Department of Chemistry, DePaul University , 1110 West Belden Avenue, Chicago, Illinois 60614, United States.
J Org Chem. 2018 Feb 2;83(3):1493-1501. doi: 10.1021/acs.joc.7b03125. Epub 2018 Jan 19.
A catalytic redox-neutral method for the synthesis of spirolactams proceeding through the dearomative spirocyclization of N-aryl alkynamides is reported. In contrast to stoichiometric activating agents employed for related transformations, we show that the use of 5 mol % of Au(PPh)Cl and AgOTf in dichloroethane at 50-80 °C leads to selective spirocyclization, furnishing the products in yields of 35-87%. The substrate scope of the reaction is good, with both electron-donating and electron-withdrawing groups being tolerated around the arene ring, as well as substitution at the amide nitrogen. The identity of the para-alkoxy group on the arene ring is key to achieving selectivity for spirocyclization over alternative mechanistic pathways. While the presence of a para-methoxy group leads to trace amounts of the desired spirolactams, the para-tert-butoxy or para-hydroxy substrate analogues furnish the spirolactams in good yield with high selectivity.
报道了一种通过 N-芳基炔酰胺的去芳构化螺环化反应来合成螺内酯的催化氧化还原中性方法。与用于相关转化的化学计量激活剂相比，我们表明在二氯乙烷中使用 5 mol%的 Au(PPh)Cl 和 AgOTf 在 50-80°C 下导致选择性螺环化，以 35-87%的收率得到产物。该反应的底物范围良好，芳环周围可以容忍供电子和吸电子基团，以及酰胺氮上的取代。芳环上对位烷氧基的性质是实现螺环化选择性的关键，而不是其他可能的反应途径。虽然对位甲氧基的存在会导致痕量所需的螺内酯，但对位叔丁氧基或对位羟基地位类似物以高选择性得到螺内酯，产率良好。
