1: 1-hydroxy-3-methyl-2,5-dihydro-1H-phosphole 1-oxide With 1-propanephosphonic acid cyclic anhydride in ethyl acetate 0.166667 h; Green chemistry; 2: isopropyl alcohol in ethyl acetate T=25°C; 3 h; Green chemistry;

N-benzyl-N,N,N-triethylammonium chloride; potassium carbonate T=100°C; P=1500.15 - 2250.23 Torr; 1 h; Microwave irradiation;

potassium hydroxide T=40 - 50°C;