Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
Org Lett. 2010 Mar 19;12(6):1232-5. doi: 10.1021/ol1000878.
The one-carbon bridge stereochemistry of bicyclo[3.3.1]nonane products formed in the Robinson annulation reactions of 2-substituted cyclohex-2-enones was investigated. In contrast to previous reports, it was found that the major diastereomer formed places the one-carbon bridge substituent anti to the beta-keto ester/amide unit introduced in the Robinson annulation. This stereoselectivity appears to be kinetically controlled. In the case of a beta-keto amide product derived from carvone, it was demonstrated, through base-catalyzed epimerization, that thermodynamic control favors the syn isomer.
研究了 Robinson 环合反应中 2-取代环己-2-烯酮形成的双环[3.3.1]壬烷产物中单碳桥立体化学。与先前的报告相反，发现形成的主要非对映异构体将单碳桥取代基置于 Robinson 环合中引入的β-酮酯/酰胺单元的反式位置。这种立体选择性似乎是动力学控制的。对于来源于香芹酮的β-酮酰胺产物，通过碱催化的差向异构化证明热力学控制有利于顺式异构体。
