PREPARATION OF 2-(2-PYRIDYL)-3-MORPHOLINO-2,3-DIHYDROBENZO[b] THIOPHENE 1,1-DIOXIDE-6-SULFONYLMORPHOLIDATE FROM THE REACTION OF 2-STYRYLPYRIDINE WITH CHLOROSULFONIC ACID

Abstract Styrylpyridine (1) reacted with chlorosulfonic acid (6 mole equivalents) and excess thionyl chloride to the give the corresponding para sulfonyl chloride, which was characterized as the N,N-dimethyl sulfonamide. The pyridine ring appeared to deactivate the double bond sufficiently to inhibit the substrate degradation observed previously with analogous hydrocarbon systems. The reaction of styrylpyridine (1) with chlorosulfonic acid, (12 mole equivalents, 24 hour reflux) under more forcing conditions, caused a further cyclisation of the substrate which was characterized as 2-(2-Pyridyl-)3-morpholino-2,3-dihydrobenzo[b]thiophene 1,1-dioxide-6-sulfonylmorpholidate (3) by reaction with excess morpholine.