Bartelson Keith J, Singh Ravi P, Foxman Bruce M, Deng Li
Department of Chemistry, Brandeis University, Waltham, MA, 02454-9110, USA.
Chem Sci. 2011 Oct;2(10):1940-1944. doi: 10.1039/c1sc00326g.
We describe an unprecedented cycloaddition reaction of 2-pyrones with aliphatic nitroalkenes catalyzed by a new bifunctional cinchona alkaloid-derived catalyst bearing a bulky TIPS-ether at the 9-position. The [2.2.2] bicyclic adducts were obtained in good yield with excellent diastereo- and enantioselectivity. Carbon isotope effects were measured by (13)C NMR and are indicative of a stepwise mechanism. Finally, a synthetic application is demonstrated, highlighting the utility of the cycloadducts.
我们描述了一种前所未有的反应,即2-吡喃酮与脂肪族硝基烯烃在一种新型双功能金鸡纳生物碱衍生催化剂的催化下发生环加成反应,该催化剂在9位带有一个庞大的三异丙基硅基醚。[2.2.2]双环加合物以良好的产率、出色的非对映和对映选择性得到。通过(13)C NMR测量了碳同位素效应,这表明反应是分步进行的。最后,展示了该反应的合成应用,突出了环加合物的实用性。