Fig. 2: Symmetrical ultraphosphates.
a Synthesis of ultraphosphates by threefold coupling of phosphates with tris(diethylamino)phosphine 16 and subsequent oxidation. 31P{1H}-NMR spectra of the intermediary ultraphosphite 19 and the ultraphosphate 21 after oxidation and purification for R = adenosine. b Synthetic scope of the synthesis of symmetrically modified ultraphosphates and modification of the oxidation step to yield thio- and seleno analogues. The purity of the crude products is given in percent according to the 31P{1H}-NMR spectra. Yields were not determined due to uncertain quantities of counterions but the respective crude masses are reported in the supporting information along with the spectra.
