Inversion of Configuration of Alcohols with<i>O</i>-Alkyl-<i>N</i>,<i>N</i>′-dicyclohexylisoureas
作者:Rolf Jaeger
DOI:10.1055/s-1991-26495
日期:——
(S)-(+)- N,N′-Dicyclohexyl-O-(1-methylheptyl)isourea [(S)- 2] reacts with acetic acid in cyclohexane to give (R) -(-)-(1-methylheptyl) acetate [(R)- 3] with 100% inversion of configuration. Reaction of isourea (R)- 2 with phenol proceeds also with inversion of configuration (99.8%) yielding (S)-(+)-(1-methylheptyl) phenyl ether [(S)- 4] as the main product; optically active 2- and 4-(1-methylheptyl)phenols [(S)- 5] and [(S)-6], respectively, are formed simultaneously. These byproducts, besides others resulting from hydride-shifts, document that the mechanism proceeds via the methylheptyl cation intermediate.
(S)-(+)-N,N′-二环己基-O-(1-甲基庚基)异脲[(S)-2]在环己烷中与乙酸反应,生成(R)-(-)-(1-甲基庚基)乙酸酯[(R)-3],100%发生构型反转。异脲 (R)- 2 与苯酚的反应也进行了构型反转(99.8%),生成的 (S)-(+)-(1- 甲基庚基) 苯醚 [(S)-4]为主要产物;同时还分别生成了具有光学活性的 2-和 4-(1-甲基庚基) 苯酚 [(S)-5]和 [(S)-6]。除了氢化物转变产生的其他副产物外,这些副产物证明了该机制是通过甲基庚基阳离子中间体进行的。