described. The question of whether betaine formation occurs via nucleophilic attack of the phosphine on the azodicarboxylate as has been previously assumed, or via a [4+2] cycloaddition (cheletropic) reaction to give the O,N-phosphorane, followed by ring-opening to give the betaine has not been resolved. An answer to this intriguing question is provided.
先前使用膦(PH 3)和偶氮二
羧酸二甲酯的DFT计算表明,相对于
甜菜碱的形成,环状O,N-膦烷在能量上是有利的。在这项研究中,描述了对形成膦烷的有力的实验支持。如先前所假定的那样,
甜菜碱是否通过膦对偶氮二
羧酸酯的亲核攻击或通过[4 + 2]环加成(趋同性)反应生成O,N-膦烷,然后开环形成,从而发生了
甜菜碱的问题。给予
甜菜碱尚未解决。提供了对此有趣问题的答案。