Quaternary ammonium phosphotungstates

Reaction-Controlled Phase-Transfer Catalyst Based on Quaternary Ammonium Phosphotungstates 431... 

REACTION-CONTROLLED PHASE-TRANSFER CATALYST BASED ON QUATERNARY AMMONIUM PHOSPHOTUNGSTATES... 

We can also mention the gravimetric determinations of protonated amines and quaternary ammoniums as tetraphenylboron salts (see above). Furthermore, alkaloids seem to have been the subject of the greatest number of this type of gravimetric determination. Usually, the precipitation of tetraphenylboron salts is carried out in the range 3 < pH < 5. Gravimetric determinations of alkaloids as phosphotungstates and reineckates have also been proposed. 

Heteropoly acids (HPAs) such as 12-phosphomolybdic acid (PMA) and 12-phosphotungstic acid (PWA) function as a catalyst in the aziridination of alkenes with chloramine-T (Scheme 2.37) [56]. PMA catalyzed the reaction most efficiently in the presence of a quaternary ammonium cocatalyst and molecular sieves, affording aziridine products in good yields. The low stereospecificity of the reaction indicates the stepwise mechanism. The authors proposed the involvement of metallo-oxaziridine 22 as an intermediate. 

Lincoln, P. A., C. C. T. Chinnick, Quaternary ammonium compounds as phosphotungstates. 

---