Sulphonic-phosphinic anhydrides

Reference has already been made to properties of mixed phosphinic-sulphonic anhydrides. / rr-Butylphenylphosphinothioic trifluoromethanesulphonic anhydride (101) was prepared, in both racemic and optically active forms, from the phosphinothioic acid and trifluoromethanesulphonic anhydride in dichloromethane at -50 °C... 

The phosphinosulphonates (5), prepared from the appropriate phosphino-imidazole (4), are oxidizable to the phosphinyl compounds (6). More interestingly, they can isomerize into the phosphinylsulphinate (7) when allowed to come to ambient temperature. Other examples of (5) in which = R = OEt or OPr do not isomerize in this way. The preparation of phosphorus-sulphonic anhydrides (6) has been re-investigated and three efficient methods have been described for their synthesis these are (a) the trifluoromethanesulphonic acid-assisted reaction of a phosphinic acid with a sulphonic triazolide, (Jb) interaction of a phosphinyl-imidazole and a sulphonic acid, and (c) the use of a sulphonic anhydride in reaction (6). ... 

It should be finally noted that hydroxyphosphines can be converted under very smooth conditions into sulfonated phosphines by acylation with o-sulfobenzoic anhydride, as shown by Borner et al. (Eq. 5) [26]. With this methodology in hand the severe conditions commonly used for the incorporation of sulphonate groups in phosphines can be avoided. Acid-labile functional groups like acetals survive under these conditions. In comparison to the parent hydroxyphosphines the water solubility of the relevant Rh catalysts was strongly enhanced [27]. In the asymmetric hydrogenation of prochiral olefins, moderate enantioselectivities were achieved. 

Earlier, reference was made to the potential third mechanism associated with nucleophilic displacements at phosphoryl phosphorus, namely that which might involve the participation of a phosphaacylium cation. Mixed sulphonic-phosphonic or sulphonic-phosphinic anhydrides 645 (Z = O, R = Me or 4-methylphenyl) have been obtained from the free phosphorus(V) acid and the 1,2,4-triazole 646 in the presence of trifluoromethanesulphonic acid, or 645 (Z = O, R = CF3) from the imidazolides 647 and trifluoromethanesulphonic acid and / r/-butylphenylphosphinothioic acid with trifluoromethanesulphonic anhydride yield the mixed 0-anhydride 648 (R = CF3), some reactions of which are illustrated in Scheme 76 ". Of those reactions, the formation of the iodide 649, albeit in low yield when the reaction is carried out in MeOH, with stereochemical retention of configuration at phosphorus, contrasts with the inversion of configuration observed for the remainder, and which is normally encountered for Sn2(P) displacements. The reaction of648 with methoxybenzene to yield the phosphine sulphide 650 in a solvent of high ionizing power (1,1,1,3,3,3-hexafluoropropan-2-ol a lower yield was obtained in a... 

---

See also in sourсe #XX -- [ ]

---