p-Toluenesulfonyl isocyanate is a versatile reagent in organic synthesis, primarily used for the formation of urea and carbamate derivatives. It reacts with primary and secondary amines to produce N-sulfonylureas, which are important intermediates in pharmaceutical chemistry for synthesizing sulfonylurea drugs with hypoglycemic activity. With alcohols, it forms carbamate esters, useful in protecting groups or as building blocks in polymer and dye production. In biochemical applications, it is employed for the selective modification of amino acids, such as hydroxyproline determination in peptides, and for labeling proteins to study structure and function. Its high reactivity and specificity make it invaluable in both academic research and industrial processes for fine chemicals and agrochemicals.