Microwave-Assisted Esterification of Phosphinic Acids

The Use of MW in Organophosphorus Chemistry

“…This is shown on the example of the alkylation of 1-hydroxy-3-phospholene oxides 10 (Scheme 3.12, Table 3.3) [24,31]. During the alkylations, similarly to that of phenols, the combined application of MW irradiation and PTC was found to be synergistic [32,33].…”

“…The O-alkylations could, of course, be extended to 1-hydroxyphospholane oxides and to a 1-hydroxy-1,2,3,4,5,6-hexahydrophosphinine oxide [24].…”

Environmentally Friendly Chemistry with Organophosphorus Syntheses in Focus

“…A series of phosphinic acids underwent efficient esterification using alcohols with longer chain at around 200°C on MW irradiation (Scheme 7) [43,[46][47][48]. The esterification of cyclic phosphinic acids, such as 1-hydroxy-3-phospholene oxides (8a and 8b), 1-hydroxyphospholane oxides (8c and 8d) and 1-hydroxy-1,2,3,4,5,6-hexahydrophosphinine oxide (8e) was carried out in a closed vessel to afford the phosphinates (9a-e) in acceptable to excellent yields [43,[46][47][48]. The method elaborated by us is of a more general value.…”

“…Quaternary ammonium salts served as special alkylating agents [41]. In the MW-assisted O-alkylation of phosphinic acid, the use of a phase transfer catalyst was useful, when alkyl halides of normal or decreased reactivity were used [42,43].…”

“…Fig. 2 shows geminal-bisphosphonates (42) and the pyrophosphate analogues (43). The methylene-function of bisphosphonates presents a basis for tailoring the biological and physiological properties through the appendage of R 1 and R 2 side-chains.…”