当以β-取代的α，β-不饱和羰基受体为接受体时，完全是非对映选择性的；4)偶极/Lewis酸的络合物是由羟亚胺或金属酰肼与烯丙基反应形成的；5)在与2-(1-羟基烷基)丙烯酸酯的反应中，丁腈氧化物/MgBrCl络合物表现出高的合成选择性；6)α-手性烯丙醇的丁腈氧化物与镁醇盐的环加成反应具有高度的同步选择性；7)内烯丙醇的镁醇盐在丁腈环加成反应中仅具有区域选择性，生成异恶唑啉-5-甲醇衍生物；8)丁腈氧化物与烯丙醇的镁醇烷氧化合物的环加成反应大大加速；9)在Lewis酸催化的硝酮与烯丙醇的环加成反应中，观察到了类似的速度加速、区域和立体控制。通过本研究，可以清楚地看到，在偶极环加成反应中使用合适的Lewis酸催化剂可以大大提高反应速度，提高立体选择性和区域选择性。可以肯定的是，这种新的方法学将为偶极环加成反应在有机合成中的广泛应用开辟一条新的途径。

Unprecedented Lewis acid catalyzed stereo- and regiocontrol of 1, 3dipolar cycloaddition reactions have been achieved. Major results are as follows: 1) Lithium Z-enolates derived from (alkylideneamino)acetates act as 1, 3-dipoles in reactions to alpha,beta-unsaturated carbonyl compounds to give pyrrolidine-2-carboxylates in a highly stereoselctive fashion; 2) (Alkylideneamino)acetates derived from bulky aldehydes or ketones undergo anti-selective Michael additions to alpha,beta-unsaturated carbonyl compounds; 3) Michael additions using camphor imines of glycinates as donors are exclusively diastereoselective when beta-substituted alpha,beta-unsaturated carbonyl acceptors are used as acceptors; 4) Dipole/Lewis acid complexes are formed on treatment of hydroximoyl or hydrazonoyl chlorides with organometallics; 5) Nitrile oxide/MgBrCl complexes show high syn-selectivities in reactions with 2-(1-hydroxyalkyl)acrylates; 6) Nitrile oxide cycloadditions to magnesium alkoxides of alpha-chiral allylic alcohols proceed in a highly syn-selective manner; 7) Magnesium alkoxides of internal allylic alcohols are exclusively regioselctive in nitrile oxide cycloadditions to give isoxazoline-5-methanol derivatives; 8) Nitrile oxide cycloadditions to magnesium alkoxides of allylic alcohols are greatly accelerated; 9) Similar rate acceleration, regio- and stereocontrol are observed in Lewis acid-catalyzed nitrone cycloadditions to allylic alcohols.Through the present research, it is now clear that employment of an appropriate Lewis acid catalyst in dipolar cycloadditions leads to great enhancement of reaction rate and high improvement of stereoselectivity and regioselectivity. It is quite certain that this new methodology will open an entry to wide synthetic applications of dipolar cycloaddition reactions in organic synthesis.