Pd-catalysed intramolecular transformations of indolylbenzenesulfonamides: ortho-sulfonamido-bi(hetero)aryls via C2-arylation and polycyclic sultams via C3 arylation.

Palladium-catalysed and base-dependent intra-molecular ipso-substitution and cyclisation strategies involving N-indolyl-substituted aryl-sulfonamides for the rapid construction of 2-aryl indole and indole-fused six-membered sultams are described. The Pd(OAc)2/Ph3P/Et3N combination delivers indolyl C2 arylated motifs via C(2)-N bond cleavage followed by C-C bond formation. In sharp contrast to this, the Pd(OAc)2/Ph3P/K2CO3 combination induced intramolecular-Heck cross-coupling affords polycyclic sultams exclusively. Thus, this strategy is completely additive-dependent. It also shows a broad substrate scope and delivers the corresponding products in good to high yields.

Cu(I)-Catalyzed Ligand-Free Tandem One-Pot or Sequential Annulation via Knoevenagel Intermediates: An Entry into Multifunctional Naphthalenes, Phenanthrenes, Quinolines, and Benzo[b]carbazoles.

A simple but efficient one-pot or sequential copper-catalyzed protocol using 2-bromoaldehydes and active methylene group containing substrates that affords multifunctional naphthalenes, phenanthrenes, quinolines, and benzo[b]carbazoles via Knoevenagel condensation, C-arylation, and decarboxylation, followed by aromatization, is developed. The reaction utilizes the potential of Knoevenagel intermediates and does not require any ancillary ligand. The phenanthrene products thus obtained show moderate fluorescence activity. Structural elaboration of the products to obtain dihydrobenzoquinazolines is also highlighted.

InCl3 mediated heteroarylation of indoles and their derivatization via CH activation strategy: Discovery of 2-(1H-indol-3-yl)-quinoxaline derivatives as a new class of PDE4B selective inhibitors for arthritis and/or multiple sclerosis.

A new class of PDE4 inhibitors were designed and synthesized via the InCl3 mediated heteroarylation of indoles and their further derivatization through the Pd(II)-catalyzed CH activation strategy. This effort allowed us to discover a series of 2-(1H-indol-3-yl)-quinoxaline based inhibitors possessing PDE4B selectivity over PDE4D and PDE4C. One of these compounds i.e. 3b (PDE4B IC50 = 0.39 ±â€¯0.13 µM with ∼27 and > 250 fold selectivity for PDE4B over PDE4D and C, respectively) showed effects in Zebrafish experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis when dosed at 3, 10 and 30 mg/kg intraperitoneally. Indeed, it halted the progression of the disease across all these doses tested. At an intraperitoneal dose of 30 mg/kg the compound 3b showed promising effects in adjuvant induced arthritic rats. The compound reduced paw volume, inflammation and pannus formation (in the knee joints) as well as pro-inflammatory gene expression/mRNA levels significantly in arthritic rats. Moreover, this compound was found to be selective towards PDE4 over other families of PDEs in vitro and safe when tested for its probable toxicity (e.g. teratogenicity, hepatotoxicity and cardiotoxicity) in Zebrafish.

Use of AlCl3 in Friedel Crafts arylation type reactions and beyond: an overview on the development of unique methodologies leading to N-heteroarenes.

As a privileged class of heterocyclic compounds N-heteroarenes have found enormous applications in many areas including medicinal/pharmaceutical chemistry and drug discovery. Consequently, a wide variety of methods have been reported for their synthesis. While not free from their own limitations the AlCl3 mediated methods appeared to have some particular advantages in preparing a number of useful N-heteroarenes. Besides the famous Friedel-Crafts (FC) alkylation/acylation reactions one such example is AlCl3-induced heteroarylation of arenes and heteroarenes (FC arylation type reactions) that can be used to prepare a certain class of N-heteroarenes in an operationally simple, efficient and cost effective manner. Interestingly, pyridine is not a good substrate in FC alkylation/acylation reactions whereas 2-chloropyridines are indeed effective in heteroarylation reaction. However, no systematic and detailed study regarding the application potential of this method was performed until 2002. Some other examples that emerged in the recent past include AlCl3 induced heteroarylation-cyclization, hydroarylation-heteroarylation, sulfonyl group migration etc. All these innovative methodologies allowed the direct access to several unique and novel N-heteroarenes some of which showed interesting pharmacological properties including anti-inflammatory, anti-cancer and antibacterial activities when tested in vitro. While unlike FC reactions many of these AlCl3 mediated methodologies are still in their initial stage of developments, a continuing effort to uncover their further potential in organic synthesis/medicinal chemistry is necessary. The current article provides an overview of these unique methodologies that highlight the use of AlCl3 beyond FC reactions leading to new N-heteroarenes.

Ligand-free MCR for linking quinoxaline framework with a benzimidazole nucleus: a new strategy for the identification of novel hybrid molecules as potential inducers of apoptosis.

We report a true MCR involving the reaction of N-(prop-2-ynyl)quinoxalin-2-amine derivatives with 2-iodoanilines and tosyl azide in the presence of 10 mol% of CuI and Et3N in DMSO to afford the pre-designed hybrid molecules containing quinoxaline framework linked with a benzimidazole nucleus. The MCR proceeds in the absence of any ligand and/or lateral addition of the catalyst/base affording products within 30 min in good yields, some of which showed encouraging apoptosis inducing properties in zebrafish.

Vinylic amino group activation: a new and general strategy leading to functionalized fused heteroaromatics.

A conceptually new and general strategy has been developed for the construction of a benzimidazole or a benzoxazole ring fused with isoquinolinone affording a diverse and unique class of small molecules as potential and novel inhibitors of PDE4.

Facile assembly of two 6-membered fused N-heterocyclic rings: a rapid access to novel small molecules via Cu-mediated reaction.

A rapid, versatile and one-pot Cu-mediated domino reaction has been developed for facile assembly of two six membered fused N-heterocyclic rings leading to novel small molecules as potential inhibitors of PDE4.