Asymmetric synthesis of (2-carbamoyloxy-1-alkenyl)cyclopropanes by intramolecular cycloalkylation
作者:Sven Brandau、Dieter Hoppe
DOI:10.1016/j.tet.2005.09.110
日期:2005.12
Enantioenriched, diastereomerically pure (2-carbamoyloxy-1-alkenyl)cyclopropanes 22 are easily prepared via deprotonation of different allyl carbamates with n-butyllithium and (−)-sparteine (4). The mechanism of the cyclization reaction was determined and several substituted (S)-configured vinylcyclopropanes 32 were synthesized by two different methods. The configurational stability of the intermediate
对映体富集,非对映体纯的(2-氨基甲酰氧基-1-烯基)环丙烷22很容易通过不同烯丙基氨基甲酸酯的脱质子化作用制备的Ñ丁基锂和( - ) -鹰爪豆碱(4)。确定了环化反应的机理,并通过两种不同的方法合成了几个取代的(S)构型的乙烯基环丙烷32。在一系列甲硅烷基化实验中研究了中间锂化烯丙基氨基甲酸酯的构型稳定性和差向异构化的半衰期,在动力学控制的对映体-去分化去质子化反应中,ee达到了90%。