[55881-03-3] · C12H36B2F8N6OP2 · m-Oxobis[tris(dimethylamino)phosphonium] Bis(tetrafluoroborate) · (MW 516.10)
Alternate Name: Bates' reagent.
Physical Data: mp 194-204 °C.
Solubility: insol ether, EtOAc, THF, CH2Cl2, CHCl3; sol MeCN, DMF, HMPA.
Form Supplied in: white crystalline solid; limited commercial availability.
Preparative Methods: by treatment of Hexamethylphosphoric Triamide with p-toluenesulfonic anhydride at 55 °C for 3 h, isolation of the bis(p-toluenesulfonate), then treatment with NaBF4 in MeCN.2
Handling, Storage, and Precautions: can be used with care without special precautions; however, it reacts with water to produce HMPA (carcinogenic) and HBF4 (corrosive).
Bates' reagent is a dehydrating agent used in the synthesis of peptides (eq 1).1 It has the advantage over 1,3-Dicyclohexylcarbodiimide (DCC) that the byproducts of the reaction (HMPA, etc.) are water-soluble and easily removed. A disadvantage is that it results in extensive racemization. This can be overcome, however, by the addition of 1-Hydroxybenzotriazole (HOBT).1 Bates' reagent, even in conjunction with HOBT, is not as popular as the closely related reagent Benzotriazol-1-yloxytris(dimethylamino)phosphonium Hexafluorophosphate (BOP).4 The latter reagent is more readily available, considerably cheaper, has a lower molecular weight (less reagent is required), produces less acid (less base is required), and is more efficient for solid-phase peptide synthesis.5
Bates' reagent is a useful reagent for the Beckmann rearrangement of ketoximes (eq 2), dehydration of aldoximes to nitriles (eq 3), and Lossen-type rearrangement of hydroxamic acids (eq 4).3
It is much less reactive as an activating/dehydrating agent than is the analogous Ph3
Ian D. Jenkins
Griffith University, Brisbane, Australia