Reagent-Controlled One-Pot Assembly of Divergent Indolopyrido-Quinazolinones via Uninterrupted C-Propargylation/N-Annulation

Herein, a novel synthesis of different indolopyrido-quinazolinones by the reaction of easily accessible 2-indolyl quinazolinone with propargylic alcohols has been developed. This [4 + 2] annulation proceeds through sequential acid-catalyzed C-propargylation and base-promoted aza-annulation by forming C-C and C-N bonds in a one-pot operation. Interestingly, the reagent-controlled regiodivergent annulations were observed leading to diversely fused N1-C2 or C2-N3 indolopyrido-quinazolinones. This approach demonstrates access to 7,8-substituted dehydrorutaecarpine alkaloids and their unique structural isomers.