Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of hospitalizations and mortality from bacterial infections and is considered a national priority for disease control. In this work we synthesized and evaluated twenty novel C-3 arylazo-coupled indoles and one 4-arylazo-benzo[d]imidazole. The substituents on the C3-aromatic moiety included alkyl, halogen, amino, alkoxy, alkylsulfonyl at positions ortho, meta and para. The indoles utilized were 4-bromo, 5,6-methylenedioxy, 7-aza. In this effort, several azo-indoles showed promising anti-MRSA activities with MIC values as low as 3 μM. Another important finding of this work that sets that stage for a further larger investigation is that 4-arylazo-benzo[d]imidazole is a previously unexplored scaffold with potent anti-MRSA activity.

A new protocol employing arylative sequential reaction of alkynes with boronic acids in one-pot has been developed to access benzo[cd]indoles as products via carbometalation of alkyne followed by intramolecular Michael addition. The one-pot reaction of 4-alkynyl-3-alkenyl indoles bearing a Michael acceptor at the 3-position with boronic acids catalyzed by palladium/triflic acid furnished the products through intramolecular dearomative-aromatization (benzannulation).

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.

A novel strategy for the synthesis of 3-hydroxycarbazoles involving the consecutive propargylation/palladium-catalyzed hydroxylative benzannulation of indole-2-carbonyls with propargylic alcohols has been exploited. This one-pot procedure leads to a wide range of substituted 3-hydroxycarbazoles in high yield with a broad substrate scope. The method was further extended to access furano-carbazole derivatives from dialkynols via tandem annulations.

A novel and efficient domino annulation for the construction of unrevealed polycyclic 3, 4-fused indoles involving rhodium(III)-catalyzed alkyne insertion followed by aza-Michael addition is presented. A variety of N-(pivaloyloxy)arylamides and N-(pivaloyloxy)-1H-indole-1-carboxamides were utilized in this annulation with 4-alkynyl-3-alkenyl indoles.

Herein, we present our findings on the synthesis of 3,4-oxepino-fused indoles by a two-step reaction sequence involving an initial allylic substitution followed by Rh(III)-catalyzed intramolecular [3+2] annulation via C-H activation starting from Morita-Baylis-Hillman (MBH) acetates of acetylenic aldehydes. The strategy is amenable to broad range of MBH acetates providing a facile access to 3,4-oxepino-fused indoles in good yield.

An efficient acid-catalyzed propargylation/aza-annulation sequence was developed under metal-free reaction conditions, thus leading to a one-pot synthesis of a variety of substituted β-carbolines starting from propargylic alcohols and indole 2-carbonyls. This versatile strategy was further extended to the synthesis of 5-azaindoles and 5-azabenzothiazoles. Optical properties suggested that manipulation of electron donor and acceptor moieties on β-carbolines has an impact on their ground and excited state electronic behavior. This leads to blue or green emission and should facilitate the development of organic light emitting diodes (OLEDs). Electrochemical and stability studies revealed that 4a-6 shows ease of redox activity and photostability during illumination.

An efficient and practical one-pot [4 + 2] benzannulation method to produce highly substituted indoles and 1-benzothiophenes via sequential acid-catalyzed propargylation/base-mediated cycloisomerization reactions has been developed. This method allows access to differently substituted (mainly on phenyl ring) indoles and 1-benzothiophenes from the reaction of 3-alkenylpyrroles/-thiophenes as C4 synthons with 1-aryl/1-heteroaryl propargylic alcohols as C2 synthons. Interestingly, dialkynyl substrates can undergo tandem benzannulations to give substituted aza[5]helicenes in 82-83% yield.