Chlorosulphonation of Some N-Phenyl-N'-pyridylureas

Abstract

Chlorosulphonation of N-phenyl-N?-2-pyridylurea (1; X = O) and the corresponding thiourea (1 ; X = S) gave the 2?,4?-disulphonyl chloride (2; X = O, Y = Z = SO₂Cl) and the 4?-sulphonyl chloride (2; X = S, Z = H, Y = SO₂Cl) respectively. The sulphonyl chlorides were converted into the corresponding hydrazides, hydrazones and azides. The additional ortho-sulphonation occurring with the urea (1; X = O) is explained in terms of neighbouring group participation, and dichlorosulphonation was confirmed by the N.M.R. spectrum of the acetone disulphonohydrazone (3). In agreement with this theory, chlorosulphonation of N-phenyl-N?- 4-pyridylurea (6) gave the 4?-sulphonyl chloride (7).