2-aminobenzyl Alcohol Research Articles

Cu-catalyzed Synthesis of Quinolines by Dehydrogenative Reaction of 2-Aminobenzyl Alcohol and Ketones: A Combined Experimental and Computational Study.

Quinoline derivatives are important moieties in bioactive molecules and advanced materials. However, an efficient strategy to synthesize quinoline derivatives remains challenging. Herein, we describe an efficient and practical method for the synthesis of quinolines by Cu-catalyzed cyclization of 2-amino benzyl alcohol with ketones (or secondary alcohols) via an acceptorless dehydrogenation pathway. Interestingly, a range of highly functionalized quinolines is prepared in good yields using low catalyst loading under relatively mild conditions. Furthermore, density functional theory (DFT) calculations are carried out to investigate mechanistic insights for the acceptorless dehydrogenation pathway.

Dehydrogenative Synthesis of Quinolines and Quinazolines via Ligand-Free Cobalt-Catalyzed Cyclization of 2-Aminoaryl Alcohols with Ketones or Nitriles

We present a convenient and efficient protocol to synthesize quinolines and quinazolines in one pot under mild conditions. A variety of substituted quinolines were synthesized in good to excellent yields (up to 97% yield) from the dehydrogenative cyclizations of 2-aminoaryl alcohols and ketones catalyzed by readily available Co(OAc)2·4H2O. This cobalt catalytic system also showed high activity in the reactions of 2-aminobenzyl alcohols with nitriles, affording various quinazoline derivatives (up to 95% yield). The present protocol offers an environmentally benign approach for the synthesis of N-heterocycles by employing an earth-abundant cobalt salt under ligand-free conditions.

Transition-metal-free reaction sequence on solid base: One-pot synthesis of quinoline derivatives catalyzed by Mg-Al hydrotalcite

Quinoline derivatives are important intermediates in the production of pharmaceutical products. Recently, a modified Friedländer quinoline synthesis using stable 2-aminobenzyl alcohols and ketones over transition metal catalysts and inorganic bases have been investigated. In this study, we found that only simple Mg-Al hydrotalcite (HT) was active toward the modified Friedländer quinoline synthesis. Various HT samples were prepared by the co-precipitation method under several pH and Mg-Al ratio conditions. Mg-Al HT prepared at pH 11 exhibited the highest activity among the HT samples and other solid base catalysts. Kinetic and spectroscopic analyses revealed that quinoline formation occurs via base-catalyzed hydrogen transfer between 2-aminobenzyl alcohol and a ketone, followed by the cyclization of the corresponding aldehyde intermediate with a ketone. Mg-Al HT showed wide applicability toward the one-pot synthesis quinoline using various alcohols and ketones and afforded the corresponding products in high yield.

Iridium-Catalyzed Acceptorless Dehydrogenative Coupling of 2-Aminoarylmethanols with Amides or Nitriles to Synthesize Quinazolines

AbstractAn efficient iridium-catalyzed acceptorless dehydrogenative coupling (ADC) reaction for the preparation of various quinazolines from 2-aminoarylmethanols and amides or nitriles had been developed. A wide range of substituted 2-aminobenzyl alcohols and (hetero)aryl or alkyl benzamides and nitriles were well compatible to afford various quinazolines in excellent yields. Merits of this new strategy are the high atom-economy, mild reaction conditions, and simple operation, and the methodology is suitable for a variety of substrates.

Unexpected Annulation between 2-Aminobenzyl Alcohols and Benzaldehydes in the Presence of DMSO: Regioselective Synthesis of Substituted Quinolines.

An unexpected annulation among 2-aminobenzyl alcohols, benzaldehydes, and DMSO to quinolines has been disclosed. For the reported annulation between 2-aminobenzyl alcohols and benzaldehydes, the change of the solvent from toluene to DMSO led to the change of the product from the diheteroatomic cyclic benzoxazines to monoheteroatomic cyclic quinolines. This annulation can be used to synthesize regioselectively different substituted quinolines by the choice of different 2-amino alcohols, aldehydes, and sulfoxides as substrates. Interestingly, introducing substituent groups to the α-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines. On the basis of the control experiments and literatures, a plausible mechanism for this annulation was proposed.

Iridium-Catalyzed Transfer Hydrogenation for Construction of Quinolines from 2-Aminobenzyl Alcohols with Enones in Water

AbstractHerein, we describe a method for the synthesis of functionalized quinolines from 2-aminobenzyl alcohols with α,β-unsaturated ketones. This method exhibits tolerance to various functional groups and high efficiency, is environmentally benign, and can be performed on a gram scale. Control experiments suggest that this transformation is accomplished by iridium complex catalyzed transfer hydrogenation, which is then followed by Friedländer cyclization. The results display that alkali is essential for the high selectivities of this catalytic system.

Visible-Light-Mediated Oxidative Cyclization of 2-Aminobenzyl Alcohols and Secondary Alcohols Enabled by an Organic Photocatalyst

This paper describes a visible-light-mediated oxidative cyclization of 2-aminobenzyl alcohols and secondary alcohols to produce quinolines at room temperature. This photocatalytic method employed anthraquinone as an organic small-molecule catalyst and DMSO as an oxidant. According to this present procedure, a series of quinolines were prepared in satisfactory yields.

Mild and efficient copper-catalyzed oxidative cyclization of oximes with 2-aminobenzyl alcohols at room temperature: synthesis of polysubstituted quinolines.

A simple and efficient ligand-free Cu-catalyzed protocol for the synthesis of polysubstituted quinolines via oxidative cyclization of oxime acetates with 2-aminobenzyl alcohols at room temperature has been developed. The presented approach provides a new synthetic pathway leading to polysubstituted quinolines with good functional group tolerance under mild conditions. Moreover, this transformation can be applied for the preparation of quinolines on a gram scale. Oxime acetates serve as the internal oxidants in the reactions, thus making this method very attractive.

The preparation of a Co@C3N4 catalyst and applications in the synthesis of quinolines from 2-aminobenzyl alcohols with ketones

A Co@C3N4 composite was synthesized through Co-doping of C3N4 and revealed high catalytic activity for the synthesis of quinolines.

Synthesis of Tetrahydroquinolines via Borrowing Hydrogen Methodology Using a Manganese PN3 Pincer Catalyst.

A straightforward and selective synthesis of 1,2,3,4-tetrahydroquinolines starting from 2-aminobenzyl alcohols and simple secondary alcohols is reported. This one-pot cascade reaction is based on the borrowing hydrogen methodology promoted by a manganese(I) PN3 pincer complex. The reaction selectively leads to 1,2,3,4-tetrahydroquinolines thanks to a targeted choice of base. This strategy provides an atom-efficient pathway with water as the only byproduct. In addition, no further reducing agents are required.

Microwave-assisted One-pot Synthesis of 2-Substituted Quinolines by Using Palladium Nanoparticles as a Catalyst developed from Green Alga Botryococcus braunii

Background:Quinoline is a type of N-based organic heterocyclic biologically active compound. Quinolines have grasped the interest of scientists because of their wide scope of applications. Several methods have been developed for the synthesis of quinoline and its derivatives. In this study, a new, efficient, simple, one-pot synthesis of the substituted quinolines was developed by using palladium nanoparticles as a catalyst.Methods:Catalyst synthesized by algal extract of green alga Botryococcus braunii and palladium acetate solution, and characterized by different instrumental techniques like FTIR, SEM, and XRD. The synthesized palladium nanoparticles explored for the catalytic activity in the synthesis of quinoline derivatives by the use of 2-aminobenzyl alcohol in toluene with acetyl derivatives followed by the addition of potassium hydroxide. The formation of the product was confirmed by 1HNMR, 13C NMR, and electron ionization mass spectra.Results:The formation of palladium nanoparticles characterized by visual observation means the color change from light pale yellow to dark brown indicates the reduction of palladium ions into palladium nanoparticles. Synthesized palladium nanoparticles characterized by FTIR spectrum of the algal extract of green algae B. braunii for the presence of proteins, lipids, carbohydrates, carotenoids, vitamins and other secondary metabolites in algal extract, which function as active components for bioreduction. The morphology of the catalyst was confirmed by SEM and X-ray diffraction measurements for shape, crystalline nature and size. The synthesized palladium nanoparticles explored for the catalytic activity in the synthesis of quinoline derivatives by use of 2-aminobenzyl alcohol in toluene and added acetyl derivatives followed by the addition of potassium hydroxide. In order to establish the optimum heating method, a comparative study between conventional and microwave heating method was carried out in the presence of palladium nanoparticles as a catalyst.Conclusion:This protocol provides a convenient and practical procedure for the preparation of quinoline derivatives from 2-aminobenzyl alcohol, acetyl derivatives, potassium hydroxide and palladium nanoparticles as a catalyst. This protocol will be helpful in synthesizing other quinoline derivatives and several organic heterocycles which are used in different fields such as biological, industrial, pharmaceutical, chemical, medical, etc.

Manganese(I)-Catalyzed Sustainable Synthesis of Quinoxaline and Quinazoline Derivatives with the Liberation of Dihydrogen.

Direct synthesis of N-heterocycles via the acceptorless dehydrogenative coupling is very challenging and scarcely reported under 3d transition-metal catalysis. Here, we have developed an efficient Mn(I)-catalyzed sustainable synthesis of various quinoxalines from 1,2-diaminobenzenes and 1,2-diols via the acceptorless dehydrogenative coupling reaction. Further, this strategy was successfully applied for the unprecedented synthesis of quinazolines by the reaction of 2-aminobenzyl alcohol with primary amides. The present protocol provides an atom-economical and sustainable route for the synthesis of various quinoxaline and quinazoline derivatives by employing an earth-abundant manganese salt and simple phosphine-free NNN-tridentate ligand.

N-Heterocyclic Carbene Catalysis Exploiting Oxidative Imine Umpolung for the Generation of Imidoyl Azoliums

Although NHC-catalyzed umpolung of imines are known, the related reactions under oxidative conditions are limited. Described herein is the two-step process involving the initial formation of aldimines from the corresponding aldehydes and 2-amino benzyl alcohols followed by NHC-catalyzed cyclization proceeding via the imidoyl azoliums under oxidative conditions. The reaction allowed the synthesis of trifluoromethylated 3,1-benzoxazines in good yields and broad scope. The role of NHC in the intramolecular cyclization and preliminary mechanistic experiments are also provided.

Synthesis of New Derivatives of 4-Methyl-3-nitro-6H-pyrimido[2,1-b]quinazoline

–Various derivatives of 2-chloro-4-methyl-5-nitropyrimidine were synthesized by the reaction of 2,4-dichloro-6-methyl-5-nitro pyrimidine with amines. The synthesized derivatives were reacted with 2-aminobenzyl alcohol in m-xylene to obtain derivatives of a novel 4-methyl-3-nitro-6H-pyrimido[2,1-b]quinazoline heterocyclic system. The composition and structure of the products was confirmed by CHN analysis, IR, 1H NMR, and 13C NMR spectroscopy, and mass spectrometry.

Ruthenium(II) Complexes of Heteroditopic N-Heterocyclic Carbene Ligands: Efficient Catalysts for C-N Bond Formation via a Hydrogen-Borrowing Strategy under Solvent-Free Conditions.

Both imidazol-2-ylidene (ImNHC) and 1,2,3-triazol-5-ylidene (tzNHC) have evolved to be elite groups of N-heterocyclic carbene (NHC) ligands for homogeneous catalysis. To develop efficient ruthenium(II)-based catalysts incorporating these ligands for C-N bond-forming reactions via hydrogen-borrowing methodology, we utilized chelating ligands integrated with ImNHC and mesoionic tzNHC donors connected via a CH2 spacer with a diverse triazole backbone. The synthesized ruthenium(II) complexes 3 are found to be highly efficient for C-N bond formation across a wide range of primary amine and alcohol substrates under solvent-free conditions, and among all of the complexes studied here, catalyst 3a with a mesityl substituent displayed maximum activity. To our delight, catalyst 3a is also effective for the selective mono-N-methylation of various anilines utilizing methanol as a coupling partner, known to be relatively more difficult than other alcohols. Furthermore, complex 3a also delivers various substituted quinolines successfully via the reaction of 2-aminobenzyl alcohol with several secondary alcohols. Importantly, catalyst 3a exhibited the highest activity among the reported ruthenium(II) complexes for both the N-benzylation of aniline [achieving a turnover number (TON) of 50000] and the realization of quinoline 8a by reacting 2-aminobenzyl alcohol with 2-phenylethanol (attaining a TON of 30000).

Aza-crown compounds synthesised by the self-condensation of 2-amino-benzyl alcohol over a pincer ruthenium catalyst and applied in the transfer hydrogenation of ketones.

A well-defined PNN-Ru catalyst was revisited to self-condense 2-aminobenzyl alcohol in forming a series of novel aza-crown compounds [aza-12-crown-3 (1), aza-16-crown-4 (2) and aza-20-crown-5 (3)]. All aza-crown compounds are separated and determined by NMR, IR, and ESI-MS spectroscopy as well as X-ray crystallography, indicating the saddle structure of 1 and the twisted 1,3-alternate conformation structure of 3. These aza-crown compounds have been explored to study ferric initiation of transfer hydrogenation (TH) of ketones into their corresponding secondary alcohols in the presence of 2-propanol with a basic t-BuOK solution, achieving a high conversion (up to 95%) by a ferric complex with 2 in a low loading (0.05 mol%).

Employing TosMIC as a C1N1 “Two-Atom Synthon” in Imidazole Synthesis by Neighboring Group Assistance Strategy

We report an I2/FeCl3-co-promoted formal [2 + 2+1] annulation of aryl methyl ketones, 2-aminobenzyl alcohols, and p-toluenesulfonylmethyl isocyanide (TosMIC) by neighboring group (-CH2OH) assistance. This is a novel example of using the Van Leusen reagent as a unique C1N1 "two-atom synthon" in the synthesis of imidazoles. Preliminary mechanism studies showed that TsCH2NH2 might be the key intermediate in this reaction. Furthermore, this reaction not only unlocks a novel strategy for imidazole synthesis, but also exploits a new reactivity of TosMIC.

Recyclable thermoset hyperbranched polymers containing reversible hexahydro-s-triazine

Thermoset materials containing about 70 wt% epoxy resin are widely used in critical aerospace and wind power structures, generating enormous amounts of waste (such as offcuts and damaged, worn and disposed parts) that affect both the environment and the sustainable development of human society. Owing to their irreversible crosslinked networks, thermoset materials pose major challenges for rapid degradation and high-efficiency recycling. Here we report the synthesis of thermoset hyperbranched polymers (HER-HTn) containing a reversible heterocyclic structure (hexahydro-s-triazine) that can be degraded under relatively mild conditions. The cured HER-HTn exhibit excellent mechanical and thermal properties, as well as rapid degradability in more environmentally friendly phosphoric acid solutions. Controlled degradation experiments show that the cured HER-HTn can be completely digested at relatively low temperatures (90 °C) in a short period (2 h) to recover 2-aminobenzyl alcohol at a high recycling efficiency (85.1%). The recovered 2-aminobenzyl alcohol can then be used to produce the initial hexahydro-s-triazine monomer, which demonstrates the reversibility of the hexahydro-s-triazine structure and recoverability of the thermoset hyperbranched polymers. This investigation provides a method for the synthesis of a degradable thermoset matrix and the cyclic use of high-value materials in the thermoset and its composites. The degradation and recycling of thermoset materials are major sustainability challenges. The synthesized thermoset hyperbranched polymers (HER-HTn) reported in this study exhibit recoverability and rapid degradability in more environmentally friendly phosphoric acid solutions.

Ligand-controlled phosphine-free Co(II)-catalysed cross-coupling of secondary and primary alcohols

Cobalt(II) complexes (5 mol% Co) bearing phosphine-free N˄N˄N pincer ligands efficiently catalyze C–C coupling of secondary and primary alcohols to selectively form α-alkylated ketones with a good functional group compatibility using NaOH (20 mol%) as a base at 120 °C. The NH group on the N˄N˄N–Co(II) precatalyst controls the activity and selectivity. This simple catalytic system is involved in the synthesis of quinolones via the dehydrogenative annulation of 2-aminobenzyl alcohols with secondary alcohols.

I2-Promoted Multicomponent Dicyclization and Ring-Opening Sequences: Direct Synthesis of Benzo[e][1,4]diazepin-3-ones via Dual C-O Bond Cleavage.

A novel and efficient formal [4 + 2+1] annulation of aryl methyl ketones and 2-aminobenzyl alcohols for the synthesis of benzo[e][1,4]diazepin-3-ones is reported. This reaction successfully affords diverse seven-membered ring lactams via dual C-O bond cleavage. A preliminary mechanistic study showed that a multicomponent dicyclization and ring-opening sequence might occur, with the introduction of methyl sulfide proposed as the last step. This efficient strategy with mild reaction conditions and a broad substrate scope has potential applications in chemistry and medicine.