Synthetic Study of Functionalized Amino Acids Using An Umpolung Addition to α-Imino Esters

当使用适当的亲核试剂时，α-亚氨基酯在其氮原子处以“极化”方式表现为亲核试剂的受体。几种α-亚氨基酯与有机铝的串联N-烷基化-C-烯丙基化和N-烷基化-C-氰化反应以良好至优异的产率进行，其中两个亲核试剂攻击C=N双键。此外，乙醛酸乙酯衍生的α-亚氨基酯、铝试剂和各种亲电试剂进行了三组分偶联反应，得到了高产率的加成产物。烷氧羰基亚胺鎓盐可以通过氧化氨基烯酮甲硅烷基缩醛容易地制备，随后与该亚胺鎓物种进行亲核加成，以良好的产率有效地得到α-氨基酯。

α-Imino esters behave as acceptors of nucleophiles at their nitrogen atoms in an "umpoled" manner, when appropriate nucleophiles are used. The tandem N-alkylation-C-allylation and N-alkylation-C-cyanation reaction of several α-imino esters with organoaluminums are carried out in good to excellent yields, where two nucleophiles attack across the C=N double bond. Moreover, three components coupling reaction of α-imino ester derived from ethyl glyoxylate, aluminum reagent, and various electrophiles proceeded to give the addition products in good yields. The alkoxycarbonyl iminium salt is easily prepared using the oxidation of amino ketene silyl acetal, and subsequent nucleophilic addition to this iminium species proceeds efficiently to afford the α-amino esters in good yields.