Formation of 2-oxido-4-quaternary ammonium-s-triazinyl betaines from dichloro-s-triazinyl compounds: evidence for a bis-quaternary ammonium-s-triazinyl intermediate

Abstract

The reaction of pyridine and nicotinic acid with 2,4-dichloro-6-p-sulphoanilino-s-triazine to furnish 2-oxido-4-quaternary ammonium-s-triazinyl betaines has been shown to be a general reaction for a range of aliphatic and heterocyclic tertiary bases. Triethylamine proved to be an exception, with failure to react being ascribed to steric factors. Reaction of with N,N-dimethylethanolamine in aqueous medium gave two main products. One was the expected betaine, 4-(N,N-dimethyl)-β-hydroxyethanaminium-6-sulphoanilino-s-triazinyl-2-oxide and the other 4-(N,N-dimethyl)-β-hydroxyethanaminium-2-(β-dimethylamino)-ethoxy-6-p-sulphoanilino-s-triazine (IX). Formation of the latter product is rationalised in terms of an internal aromatic nucleophilic substitution (Smiles rearrangement) of a highly electrophilic bis-quaternary ammonium triazinyl species. This highly reactive species has been isolated in an impure state, characterised by NMR, and rearranged to the triazinyl ether (IX) confirming both the Smiles rearrangement and the mechanistic pathway for the formation of triazinyl betaines from dichloro-s-triazinyl compounds and tertiary bases.