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A series of 3-substituted-2-hydroxy-1,4-naphthoquinone derivatives with a variety of side chains were successfully synthesized by Mannich reaction of 2-hydroxy-1,4-naphthoquinone (lawsone) with selected amines and aldehydes. All substances (1-16) were evaluated for in-vitro antimalarial activity against strains of Plasmodium falciparum by microculture radioisotope technique. Bioassay data revealed that ten derivatives (1-8, 11 and 13) displayed significantly good activity with values of IC50 ranging from 0.77 to 4.05 µg/mL. The best biological profile (IC50 = 0.77 µg/mL) was observed in compound 1, possessing a n-butyl substituted aminomethyl group. Experimental results support the potential use of our active Mannich components as promising antimalarial agents in the fight against malaria infections and multidrug resistance problems.

This study evaluated the use of a new redox catalyst (2-hydroxy-1,4-naphthoquinone, HNQ) in order to contribute to the preservation of the carbohydrate fraction and to increase delignification of s...

Oxalic acid and proline based deep eutectic solvent (DES) has been identified as an effective catalyst and environmentally benign reaction medium for one-pot synthesis of 13-aryl-13H-benzo[g]benzothiazolo[2,3-b]quinazoline-5,14-diones via three-component reaction of aromatic aldehydes, 2-aminobenzothiazole and 2-hydroxy-1,4-naphthoquinone under microwave irradiation. The reported approach shows significant advantages such as easy work-up, environment-friendly process, short reaction times, excellent yields, one-pot multicomponent reaction, chromatography-free purification, the recycling and the re-use of the DES.

2-hydroxy-1,4-naphthoquinone molekulu ile Mn(II) kompleksi ((2HNQ) 2 Mn) ilk kez hazirlandi. Hazirlanan bu kompleksin elemental analizleri yapildi, infrared ve Raman spektrumlari 4000-30 cm -1 araliginda kaydedildi ve yapisi hakkinda tahminde bulunuldu. Yine Deneysel olarak gozlenen titresim bantlari ve siddetleri, teorik olarak, HF metoduyla 6-31G(dp) temel fonksiyonu kullanilarak hesaplandi. Deneysel ve teorik olarak elde edilen degerler bire-bir karsilastirildi.

A green and efficient method for oxazine ring formation is established using the reaction of 2-hydroxy-1,4-naphthoquinone and aromatic aldehydes with methyl carbamate catalysed by p-toluenesulfonic acid in aqueous media to afford 4-aryl-3,4-dihydronaphtho[3,4- e][1,3] oxazine-2,5,10-triones in excellent yields. The salient features of this protocol are short reaction times and high yields while avoiding any hazardous organic solvent. Therefore, this procedure could be classified as green chemistry.

The Mannich reaction of lawsone with various aldehydes and 4 H-1,2,4-triazol-4-amine gave unexpected 3,3′-(arylmethylene)bis(2-hydroxynaphthalene-1,4-dione) derivatives. With 2,4-dihydroxybenzaldehyde under the same conditions, it led to the formation of 3-hydroxy-12-(3-hydroxy-1,4-dioxo-1,4-dihydronaphthalen-2-yl)-6 H-benzo[ b]xanthene-6,11(12 H)-dione instead of various triazolylaminonaphthoquinones.

Structurally diverse benzo[g]chromenes were conveniently synthesized by one-pot, multi-component reaction of N-alkyl-1-(methylthio)-2-nitroethenamine (derived from the reaction of nitroketene dithioacetal with various amines), aromatic aldehydes and 2-hydroxy-1,4-naphthoquinone in CH3CN at room temperature within 10–25 min, without any catalyst. The notable advantages of the protocol are mild reaction conditions, absence of catalyst, very short reaction time, simple purification process involving no chromatographic process, compatibility with various functional groups and excellent product yields.

α-Azidochalcones were coupled with 1/2-naphthols or 2-hydroxy-1,4-naphthoquinone using Ru(bpy)3(PF6)2 as a photocatalyst under blue LED light irradiation to yield 2,3-fused pyrroles in high yields ...

The enantioselective formal [3 + 3] annulation reaction of isatin-derived β,γ-unsaturated α-ketoesters with 3-hydroxy-4H-chromen-4-ones or 2-hydroxy-1,4-naphthoquinone was successfully implemented under catalysis of quinine-derived bifunctional tertiary amine-thiourea catalysts. The efficient tandem Michael-cyclization has provided facile access to optically active spiro[oxindole-pyrano[3,2-b]chromenone] and spiro[oxindole-benzo[g]chromene-dione] derivatives in high yields with excellent diastereo- and enantioselectivities.

Monofluorinated 3-alkyl-2-hydroxy-1,4-naphthoquinone 4 was prepared in eight steps from commercially available 8-bromooctanoic acid ( 10 ). The key step involved l -proline-catalyzed three-component reductive alkylation (TCRA) of 2-hydroxy-1,4-naphthoquinone ( 5 ) with the optically active aldehyde 7 .

A concise, facile and straightforward synthetic method has been described for the synthesis of 2-(3-amino-2-oxoindolin-3-yl)-3-hydroxynaphthalene-1,4-dione derivatives by a one-pot, three-component reaction of isatins, 2-hydroxy-1,4-naphthoquinone and ammonium acetate under catalyst-free conditions in ethanol. This protocol becomes highly efficient due to its mild reaction conditions, operational simplicity, and overall good to excellent yields (80–99%).

The one-pot multicomponent synthesis of benzo[g]imidazo[1,2-a]quinolone-6,11-dione derivatives in good to high yields, from readily available starting materials including ethylenediamine, 1,1-bis(methylthio)-2-nitroethene, 2-hydroxy-1,4-naphthoquinone and aromatic aldehydes is described. This protocol has the advantages of simple work-up, mild reaction conditions and provides a powerful entry into fused polycyclic structures related to bioactive heterocycles.

A simple one-pot three-component synthesis of fused thiouracils from readily available starting materials including 2-hydroxy-1,4-naphthoquinone, aromatic aldehydes and 6-amino-2-thiouracil in good yields is described. The sequences of cascade reactions include Knoevenagel condensation, Michael addition and cyclocondensation.

A new type of O-alkylation of 2-hydroxy-1,4-naphthoquinone with alkoxymethyl chlorides is described. The reaction course can be controlled by the choice of base and yields O-alkylated or O-alkoxymethylated products in high yield with high selectivity.

A simple and convenient procedure for the synthesis of 5Hdibenzo[b,i]xanthene-tetraones and aryl-14H-dibenzo[a,j]xanthenes is described through the condensation of aldehydes with 2-naphthol or 2-hydroxy-1, 4-naphthoquinone under solvent-free conditions in the presence of ferric chloride hexahydrate. This method has the advantages of high yields, cleaner reaction, simple work-up and cost efficiency.

A simple synthesis of novel 13-aryl-13H-benzo[g]benzothiazolo [2,3-b]quinazoline-5,14-dione derivatives was accomplished in excellent yields via the reaction of 2-aminobenzothiazole, aromatic aldehydes and 2-hydroxy-1,4-naphthoquinone in the presence of amberlyst-15. The antiproliferative activities of all the synthesized compounds were assessed on two different human cancer cell lines (HepG2 and Hela), and the results showed that most of the new compounds showed good to potent cytotoxic activities.

A set of BINOL–quinine–squaramides were synthesized, and then used as organocatalysts to promote the catalytic enantioselective Michael addition reaction of 2-hydroxy-1,4-naphthoquinone to nitroalkenes with excellent yields and ees (up to 99% yield and 93% ee) at low catalyst loading (0.5 mol %).

The efficient base-catalyzed synthesis of 3-substituted 2-aminonaphtho[2,3-b]furan-4,9-dione derivatives from readily available precursors such as 2-hydroxy-1,4-naphthoquinone and nitroalkenes under aqueous conditions is described. Interesting features of this methodology are the conversion of a nitro functionality into an amino functionality in the absence of a reducing agent and the development of a three component reaction for accessing the same product from an aldehyde, 2-hydroxy-1,4-naphthoquinone and nitromethane.

A highly enantioselective Michael addition of 2-hydroxy-1,4-naphthoquinone to β-nitrostyrenes has been achieved using a novel class of sugar-Cinchona thiourea conjugates. The method offers significant advantages such as low catalyst loading (1 mol%), high enantioselectivity (up to 99% ee), short reaction times and ambient reaction conditions.

The enantioselective formal [3 + 3] annulation reaction of isatin-derived β,γ-unsaturated α-ketoesters with 3-hydroxy-4H-chromen-4-ones or 2-hydroxy-1,4-naphthoquinone was successfully implemented under catalysis of quinine-derived bifunctional tertiary amine-thiourea catalysts. The efficient tandem Michael-cyclization has provided facile access to optically active spiro[oxindole-pyrano[3,2-b]chromenone] and spiro[oxindole-benzo[g]chromene-dione] derivatives in high yields with excellent diastereo- and enantioselectivities.

A novel etherification of 2-hydroxy-1,4-naphthoquinone derivatives with alkoxyalkyl chlorides and hydride bases is described. Precise study of the conditions and substrate scope suggested that the reaction occurs specifically in the molecule having a 2-hydroxy-1,4-benzoquinone skeleton. A chemoselective O-methylation reaction was achieved to afford a synthetically important intermediate, which offered easy access to a natural product possessing anti-tumor activity.

Facile and convenient procedures have been described for the synthesis of 4H-benzo[g]chromenes by one-pot condensation of aromatic aldehydes, malononitrile/ethyl cyanoacetate, and 2-hydroxy-1,4-naphthoquinone. The reaction has been accomplished using catalytic cetyltrimethylammonium bromide (CTAB) in water under reflux or under neat conditions at 110 °C. A task-specific ionic liquid, 1-butyl-3-methyl imidazolium hydroxide ([bmim]OH), has also been found to be an effective catalyst for this transformation. The protocols prove to be environmentally benign and offer advantages of good yields, short reaction times, and simple workup procedures. The ionic liquid could be recycled and reused for up to four runs without appreciable loss in the activity.

C-Alkylation of 2-hydroxy-1,4-naphthoquinone to various nitroolefins was achieved under catalyst-free employing ‘on water’ conditions. The mechanism for the formation can be explained on the basis of dual activation of nitroalkene and 2-hydroxy-1,4-naphthoquinones via hydrogen bonding. Simple reaction conditions, high yields of the products, and environmentally benign medium are attractive features of this method.

The toxic profile of lawsone (2-hydroxy-[1,4]naphthoquinone) and a series of [1,4]naphthoquinone derivatives was evaluated against the brine shrimp Artemia salina and against the mollusk Biomphalaria glabrata, the main transmitting vector of schistosomiasis in Brazil. Of the seventeen compounds tested nine fell below the threshold of 100 µg/mL set for potential molluscicidal activity by the World Health Organization. As a general rule derivatives with non-polar substituents presented the highest molluscicidal activities. These substances showed significant toxicity in A. salina lethality bioassay.A toxicidade da lausona (2-hidroxi-1,4)-naftoquinona e de diversos derivados foi avaliada frente à Artemia salina e ao molusco Biomphalaria glabrata, o principal vetor de transmissão da esquistossomose no Brasil. Entre os dezessete compostos testados, nove apresentaram um perfil de toxicidade menor que 100 µg/mL, sendo potenciais agentes moluscicidas de acordo com as designações da Organização Mundial da Saúde. No presente estudo, os compostos contendo substituintes apolares exibiram as maiores atividades. Estes compostos também se mostraram significantemente tóxicos frente à A. salina.

The regioselective three-component condensation reaction of 2-hydroxy-1,4-naphthoquinone with isocyanides in the presence of a variety of aldehydes offers an easy one-pot access to linear naphtho[2,3-b]-furan-4,9-dione derivatives. This method has the advantage of good yields, high regioselectivity, and uses readily accessible substrates and reagents. The elucidation of regiochemistry has been accomplished by X-ray determination of some representative compounds.

The Pd(PPh 3 ) 4 -catalyzed reaction of 2-hydroxy-1,4-naphthoquinone (lawsone) with allyl alcohols and allyl esters offers an easy access to 3-allyl-2-hydroxy-1,4-naphthoquinones, compounds with interesting biological activity. The reaction finds application in the preparation of lapachol. Other 2-hydroxy-1,4-benzoquinones give allylation products in low yields.

Derivatives (Iva,b,d), (VIb), (IX), as well as (XII) exhibit cytotoxic activity against HEL and MCF7 cell lines.

2,3-Dihydro-3-O-(1,4-naphthoquinon-2-yl)-2-oxo-1,4-naphthoquinones are the products of oxidative coupling of substituted 2-hydroxy-1,4-naphthoquinones (regardless of the presence of peri-hydroxy groups in their structures) under the action of lead dioxide.

The phenyliodonium ylide of 2-hydroxy-1,4-naphthoquinone reacts with aminoesters, ureas, aminoalcohols and aminophenols in refluxing dichloromethane to afford good yields of indanedione 2-carboxamido compounds, that in solution exist in an enol-amide form. The same reactants in a copper-catalyzed reaction afford mainly the corresponding N-arylo compounds. Arylhydrazines are mainly oxidized by the ylide and arylation occurs only in a low yield.

An efficient synthesis of biologically active dehydro‐α‐lapachone and α‐lapachone has been carried out starting from 2‐hydroxy‐1,4‐naphthoquinone by a tandem Knoevenagel‐electrocyclic reaction.

Aryliodonium ylides of 2-hydroxy-1,4-naphthoquinone react with amines in refluxing dichloromethane to afford good yields of indanedione 2-carboxamides 5, through a ring-contraction and alpha,alpha'-dioxoketene formation reaction. These amides exist in solution in an unusual enol-amide form. In contrast, the same reactants in a copper-catalyzed reaction afford arylamines and 3-iodo-4-hydroxy-1,2-naphthoquinone.

A set of BINOL–quinine–squaramides were synthesized, and then used as organocatalysts to promote the catalytic enantioselective Michael addition reaction of 2-hydroxy-1,4-naphthoquinone to nitroalkenes with excellent yields and ees (up to 99% yield and 93% ee) at low catalyst loading (0.5 mol %).

Reaction between caproaldehyde 2 and 2-hydroxy-1,4-naphthoquinone 1 under both acidic and basic conditions resulted in the formation of useful compounds including the desired 2-hydroxy-3(1′-hexenyl)-1,4-naphthoquinone 3. The varied results on the reaction conditions and factors affecting the reaction are discussed.

The carbonyl stretching vibrations of the title compounds were studied using DFT calculations at the B3LYP/6-311G** level and the IR spectra in terms of the intramolecular hydrogen bond (H-bond). T...

An efficient one-pot synthesis of hydroxylnaphthalene-1,4-dione derivatives is accomplished by a three-component reaction of 2-hydroxynaphthalene-1,4-dione, aromatic aldehydes, and amines in water under ambient temperature catalyzed by phenylphosphinic acid. This method has the advantages of good yield, mild reaction conditions, simple workup, environmental friendliness and cost efficiency.

An efficient one-pot four-component domino protocol for the combinatorial synthesis of novel 1,4-dihydropyrano[2,3-c]pyrazol-6-amines has been achieved. This transformation presumably occurs via cyclization–Knoevenagel condensation–Michael addition–tautomerism–intramolecular O-cyclization–elimination sequence of reactions. The significant features of this reaction include expedient one-pot process, short reaction time, no column chromatographic purification, excellent yield, and readily available starting materials.

Nevertheless, there are still some drawbacks in theseprocedures, such as high catalyst loading and long reactiontime for high enantioselectivity. Accordingly, the develop-ment of alternative catalysts for the enantioselective Michaeladdition of 2-hydroxy-1,4-naphthoquinones to β,γ-unsatu-rated α-keto esters is highly desirable.As part of our research program related to the develop-ment of synthetic methods for the enantioselective construc-tion of stereogenic carbon centers

Kinetic and thermodynamic studies were conducted with the natural dye lawsone (2-hydroxy-1, 4-naphthoquinone) on six substrates at various temperatures. All the substrates showed high dye uptake and were dyed to deep shades. The adsorption isotherms, rate of dye uptake, diffusion coefficients, standard affinity, enthalpy and heat of dyeing have been calculated and discussed.

Background. Very few studies are available in which the components of henna products used by tattoo artists have been analysed. Objective. The aim of this study was to quantify the amounts of lawsone (2-hydroxy-1,4-naphthoquinone, the active ingredient in henna) and p-phenylenediamine (PPD) in products used by tattoo artists and in commercial henna preparations used as hair dyes or to create temporary tattoos. Methods. We used high-performance liquid chromatography to detect and quantify lawsone and PPD concentrations in three products used by henna tattoo artists, 11 commercially available henna preparations, and a batch of henna leaves (Lawsonia inermis). Results. The henna leaves contained 1.85–1.87% lawsone. Only one of the three preparations used by tattoo artists contained lawsone (0.21–0.35%), and all three were adulterated with PPD (1–64%). Of the 11 commercial henna preparations analysed, nine contained lawsone (1–2%) and two contained PPD (2% and 12%). Conclusions. Products purporting to be henna, but that in fact contain no henna, are being offered. Moreover, these products may contain PPD, which is associated with health risks, especially severe allergic reactions.

The title reaction is catalyzed by a readily available cinchona-derived squaramide at low loading.

The manganese(III) initiated oxidative free radical reaction between 2-hydroxy-1,4-naphthoquinone and β-enamino carbonyl compound 2 is described. Enamine radical 5 can be generated effectively from the oxidation of enamine 2 by manganese(III) acetate. Spirolactam 3 was prepared effectively from readily available 2-hydroxy-1,4-naphthoquinone and enamine 2 .

The manganese(III) initiated oxidative free radical reaction between 2-hydroxy-1,4-naphthoquinone and β-enamino carbonyl compound 2 is described. Enamine radical 5 can be generated effectively from the oxidation of enamine 2 by manganese(III) acetate. Spirolactam 3 was prepared effectively from readily available 2-hydroxy-1,4-naphthoquinone and enamine 2 .