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.

Automated summary

This study aims to find efficient initiators for electrophilic cyclizations of 2-(3-butenyl)quinazolin-4(3H)-ones, and the reactions with several acids and halogenating agents were tested. It was found that CF3SO2OH can be used to synthesize linear products, while I2, NIS, or NBS yield angular products.