Ethylenediphosphonic acid

The synthesis of the Al2[03PC2H4P03](H20)2F2 H20 (7) was performed by mixing Al2(S04)3-18H20 (Aldrich), ethylenediphosphonic acid (Lancaster), HF/ pyridine (70 wt % HF, Aldrich), pyridine (Aldrich), and de-ionised water in the molar ratio 1 2.16 8.7 54 144. The reaction mixture (initial pH = 6) was sealed in a Teflon-lined steel autoclave and heated under autogenous conditions at 170 °C for 5 days. Al2[03PC3H6P03](H20)2F2 H20 II) was synthesized using a similar synthesis procedure. The obtained crystalline products were separated by suction filtration, washed in distilled water and acetone, and dried in air. 

The reactions of trialkyl phosphites with dialkyl acetylenedicarboxylates have been studied in some detail, and the products explained as proceeding via 1 1 intennediates. Thus, the addition of a solution of dimethyl acetylenedicarboxylate to either (MeO 13 or (EtOjjP (2 eq) at 0°C leads to the formation of the corresponding 1,2-diphosphoranes. Treahnent of the diphosphorane with anhydrous HBr leads to protonation and subsequent dealkylation to give tetramethyl l,2-/ (meth-oxycarbonyl)-l,2-ethylenediphosphonate in 94% yield (Scheme 8.49). Trialkyl phosphites add vigorously to acetylenedicarboxylic acid in EtjO to give tetraalkyl 1,2-Z z5 (alkoxycarbonyl)-1,2-ethylenediphosphonates in modest yields. ... 

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