Palladium-catalyzed synthesis of endocyclic allenes and their application in stereoselective [2 + 2]cycloaddition with ketenes.
Palladium-catalyzed synthesis of endocyclic allenes and their application in stereoselective [2 + 2]cycloaddition with ketenes.
复制标题
DOI：
10.1021/ol802280c
复制
发表时间：
2009-05
期刊：
影响因子：
5.2
通讯作者：
M. Ogasawara;A. Okada;K. Nakajima;Tamotsu Takahashi
中科院分区：
文献类型：
--
作者：
M. Ogasawara;A. Okada;K. Nakajima;Tamotsu Takahashi
研究了钯催化各种2-溴-3-外甲基环烯与稳定亲核试剂的反应。当碳环大于等于9元时，相应的内环烯的分离率很高。在八元环底物的反应中，检测到环-1,2-二烯衍生物的初始形成；然而，它的二聚化很慢。七元碳环对反应是惰性的。采用手性钯催化剂，在65%的ee下得到了轴手性内环烯。将环烯烯与烯酮进行[2 + 2]环加成反应，并对其立体选择性进行了研究。
Palladium-catalyzed reactions of various 2-bromo-3-exo-methylenecycloalkenes with a stabilized nucleophile were examined. When the carbocycles were nine-membered or larger, the corresponding endocyclic allenes were isolated in excellent yields. In a reaction of the eight-membered cyclic substrate, initial formation of a cycloocta-1,2-diene derivative was detected; however, it dimerized slowly. The seven-membered carbocycle was inert to the reaction. Using a chiral Pd-catalyst, an axially chiral endocyclic allene was obtained in 65% ee. The cyclic allenes were applied to [2 + 2]cycloaddition with ketenes, and the stereoselectivity was studied.