Abstract
It is well-known that the P-acids including phosphonic acids resist undergoing direct esterification. However, it was found that a series of alkylphoshonic acids could be involved in monoesterification with C2–C4 alcohols under microwave (MW) irradiation in the presence of [bmim][BF4] as an additive. The selectivity amounted to 80–98%, while the isolated yields fell in the range of 61–79%. The method developed is a green method for P-acid esterification. DFT calculations at the M062X/6–311+G (d,p) level of theory (performed considering the solvent effect of the corresponding alcohol) explored the three-step mechanism, and justified a higher enthalpy of activation (160.6–194.1 kJ·mol−1) that may be overcome only by MW irradiation. The major role of the [bmim][BF4] additive is to increase the absorption of MW energy. The specific chemical role of the [BF4] anion of the ionic liquid in an alternative mechanism was also raised by the computations.
Highlights
Dialkyl phosphonates and their derivatives may be important intermediates or s 1.ing
The alkyl phenyl-H-phosphinates (VI) so o were oxidized by m-chloro-perbenzoic acid to the corresponding phosphonic est According to a newer approach, were direct based esterification on the direct esterification (VII)
The ionic liquids comprising a cation and an anion arepressure regarded solvents thisinflammability, article, we describe the MW-assisted monoesterification of alkylpho due toIn their negligible vapor, and due solvation to their inflammability, negligible vapor pressure, and solvation power
Summary
Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, MedicinalItChemistry However, it was found that a series of alkylphoshonic acids could be involved in 3terification. 4] as an additive. The selectivity amounted to 80–98%, while the isolated yields fell i range of 61–79%. The method developed is a green method for P-acid esterification. DFT ca Citation: Harsági, N.; Henyecz, R.; Ábrányi-Balogh, P.; Drahos, L.; Keglevich, G. Microwave-Assisted Study. 2021, 26, x.
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