Proton- and halogen-induced cyclizations of 2-(3-butenyl)quinazolin-4(3H)-ones in the synthesis of pyrrolo[2,1-b]- and pyrrolo[1,2-a]quinazolinone derivatives

With the aim of finding efficient initiators for electrophilic cyclizations of 2-(3-butenyl)quinazolin-4(3H)-ones, their reactions with a number of acids (HCl, CF3COOH, H2SO4, polyphosphoric acid, CF3SO2OH) and halogenating agents (I2, Br2, NIS, NBS) have been studied. As established, CF3SO2OH can be successfully applied in the synthesis of linear 1-methyl-2,3-dihydropyrrolo[2,1-b]quinazolin-9(1H)-ones while the use of I2, NIS, or NBS readily leads to angular 1-(halomethyl)-2,3-dihydropyrrolo[1,2-a]quinazolin-5(1H)-ones.