Scheme 1.

Synthesis of 4-(4′,6′-dichloro-1′,3′,5′-triazin-2′-ylamino)-benzene-sulfonamide precursor 1. Reagents and conditions: 4-aminobenzenesulfanilamide, cyanuric chloride, acetone, at 0 °C, was added to an aqueous solution of NaOH, stirred for 1 h, and the reaction was subsequently quenched by the addition of slush (100 mL), after which the solid was filtered off. The scheme is reprinted from [4], with permission of the publisher. Product yield: 95%.