Synthesis and crystal structure of ethyl benzimidazole-2-yl phosphonate

When N‐cyanoimido‐(O,O‐diethyl)phosphonyl/S‐methyl thiocarbonate (1) was treated with o‐phenylenediamine in the presence of Et₃N in ethanol, diethyl benzimidazole‐2‐yl phosphonate (2) was obtained and hydrolyzed during the recrystallization in MeOH/H₂O, generating ethyl benzimidazole‐2‐yl phosphonate (3). The crystal structure of compound 3 was determined by X‐ray diffraction method. The crystals belong to monoclinic, space group C2/c, a = 1.78406(18), b = 0. 83725(9), c= 1.67401(18) nm, β= 118.997(2)°, V = 2. 1870(4) nm³ Z = 8, D_c = 1.374 g/cm³, F(000) = 944. The final R and wR are 0.0499 and 0.1436, respectively. The mechanism of the above reaction is also discussed.