Highly selective base-catalyzed ring closing Ugi-adducts from the reaction of 2-formylindole, 2-bromoacetic acid, amines and isocyanides

The intermediate products of the Ugi reaction between indole-2-carboxaldehyde, 2-bromoacetic acid, amines and isocyanides were treated with Cs2CO3 in DMF to form a series of novel cyclized 1,2-dihydropyrazino[1,2-a]indol-3(4H)-ones (indole -NH cyclization) as major and piperazin-2-ones (amide -NH cyclization) as minor products.