Heteroaromatic Aldehydes Research Articles

Reductive Amination Revisited: Reduction of Aldimines with Trichlorosilane Catalyzed by Dimethylformamide─Functional Group Tolerance, Scope, and Limitations.

Aldimines, generated in situ from aliphatic, aromatic, and heteroaromatic aldehydes and aliphatic, aromatic, and heteroaromatic primary or secondary amines, can be reduced with trichlorosilane in the presence of dimethylformamide (DMF) as an organocatalyst (≤10 mol %) in toluene or CH2Cl2 at room temperature. The reduction tolerates ketone carbonyls, esters, amides, nitriles, sulfones, sulfonamides, NO2, SF5, and CF3 groups, boronic esters, azides, phosphine oxides, C═C and C≡C bonds, and ferrocenyl nucleus, but sulfoxides and N-oxides are reduced. α,β-Unsaturated aldimines undergo 1,2-reduction only, leaving the C═C bond intact. N-Monoalkylation of primary amines is attained with a 1:1 aldehyde to amine ratio, whereas excess of the aldehyde (≥2:1) allows second alkylation, giving rise to tertiary amines. Reductive N-alkylation of α-amino acids proceeds without racemization; the resulting products, containing a C≡C bond or N3 group, are suitable for click chemistry. This reaction thus offers advantages over the traditional methods (borohydride reduction or catalytic hydrogenation) in terms of efficiency and chemoselectivity. Solubility of some of the reacting partners appears to be the only limitation. The byproducts generated by the workup with aqueous NaHCO3 (i.e., NaCl and silica) are environmentally benign. As a greener alternative, DMA can be employed as a catalyst instead of DMF.

Ultrases Destekli 9-(Substitue heteroaril) akridindion Türevlerinin Tek Basamakta Sentezi

An efficient green approach for the synthesis of 9-heteroaryl-acridine-1,8-dione derivatives (3a-f) was accomplished via reactions of dimedone (1) with various heteroaromatic aldehydes (2a-f) and ammonium acetate through one-pot multicomponent reactions in water under mild conditions using ultrasound irradiation in excellent yields. Of the synthesized compounds, 3d-f were novel and this process presents the advantages of high yields and easy work-up procedures. Spectral analyses were accomplished by FTIR, 1H NMR, 13C NMR and LC-MS TOF analyses.

Exploring the Role of Aminocatalysis in the Dearomatization and Regioselectivity of Heteroaromatic Aldehydes.

Heteroaromatic aldehydes have recently received a lot of attention as a scaffold for aminocatalytic functionalization as they allow for the construction of remote stereocenters and highly complex heterocyclic compounds. In this paper, we employ computational methods (M06-2X/cc-pVTZ//M06-2X/6-31 + G(d,p) and MP2/cc-pVTZ//M06-2X/6-31 + G(d,p)) to examine the abilities of secondary amines to activate several model heteroaromatic aldehydes by promoting loss of aromaticity and formation of the reactive trienamine intermediate. The hyperhomodesmotic equations used to assess the energy penalty for dearomatization show that the formation of the iminium ion decreases the energy cost for dearomatization, especially when X = O and S. Furthermore, we also investigated the role that the catalyst and heteroatom may have on the orbital coefficients of the various positions of the trienamine intermediary in order to better understand and/or predict the regioselectivity these systems may showcase. Synergistic effects between the catalyst and the heteroatom of the aromatic ring were observed to increase electron density at the most remote positions of several of the model systems studied.

3H-Pyrazolo[4,3-f]quinoline-Based Kinase Inhibitors Inhibit the Proliferation of Acute Myeloid Leukemia Cells In Vivo

The 3H-pyrazolo[4,3-f]quinoline moiety has been recently shown to be a privileged kinase inhibitor core with potent activities against acute myeloid leukemia (AML) cell lines in vitro. Herein, various 3H-pyrazolo[4,3-f]quinoline-containing compounds were rapidly assembled via the Doebner-Povarov multicomponent reaction from the readily available 5-aminoindazole, ketones, and heteroaromatic aldehydes in good yields. The most active compounds potently inhibit the recombinant FLT3 kinase and its mutant forms with nanomolar IC50 values. Docking studies with the FLT3 kinase showed a type I binding mode, where the 3H-pyrazolo group interacts with Cys694 in the hinge region. The compounds blocked the proliferation of AML cell lines harboring oncogenic FLT3-ITD mutations with remarkable IC50 values, which were comparable to the approved FLT3 inhibitor quizartinib. The compounds also inhibited the growth of leukemia in a mouse-disseminated AML model, and hence, the novel 3H-pyrazolo[4,3-f]quinoline-containing kinase inhibitors are potential lead compounds to develop into anticancer agents, especially for kinase-driven cancers.

C2 symmetric copper (II) complexes of l-valine and l-phenyl alanine based chiral diimines for catalytic asymmetric Henry reaction

New C2 symmetric chiral diimines were synthesized from the amino acids l-valine and l-phenyl alanine. In situ copper (II) complexes of the chiral diimine ligands were found to catalyze asymmetric Henry reaction. The chiral nitro aldols were formed in excellent yield (99%) and ee (99%). The synthetic utility of the chiral catalysts were screened with various substituted prochiral aromatic and heteroaromatic aldehydes. Possible catalytic cycle for the chiral diimine copper complex catalyzed asymmetric Henry reaction has been proposed. The stereoselectivity of the asymmetric Henry reaction was discussed based on the transition state in the catalytic cycle.

4,4'-trimethylenedipiperidine as a nitrogen heterocycle solvent and/or catalyst: Liquid phase tandem Knoevenagel-Michael condensation.

Liquid phase tandem Knoevenagel–Michael condensation of various aromatic and heteroaromatic aldehydes with barbituric acid or 2-thiobarbituric acid and malononitrile was studied in a one-pot three-component reaction. For the first time, TMDP was employed as a safe and efficient solvent and/or catalyst in the liquid and aqueous ethanol medium, respectively, for the practical and eco-friendly Knoevenagel–Michael condensation. The reactions were carried out by using greener procedures, including a) the use of TMDP as an N-heterocycle organocatalyst in a green medium including water and ethanol (1:1 v/v) at reflux temperature, and b) the use of TMDP as a dual solvent-catalyst at 65 °C in the absence of any solvent. High to excellent yields of the desired pyrano[2,3- d ]pyrimidinones were obtained under the two earlier mentioned conditions. The current methodologies have advantages, including (a) avoiding hazardous, toxic, volatile, and flammable materials and solvents, (b) avoiding tedious processes, harsh conditions, and multiple steps for the preparation of catalysts, (c) using a less toxic and noncorrosive catalyst, (d) minimizing hazardous waste generation and simple workup process, and (e) high recyclability of TMDP. Another important result of this work is that the TMDP can be a promising alternative for toxic, volatile, and flammable base reagents such as piperidine and triethylamine in liquid phase organic syntheses owing to its unique properties such as being less toxic, nonflammable, and nonvolatile, and having a low melting point, broad liquid range temperature, high thermal stability, and safe handling and storage.

Vinylogous hydrazone strategy for the organocatalytic alkylation of heteroaromatic derivatives.

A new umpolung approach for the asymmetric Friedel-Crafts-type alkylation of electron-poor heteroaromatic systems has been developed. It is based on the vinylogous reactivity of hydrazones derived from heteroaromatic aldehydes. The donating effect of the hydrazone moiety can be efficiently transferred over the heteroaromatic system activating it towards an asymmetric Friedel-Crafts reaction with α,β-unsaturated aldehydes realized under aminocatalytic conditions. Excellent enantioselectivities have been obtained owing to the application of a MacMillan imidazolidinone catalyst. Unmasking of the hydrazone moiety has also been realized resulting in the development of a unique strategy for the asymmetric functionalization of electron-poor heteroaromatic systems.

Preparation of hexafluoroisopropyl esters by oxidative esterification of aldehydes using sodium persulfate.

A simple, metal-free route for the oxidative esterification of aldehydes to yield hexafluoroisopropyl esters is reported. The methodology employs sodium persulfate and a catalytic quantity of a nitroxide and is applicable to aromatic, heteroaromatic, and aliphatic aldehydes.

CeO2–nanocubes as efficient and selective catalysts for the hydroboration of carbonyl groups

An efficient and reusable CeO2 nanocatalyst has been developed for the selective hydroboration of carbonyl compounds, including aromatic, heteroaromatic, aliphatic, and (hetero)aliphatic aldehydes and ketones.

Enantioselective H-bond-directed vinylogous iminium ion strategy for the functionalization of vinyl-substituted heteroaryl aldehydes.

In this work the first H-bond-directed vinylogous iminium ion strategy has been developed as a convenient strategy for the γ,δ-functionalization of vinyl-substituted heteroaromatic aldehydes. Their reaction with α-mercaptoketones proceeds in a cascade manner involving 1,6-addition followed by intramolecular aldol reaction. Excellent stereoselectivities have been obtained as a result of the H-bond interactions controlling the outcome of the cyclization step. The application of the strategy for the synthesis of tricyclic compounds bearing furan, tetrahydrothiophene and dihydropyran moieties has also been demonstrated.

1,3,4-Thiadiazolo (3,2-Α) Pyrimidine-6-Carbonitrile Scaffold as PARP1 Inhibitors.

1,3,4-thiadiazolo pyrimidine is a lead molecule that is versatile for a wide variety of biological activities and in continuation of our interest in establishing some novel heterocyclic compounds for antitumor activity. The objective of the study was to synthesize a series of 5-amino-7-(substituted aldehyde)-2[(naphthalene- 2-yloxy)methyl] -[1,3,4]thiadiazolo-[3,2-α]-pyrimidine-6- carbonitrile derivatives and evaluate their possible in vitro and in vivo anticancer activity. Herein, we report the synthetic scheme, which was followed for the preparation of a series of title compounds B1- B9 outlined in scheme 1. The intermediate 5-[(naphthalen-2- yloxy)methyl]-1,3,4-thiadiazolo- 2-amine was prepared by heating 2-naphthoxyacetic acid and thiosemicarbazide in the presence of phosphoryl chloride at a temperature of 65-75°C. The obtained compound reacted with malononitrile and an appropriate amount of aromatic and heteroaromatic aldehydes in refluxing ethanol yielded 5-amino-7-(substituted aldehyde)-2[(naphthalene-2-yloxy)methyl] -[1,3,4]thiadiazolo-[3,2-α]-pyrimidine-6- carbonitrile derivatives (B1 - B9). The purity of the synthesized compounds was ensured by various spectral analyses. In in silico molecular docking studies, compounds B3 and B9 show binding affinity like known PARP1 inhibitor olaparib. The cellular evaluation indicates that the anticancer profile of compounds B1, B3, and B9 is significant when compared to the standard drug (olaparib) against MDA-MB-232 cell line and compounds B3, B6, and B7 are the most active against MCF-7 cell lines. The most active compound B3 was subjected to acute oral toxicity studies by OECD 423 guidelines and in vivo anti-cancer studies were carried out using DMBA induced model. The in silico docking study of the newly synthesized compounds was performed; the results showed good binding mode in the active site of PARP1 enzyme. In silico ADME properties of synthesized compounds were also studied and showed good drug-like properties.

Ruthenium(II)-catalyzed synthesis of 2-arylbenzimidazole and 2-arylbenzothiazole in water

Benzimidazoles/benzothiazoles are heterocyclic compounds which contain a five membered heteroatom and a benzene ring. They constitute a crucial structural unit of numerous bioactive compounds and natural products. Since the compounds containing benzimidazole/benzothiazole core and their derivatives possess interesting biological activity, steady efforts are being made on the development of an improved synthetic methodology for the synthesis of these biologically important class of compounds. Inspired by their biological properties, synthesis of 2-arylbenzimidazoles and 2-aryl benzothiazoles has been attempted using N^O chelate ruthenium(II)-catalyst in water. A series of 2-arylbenzimidazoles and 2-arylbenzothiazoles including a few new derivatives have been prepared by the reaction of ortho-phenylenediamine or ortho-aminothiophenol with aromatic aldehydes in the presence of 5 mol% of ruthenium(II)-catalyst under nitrogen without the use of additive in water. This reaction was extended to various heteroaromatic aldehydes obtaining up to 88% yield of the desired 2-arylbenzimidazoles/2-arylbenzothiazoles. In a few cases, a small amount of diarylated compounds was formed depending on the aldehydes used. Additionally, antibiotic properties of the synthesized compounds have been screened using the standard disc diffusion method.

Polyethylene glycol (PEG‐400) Mediated One‐pot Green Synthesis of 4,7‐Dihydro‐2H‐pyrazolo[3,4‐b]pyridines Under Catalyst‐free Conditions

AbstractPolyethylene glycol (PEG‐400) was proved a highly efficient and green solvent reaction medium for the synthesis of series of novel 3,6‐dimethyl‐4,7‐dihydro‐2H‐pyrazolo[3,4‐b]pyridine derivatives with excellent yields by a three‐component reaction of 1H‐pyrazol‐3‐amino‐5‐methyl, various aromatic or heteroaromatic aldehydes and chosen CH‐active compounds under catalyst‐free conditions via one‐pot strategy. This transformation is compatible with a broad diversity of functional group tolerance. Rapid synthesis, mild reaction conditions, high yields, no catalyst or column chromatography, cost‐effectiveness and green solvent are the benefits of this protocol.

Concentrated Solar Radiation Aided Green Approach for Preparative Scale and Solvent‐Free Synthesis of 3‐Methyl‐4‐(hetero)arylmethylene Isoxazole‐5(4H)‐ones

AbstractAn efficient, clean, and environmentally benign approach for the synthesis of 3‐methyl‐4‐arylmethylene isoxazole‐5(4H)‐ones has been developed using concentrated solar radiations (CSR). One pot, multicomponent synthesis from aromatic / heteroaromatic aldehydes, ethyl acetoacetate and hydroxylamine hydrochloride leads to title compounds in high yields. Notably the reaction has been carried out in under solvent and catalyst‐free conditions within a very short time (3 min). Further, the reaction was scaled up to 50 mmol. The present method is also energy efficient and saves almost more than 87 % of energy as compared to the conventional method.

Optimization of Catalyst Structure for Asymmetric Propargylation of Aldehydes with Allenyltrichlorosilane

AbstractThe design of catalysts for asymmetric propargylations remains a challenging task, with only a handful of methods providing access to enantioenriched homopropargylic alcohols. In this work, guided by previously reported computational predictions, a set of atropisomeric bipyridine N,N’‐dioxides was tested as Lewis base catalysts for the asymmetric propargylation of aldehydes with trichloroallenylsilane. The catalysts are easily prepared in four simple steps starting from readily available methyl ketones. Aryl‐substituted derivatives proved to be highly active and showed a high level of enantiocontrol even at 1 mol% loading. The reaction scope includes a wide range of aromatic, heteroaromatic, and unsaturated aldehydes. New computations confirm that the key stereodetermining transition state structures for the synthesized catalysts are similar to those previously reported for the model structure.magnified image

Simple Synthesis of Dimethyl Nitrobenzhydrylphosphonates and Heteroarylnitroarylacetonitriles via Vicarious Nucleophilic Substitution (VNS) Reaction

Acetals of dimethyl phenyl- and heteroaryl-α-hydroxymethanephosphonates were deprotonated to generate carbanions, which enter the vicarious nucleophilic substitution (VNS) of hydrogen in aromatic nitro compounds to form 4-nitrobenzhydrylphosphonates and α-heteroaryl-4-nitrobenzylphosphonates. Similarly acetals of cyano­hydrins of heteroaromatic aldehydes (furfural and 2-formylthiophene) react to form heteroaryl 4-nitroarylacetonitriles. The anion of the hemiacetal of acetaldehyde is an efficient leaving group in the base-induced β-elimination step – the crucial step in the VNS reaction. The reaction selectively occurred at the para-position to the nitro group.

Metal-Free Synthesis of Pyrimidinone Derivatives via Biginelli Reaction Using Aqueous NaICl2

Metal-free synthesis of pyrimidinone (alky/aryl) via Biginelli reaction in the presence of aqueous sodium dichloroiodate (NaICl2) was studied under reflux conditions. Herein, we first time report the synthesis of the aliphatic Biginelli product by using aliphatic aldehyde, cyclopentane, and urea. Several aromatic and heteroaromatic aldehydes were studied for the confirmation of the wide applicability of aq. NaICl2 for the synthesis of corresponding Biginelli products. The obtained desired products provide good to excellent yield.

Design, Synthesis, and Biological Investigation of Novel Classes of 3-Carene-Derived Potent Inhibitors of TDP1.

Two novel structural types of tyrosyl-DNA phosphodiesterase 1 (TDP1) inhibitors with hexahydroisobenzofuran 11 and 3-oxabicyclo [3.3.1]nonane 12 scaffolds were discovered. These monoterpene-derived compounds were synthesized through preliminary isomerization of (+)-3-carene to (+)-2-carene followed by reaction with heteroaromatic aldehydes. All the compounds inhibit the TDP1 enzyme at micro- and submicromolar levels, with the most potent compound having an IC50 value of 0.65 μM. TDP1 is an important DNA repair enzyme and a promising target for the development of new chemosensitizing agents. A panel of isogenic clones of the HEK293FT cell line knockout for the TDP1 gene was created using the CRISPR-Cas9 system. Cytotoxic effects of topotecan (Tpc) and non-cytotoxic compounds of the new structures were investigated separately and jointly in the TDP1 gene knockout cells. For two TDP1 inhibitors, 11h and 12k, a synergistic effect was observed with Tpc in the HEK293FT cells but was not found in TDP1 −/− cells. Thus, it is likely that the synergistic effect is caused by inhibition of TDP1. Synergy was also found for 11h in other cancer cell lines. Thus, sensitizing cancer cells using a non-cytotoxic drug can enhance the efficacy of currently used pharmaceuticals and, concomitantly, reduce toxic side effects.

Click chemistry‐inspired design, synthesis, and molecular docking studies of biscoumarin derivatives using carbon‐based acid catalyst

AbstractA green and eco‐benign synthesis of biscoumarin derivatives using carbon sulfonic acid, a solid support catalyst has been described. The reaction involved a one‐pot two‐component reaction of 4‐hydroxycoumarin and aldehyde using carbon sulfonic acid involving Knoevenegal‐Michael condensation. A series of aromatic (bearing electron withdrawing and releasing group) and heteroaromatic aldehydes has been converted to biscoumarins with excellent isolated yields. The reaction is in compliance with green principles, that is, inexpensive catalyst, easy to prepare, nontoxic, easy handling, reusable up to five recycle runs, easy separation, short reaction time, no need of time consuming column purification, high yielding, and so on. The synthesized catalyst and biscoumarin derivatives were well characterized by spectral analysis. The molecular modeling studies showed that the designed molecular scaffolds (3a‐j) showed outstanding interaction with methylenetetrahydrofolate reductase (MTHFR) and cytochrome P450 3A4 (CYP3A4) proteins. It was noticed that 3f (−17.55 kJ/mol) and 3d (−26.23 kJ/mol) showed the highest docking score against CYP3A4 and MTHFR proteins, respectively.

Synthesis of 5-(Het)arylidene-3-[2-(4-hydroxyphenyl)ethyl]-2-thioxothiazolidine-4-one Derivatives and Study of Their Antitumor and Anti-Inflammatory Activity

The reaction of aromatic and heteroaromatic aldehydes with 3-[2-(4-hydroxyphenyl)ethyl]-2-thioxothiazolidine-4-one was studied. A series of new 5-(het)arylidene-3[2-(4-hydroxyphenyl)ethyl]-2-thioxothiazolidine-4-ones was obtained. For synthesized compounds, antitumor and anti-inflammatory activity was studied. Hit-compounds were identified that exceeded the known comparison drugs in their action.