Kiani, Adeleh published the artcileDirect synthesis of sulfonyl azides from sulfonic acids, Application In Synthesis of 636-73-7, the publication is Journal of Sulfur Chemistry (2014), 35(2), 119-127, database is CAplus.
A one-pot process for the synthesis of various sulfonyl azides (RSO2N3) by treating sulfonic acids with PPh3-trichloroisocyanuric acid-sodium azide at room temperature was described. A wide range of arenesulfonyl and alkanesulfonyl azides was obtained in excellent yields under mild conditions.
Journal of Sulfur Chemistry published new progress about 636-73-7. 636-73-7 belongs to pyridine-derivatives, auxiliary class Pyridine,Sulfonic acid, name is Pyridine-3-sulfonic acid, and the molecular formula is C5H5NO3S, Application In Synthesis of 636-73-7.
Referemce:
https://en.wikipedia.org/wiki/Pyridine,
Pyridine | C5H5N – PubChem