Stability of five- and six-membered heteroaromatic sulfonyl halides – essential reactants in various fields of chemistry – has been comprehensively studied. Based on experimental data obtained for over 200 representatives, several decomposition pathways were established, along with the stability trends for each heterocyclic system. These pathways include formal SO2 extrusion (characteristic of alpha- and gamma-isomeric pyridines and most diazine derivatives), hydrolysis by trace water (typical for beta-isomeric pyridines and some azoles), reactions at other functional groups (specific to the substrate), and complex decomposition likely related to the limited stability of the heterocycle itself in the presence of electrophilic moieties (observed for furan, isoxazole, and some isothiazole derivatives). Based on these results, simple rules of thumb are proposed for selecting an appropriate heterocyclic sulfonyl halide to use in chemical synthesis, i.e., chloride versus more stable but less reactive fluoride.
Shevchuk et al. (Tue,) studied this question.