conversion of substituted 1,3-cyclohexanediones to the alkyl ethers of resorcinol using a Pd/C–ethylene system is reported. In these reactions, ethylene works as a hydrogen acceptor. The efficient synthesis of resveratrol was achieved using this protocol as a key step. In addition, the direct formation of substituted resorcinols was carried out by adding K2CO3 into the reaction media.
据报道,使用Pd / C-乙烯系统将取代的1,3-环己二酮转化为间苯二酚的烷基醚。在这些反应中,乙烯充当氢受体。使用该方案作为关键步骤,可实现白藜芦醇的有效合成。另外,通过向反应介质中加入K 2 CO 3来直接形成取代的间苯二酚。
Chiral Dinuclear Vanadium Complex-Mediated Oxidative Coupling of Resorcinols
A method for the highly regio- and enantioselective oxidativecoupling of resorcinols has been established by using dibrominated dinuclear vanadium(V) catalyst 1c under air. When resorcinols bearing an aryl substituent were applied as substrates to the coupling, axially chiral biresorcinols were obtained as single regioisomers in high yield with up to 98% ee.
Regioselectivity of Birch Reductive Alkylation of Biaryls
作者:Raphaël Lebeuf、Frédéric Robert、Yannick Landais
DOI:10.1021/ol051377i
日期:2005.10.1
regioselectivity of the Birchreductive alkylation of polysubstituted biaryls has been investigated. Results indicate that regioselectivity is affected by the electronic nature of substituents on both aromatic rings. The electron-rich 3,5-dimethoxyphenyl moiety is selectively reduced and then alkylated, while phenols and aniline are not dearomatized under these conditions. Biaryls possessing a phenol moiety are
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。