Quinquevalent phosphorus acids

Abstract

This chapter shows, as in previous years, the most important achievements of the 2021 year in the area of organo-phosphorus compounds containing: three P–O bonds (Section 2: phosphoric acids and their derivatives), two P–O and one P–C bonds (Section 3: phosphonic acids and their derivatives) as well as one P–O and two P–C bonds (Section 4: phosphinic acids and their derivatives), in addition to the phosphoryl group P═O, present in all three groups of compounds. Each of the main sections covers “synthesis and reactions” including pure synthesis without applications, “synthesis and biological applications” and “synthesis and miscellaneous applications” including synthesis directed towards non-biological applications. At the end of each subsection, the corresponding achievements are shown for hetero-analogues in which phosphorus–oxygen bonds have been replaced by phosphorus–heteroatom P–X and/or P═Y bonds (X, Y = N, S or Se). The subsection on quinquevalent phosphorus acids and their derivatives as catalysts has been placed, as usual, at the end of the entire chapter, after a review of all three main groups of compounds. As in previous years, the area devoted to phosphoric and phosphonic acids and their derivatives dominated over a smaller section of phosphinic acids and their derivatives, and literature references for these sections remained at a ratio of 4 : 12 : 1. A dynamic, five-fold increase in the number of works, in the subject of chiral phosphoric acids as catalysts, has been recorded in this year.