Oxidation converts a PPI sulfide intermediate into the sulfoxide required for drugs such as omeprazole. The main process questions are selective oxidation and control of the further-oxidized sulfone.
What changes during oxidation
An oxygen atom is introduced at the sulfide sulfur. In an enantioselective route, control at this sulfur center is also needed to obtain the required sulfoxide enantiomer.
Published PPI processes describe peroxide-based systems and, for some asymmetric routes, catalysts. The oxidant, addition profile and reaction environment determine the balance between remaining sulfide, desired sulfoxide and sulfone impurity.
DMSO can belong to an earlier step
A separate esomeprazole-intermediate process uses DMSO during coupling of pyridine and mercaptobenzimidazole fragments. That is a solvent use in sulfide preparation, not evidence that DMSO performs the subsequent oxidation.
This distinction helps define solvent requirements. The coupling step needs a suitable reaction medium; the oxidation step needs its own oxidant, selectivity controls and work-up. Swern oxidation, which uses activated DMSO to oxidize alcohols, is a different transformation.
When evaluating either operation, track starting material, desired product and relevant oxidation impurities. Residual-solvent and impurity limits should follow the specific product and established manufacturing process.