Refluxing 2-methylpyridine-3-carboxylic acid with thionyl chloride for 6-7 h gave (≊ 50%) title compound dichlorothienolactone 2 as was confirmed by a X-ray structure analysis. The propylaminolysis of 2 provides a new and convenient access to highly functionalised pyrrolo [3, 4-b] pyridine derivatives.
![thieno[3,4-b]pyridine-5,7-dione Structure](https://image.chemsrc.com/caspic/199/69094-37-7.png)
![7,7-dichloro-5,7-dihydro-thieno[3,4-b]pyridin-5-one Structure](https://image.chemsrc.com/caspic/306/1030470-98-4.png)