Barluenga José, Suero Marcos G, Pérez-Sanchez Ivan, Flórez Josefa
Instituto Universitario de Química Organometálica "Enrique Moles" Unidad Asociada al CSIC, Universidad de Oviedo Julián Clavería 8, 33006 Oviedo, Spain.
J Am Chem Soc. 2008 Mar 5;130(9):2708-9. doi: 10.1021/ja074363b. Epub 2008 Feb 8.
Treatment of aryl/heteroaryl methoxycarbene complexes of chromium with -substituted ketone lithium enolates between -78 degrees C and room temperature resulted in the diastereoselective synthesis of 1,2,2,3-tetrasubstituted cyclopropanols. An exception has been observed in the reaction with cyclohexanone lithium enolate that yielded a bicyclic 2-buten-4-olide. 1,2-Dimethoxycyclopropanes and 1-methoxy-2-trimethylsilyloxycyclopropanes were isolated by quenching the reactions with MeOTf or Me3SiCl, respectively. This novel cyclopropanation process involves formation of lithium (3-oxoalkyl)pentacarbonylchromate intermediates which on warming undergo intramolecular addition to the carbonyl group. This cyclization is equivalent to the cyclopropanation in smooth conditions of electron-rich alkenes with Fischer carbene complexes.
在-78℃至室温下，用α-取代的酮酸锂烯醇盐处理铬的芳基/杂芳基甲氧基卡宾配合物，可实现1,2,2,3-四取代环丙醇的非对映选择性合成。在用环己酮酸锂烯醇盐反应时观察到一个例外情况，反应生成了一种双环2-丁烯-4-内酯。分别用MeOTf或Me3SiCl淬灭反应，分离得到了1,2-二甲氧基环丙烷和1-甲氧基-2-三甲基硅氧基环丙烷。这种新型环丙烷化过程涉及形成锂(3-氧代烷基)五羰基铬酸盐中间体，该中间体在升温时会发生分子内加成到羰基上。这种环化反应等同于在温和条件下用费歇尔卡宾配合物对富电子烯烃进行环丙烷化反应。
