Assembly of 4H-chromenes, imidazobenzothiazines and quinazolines via copper-catalyzed domino reactions using 2-halobenzyl tosylates as substrates

Formation of 2H- and 4H-chromene Rings in Intramolecular Rauhut-Currier Reaction, Catalyzed by Lithium Selenolates

In this paper, we present the first example of using a catalytic amount of a nucleophilic seleno-organic catalyst in a tandem seleno-Michael/Michael reaction, leading to the formation of 2H/4H-chromenes. Chromenes represent a highly significant group of oxygen-containing heterocycles commonly found as structural scaffolds in a diverse range of fields such as medicinal chemistry, pharmaceutical agents, drug candidates, synthetic chemistry, and materials chemistry. Various preparation methods have been developed, utilizing different substrates in conjunction with metal catalysts, organocatalysts, Brønsted acids, bases, or Lewis acids. The synthetic utility of lithium selenolates has been demonstrated as efficient nucleophilic catalysts in the Rauhut-Currier cyclization of chalcone derivatives. This methodology allows for the synthesis of 2H- and 4H-chromenes depending on the substituents directly connected to the carbonyl group. The investigation focuses on the impact of various substituents in the aromatic fragment as well as conditions and selenolates. The scope of different starting materials was also considered.

Efficient approach to 1,1'-bisindoles via copper(I)-catalyzed double domino reaction

A highly efficient copper(I)-catalyzed approach for the synthesis of 1,1'-bisindoles that is based on the formation of four bonds in one step has been developed. The unprecedented three component reaction between one molecule of a 1,2-bis(2-bromoaryl)hydrazine and two molecules of a 1,3-diketone employing 10 mol% CuI as a catalyst and Cs2CO3 as a base in DMSO at 100 °C for 24 h delivers substituted 1,1'-bisindoles with yields up to 92%. The new method proceeds as a double domino condensation/Ullmann type C-C coupling. It allows an efficient and practical access to substituted 1,1'-bisindoles in one step from easily available starting materials.

Flexible Approach for the Synthesis of Annulated 4H-Pyrans Based on a Cu(I)-Catalyzed C-Allylation/O-Vinylation Reaction of Cyclic 1-Bromoallyl Tosylates with Cyclic and Acyclic 1,3-Dicarbonyls

The Cu(I)-catalyzed reaction between five-, six-, seven-, and eight-membered cyclic 1-bromoallyl tosylates and five- and six-membered cyclic 1,3-dicarbonyls in DMF at 80 °C using Cs₂CO₃ as a base and 2-picolinic acid as an additive selectively delivers a wide array of bisannulated 4H-pyrans in a single step with yields up to 92%. The transformations are considered to proceed as intermolecular C-allylations/intramolecular O-vinylations. With six-membered cyclic 1-bromoallyl tosylates and acyclic β-ketoesters as substrates, the corresponding 5,6,7,8-tetrahydro-4H-chromene-3-carboxylates are obtained with yields up to 59%.

Direct Formation of 2-Substituted 2H-Indazoles by a Pd-Catalyzed Reaction between 2-Halobenzyl Halides and Arylhydrazines

A direct and operationally simple method for the regioselective synthesis of 2-aryl-substituted 2H-indazoles is reported. The Pd-catalyzed reaction between easily available 2-bromobenzyl bromides and arylhydrazines employing Cs₂CO₃ as the base and t-Bu₃PHBF₄ as the ligand in DMSO at 120 °C in a sealed tube delivers the 2-substituted-2H-indazoles in a single synthetic step with yields up to 79%. The new method is based on a regioselective intermolecular N-benzylation followed by intramolecular N-arylation and oxidation.

Mn(iii)-mediated cascade cyclization of 1-(azidomethyl)-2-isocyanoarenes with organoboronic acids: construction of quinazoline derivatives

A novel and efficient Mn(iii)-mediated oxidative radical cascade reaction of 1-(azidomethyl)-2-isocyanoarenes with organoboronic acids is reported.

Iodine/potassium iodide catalyst for the synthesis of trifluoromethylated quinazolines via intramolecular cyclization of 2,2,2-trifluoro-N-benzyl-N'-arylacetimidamides

An efficient and simple protocol for the synthesis of trifluoromethylated quinazolines has been described by I₂-/KI-promoted oxidative C(sp³)-C(sp²) bond under the optimal oxidative cyclization reaction conditions. The required 2,2,2-trifluoro-N-benzyl-N'-arylacetimidamides are readily prepared from the corresponding acetimidoyl chlorides and benzylamines under a nucleophilic substitution reaction in the form of in situ. The merits of this protocol are the use of inexpensive molecular iodine, metal-free oxidative coupling and good to excellent yields.

A divergent and metal free synthesis of sulfoximine tethered imidazoles, imidazopyridines, imidazothiazoles, imidazobenzothiazines, thiazoles and selenazoles

A divergent and metal free approach has been successfully developed for the synthesis of sulfoximine tethered heterocycles from a α-bromoalkanone building block.

Meglumine catalyzed one-pot, three-component combinatorial synthesis of pyrazoles bearing a coumarin unit

Meglumine has been found to be an efficient catalyst for the synthesis of pyrazolylcoumarins by one-pot three-component reaction of salicylaldehyde, 4-hydroxy-6-methyl-2H-pyran-2-one, and hydrazine.

One-pot synthesis of 2,3-substituted benzo[b]thiophenes via Cu(i) catalysed intramolecular cyclisation from dithioesters

The novel route involves CuI catalyzed C–S bond formation using dithioesters. This approach is valuable for synthesis of rolaxifene analogues.

A novel ruthenium-catalyzed dehydrogenative synthesis of 2-arylquinazolines from 2-aminoaryl methanols and benzonitriles

By employing a commercially available Ru3(CO)12/Xantphos/t-BuOK catalyst system, a novel and straightforward ruthenium-catalyzed dehydrogenative synthesis of 2-arylquinazolines has been demonstrated. A series of 2-aminoaryl methanols were efficiently converted in combination with different types of benzonitriles into various desired products in moderate to good yields upon isolation. The synthetic protocol proceeds with the advantages of operational simplicity, high atom efficiency, broad substrate scope, and no need for the use of less environmentally benign halogenated reagents, offering an important basis for accessing 2-arylquinazolines.