Synthesis of fused hydantoins by intramolecular amidoalkylation

Several 1-(2-arylcthyl)hydantoins 2 have been cyclized through their 5-bromo derivatives. The hydantoins 2a and 2b , unsubstituted in the 5-posilion, require stannic chloride catalysis of the cyclization to 3a and 3b , respectively. However, the 5-phenyl analog 2c (n = 2) cyclizes spontaneously and essentially quantitatively to 5 during bromination. This reaction is limited to the formation of a 6-membered ring.