2-Amino-4-(4-aminophenyl)thiazole → 4-Amino-benzylidene-hydantoin

Participants

Reaction Steps

To 3 g (12.9 mmol) of crude 4-nitro-benzylidene-hydantoin, melting point 300° C. (prepared as described in Example 6 under (a)) in 50 ml 80% acetic acid are added 3 g of iron powder at 100°. After 30 minutes the mixture is filtered over kieselguhr and the filtrate is evaporated down in vacuo. The evaporation residue is divided between EtOac and dilute aqueous ammonia solution; before the separation of the phases the mixture is filtered once more through kieselguhr. The organic phase is washed with water, dried, filtered and evaporated down in vacuo. The yellow foam obtained (0.80 g; 30.6% of theory) predominantly contains 4-amino-benzylidene-hydantoin (A) (Rf =0.55), but no 4-amino-benzyl-hydantoin (B) (Rf =0.48), according to DC (silica gel; toluene/EtOac/EtOH (4:2:1)).

Provenance & Evidence