Reaction of elemental phosphorus (P4) and sulfur with amines in the presence of alkylene glycols: New method to prepare octathiotetraphosphetane ammonium salts

Abstract

Syntheses based on cleavage of the phosphorusphosphorus bond in the molecule of elemental (white) phosphorus open the easiest and environmentally friendly opportunities to prepare many useful organophosphorus compounds [1][2][3].We have recently demonstrated that reactions of white phosphorus (P 4 ) and elemental sulfur with proton-donating reagents easily proceed in the presence of amines [4][5][6], yielding ammonium salts of phosphorous and hypophosphorous acids and diesters of dithiophosphoric acid. The reaction of white phosphorus and sulfur with aliphatic thiols in the presence of amines has been shown to give the fourmembered cyclic phosphorus compounds, ammonium salts of 1,2,3,4-tetramercapto-1,2,3,4-tetrathioxotetraphosphetane [7,8], with moderate yields. These salts were prepared previously [9, 10] along with other cyclic thiophosphates via the reaction of white phosphorus with polysulfides, hydrogen sulfide, and amines.Extending the above-listed results, herein we demonstrate a new method to yield octathiotetraphosphetane via the reaction of P 4 , sulfur, and amines in the presence of 1,3-propanediol as protonodonor.The reaction was carried out in acetonitrile at 55-70ºC during 8-10 h. The conversion of phosphorus was complete, and no hydrogen sulfide formation was observed. By cooling the reacted mixture down, we isolated compounds revealing the δ P 120-122 ppm signal in 31 P NMR spectra, identified as octathiophosphetane ammonium salts (Scheme 1).The salts obtained crystallized readily. Physicochemical and spectral parameters of the products Ia-Ie completely coincided with those of the compounds obtained via the reaction of P 4 , sulfur, and amines in the presence of thiols. The latter products were studied by IR, Raman, 31 P NMR, and 1 H NMR spectroscopy in combination with Density Functional Theory simulation; structure of the salts Ia-Ic was confirmed by X-ray diffraction analysis [7,8].R 1 = R 2 = Et (a); R 1 = H, R 2 = -(CH 2 ) 5 -(b); R 1 = H, R 2 = Et (c); R 1 = Me, R 2 = (CH 2 CH 2 ) 2 O (d); R 1 = CH 2 C 6 H 5 , R 2 = Me (e). P 4 R 1 NR 2 + P P P P S SH SH SH SH S S S

Elemental sulphur in the synthesis of sulphur-containing polymers: reaction mechanisms and green prospects

“…It is very likely that in the presence of amines, the mechanism of S 8 ring opening is anionic. [119][120][121] The anionic opening of the S 8 ring has been suggested for the Willgerodt-Kindler reaction, 122,123 as well as for the transformation of benzothiadiazoles into benzopentathiepines [124][125][126] under nucleophilic catalysis using DABCO (Scheme 6), 126 although in the latter case, the reaction takes place at temperatures >433 K.…”

Recent Advances in Organic Reactions Involving Elemental Sulfur

“…The combination of white phosphorus P 4 , elemental sulfur S 8 and aliphatic secondary/tertiary amines in the presence of an external reducing agent such as thiols or 1,3‐propanediol led to octathiotetraphosphetane ammonium salts in low yields (Scheme ). The four‐membered ring structure was determined unambigously by X‐ray diffraction analysis …”