Three-component Povarov Reaction Research Articles

Photocatalytic Synthesis of Quinoline-Linked Covalent Organic Frameworks via Three-Component Povarov Reaction

Photocatalytic Synthesis of Quinoline-Linked Covalent Organic Frameworks via Three-Component Povarov Reaction

Phenolic Dienes as Highly Selective Dienophiles in the Asymmetric Organocatalyzed Three-Component Vinylogous Povarov Reaction.

Our study presents a novel enantioselective route for the synthesis of 1,2,3,4-tetrahydroquinolines via a chiral phosphoric acid-catalyzed three-component Povarov reaction, employing phenolic dienes as dienophiles. This approach produces a diverse array of 2,3,4-trisubstituted tetrahydroquinolines, each featuring a styryl group at position 4, in high yields with excellent regio-, diastereo-, and enantioselectivities (>95:5 dr and up to >99% ee).

Catalytic Enantioselective Synthesis of Inherently Chiral Calix[4]arenes via Sequential Povarov Reaction and Aromatizations.

Inherently chiral calix[4]arenes represent a unique type of chiral molecules with significant applications, yet their catalytic enantioselective synthesis remains largely underexplored. We report herein the catalytic enantioselective synthesis of inherently chiral calix[4]arenes through the sequential organocatalyzed enantioselective Povarov reaction and aromatizations. The chiral phosphoric acid catalyzed three-component Povarov reaction involving amino group-substituted calix[4]arenes, aldehydes and (di)enamides desymmetrized the prochiral calix[4]arene substrates, which was followed by various aromatization methods, resulting in a diverse array of novel quinoline-containing calix[4]arenes with good yields and high enantioselectivities (up to 75 % yield, 99 % ee). The large-scale enantioselective synthesis and diverse derivatizations of the chiral calix[4]arene products highlight the value of this method. Furthermore, preliminary exploration into their photophysical and chiroptical properties demonstrate the potential applications of these novel calix[4]arene molecules.

Hydroxyl-functionalized ionic liquid-modified covalent organic frameworks for efficient CO2 cycloaddition conversion

Converting CO2 into high-value chemicals is an essential way to mitigate greenhouse impact and realize sustainable utilization of resources. In this work, the COF materials named X-QCOF (X = OH, OCH3) were synthesized by a three-component Povarov reaction, followed by chemical grafting of hydroxyl‑functionalized ionic liquid into the COFs neutral backbone via quaternization to obtain the hybrid materials IL-X-QCOF (X = OH, OCH3). The resultant IL-X-QCOF can efficiently catalyze the cycloaddition reaction of CO2 and epoxides in the absence of metals, additives and solvents. Among them, IL-OH-QCOF exhibits a yield of 97.2% of cyclochloroallyl carbonate with a high turnover frequency (TOF) value of 217.7. The inherent high specific surface area of the COF-based materials promotes mass transfer efficiency, and meanwhile the abundant hydroxyl groups and bromine anions occurring in the backbone create excellent catalytic effect. Attributed to the chemical grafting approach, the product yield keeps over 90% when IL-OH-QCOF is reused for 6 cycles.

Chalcogen-Bond Catalysis: Telluronium-Catalyzed [4+2]-Cyclocondensation of (in situ Generated) Aryl Imines with Alkenes.

In the chalcogen series, tellurium species exhibit the strongest chalcogen bonding (ChB) interaction with electron-rich atom. This property explains the renewed interested toward tellurium-based derivatives and their use in different applications, such as organocatalysis. In this context, the catalytic activity of telluronium salts in the Povarov reaction is presented herein. Different dienophiles, as well as imines of variable electronic nature, efficiently react in the presence of catalytic amount of either diarylmethyltelluronium or triaryltelluronium salts. Both catalysts could also readily perform the three-component Povarov reaction starting from aldehyde, aniline and dihydrofuran. The reactivity of telluroniums towards imines and aldehydes was confirmed in the solid state by the ability of Te atom to interact through ChB with the oxygen carbonyl of acetone, and in solution with significant shift variations of the imine proton and of the tellurium atom in 1 H and 125 Te NMR spectroscopy. For the most active telluronium catalysts bearing CF3 groups, association constants (K) with N-phenyl phenylmethanimine in the range 22-38 M-1 were measured in dichloromethane.

Enantioselective synthesis of pyrroloquinolines via a three-component Povarov reaction with aminoindoles

This protocol provides concise access to enantioenriched pyrroloquinolines, and presents an alternative methodology for functionalizing the carbocyclic ring of indoles.

Highly Enantioselective Three-Component Povarov Reaction for Direct Construction of Azaspirocycles.

An asymmetric organocatalyzed three-component Povarov reaction to construct azaspirocycles has been developed. A chiral phosphoric acid OCF-CPA bearing o-CF3-aryl on the H8-BINOL-framework is highly efficient in the reaction. The reaction was carried out under mind conditions for synthesis of a range of azaspirocycles in high yields and high to excellent enantioselectivities, thus expending the substrate scope of the traditional Povarov reaction.

Study and application of graphene oxide in the synthesis of 2,3-disubstituted quinolines via a Povarov multicomponent reaction and subsequent oxidation.

The carbocatalyzed synthesis of 2,3-disubstituted quinolines is disclosed. This process involved a three-component Povarov reaction of anilines, aldehydes and electron-enriched enol ethers, which gave the substrate for the subsequent oxidation. Graphene oxide (GO) was exploited as a heterogeneous, metal-free and sustainable catalyst for both transformations. The multicomponent reaction proceeded under simple and mild reaction conditions, exhibited good functional group tolerance, and could be easily scaled up to the gram level. A selection of tetrahydroquinolines obtained was subsequently aromatized to quinolines. The multistep synthesis could also be performed as a one-pot procedure. Investigation of the real active sites of GO was carried out by performing control experiments and a by full characterization of the carbon material by X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (ssNMR).

Enantioselective synthesis and selective functionalization of 4-aminotetrahydroquinolines as novel GLP-1 secretagogues.

Polysubstituted tetrahydroquinolines were obtained in moderate to high yields (28% to 92%) and enantiomeric ratios (er 89:11 to 99:1) by a three-component Povarov reaction using a chiral phosphoric acid catalyst. Significantly, post-Povarov functional group interconversions allowed a rapid access to a library of 36 enantioenriched 4-aminotetrahydroquinoline derivatives featuring five points of diversity. Selected analogs were assayed for their ability to function as glucagon-like peptide-1 (GLP-1) secretagogues.

Synthesis and Characterization of 4-Amino-Tetrahydroquinoline Derivatives via Organocatalyst

4-Aminotetrahidrokinolin türevleri; organo Brønsted asit katalizörü eşliğinde anilin, N-vinilkarbamat ve substitüe halojen içeren aldehitin bir balona konulmasıyla tek kademede sentezlendi. 3 bileşenli Povarov reaksiyonu yöntemi kullanıldı. 4 farklı 4-Aminotetrahidrokinolin türevi sentezlendi ve 1H, 13C, Infrared Spektroskopisi (IR), Erime noktası (EN) ve Yüksek Çözünürlüklü Kütle Spektroskopisi (HRMS) gibi çeşitli metotlar kullanılarak yapı karakterizasyonları yapıldı.

Organocatalytic Asymmetric Three-Component Povarov Reactions of Anilines and Aldehydes.

We report the first highly enantio- and diastereoselective three-component Povarov reaction between anilines and aldehydes catalyzed by a chiral amine catalyst. A wide variety of substituted tetrahydroquinolines were obtained with moderate to good yields and excellent enantioselectivity and diastereoselectivity (up to 99% ee and >95:5 dr) under the reaction conditions. Furthermore, the reaction intermediates could be efficiently converted to other valuable building blocks.

Tetrahydroquinolines by the multicomponent Povarov reaction in water: calix[n]arene-catalysed cascade process and mechanistic insights.

The catalyst p-sulfonic acid calix[4]arene was effectively used in the three-component Povarov reaction between aromatic anilines and two equivalents of 2,3-dihydrofuran to obtain furano[3,2-c]-1,2,3,4-tetrahydroquinolines. These reactions proceeded efficiently using water as a green solvent and nontoxic catalysts that could be efficiently reused; the reactions were metal-free and used only inexpensive and easily available compounds. Together with a simple workup procedure, these advantages make this protocol a very efficient and green alternative to the traditional methods for constructing tetrahydroquinoline structures, through the formation of two new C-C bonds and one C-N bond. Isotopic labelling experiments revealed the mechanism for the Povarov reactions, showing that the reaction proceeds through a sequence of steps via ionic intermediates, and the proposed reaction mechanism was validated.

Calix[n]arene-Catalyzed Three-Component Povarov Reaction: Microwave-Assisted Synthesis of Julolidines and Mechanistic Insights.

A new one-pot cascade reaction-based application of Povarov reactions with a p-sulfonic acid calix[4]arene catalyst for the synthesis of a series of 34 julolidine derivatives with substituents at C8 or C9 in good to excellent yields is reported. These microwave-assisted reactions proceeded efficiently, had short reaction times, were metal-free, were low cost, and used an inexpensive, easily available and nontoxic catalyst. These advantages, along with a simple workup procedure, make this protocol a very efficient and green alternative to the traditional methods for constructing these types of N-heterocyclic skeletons. In addition, this protocol allows the formation of julolidine structures, which requires the construction of four new C-C bonds and two C-N bonds. A mechanism for the Povarov reaction involving a stepwise sequence via ionic intermediates was proposed and validated.

Synthetic Strategy toward the Pentacyclic Core of Melodinus Alkaloids.

The three-component Povarov reaction is efficiently utilized for construction of the pentacyclic framework of complex Melodinus alkaloids, which is amenable to expansion to other complex natural products. The key steps were Povarov reaction, one-pot reductive cyclization, and ring-closing metathesis (RCM) reaction.

Zn(OTf)2-mediated C[sbnd]H activation: An expeditious and solvent-free synthesis of aryl/alkyl substituted quinolines

Zinc(II) triflate catalyzed three-component coupling reactions of alkynes, amines and aldehydes leading to the formation of aryl/alkyl substituted quinolines has been described. Notably, the reaction proceeded efficiently and effectively without the use of ligand, co-catalyst, solvent or inert atmosphere. This robust solvent-free process operates under an ambient atmosphere and avoids the use of precious metals, hazardous solvents and harsh reaction conditions. This atom economic process eliminates the waste generated in the multistep synthesis. Additionally, a pseudo three-component Povarov reaction of amines and butanal proceeds under the same green conditions enabling the formation of 2,3-dialkyl quinolines.

A diastereoselective synthesis of tetrahydro- and dihydro-pyrido[2,3-c]coumarin derivatives via a one-pot three-component Povarov reaction catalyzed by bismuth(III) chloride

A diastereoselective synthesis of tetrahydro- and dihydro-pyrido[2,3-c]coumarin derivatives has been achieved via a one-pot three-component aza-Diels–Alder reaction of aromatic aldehydes, 3-aminocoumarin and dienophiles catalyzed by BiCl3. NOE studies proved that exo-isomers were obtained in all cases with high selectivity. The reaction proceeded at room temperature providing good yields of products as well as applicability on a wide range of substrates. Among all the synthesized derivatives, compounds 4i and 4k showed promising DPPH radical scavenging activity as compared to other tested derivatives.

Tritylium Cation as Low Loading Lewis Acidic Organocatalyst in Povarov Reactions

Triphenylmethylium cation catalyzed Povarov reactions with excellent yields in 1 h with a remarkably low loading (0.5 mol %) are disclosed. A Lewis acidic carbenium catalysis mechanism was proposed and validated. A three-component Povarov reaction in a batch was transferred into a two-stage microflow process, which resulted in a 60-fold reduction in reaction time from 2 h to 2 min with 89% separated yield.

A facile one-pot synthesis of 2-(2-pyridyl)quinolines via Povarov reaction

An efficient synthesis of 2-(2-pyridyl)quinolines was achieved via a three-component Povarov reaction of aromatic aldehydes, anilines, and ethyl vinyl ether under boron trifluoride methyl etherate (BF3·O(CH3)2) acid catalysis. The developed methodology for the preparation of 2-(2-pyridyl)quinolines offers several advantages over previous methods including mild reaction conditions, easy work-up, a wide range of substrate applicability, and products in good yields.

Chiral Phosphoric Acid-Catalyzed Enantioselective Three- Component Aza-Diels-Alder Reactions of Aminopyrroles and Aminopyrazoles

The back cover picture, provided by Géraldine Masson, illustrates the straightforward three-component process catalyzed by chiral phosphoric acid. The authors reveal the first use of aminopyrroles and aminopyrazoles as partners in the asymmetric three-component Povarov reaction providing an access to novel chiral heterocyclic structures in excellent diastereoselectivities as well as good yields and enantioselectivities, as reported in the communication on pages 1719–1724 (J. Brioche, T. Courant, L. Alcaraz, M. Stocks, M. Furber, J. Zhu, G. Masson, Adv. Synth. Catal. 2014, 356, 1719–1724; DOI: 10.1002/adsc.201400093).

Three-component aza-Diels–Alder reactions using Yb(OTf)3 catalyst under conventional/ultrasonic techniques

The Yb(OTf)3 catalyzed formal aza-Diels–Alder (or Povarov) reaction of cyclopentadiene and 1,3-cyclohexadiene with in situ-generated N-arylimines under conventional/ultrasonic techniques is herein described. This kind of three-component Povarov reaction results in quinoline and phenanthridine derivatives, which are important biological compounds.