We have revisited the traditional consecutive Michael-Claisen [3 + 3] process (MC-[3 + 3]) promising the synthesis of a cyclohexane-1,3-dione derivatives from nonactivated simple ketones and enoates and evaluated its potential in modern organic synthesis. Twenty to thirty examples were demonstrated to be effective. The reactions exhibited remarkable regioselectivity with the Michael addition proceeding through nucleophilic attack by the more hindered site of the ketones without exception. The subsequent Claisen condensation resulted in the formation of carbon-carbon bonds between less hindered site of the ketones and acyl carbon of the enoates. The MC-[3 + 3] process described is useful for the synthesis of Taxol A-ring synthons in multigram quantities and for the synthesis of other six-membered carbocyclic compounds. A number of control experiments have been conducted to provide strong support for the mechanism of this MC-[3 + 3].
Dehydrogenative Formation of Resorcinol Derivatives Using Pd/C–Ethylene Catalytic System
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。
Vorlaender; Erig, Justus Liebigs Annalen der Chemie, 1897, vol. 294, p. 316