On the Acylation of the Phosphoryl Oxygen. I. Acyloxyphosphonium Salts from HMPT and Carboxylic Acid Derivates

Acylation equilibria with participation of acyloxyphosphonium ions exist in solutions of HMPT and carboxylic chlorides, or anhydrides, respectively, as can be shown by 31P-n.m.r. after trapping the counter ion with SbCl5. Moderately stable acyloxyphosphonium salts have been isolated for the first time by acylation of HMPT. In the alternative reaction of (Me2N)3P with CCl4 and carboxylic acids, acyloxyphosphonium salts are formed only after prolonged reaction times, due to the stability of the intermediate chlorotris-(dimethylamino)-phosphonium ion.