Synthesis of indolo- and pyrrolo[1,2-a]quinoxalinones through a palladium-catalyzed oxidative carbonylation of the C position of indole.

A methodology that involves the Pd-catalyzed direct C(sp2)-H bond carbonylation of the C2 position of indole has been introduced for the synthesis of indolo[1,2-a]quinoxalin-6(5H)-ones. The methodology developed herein was used for the synthesis of pyrrolo[1,2-a]quinoxalin-4(5H)-ones. The reaction of N-substituted 2-(1H-indol-1-yl)anilines or 2-(1H-pyrrol-1-yl)anilines and carbon monoxide in the presence of Pd(OCOCF3)2 as a catalyst and Cu(OAc)2 as an oxidant in toluene at 80 °C forms the corresponding quinoxalinones as exclusive products in good yields.

Palladium catalyzed carbonylative annulation of the C(sp)-H bond of N,1-diaryl-1H-tetrazol-5-amines and N,4-diaryl-4H-triazol-3-amines to quinazolinones.

Pd(ii) catalyzed direct C-H carbonylative annulation of N,1-diaryl-1H-tetrazol-5-amines and N,4-diaryl-4H-1,2,4-triazol-3-amines gave the corresponding triazole and tetrazole fused quinazolinones in good yields. This methodology offers a convenient method for the synthesis of these important heterocyclic scaffolds in a highly atom economical process. On the mechanistic aspect weakly nucleophilic triazole and tetrazole moieties function as both directing as well as intramolecular nucleophiles.

Selective Synthesis of 3-Arylbenzo-1,2,3-triazin-4(3H)-ones and 1-Aryl-(1H)-benzo-1,2,3-triazoles from 1,3-Diaryltriazenes through Pd(0) Catalyzed Annulation Reactions.

Pd(0) catalyzed carbonylative annulation reaction of 1-(2-iodophenyl)-3-aryltriaz-1-enes in the presence of DABCO and 1 atm of carbon monoxide in toluene at 80 °C gave the corresponding 3-arylbenzo-1,2,3-triazin-4(3H)-ones with high selectivity and in excellent yields. Substrate scope of this reaction is demonstrated with 24 examples with various halo, alkyl, and alkoxy substituents on either of the aromatic rings. Bromo substituted triazenes were less reactive as starting materials toward the carbonylative annulation reaction and yielded 3-arylbenzo-1,2,3-triazin-4(3H)-ones in good to moderate yields in the presence of only xantphos as an additive.