Heteroaromatic Amines Research Articles

Rh2(esp)2‐Catalyzed Coupling of α‐Diazo‐γ‐butyrolactams with Aromatic Amines

Decomposition of α‐diazo‐γ‐butyrolactams in the presence of aromatic and heteroaromatic amines, under Rh2(esp)2 catalysis, led to corresponding α‐arylamino‐γ‐butyrolactams, which are of significant value for medicinal chemistry. The reaction scope encompasses primary as well as secondary, diversely substituted anilines and heteroaromatic amines. Insertion into the anilinic amino group was shown to be selective over amide and sulfonamide N–H insertion.

Aza-BODIPY synthesis towards vis/NIR functional chromophores based on a Schiff base forming reaction protocol using lactams and heteroaromatic amines.

aza-BODIPY is a class of heteroatom-containing BODIPY analogues targeting near infrared (NIR) chromophores and fluorophores. As a synthetic strategy towards aza-BODIPY structures, we have, recently, developed a Schiff base forming reaction using readily available lactams and heteroaromatic amines. Absorption and fluorescence of a series of compounds cover the whole range of the ultraviolet (UV)/visible (vis)/NIR regions. In addition, some compounds exhibit solid state emission, aggregation-induced emission enhancement, tunable fluorescence in the vis/NIR regions and non-linear optical properties. Furthermore, simple dimerization of aza-BODIPY chromophores caused unusual panchromatic absorption, whereas in combination with an N-confused porphyrin skeleton, multi-state NH tautomerism was achieved. In this Feature Article, wide applicability of this Schiff base forming reaction and optical and electrochemical properties of aza-BODIPY analogues thus synthesized are summarized including recent applications, such as bioimaging, photothermal cancer therapy and organic photovoltaics.

Regio- and Enantioselective Iridium-Catalyzed Amination of Racemic Branched Alkyl-Substituted Allylic Acetates with Primary and Secondary Aromatic and Heteroaromatic Amines.

The air- and water-stable π-allyliridium C,O-benzoate modified by ( S)-tol-BINAP, ( S)-Ir-II, catalyzes highly regio- and enantioselective Tsuji-Trost-type aminations of racemic branched alkyl-substituted allylic acetates using primary or secondary (hetero)aromatic amines. Specifically, in the presence of ( S)-Ir-II (5 mol%) in DME solvent at 60-70 °C, α-methyl allyl acetate 1a (100 mol%) reacts with primary (hetero)aromatic amines 2a-2l (200 mol%) or secondary (hetero)aromatic amines 3a-3l (200 mol%) to form the branched products of allylic amination 4a-4l and 5a-5l, respectively, as single regioisomers in good to excellent yield with uniformly high levels of enantioselectivity. As illustrated by the conversion of heteroaromatic amine 3m to adducts 6a-6g, excellent levels of regio- and enantioselectivity are retained across diverse branched allylic acetates bearing normal alkyl or secondary alkyl substituents. For reactants 3n-3p, which incorporate both primary and secondary aryl amine moieties, regio- and enantioselective amination occurs with complete site-selectivity to furnish adducts 7a-7c. Mechanistic studies involving amination of the enantiomerically enriched, deuterium-labeled acetate 1h corroborate C-N bond formation via outer-sphere addition.

Design, Synthesis, Anticancer Properties and In Silico Evaluation of C(4) N‐Heteroaryl 4H‐Chromenes

AbstractThe C(4) N‐heteroaryl 2‐amino‐3‐nitro‐4H‐chromenes are podophyllotoxin (POD) mimics as they possess the pharmacophore features of the anticancer natural product. We have achieved a facile synthesis of several such 4H‐chromenes by substitution of C(4) SMe in N‐alkyl 4‐(methylthio)‐3‐nitro‐4H‐chromen‐2‐amines with heteroaromatic amines like 2‐aminopyridines and 2‐aminopyrimidines. Resulting 4H‐chromenes were evaluated for anticancer activity against prostate and lung cancer cell lines. Two of the 4H‐chromenes showed significant anti‐cancer activity, even better than POD. Both of them were non‐toxic towards normal cell‐lines. In silico ADMET studies revealed drug‐likeliness of all the 4H‐chromenes. Molecular docking studies with αβ tubulin concurred with in vivo results and revealed that the 4H‐chromenes bind to the active site of POD. Molecular dynamics simulation studies on the complexes of αβ tubulin with the two best 4H‐chromenes revealed high stability. Overall, our studies revealed that the two 4H‐chromenes could act as lead compounds for further development of potent anticancer drugs.

Aerobic Oxidation of Primary Amines to Imines in Water using a Cobalt Complex as Recyclable Catalyst under Mild Conditions.

Oxidative coupling of primary amines to imines has been achieved by using a water soluble cobalt complex as catalyst and air as the oxidant at near ambient conditions. Aromatic, heteroaromatic and aliphatic amines were successfully converted to the corresponding imines with yields of up to 96 %. A 20 gram scale reaction for the synthesis of imine from benzylamine in good yield is also demonstrated with this method. The catalyst has been found to be reusable with up to five cycles. It is highly efficient, gives a turnover number (TON) of up to 128, and shows chemoselectivity with the only byproducts being water and ammonia. Control experiments and mechanistic studies indicate that the CoII /CoIII catalytic cycle is responsible for these oxidative transformations. Some of the reactive intermediates of this reaction have also been isolated and structurally characterized.

Intramolecular π-stacks in mixed-ligand copper(II) complexes formed by heteroaromatic amines and antivirally active acyclic nucleotide analogs carrying a hydroxy-2-(phosphonomethoxy)propyl residue‡

Acyclic nucleoside phosphonates (ANPs) are of medical relevance and deserve detailed chemical characterization. We focus here on 1-[2-(phosphonomethoxy)ethyl]cytosine (PMEC), (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC), 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA), and (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine (HPMPA) and include for comparison the nucleobase-free (phosphonomethoxy)ethane (PME) and (R)-hydroxy-2-(phosphonomethoxy)propane (HPMP). The acidity constants of H3(ANP)+ and H2(NP) (NP2– = nucleoside phosph(on)ate derivative) are needed to understand the properties of the ternary neutral Cu(Arm)(ANP/NP) [Arm = 2,2′-bipyridine (Bpy) or 1,10-phenanthroline (Phen)] and the monoprotonated Cu(Arm)(H;ANP)+ complexes. The Cu(Arm)(ANP) species are considerably more stable than the corresponding Cu(Arm)(R-PO3), where R- represents a phosph(on)ate ligand with a non-coordinating group R. The observed stability enhancements are due to intramolecular stack formation (st) between the aromatic rings of Arm and the nucleobase residues and also to the formation of five-membered chelates involving the ether oxygen of the –CH(R)–O–CH2– residue (cl/O) (R = H or CH2–OH). In intramolecular equilibria, three structurally different Cu(Arm)(ANP) isomers occur; for example, of Cu(Phen)(HPMPA) about 5% exist as an open (op) Cu(Phen)(HPMPA)op isomer, 17% as Cu(Phen)(HPMPA)cl/O, and 78% as Cu(Phen)(HPMPA)st. In Cu(Arm)(ANP) the stacking tendency decreases in the order PMEA2– > HPMPA2– > PMEC2– > HPMPC2–. In monoprotonated Cu(Arm)(H;ANP)+ both H+ and Cu(Arm)2+ are at undergoing similar intramolecular equilibria as indicated above.

"On Water'' Promoted Ullmann-Type C-N Bond-Forming Reactions: Application to Carbazole Alkaloids by Selective N-Arylation of Aminophenols.

The Ullmann-type cross coupling of a variety of aromatic, aliphatic amines with aryl halides is reported using a CuI-based catalytic system in combination with an easily accessible prolinamide ligand in aqueous media. The method is mild and tolerant to air, moisture, and a wide range of functional groups, providing a novel way to access a variety of aminated products. Secondary amines like heteroaromatic amines and nucleobases have also been used, affording the corresponding coupling products in good to excellent yields. Moreover, this method has been employed for chemoselective C-N arylation of aminophenols and further utilized for the synthesis of carbazole natural products, avoiding the protection and deprotection steps.

A waste-minimized protocol for copper-catalyzed Ullmann-type reaction in a biomass derived furfuryl alcohol/water azeotrope

We report the use of biomass-derived furfuryl alcohol as an effective bidentate ligand able to promote the Ullmann-type copper-catalyzed coupling of aryl halides with heteroaromatic or aliphatic amines.

Novel Phenolic 1-aryl-3-arylamino-1-propanones: Synthesis and Characterization

Abstract A small collection of 1-aryl-3-arylamino-1-propanones having a phenolic moiety in their structure has been obtained by the replacement of the tertiary amino group in ketonic Mannich bases with (hetero)aromatic amines. The installment of the phenolic moiety took place either through the N-alkylation of 4-aminophenol with ketonic Mannich base hydrochlorides, or via amine exchange in ketonic Mannich bases derived from either 2′-hydroxyacetophenone or 4′-hydroxyacetophenone.

Oxidative Amidation of Methylarenes and Heteroamines under Metal‐Free Conditions

AbstractSynthesis of heteroamides through oxidative amidation of methylarenes with hetero aromatic amines using tert‐Butyl hydroperoxide (TBHP) as oxidant has been described. The present method represents a significant development for the oxidative amidation of methylarenes to obtain heteroamides which does not require metal catalyst and TBHP act as only oxidant. Methylarenes are easy to handle, stable, commercially available (by‐products in gasoline industry) and used as carbonyl source for amide synthesis. The reaction proceeds through the imine intermediate formation and its subsequent oxidation by TBHP provides the desired amides.

Zinc Acetate-Promoted Buchwald-Hartwig Couplings of Heteroaromatic Amines.

Zinc salts have been shown to promote the Buchwald-Hartwig coupling of azaindoles and azaindazoles with heteroaryl chlorides to provide the corresponding 1-aryl-1H-azaindoles and 1-aryl-1H-azaindazoles. The substrate scope and mechanistic aspects of this reaction were explored.

Erratum to: S-(3-Aminobenzanthron-2-yl)cysteine in the globin of rats as a novel type of adduct and possible biomarker of exposure to 3-nitrobenzanthrone, a potent environmental carcinogen.

3-Nitrobenzanthrone (3-NBA), a potent environmental mutagen and carcinogen, is known to be activated in vivo to 3-benzanthronylnitrenium ion which forms both NH and C2-bound adducts with DNA and also reacts with glutathione giving rise to urinary 3-aminobenzanthron-2-ylmercapturic acid. In this study, acid hydrolysate of globin from rats dosed intraperitoneally with 3-NBA was analysed by HPLC/MS to identify a novel type of cysteine adduct, 3-aminobenzanthron-2-ylcysteine (3-ABA-Cys), confirmed using a synthesised standard. The 3-ABA-Cys levels in globin peaked after single 3-NBA doses of 1 and 2 mg/kg on day 2 to attain 0.25 and 0.49 nmol/g globin, respectively, thereafter declining slowly to 70–80% of their maximum values during 15 days. After dosing rats for three consecutive days with 1 mg 3-NBA/kg a significant cumulation of 3-ABA-Cys in globin was observed. 3-ABA-Cys was also found in the plasma hydrolysate. Herein, after dosing with 1 and 2 mg 3-NBA/kg the adduct levels peaked on day 1 at 0.15 and 0.51 nmol/ml plasma, respectively, thereafter declining rapidly to undetectable levels on day 15. In addition, sulphinamide adducts were also found in the exposed rats, measured indirectly as 3-aminobenzanthrone (3-ABA) split off from globin by mild acid hydrolysis. Levels of both types of adducts in the globin samples parallelled very well with 3-ABA/3-ABA-Cys ratio being around 1:8. In conclusion, 3-ABA-Cys is the first example of arylnitrenium-cysteine adduct in globin representing a new promising class of biomarkers to assess cumulative exposures to aromatic amines, nitroaromatics and heteroaromatic amines.

Conducting Molecularly Imprinted Polymer (MIP) Chemical Sensors for Toxic N-Nitrosamines Selective Determination in Heat Processed Food of Animal Origin

High-temperature processing of meat food generates in it toxic heteroaromatic amines and nitrosamines (NAs)1,2 causing chronic diseases including hormonal dysfunctions and cancer.3 Therefore, we devised and fabricated chemical sensors for selective determination of the N-nitroso-L-proline (Pro-NO)4 and N-nitroso-thiazolidine-4-carboxylic acid (NT4A) toxins in this food. We applied films of conducting polymers molecularly imprinted (MIPs) with either the Pro-NO or NT4A template as recognition units of these chemosensors. For selection of most appropriate functional monomers, we used DFT at the B3LYP/3-21G(*) level modeling to find phenolic derivative of bis(bithiophene) and a thiosalenCo(III) complex (CS)5,6 suitable to form pre-polymerization complexes with Pro-NO and NT4A, respectively, at the 1:2 template/monomer stoichiometry. The calculated Gibbs free energy gain due to formation of these complexes with a series of NAs was proportional to the UV-vis spectroscopy determined stability constants of these complexes. These constants were relatively high equalling 3.14×109 M-2 and 2.72×1010 M-2for Pro-NO and NT4A, respectively. Then, we electrochemically polymerized these complexes under potentiodynamic conditions. This electropolymerization resulted in depositing thin MIP films on different electrode substrates. After subsequent extraction of the Pro-NO and NT4A templates from MIPs, we used the resulting MIPs with empty imprinted cavities for determination of Pro-NO and NT4A analytes in grilled pork neck samples. We confirmed the presence and then absence of NA templates in the MIP films before and after extraction, respectively, with FTIR spectroscopy and XPS, and then characterized morphology of the films with AFM. For analytical signal transduction, we used piezoelectric microgravimetry (PM) at the Au-QCR/MIP electrodes of EQCM as well as DPV and EIS at the Pt/MIP electrodes. Limits of detection of the chemosensors were 36.9 nM Pro-NO (with EIS) and 46 nM NT4A (with DPV). The chemosensors selectively responded to the target toxins in the presence of interfering compounds of similar composition and structure. Successful selective determination of Pro-NO and NT4A in the food extract samples indicates that the chemosensors are promising as tools for determination of these toxins in food of animal origin.

S-(3-Aminobenzanthron-2-yl)cysteine in the globin of rats as a novel type of adduct and possible biomarker of exposure to 3-nitrobenzanthrone, a potent environmental carcinogen.

3-Nitrobenzanthrone (3-NBA), a potent environmental mutagen and carcinogen, is known to be activated in vivo to 3-benzanthronylnitrenium ion which forms both NH and C2-bound adducts with DNA and also reacts with glutathione giving rise to urinary 3-aminobenzanthron-2-ylmercapturic acid. In this study, acid hydrolysate of globin from rats dosed intraperitoneally with 3-NBA was analysed by HPLC/MS to identify a novel type of cysteine adduct, 3-aminobenzanthron-2-ylcysteine (3-ABA-Cys), confirmed using a synthesised standard. The 3-ABA-Cys levels in globin peaked after single 3-NBA doses of 1 and 2mg/kg on day 2 to attain 0.25 and 0.49nmol/g globin, respectively, thereafter declining slowly to 70-80% of their maximum values during 15days. After dosing rats for three consecutive days with 1mg 3-NBA/kg a significant cumulation of 3-ABA-Cys in globin was observed. 3-ABA-Cys was also found in the plasma hydrolysate. Herein, after dosing with 1 and 2mg 3-NBA/kg the adduct levels peaked on day 1 at 0.15 and 0.51nmol/ml plasma, respectively, thereafter declining rapidly to undetectable levels on day 15. In addition, sulphinamide adducts were also found in the exposed rats, measured indirectly as 3-aminobenzanthrone (3-ABA) split off from globin by mild acid hydrolysis. Levels of both types of adducts in the globin samples parallelled very well with 3-ABA/3-ABA-Cys ratio being around 1:8. In conclusion, 3-ABA-Cys is the first example of arylnitrenium-cysteine adduct in globin representing a new promising class of biomarkers to assess cumulative exposures to aromatic amines, nitroaromatics and heteroaromatic amines.

Visible-light-promoted selective C-H amination of heteroarenes with heteroaromatic amines under metal-free conditions.

The regioselective C-H amination of quinoline amides (C5) and imidazopyridines (C3) under transition-metal-free conditions at room temperature with a high degree of functional group tolerance is reported. The C-H amination promoted by visible light in the presence of a photocatalyst with a wide range of heteroamines makes the present protocol more sustainable.

An efficient method for regioselective ring opening of epoxides by amines under microwave irradiation using Bi(NO3)3·5H2O as a catalyst

Bi(NO3)3·5H2O a highly efficient environmentally benign catalyst, is used for the nucleophilic ring opening of epoxides with aromatic, aliphatic and heteroaromatic amines under solvent free microwave conditions to afford the corresponding β-amino alcohols in good to excellent yields with high regioselectivity.

ВИКОРИСТАННЯ 3-АРИЛІЗОКУМАРИНІВ У СИНТЕЗІ 3-АРИЛІЗОХІНОЛОНІВ

The review systematizes and analyzes the literature data (100 sources) regarding the recyclization of 3-arylisocoumarins (3-aryl-1H-isochromen-1-ones) under the action of primary N-nucleophiles that leads to the formation of 3-arylisoquinolones (3-arylisoquinolin-1(2H)-ones). This reaction may be carried out with a wide range of primary aminogroup-containing compounds: ammonia, primary aliphatic, aromatic, and heteroaromatic amines, hydrazine, and hydroxylamine. This transformation is not hindered by the presence of active functional groups (hydroxyl, acetal, carboxyl, ester, nitrile groups, or additional aminogroup) neither in 3-arylcoumarin nor in the primary amine. A special attention has been paid to reaction conditions (temperature regime, duration, solvent, catalysts), which may vary greatly. In particular, it is pointed out that in most cases to carry out high-temperature recyclization of 3-arylisocoumarins with ammonia and volatile amines with low molecular weight the use of closed reactors and high-pressure flasks was required. The cases of successful recyclization of 11,12-dihydrodibenzo[c,h]chromen-6-ones, indeno[1,2-c]isochromen-5(11H)-ones, isochromeno[4,3-c]chromen-6,11-dione and 5H-benzofuro[3,2-c]isochromen-5-one are reviewed separately. The polycondensated heterocyclic system of these compounds contains a 3-arylisocoumarin fragment. The biological activity data is presented for the compounds obtained via this transformation – 3-arylisoquinolin-1(2H)-ones, and also polycondensated systems that contain this fragment, e.g. 11,12-dihydrobenzo[c]phenanthridin-6(5H)-ones and 6H-indeno[1,2-c]isoquinoline-5,11-diones. The opportunities to use 3-arylisoquinolin-1(2H)-ones in the synthesis of other compounds of isoquinoline family, e.g. natural benzo[c]phenanthridinealocoloids, are demonstrated.

Nickel-catalyzed N-vinylation of heteroaromatic amines via C–H bond activation

Here, we report a ligand- and reductant-free nickel-catalyzed N-vinylation of heteroaromatic amines using biorenewable p-cymene as a solvent. This unprecedented cross-coupling strategy has high functional group tolerance (halides, alkoxy, cyano, chiral motif, etc.) and proceeded via C-H bond activation.

A matrix-focused structure-activity and binding site flexibility study of quinolinol inhibitors of botulinum neurotoxin serotype A

Our initial discovery of 8-hydroxyquinoline inhibitors of BoNT/A and separation/testing of enantiomers of one of the more active leads indicated considerable flexibility in the binding site. We designed a limited study to investigate this flexibility and probe structure-activity relationships; utilizing the Betti reaction, a 36 compound matrix of quinolinol BoNT/A LC inhibitors was developed using three 8-hydroxyquinolines, three heteroaromatic amines, and four substituted benzaldehydes. This study has revealed some of the most effective quinolinol-based BoNT/A inhibitors to date, with 7 compounds displaying IC50 values ⩽1μM and 11 effective at ⩽2μM in an ex vivo assay.

Mutagenicity of heteroaromatic amines: Computational study on the influence of methyl substituents

Quantum mechanical calculations were performed to elucidate the factors determining the variations in mutagenic activity within groups of isomeric heteroaromatic amines that differ in the position of methyl substituents. Formation energies for noncovalent complexes and covalent DNA adducts were evaluated by means of high level quantum chemical methods. According to the computational results in this work, covalent adduct stability is proposed to influence the relative mutagenicities of structurally related heterocyclic amines. The stability of covalent C8-dG DNA adducts was found to be mainly determined by π-stacking interactions between the fused ring system of the heteroaromatic amines and the flanking nucleobases. Relative mutagenicity of amines of very related structure is proposed to be regulated by both nitrenium ion and covalent adduct stabilities.