Sr.No. Chemical Name CAS No. Used for 
Pioglitazone hydrochloride
1 5-Hydroxy Pioglitazone

(5-[[4-[2-(5-Ethyl-2-pyridinyl)ethoxy]phenyl]methyl]-5-hydroxy-2,4-thiazolidinedione)

625853-74-9 Imp A as per EP
  Didehydro Pioglitazone Impurity

(5-{4-[2-(5-Ethyl-2-pyridinyl) ethoxy] benzylidene}-2,4-thiazolidinedione)

136401-69-9 Imp B as per EP
2 5-[[4-[2-(5-Ethyl-2-pyridinyl)ethoxy] phenyl]methyl]-N-[2-(5-ethylpyridin-2-yl)ethyl]-2,4-thiazolidinedione 952188-00-0 Imp C as per EP
3 Ethyl (2RS)-2-(carbamoylsulphanyl)-3-[4-[2-(5-ethylpyridin-2-yl) ethoxy] phenyl] propanoate 868754-42-1 Imp D as per EP
4 Ethyl 3-(4-(2-(5-ethylpyridin-2-yl)ethoxy)phenyl)propanoate 868754-42-1 Imp E as per EP
5 2-(2-(4-((2,4-dioxothiazolidin-5-yl)methyl)phenoxy)ethyl)-5-ethylpyridine 1-oxide 145350-09-0  –
6 4-(2-(5-ethylpyridin-2-yl)ethoxy)benzaldehyde 114393-97-4 Aldehyde imp.
7 (4-(2-(5-ethylpyridin-2-yl)ethoxy)phenyl)methanol 144842-17-1
8 5-(4-hydroxybenzyl)thiazolidine-2,4-dione 74772-78-4 Metaboite
9 5-Ethyl-2-vinylpyridine 5408-74-2