A Convenient (E)-Stereoselective Synthesis of Alkenylphosphonates
摘要:
Diethyl (E)-alkenylphosphonates have been prepared stereoselectively by dehydration of the corresponding beta-hydroxyphosphonates using DCC/CuCl2 in refluxing toluene. Starting beta-hydroxyphosphonates were obtained in high yield from diethyl methylphosphonate.
Interestingly, when using activatedaryl bromides the palladium loading could be lowered to only 0.25 mol%. While highlyactive when coupling aryl iodides (i.e. only 0.15 mol% required), the PdO/SiO2 catalyst was found to be inactive when considering aryl bromides. Deep study of this catalytic material revealed that in the case of aryl bromides, absence of in situ reduction of the catalyst precursor prevents
Pd-catalysed procedures for the direct Heck arylation of diethyl vinylphosphonate with various aryl or heteroaryl halides toward the synthesis of diethyl2-(aryl)vinylphosphonates are reported. Several homogeneous catalytic systems (i.e. Herrmann palladacycle, Nolan (NHC)-palladium catalyst, Pd(OAc)2/PPh3) were used and compared within the study. High conversions and selectivities were achieved under
报道了钯催化的乙烯基膦酸二乙酯与各种芳基或杂芳基卤化物直接进行Heck芳基化反应以合成2-(芳基)乙烯基膦酸二乙酯的方法。在研究中使用了几种均相催化体系(即,Herrmann palladacycle,Nolan(NHC)-钯催化剂,Pd(OAc)2 / PPh 3)。无论使用何种均相催化剂,在最佳条件下(2摩尔%[Pd],NMP,K 2 CO 3和140°C)都可以实现高转化率和选择性。
Manganese(<scp>iii</scp>)-mediated alkenyl C<sub>sp2</sub>–P bond formation from the reaction of β-nitrostyrenes with dialkyl phosphites