Synthesis and properties of carbamoyl derivatives of photolabile benzoins

Carbamoyl derivatives of photolabile benzoins, particularly of 3',5'-dimerhoxybenzoin, are readily prepared via the mixed p-nitrophenyl carbonate of the benzoin. The method is most suitable for secondary amines, since many primary amines exist in varying proportions as the cyclic hydroxyoxazolidinone tautomer. In alkaline solution (0.2 M NaOH) the carbamates of unsymmetrical benzoins are readily equilibrated. Flash photolysis of 3',5'-dimethoxybenzoin carbamates generates the carbamate anion in a fast heterolytic process and liberation of the amine is controlled by the rare of decarboxylation. (C) 1997 Elsevier Science Ltd.