Quinoline, quinazoline and acridone alkaloids

TBAB-catalyzed cascade reactions: facile synthesis of 1-trifluoromethyl-3-alkylidene-1,3-dihydrofuro[3,4-b]quinolines via 5-exo-dig cyclization of o-arylalkynylquinoline aldehydes

TBAB-catalyzed cascade reaction condition is developed for the synthesis of 1-trifluoromethyl-3-alkylidene-1,3-dihydrofuro[3,4-b]quinolines from o-arylalkynylquinoline aldehydes via 5-exo-dig cyclization.

Water-mediated and promoted eco-friendly one-pot synthesis of azaarene substituted isoxazoles

An efficient and green approach for the sp³ C–H bond functionalization of 2-methyl azaarenes to 3-methyl-4-nitro-5-styrylisoxazoles in water has been described.

An efficient one-pot approach for the regio- and diastereoselective synthesis of trans-dihydrofuran derivatives: cytotoxicity and DNA-binding studies

A facile one-pot, three component strategy has been developed for the construction oftrans-2,3-dihydrofuran derivatives. All the synthesized compounds have been evaluated for their cytotoxic activity.

Pyridine C3-arylation of nicotinic acids accessible via a multicomponent reaction: an entry to all-substituted-3,4-diarylated pyridines

An efficient route for the synthesis of all-substituted/functionalized pyridines has been developed. Several of the synthesized compounds exhibited significant anti-proliferative properties.

Synthesis of benzyl esters from the commercially available alcohols catalyzed by TBAI via C(sp3)–H bond functionalization

The direct esterification of alcohol catalyzed by TBAI via C(sp³)–H bond functionalization was achieved under mild and clean conditions with good to excellent yields.

Acid-catalyzed tandem reaction for the synthesis of pyridine derivatives via CC/C(sp3)–N bond cleavage of enones and primary amines

2,4,6-Trisubstituted pyridines can be generated from an acid-catalyzed tandem reaction via CC/C(sp³)–N bond cleavage of enones and primary amines.

One Pot Synthesis of 6-(4-carboxy-3-methyl-2-phenylquinolin-6-ylsulfonyl)-3-methyl-2-phenylquinoline-4-carboxylic Acids from Dapsone and α-ketobutyric Acid by a Doebner Reaction

A series of new 6-(4-carboxy-3-methyl-2-phenylquinolin-6-ylsulfonyl)-3-methyl-2-phenylquinoline-4-carboxylic acids were synthesised by a one-pot reaction of dapsone, α-ketobutyric acid, and aromatic aldehydes in the presence of CuBr2 as a catalyst. Operational simplicity, mild reaction conditions, and eco-friendly procedure make this novel protocol a promising alternative for the preparation of quinoline-4-caboxylic acid derivatives. The structures of the products were established by elemental analyses and spectroscopic data. The biological activity of the new sulfone dimers was evaluated as having the potential for use as anticancer agents.

Palladium-Catalyzed Synthesis of 5-Iminopyrrolones through Isocyanide Double Insertion Reaction with Terminal Alkynes and Water

With the combination of Pd(dppf)Cl₂ and Cu(OAc)₂, a variety of 5-iminopyrrolones were synthesized in moderate to good yields from terminal alkynes, isocyanide, and water via isocyanide double insertion and cycloaddition reaction. A plausible reaction mechanism for this process is depicted. Furthermore, selected compounds 3c, 3e, and 3h exhibited good activities against HepG2 (human liver cancer), NCI-H460 (human lung cancer), and SK-OV-3 (human ovarian cancer) cell lines with IC₅₀ values in the range of 10.63-22.63 μmol L^-1.

Facile Synthesis of Azaarene-Substituted Hydroxycoumarins Possessing High Biological Activities via Three-Component C(sp(3))-H Functionalization

An unprecedented three-component C(sp(3))-H functionalization of 2-alkylazaarenes with aryl aldehydes and 4-hydroxycoumarins was realized, providing azaarene-substituted 3-benzyl-4-hydroxycoumarins in good to excellent yields. These new target compounds displayed broad-spectrum antibacterial activities, providing a new type of antibacterial skeleton.

Metal-Free Synthesis of Fully Substituted Pyridines via Ring Construction Based on the Domino Reactions of Enaminones and Aldehydes

An unprecedented domino reaction involving primary enaminones/enaminoesters and aldehydes has been developed for the synthesis of fully substituted pyridines. The construction of the products has been accomplished via the cascade generation of two C-C and one C-N bond by simply using TfOH as a promoter.

Synthesis and Reactivity of Triazaphenanthrenes

Pyridonaphthyridines (triazaphenanthrenes) were prepared in 4 steps and in 13-52% overall yield using Negishi cross-couplings between iodopicolines and 2-chloro-pyridylzinc derivatives. After chlorination, Gabriel amination and spontaneous ring-closure, the final aromatization leading to the triazaphenanthrenes was achieved with chloranil. This heterocyclic scaffold underwent a nucleophilic addition at position 6 leading to further functionalized pyridonaphthyridines. The influence of these chemical modifications on the optical properties was studied by steady-state and time-resolved optical spectroscopy. While the thiophene-substituted heterocycles exhibited the most extended absorption, the phenyl- and furan-substituted compounds showed a stronger photoluminescence, reaching above 20% quantum yield and lifetimes of several nanoseconds.

Synthesis of novel azole-fused quinazolines via one-pot, sequential Ullmann-type coupling and intramolecular dehydrogenative C-N bonding

An efficient one-pot sequential procedure is described for the synthesis of novel azole-fused quinazolines through Pd/Cu co-catalyzed, Ullmann-type coupling followed by cross dehydrogenative coupling of various azoles such as 1H-imidazole, 1H-benzimidazole and 1H-1,2,4-triazole with 2-(2-bromophenyl)-1H-imidazole/benzimidazoles. The developed strategy has offered good yields (52-81%) of diverse N-fused tetra-, penta- and hexa-cyclic frameworks in a single step.

Quinazolinones-Phenylquinoxaline hybrids with unsaturation/saturation linkers as novel anti-proliferative agents

A new series of novel quinazolinones with allylphenyl quinoxaline hybrids 9a-n were efficiently synthesized in good yields by the reaction of 3-allyl-2-methylquinazolin-4(3H)-one (5a-n) with bromophenyl)quinoxaline (8) utilizing Pd catalyzed Heck-cross coupling and evaluated for anti-proliferative activity against four cancer cell lines such as HeLa (cervical), MIAPACA (pancreatic), MDA-MB-231 (breast) and IMR32 (neuroblastoma). Compounds 9a, 9e, 9g and 9h exhibited promising anti-proliferative activity with GI50 values ranging from 0.06 to 0.2μM against four cell lines, while compounds 9e and 9k showed significant activity against HeLa and MIAPACA cell lines and compounds 9b, 9d, 9h and 9j showed selective potency against IMR32 and MDA-MB-231 cell lines. This is the first report on the synthesis and in vitro anti-proliferative evaluation of E-2-(4-substituted)-3-(3-(4-(quinoxalin-2-yl)phenyl)allyl)quinazolin-4(3H)-ones (9a-n). Docking results indicate a sign of good correlation between experimental activity and calculated binding affinity (dock score), suggesting that these compounds could act as promising DNA intercalates.

Facile Diversity-Oriented Synthesis of Polycyclic Pyridines and Their Cytotoxicity Effects in Human Cancer Cell Lines

A three-component cascade method has been developed for the direct synthesis of polysubstituted pyridines. This strategy provides a very convenient route to pyridines using a variety of β-bromo-α,β-unsaturated aldehydes, 1,3-diketones, and ammonium acetate without any additional catalyst or metal salt under mild conditions. A variety of β-ketoesters and 4-hydroxycoumarin were also used instead of 1,3-diketones for the diverse synthesis of polycyclic pyridines. One of the synthesized pyridines has been unambiguously established by a single crystal XRD study. All of the synthesized pyridine derivatives were evaluated for their antiproliferative properties in vitro against the human cancer cell lines HeLa, Me180, and ZR751. Compounds 4{4,1} and 4{2,4} showed significant cytotoxicity in the human breast cancer cell line ZR751 and cervical cancer cell line Me180, respectively, and a few other compounds were found to have moderate activities.

Catalytic α-Arylation of Imines Leading to N-Unprotected Indoles and Azaindoles

A palladium N-heterocyclic carbene catalyzed methodology for the synthesis of substituted, N-unprotected indoles and azaindoles is reported. The protocol permits access to various, highly substituted members of these classes of compounds. Although two possible reaction pathways (deprotonative and Heck-like) can be proposed, control experiments, supported by computational studies, point toward a deprotonative mechanism being operative.

Recent advances in research of natural and synthetic bioactive quinolines

Many natural products that consist of quinoline core are found to be bioactive and the versatility of quinoline and its derivatives have attracted great attention in the field of drug development. As a result, in recent years, many green and sustainable synthetic approaches for the synthesis of structurally diverse quinolines have been developed. This review covers four main aspects, namely bioactive quinoline alkaloids, the biological activity and mechanism of action of quinoline-based compounds as well as various quinoline syntheses.

Palladium-Catalyzed Benzylic Arylation of Pyridylmethyl Silyl Ethers: One-Pot Synthesis of Aryl(pyridyl)methanols

An efficient palladium-catalyzed direct arylation of pyridylmethyl silyl ethers with aryl bromides is described. A Pd(OAc)2/NIXANTPHOS-based catalyst provides aryl(pyridyl)methyl alcohol derivatives in good to excellent yields (33 examples, 57-100% yield). This protocol is compatible with different silyl ether protecting groups, affording either the protected or the free alcohols in an effective one-pot process. The scalability of the reaction is demonstrated.

Catalytic Enantioselective Functionalization of Unactivated Terminal Alkenes

Terminal alkenes are readily available functional groups which appear in α-olefins produced by the chemical industry, and they appear in the products of many contemporary synthetic reactions. While the organic transformations that apply to alkenes are amongst the most studied reactions in all of chemical synthesis, the number of reactions that apply to nonactivated terminal alkenes in a catalytic enantioselective fashion is small in number. This Minireview highlights the cases where stereocontrol in catalytic reactions of 1-alkenes is high enough to be useful for asymmetric synthesis.

Fast regioselective sulfonylation of pyridine/quinoline N-oxides induced by iodine

We describe the unprecedented reaction between pyridine/quinoline N-oxides and sulfonyl hydroazides, which was completed in the presence of iodine.

Design for carbon–carbon bond forming reactions under ambient conditions

The carbon–carbon (C–C) bond forms the ‘backbone’ of nearly every organic molecule, and lies at the heart of the chemical sciences! Let us explore designing of carbon–carbon frameworks at ambient conditions.

Transition-metal-free solid phase synthesis of 1,2-disubstituted 4-quinolones via the regiospecific synthesis of enaminones

The transition-metal-free economical solid phase synthesis of 1,2-disubstituted 4-quinolones has been developed via the novel regiospecific synthesis of enaminones.

Iodine-mediated synthesis of heterocycles via electrophilic cyclization of alkynes

Syntheses of heterocyclesvia5-exoor 6-endo-digiodocyclizations from alkynes.

Direct access to 2-(hetero)arylated pyridines from 6-substituted 2-bromopyridines via phosphine-free palladium-catalyzed C–H bond arylations: the importance of the C6 substituent

A Pd(OAc)₂ catalyst promotes the arylation of heteroarenes with 6-substituted 2-bromopyridines, via C–H bond activation, providing straightforward access to 2-(hetero)arylpyridines.

Sequential hydroarylation/Prins cyclization: an efficient strategy for the synthesis of angularly fused tetrahydro-2H-pyrano[3,4-c]quinolines

Various aldehydes undergo a smooth cascade cyclization with N-(5-hydroxypent-2-yn-1-yl)-4-methyl-N-phenylbenzenesulfonamide in the presence of 10 mol% Ph₃PAuCl/AgSbF₆/In(OTf)₃ to furnish the corresponding tetrahydro-2H-pyrano[3,4-c]quinoline derivatives.

Base-mediated synthesis of highly functionalized 2-aminonicotinonitriles from α-keto vinyl azides and α,α-dicyanoalkenes

A novel access to highly functionalized 2-aminonicotinonitriles via efficient annulations of α-keto vinyl azides and α,α-dicyanoalkenes is described.

One-pot synthesis of 2,4,6-triarylpyridines from β-nitrostyrenes, substituted salicylic aldehydes and ammonium acetate

The diversity-oriented synthesis of 2,4,6-trisubstituted pyridines via K₂CO₃-promoted multicomponent reactions of the β-nitrostyrenes, available substituted salicylic aldehydes and ammonium acetate have been developed.