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

当使用合适的亲核试剂时，α-亚氨基酯在其氮原子处以“非极化”方式充当亲核试剂的受体。几种α-亚胺酯与有机铝进行了N-烷基化-C-烯丙化和N-烷基化-C-氰化反应，反应收率高至高，两个亲核试剂跨越C=N双键攻击。此外，乙基乙酯衍生的α-亚胺酯与铝试剂和各种亲电试剂进行了三组分偶联反应，得到了收率较高的加成产物。氨基烯酮硅基缩醛氧化制备烷氧羰基亚胺盐很容易，随后对该亚胺进行亲核加成，得到收率较高的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.