Efficient syntheses of zoledronic acid as an active ingredient of a drug against osteoporosis

<p>The reaction of 1<i>H</i>-imidazol-1-ylacetic acid and two equivalents of phosphorus trichloride/phosphorous acid at 75 °C in sulfolane, or in the presence of catalytic amounts of [bmim][BF<sub>4</sub>] afforded zoledronic acid in yields up to 75%. The joint use of the ionic liquid additive and sulfolane as the solvent was synergetic affording highly valuable zoledronic acid in a record yield of 93%.</p>