Synthesis of Triazolo Isoquinolines and Isochromenes from 2‑Alkynylbenzaldehyde via Domino Reactions under Transition-Metal-Free Conditions

We describe two simple straightforward syntheses of triazolo isoquinolines (<b>3</b>) and isochromenes (<b>7</b>) from 2-alkynylbenzaldehydes (<b>1</b>) as a common synthon. The synthetic strategy for <b>3</b> involves formation of the (<i>E</i>)-1-(2-nitrovinyl)-2-(alkynyl)­benzene species <b>2</b> via condensation of synthon <b>1</b> with nitromethane followed by a [3 + 2] cycloaddition/extrusion of the nitro group/regioselective 6-endo cyclization domino sequence. In yet another strategy, the synthon <b>1</b> was condensed with nitromethane followed by electrophilic iodo cyclization of the resulting 2-nitro-1-(2-(alkynyl)­phenyl)­ethanol (<b>6</b>) to furnish iodo isochromene derivatives. The salient feature of the above two strategies involves formation of the corresponding heterocycles under metal-free conditions in good yields

Intramolecular C_sp²–C_sp² Friedel–Crafts Arylation: Substrate- and Condition-Controlled Divergent Synthesis of Fused-β-carbolines

A triple cooperative catalysis-mediated multicomponent reaction between 1-formyl-<i>N</i>-substituted-β-carbolines, a terminal alkyne, and a secondary amine allows access to unprecedented polycyclic β-carbolines via sequential A³-coupling and an intramolecular C_sp²–C_sp² Friedel–Crafts arylation reaction. The reaction is successful in a dry inert atmosphere only with substrates bearing a methoxy-substituted benzyl group at the indole nitrogen. Conversely, treating 3-amino­indolizino­[8,7-<i>b</i>]­indoles (obtained after A³-coupling) with acid in the presence of H₂O in air offers a general route to natural-alkaloid-like products

Synthesis of <i>S</i>‑(−)-5,6-Dihydrocanthin-4-ones via a Triple Cooperative Catalysis-Mediated Domino Reaction

An enantioselective synthesis of <i>S</i>-(−)-5,6-dihydrocanthin-4-ones via a triple cooperative catalysis-mediated domino reaction having a broad substrate scope is reported. The reaction between substituted 1-formyl-9<i>H</i>-β-carbolines and terminal alkynes in the presence of catalytic amounts of Jorgensen–Hayashi catalyst, copper iodide, and Hunig base proceeded via a multicascade route, affording the title compounds in good yields and excellent ees with interesting mechanistic features. These compounds were assessed for in vitro antiplasmodial activity against P. falciparum strains. Additionally, 5,6-dihydrocanthin-4-ones are demonstrated to be a versatile precursor to different fused β-carboline derivatives via simple synthetic transformations

A Strategy for the Synthesis of Anthraquinone-Based Aryl‑<i>C</i>‑glycosides

An efficient and simple strategy for the synthesis of a diverse range of anthraquinone-based aryl-<i>C</i>-glycosides has been developed. It involves the sequential Diels–Alder reaction and oxidative aromatization with the preformed glycosyl diene and dienophiles. The glycosyl dienes were obtained from simple sugars by tandem one-pot substitution and elimination reaction

Pyranocarbazoles from <i>Murraya koenigii</i> (L.) Spreng. as antimicrobial agents

<p>The bioassay guided fractionation of methanolic extract of <i>Murraya koenigii</i> (L.) Spreng. leaves resulted in the isolation of seven pyranocarbazoles. These were evaluated against four bacterial strains and ten Candida sp. including two matched pair of fluconazole sensitive/resistant clinical isolates. Out of seven, three i.e. Koenine (mk279), Koenigine (mk309) and Mahanine (mk347) exhibited significant antibacterial activity MIC90 3.12–12.5 μg/mL against bacterial strains <i>Streptococcus aureus</i> and <i>Klebsiella pneumonia</i> compared with standard drug Kanamycin MIC90 12.5 μg/mL. However, only mk309 was found active against variety of Candida species MIC90 12.5–100 μg/mL. It was observed that hydroxylation at C-6 and C-7 positions in the studied pyranocarbazoles activate the bioactivity. Simultaneously, decrease in Log P value compares with −H and −O−CH3 substituted derivatives. The study is focused on selective antifungal and antibacterial activity of pyranocarbazoles on bacterial strains <i>S. aureus</i>, <i>K. pneumonia</i> and variety of Candida species with structure activity relationship observations.</p