Synthetic optimization of rosiglitazone and related intermediates for industrial purposes

As an important newly Food and Drug Administration (FDA)-approved drug for treating diabetes, rosiglitazone (1) has received much attention from researchers in many areas. To search for an economical and convenient synthesis method for 1, we explored the reaction conditions and workup of a scalable five-step synthetic route by an orthogonal method to determine the best condition for each reaction step. The starting materials are commercially available, including 2-chloropyridine (2), N-methylethanolamine (3), 4-fluorobenzaldehyde (4a) or 4-hydroxybenzaldehyde (4b), and 1,3-thiazolidine-2,4-dione (5). The five sequential reaction steps are cyclization, alkylation, etherification, condensation, and reduction, having optimal yield of 90, 99, 59, 75, and 91 %, respectively. The best overall yield to synthesize rosiglitazone based on compound 2 was 40 %, being suitable for industrial purposes, using water as a green solvent and avoiding column chromatography during the last three reaction steps.