5-dimethoxyphenyl moiety and a phenol ring may, however, be reduced and alkylated provided the acidic phenolic proton is removed prior to the treatment with Li in NH3. Similarly, biaryls possessing a o-sulfonamide group are reduced regioselectively and alkylated with α-chloroacetonitrile or N-tosylaziridine to provide the corresponding dienes in reasonable to good yields. A survey of the alkylating agents was also
通过改变芳环上取代基的性质,进行了联芳基的桦树还原性烷基化。我们的研究集中在富含电子的取代基(例如OMe,OH和NR 2基团)上,因为它们存在于目标生物碱的骨架上。区域选择性受两个环上这些取代基的电子性质的强烈影响。3,5-二甲氧基苯基部分被选择性还原然后烷基化,而苯酚和苯胺在这些条件下不发生反应。但是,只要在用Li在NH 3中处理之前除去酸性酚质子,就可以还原同时具有3,5-二甲氧基苯基部分和酚环的联芳基并烷基化。类似地,联芳基化合物具有一个Ô-磺酰胺基区域选择性地还原,并用α-氯乙腈或N-甲苯磺酰基氮丙啶烷基化,以合理至良好的产率提供相应的二烯。还对烷基化剂进行了调查,结果表明可以在苄基位置引入各种官能团,包括酯,伯和叔酰胺,腈,环氧化物和乙缩醛,以及未官能化的空间位阻t- Bu基和环丙基取代基。引入后者的表示两个A S Ñ 2和SET机构可以在所述烷基化步骤进行。
Efficient Synthetic Approaches to the Common Scaffold of Indole Alkaloids
Birchreductivealkylation of 2-aminobiphenyls affords access to highly functionalized polyenes that react through a Pd(II)-catalyzed oxidative amination cascade or through a double 1,4-addition process to provide the tetracyclic skeleton of indole alkaloids with up to four stereogenic centers created in a single-pot operation.