Reductive step for preparation of rosiglitazone

An improved process has been developed for the production of rosiglitazone based on reductive transformation of substituted 5-benzylidenethiazolidin- 2,4-dione. Sodiumborohydridewas usedas reducingagent anddivalent cobalt complexwith dimethyglyoximas catalyst.Reaction temperatures as well as dosagemodes of the reducing agent and catalyst have been identified as significantlyimportant pa-rameters of the process. The discussed procedure ensures veryhigh conversions and yields of the reductive transformation.