A synthesis of di- and tri-substituted β,γ-unsaturated esters from aldehydes by the magnesium carbenoid 1,2-CH and 1,2-CC insertion as the key reaction
作者:Hironori Yamashita、Tsuyoshi Satoh
DOI:10.1016/j.tet.2008.11.013
日期:2009.1
insertion reactions were observed in the latter reactions. When the addition reactions were quenched with iodoalkanes, the alkylated adducts were obtained in quantitative yields. Tri-substituted β,γ-unsaturated esters, or in some case γ,δ-unsaturated esters, were obtained by the treatment of the alkylated adducts with EtMgCl. These procedures provide a good way for a new synthesis of di- and tri-substituted
源自醛的1-氯乙烯基对甲苯基亚砜与叔烯醇锂的加成反应在-78°C中的乙酸丁酯在THF中的收率高。用格氏试剂处理这些加合物会通过亚砜-镁交换反应形成类胡萝卜素镁。当加合物衍生自烷基醛或电子不足的芳族醛时,类胡萝卜素从类镁镁发生1,2-CH插入反应,得到在β-位具有取代基的β,γ-不饱和丁酸酯。另一方面,当加合物衍生自富含电子的芳族醛时,从羧甲基镁类化合物发生类胡萝卜素1,2-CC插入反应,得到在γ-位具有芳族基团的β,γ-不饱和丁酸酯。在后面的反应中观察到高度立体定向的1,2-CC插入反应。当加成反应用碘代烷烃淬灭时,烷基化的加合物以定量产率获得。通过用EtMgCl处理烷基化的加合物获得三取代的β,γ-不饱和酯,或在某些情况下为γ,δ-不饱和酯。这些程序为由具有两个或三个碳-碳键形成的醛合成二取代和三取代的β,γ-不饱和酯提供了一个好方法。