| Abstract |
The present invention relates to a process for reducing an exocyclic double bond at the 5-position of a thiazolidinedione moiety of a thiazolidinedione precursor of antihyperglycemic compound pioglitazone, rosiglitazone and troglitazone comprising the steps of: a) preparing a solution or suspension of the said thiazolidinedione precursor in a non-ether solvent medium with a base, wherein the non-ether solvent medium comprises water or a mixture of water with one or more organic solvent, which comprises methanol, ethanol, isopropanol, ethyl acetate, toluene, xylene, methylene chloride, N,N-dimethylformamide, N,N-dimethylacetamide, or a mixture thereof, and the base, which comprises an alkaline or alkaline earth carbonate, an alkaline hydrogen carbonate, an organic secondary or tertiary amine or an amidine, b )combining obtained solution or suspension with a dithionite source, wherein the dithionite source comprises sodium-, lithium-, potassium-, calcium-, magnesium-, a tetraalkylammonium- or a guanidinium-dithionite. |