Access to Functionalized 3H-Pyrrolo[2,3-c]quinolin-4(5H)-ones and Thieno[2,3-c]quinolin-4(5H)-ones via Domino Reaction of 4-Alkynyl-3-bromoquinolin-2(1H)-ones

Sodium sulphide promoted synthesis of fused quinoline at room temperature

A novel, simple and eco-friendly strategy for the synthesis of thiopyrano[4,3-b]quinolin-1-ones and pyrrolo[3,4-b]quinolin-1-ones from 2-alkynylquinoline-3-carbonitriles and sodium sulphide (Na₂S·9H₂O) under catalyst-free conditions at room temperature has been described. In this reaction, a readily available inorganic salt (Na₂S·9H₂O) serves as the sulphur source and leads to the generation of diverse functionalized thiopyrano[4,3-b]quinolin-1-ones and pyrrolo[3,4-b]quinolin-1-ones in moderate to excellent yields through sulfuration, annulation, and aerial oxidation.

Recent strategies in the synthesis of thiophene derivatives: highlights from the 2012-2020 literature

Thiophene-based analogs have been fascinated by a growing number of scientists as a potential class of biologically active compounds. Furthermore, they play a vital role for medicinal chemists to improve advanced compounds with a variety of biological effects. The current review envisioned to highlight some recent and particularly remarkable examples of the synthesis of thiophene derivatives by heterocyclization of various substrates from 2012 on.

Synthesis of Bicyclo[4.1.0]tetrahydropyridazines by a Sequential [4 + 2] and [1 + 2] Annulation Reaction of Azoalkenes and Crotonate-Derived Sulfur Ylides

The base-induced unprecedented tandem [4 + 2] and [1 + 2] annulation reaction of in situ formed 1,2-diaza-1,3-dienes and crotonate-derived sulfur ylides is reported. This protocol provides a novel and practical method for the synthesis of cyclopropane-fused tetrahydropyridazines with a quaternary carbon center in synthetically useful yield. In this tandem reaction, three new bonds were formed in one pot, and the crotonate-derived sulfur ylide serves as a C3 synthon.

Palladium-Catalysed Synthesis and Transformation of Quinolones

Palladium-catalysed reactions have had a large impact on synthetic organic chemistry and have found many applications in target-oriented synthesis. Their widespread use in organic synthesis is due to the mild conditions associated with the reactions together with their tolerance of a wide range of functional groups. Moreover, these types of reactions allow the rapid construction of complex molecules through multiple bond-forming reactions in a single step, the so-called tandem processes. Pd-catalysed reactions have been applied to the synthesis of a large number of natural products and bioactive compounds, some of them of complex molecular structures. This review article aims to present an overview of the most important Pd-catalysed reactions employed in the synthesis and transformations of quinolin-2(1H)-ones and quinolin-4(1H)-ones. These compounds are widely recognized by their diverse bioactivity, being privileged structures in medicinal chemistry and useful structural moieties for the development of new drug candidates. Furthermore, they hold significant interest due to their host⁻guest chemistry; applications in chemical, biochemical and environmental analyses and use in the development of new synthetic methods. In some cases, the quinolone formation step cannot be ascribed to a claimed Pd-catalysed reaction but this reaction is crucial to get the appropriate substrate for cyclization into the quinolone. Herein we present and discuss different economical, efficient and selective synthetic strategies to access quinolone-type compounds.

AlCl3-Catalyzed Intramolecular Cyclization of N-Arylpropynamides with N-Sulfanylsuccinimides: Divergent Synthesis of 3-Sulfenyl Quinolin-2-ones and Azaspiro[4,5]trienones

Switchable ortho/ipso-cyclization of N-arylpropynamides induced with N-sulfanylsuccinimides as general sulfur reagents is reported. In the presence of MeOH, para-fluoro N-arylpropynamides exclusively undergo the ipso-cyclization to give 3-sulfenyl azaspiro[4,5]trienones. Two kinds of bioactive heterocycles, benzothieno-[3,2-b]quinoline and -[2,3-c]quinolone, have been directly and efficiently prepared from the corresponding sulfenylated products.

Access to functionalized thienopyridines via a reagent-capsule-assisted coupling, thiolation and cyclization cascade sequence

Thienopyridines and related heterocycles were prepared by a reagent-capsule-assisted palladium-catalyzed cross-coupling, thiolation and cyclization process in moderate to good yields.

A direct and vicinal functionalization of the 1-methyl-2-quinolone framework: 4-alkoxylation and 3-chlorination

Bis(functionalization), 4-alkoxylation and 3-chlorination, of the 1-methyl-2-quinolone framework was achieved under mild conditions by a sequential treatment of 3-nitrated 1-methyl-2-quinolones with sodium alkoxide and N-chlorosuccinimide. Moreover, a succinimide group instead of an alkoxy group was introduced at the 4-position, affording a masked form of the 4-amino-3-chloro-2-quinolone derivative. Furthermore, the prepared vicinally functionalized quinolones thus obtained were subjected to a Suzuki-Miyaura coupling reaction, arylating the 3-position.

Synthesis of N-aryl 2-quinolinones via intramolecular C(sp2)–H amidation of Knoevenagel products

An efficient synthesis of N-aryl 2-quinolinones via K₂S₂O₈-mediated intramolecular C(sp²)–H amidation of Knoevenagel products was developed.

Efficient Pd-catalyzed domino synthesis of 1-phenyl-1H-indol-2-amine and 5-amino-indolo[1,2-a]quinazoline derivatives

An efficient and practical one-pot domino synthesis of 1-phenyl-1H-indol-2-amine and 5-amino-indolo[1,2-a]quinazoline derivatives from readily available 2-(2-bromophenyl)acetonitriles was developed. The overall protocol involves a Buchwald-Hartwig type coupling and a base-promoted intramolecular nucleophilic reaction. The reaction scope, advantages and limitations are discussed.