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

The reaction of 1<italic>H</italic>-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][BF4] 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%. [ABSTRACT FROM AUTHOR]