A mild and efficient one-step synthesis of quinolines

[reaction: see text] The Friedl?nder synthesis of quinolines is an extensively employed protocol, yielding the desired heterocycle in a two-step reduction-condensation sequence. We have developed a mild, efficient, high-yielding single-step variant of this methodology, which employs SnCl(2) and ZnCl(2) to effect the reaction.     

A mild and efficient one-step synthesis of quinolines

2-Aminoaryl ketones undergo condensation with α-methylene ketones in the presence of a catalytic amount of Y(OTf)₃ at room temperature under mild conditions to afford the corresponding polysubstituted quinolines in excellent yields.     

A versatile new synthesis of quinolines and related fused pyridines: Part 10. Routes to quinolines with fused azacycles

Three efficient routes to the title systems have been elaborated utilising 2-chloroquinoline-3-aldehyde acetals, 2-chloroquinoline-3-ketones or 2-aminoquinoline-3-aldehydes.     

A versatile new synthesis of quinolines and related fused pyridines. Part III.

The action of dimethylformamide in phosphorus oxychloride on acylanilides gives 2-chloro-3-substituted quinolines, which may be dechlorinated to give 3-substituted quinolines in good yield. Similarly, N-nitrosodimethylamine in phosphorus oxychloride converts acylanilides into 2-chloro-3-substituted quinoxazolines.     

A versatile new synthesis of quinolines and related fused pyridines. Part II.

The conversion of acetanilides to 2-chloroquinoline-3-aldehydes by Vilsmeier reagent proceeds efficiently in POCl₃ solution at 75°. The intermediate, in which the acetyl group has been diformylated, may in some cases be isolated and separately cyclised.     

Rh(I)-catalyzed direct arylation of pyridines and quinolines

A Rh(I)-catalyzed direct arylation of pyridine and quinoline heterocycles has been developed. The method provides rapid entry into an important class of substituted heterocycles employing inexpensive and readily available starting materials.     

A general access to 1,1-cyclopropane aminoketones and their conversion into 2-benzoyl quinolines

1,1-Cyclopropane aminoketones were efficiently synthesized in high yields by the tandem reaction of α-amino aryl ketones with vinyl sulfonium salts using DBU as the base in CH(2)Cl(2). This methodology was utilized to synthesize 2-benzoyl quinolines.     

An efficient synthesis of quinolines under solvent-free conditions

An efficient synthesis of substituted quinolines has been achieved in a one-pot reaction from o-nitrobenzaldehyde and enolizable ketones using SnCl₂·2H₂O as the reductant under microwave irradiation without any solvent or catalyst     

Synthesis of quinolines via Rh(III)-catalyzed oxidative annulation of pyridines

Selective synthesis of quinolines has been achieved via oxidative annulation of functionalized pyridines with two alkyne molecules under Rh(III)-catalyzed cascade C-H activation of pyridines using Cu(OAc)(2) as an oxidant. The selectivity of this reaction is oxidant-dependent, particularly on the anion of the oxidant.     

A convenient microwave-assisted 5-amination of flavones

A few examples of 5-aminoflavones' syntheses exist in the literature and for those, which are described, the amino group is introduced before the formation of the flavone skeleton. We describe here an efficient method, which permits the access to 5-aminoflavones by a simple procedure using an SNAr amination under microwaves irradiation.     

An efficient synthesis of novel 2,4-disubstituted tetrahydroquinolines and quinolines

A series of novel tetrahydroquinolines have been synthesized via the acid-catalyzed reaction of an azaflavan-4-ol with a variety of reactive nucleophiles. The tetrahydroquinolines were found to undergo oxidation in the presence of iodine as catalyst to generate the corresponding novel 2,4-disubstituted quinolines.     

A general and efficient method for the copper-catalyzed cross-coupling of amides and thiophenols with 6-halogenoimidazo[1,2-a]pyridines

Convenient and efficient methods for the preparation of novel 6-amido and 6-phenylsulfanylimidazo[1,2-a]pyridine derivatives that utilize copper-catalyzed methodologies are reported. These methods are particularly noteworthy because of their experimental simplicity and the low cost of the catalyst system.     

Partial hydrogenation of substituted pyridines and quinolines: a crucial role of the reaction conditions

Hydrogenation of pyridyl and quinolyl compounds 2-substituted with a carbonyl group (1a-c and 2b,c) using PtO₂ and 1 equiv. of HCl (conditions A) provides clean and total formation of the desired amino alcohol (hydrogenation of the heterocyclic ring and of the carbonyl) while under conditions B₁ and/or B₂ (concentrated HCl or pure CF₃CO₂H) the heterocyclic ring remains untouched and other aromatic parts are hydrogenated providing complex mixtures. When the heterocyclic ring is substituted by an alkyl group (quinaldine 3) conditions A provide mixtures while under conditions B₂ (pure CF₃CO₂H) the benzene ring is cleanly hydrogenated leading to a pure product.     

Solid-phase oxoalkylation of pyridines and quinolines with 1-methylcycloalkanols under the action of lead tetraacetate

A new procedure was developed for the introduction of the oxoalkyl fragment into N-heteroaromatic compounds of the pyridine and quinoline series. The procedure is based on the solid-phase reactions of lead tetraacetate with aromatic N-heterocycles and tertiary cycloalkanols.     

The electron transfer reactions of cyano substituted pyridines and quinolines with thermally generated diphenyl ketyl

Electron transfer reactions of cyano substituted pyridines and quinolines with thermally generated diphenyl ketyl are reported. When E¹/₂(-) for the heterocycle is less negative than -2V, electron transfer occurs from the ketyl to the heterocyclic base. In some cases the products obtained from the thermal reaction are the same as those obtained from the photochemical reaction with benzophenone and alcohols. In other cases different products are formed. Two bases, 2-pyridinecarbonitrile and 2,4-pyridinedicarbonitrile, undergo regiospecific reactions in which the course of the reaction is determined by the acidity of the medium. A mechanism in which the heterocyclic nitrogen is involved in the substitution process at the 2 position is proposed.