The invention of radical reactions. Part 39. The reaction of white phosphorus with carbon-centered radicals. An improved procedure for the synthesis of phosphonic acids and further mechanistic insights
作者:Derek H.R Barton、Richard A Vonder Embse
DOI:10.1016/s0040-4020(98)00729-7
日期:1998.10
long radical chain reaction with carbon radicals derived from Barton PTOC esters. The reaction is initiated by traces of oxygen and strongly inhibited by TEMPO. From the duration of the induction period the chain length can be measured as approximately one million. Each P4 molecule can add up to two carbon radicals. Oxidation of the adducts provides a convenient synthesis of phosphonic acids in high
在氩气下的四氢呋喃中的白磷在长自由基链反应中与衍生自Barton PTOC酯的碳自由基反应。反应由微量氧气引发,并受到TEMPO的强烈抑制。从诱导期的持续时间来看,链长可以测量为大约一百万。每个P 4分子最多可以添加两个碳原子团。加合物的氧化提供了高产率的膦酸的方便合成。在0°C下使用H 2 O 2氧化为合适的次膦酸的速度很快。对于敏感的天然产物,最好在室温下用过量的SO 2进一步转化为膦酸。这样,即使是亚油酸也可以高收率地转化为相应的膦酸,而不会对跳过的二烯单元产生任何攻击。TEMPO还因在暴露于氧气时稳定溶液中的白磷而著称。同样,普通的膦(如三丁基膦)也可以通过少量TEMPO稳定。