Ag-Catalyzed Domino Decarboxylative Alkylation/Dearomative Annulation: Entry to Fused-Pyrido[4,3-]Indolones.

Here we report the development of unprecedented silver-catalyzed intramolecular annulations of -acrolyl-2-(3-indolyl) benzimidazoles with alkyl carboxylic acids to construct complex fused-pentacyclic alkaloid scaffolds. Divergent reactivities are noticed with altered groups at C2-indole of the substrate. The reaction proceeds through decarboxylative alkylation, followed by dearomative annulation in a domino manner with excellent diastereoselectivity.

One-Pot Synthesis of -Fused Benzimidazo-β-carbolines through Sequential Propargylation/-Cycloisomerization Approach.

The first sequential acid-catalyzed propargylation/base-mediated -cycloisomerization between indolyl-benzimidazoles and propargylic alcohols is described. This protocol enables the one-pot construction of -fused benzimidazo-β-carbolines in good yields. The synthetic utility of this approach is demonstrated by the assembly of an -helicene and also by a gram-scale reaction.

Dearomative -Cyclization to Spiropseudoindoxyls: An Extendable Approach To Access Indolo[3,2-]quinolinones and Isocryptolepine.

A metal-free oxidative intramolecular dearomative spirocyclization of indole-3-formyl-2-carboxamides has been developed for the first time, affording spiropseudoindoxyls in good yields. This domino process proceeds through sequential oxidation, decarboxylation and -arylation. The unique feature of this approach includes the compatibility of -protected-indole-2-carboxamides.

Seleno/Thio-functionalized -Annulation of -Propiolyl-2-arylbenzimidazole to Construct Azaspiro[5,5]undecatrienones.

Till date, the -cyclization of propiolamides is limited to provide azaspiro[4,5]decatrienones. Herein, we present the first example of -carbocyclization, leading to azaspiro[5,5]-undecatrienones from -propiolyl-2-arylbenzimidazoles, involving both the radical-based and electrophilic reactions. This report establishes an access to a wide range of chalcogenated (SCN/SCF/SePh) benzimidazo-fused azaspiro[5,5]undecatrienones in good yields.

One-Pot Arylative Benzannulation of 2-Carbonyl-3-propargyl Indoles with Boronic Acids Leading to Arylated Carbazoles.

Arylative annulation of 2-carbonyl-3-propargyl indoles with boronic acids under sequential palladium/triflic acid catalysis is described. The present strategy to provide di- and triaryl carbazoles in one pot involves benzannulation through difunctionalization of alkynes. The strategy showed a good substrate scope with respect to boronic acids as well as 2-carbonyl-3-propargyl indoles to afford the corresponding carbazoles in decent yields.