Reaction of thioureidomethylenebisphosphonic acids with α-haloketones: II. Effect of pH on the reaction pathway

The rate and pathway depends in a complicated manner of the cyclization reaction of phenylthioureidomethylenebisphosphonic acid with bromoacetone on the pH of the reaction medium. The dependence is explained in terms of formation of an intramolecular hydrogen bond whose strength depends on the pH of the medium and controls the composition of the reaction mixture and the final result of the reaction.