Palladium-Catalyzed Synthesis of Endocyclic Allenes and Their Application in Stereoselective [2 + 2]Cycloaddition with Ketenes
作者:Masamichi Ogasawara、Atsushi Okada、Kiyohiko Nakajima、Tamotsu Takahashi
DOI:10.1021/ol802280c
日期:2009.1.1
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
检查了各种2-溴-3-外-亚甲基环烯烃与稳定亲核试剂的钯催化反应。当碳环为九元或更大时,以优异的产率分离出相应的环内异戊烯。在八元环状底物的反应中,检测到最初形成了环辛基1,2-二烯衍生物。但是,它缓慢地二聚化。七元碳环对反应是惰性的。使用手性Pd催化剂,在65%ee中获得轴向手性环内烯丙基。将该环状烯用于烯酮与[2 + 2]环加成反应,并研究了其立体选择性。