Medicinal Chemistry Research Group, Research Centre for Natural Sciences, 1117 Budapest, Hungary.
Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, 1521 Budapest, Hungary.
Molecules. 2022 Jul 22;27(15):4674. doi: 10.3390/molecules27154674.
The microwave (MW)-assisted direct esterification of certain P-acids is a green method. Quantum chemical calculations revealed that the activation enthalpy (Δ) for the exothermic monoalkylphosphate → dialkylphosphate transformation was on the average 156.6 kJ mol, while Δ for the dialkylphosphate → trialkylphosphate conversion was somewhat higher, 171.2 kJ mol, and the energetics of the elemental steps of this esterification was less favorable. The direct monoesterification may be performed on MW irradiation in the presence of a suitable ionic liquid additive. However, the second step, with the less favorable energetics as a whole, could not be promoted by MWs. Hence, dialkylphosphates had to be converted to triesters by another method that was alkylation. In this way, it was also possible to synthesize triesters with different alkyl groups. Eventually a green, P-chloride free MW-promoted two-step method was elaborated for the synthesis of phosphate triesters.
微波（MW）辅助的某些 P-酸的直接酯化是一种绿色方法。量子化学计算表明，放热的单烷基磷酸酯→二烷基磷酸酯转化的活化焓（Δ）平均为 156.6 kJ/mol，而二烷基磷酸酯→三烷基磷酸酯转化的Δ略高，为 171.2 kJ/mol，并且酯化反应的元素步骤的能量学不太有利。直接单酯化可以在适当的离子液体添加剂存在下进行 MW 照射。然而，第二步，由于整体上的能量学较差，不能被 MW 促进。因此，必须通过另一种方法，即烷基化，将二烷基磷酸酯转化为三酯。通过这种方式，也可以合成具有不同烷基的三酯。最终，开发了一种绿色、无 P-氯化物的 MW 促进两步法，用于合成磷酸三酯。
