A new synthesis of naphtho[2,3-C]pyrroles. Conversion of naphtho[2,3-C]thiophene-4,9-diones to naphtho[2,3-C]pyrrole-4,9-diones

A series of 2-substituted-4,9-dihydronaphtho[2,3-c]pyrrole-4,9-diones was prepared by the reaction of 4,9-dihydronaphtho[2,3-c]thiophene-4,9-diones with primary amines under mild conditions. The presence of halogen in the naphtho[2,3-c]thiophene-4,9-dione and the presence of hydroxyl, ether, or tertiary amine functions in the amine reagent do not interfere with the course of the reaction.     

Nucleophilic substitutions of 2-chloronaphtho[2,3-b]furan-4,9-dione with amines

2-Chloronaphtho[2,3-b]furan-4,9-dione 4 was allowed to react with pyrrolidine to produce 2-(1-pyrrolidinyl)naphtho[2,3-b]furan-4,9-dione 8 in 64% yield. In a similar manner, the reaction of 4 with cyclic amines (piperidine, morpholine, 4-substituted piperazines, etc.) gave the desired compounds. 2-Dimethylaminonaphtho[2,3-b]furan-4,9-dione 20 and 2-propylaminonaphtho[2,3-b]furan-4,9-dione 23 were obtained from the reactions of 4 with amines in 67% and 48% yields, respectively. Furthermore, the reactions of 4 with acyclic amines (diethylamine, dipropylamine, isopropylamine, butylamine, etc.) gave the desired compound. Compound 4 was treated with sodium azide to give 2-azidonaphtho[2,3-b]furan-4,9-dione 28 in 42% yield. All these nucleophilic substitutions were carried out at room temperature. It was found that 4 showed high reactivity for amines. Unexpectedly, 2-morpholinonaphtho[2,3-b]furan-4,9-dione 13 was obtained from the reaction of 4 with 1-morpholino-1-cyclohexene.     

Micellar electrokinetic chromatography (MEKC) separation of furanonaphthoquinones from Tabebuia impetiginosa

The separation of nine furanonaphthoquinones by micellar electrokinetic chromatography (MEKC) is described. The running electrolytes used in this method were 0.03 M sodium dodecyl sulphate (SDS) in 0.09 M borate buffer (pH 9) containing 10% methanol, with an applied voltage of 20 kV. Application of this technique in the determination of the main furanonaphthoquinones, 5-hydroxy-2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-dione, 8-hydroxy-2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-dione, and 2-(1-hydroxyethyl)naphtho[2,3-b]furan-4,9-dione, of Tabebuia impetiginosa is demonstrated in this paper.     

A new synthetic route to 2-substituted naphtho[2,3-b]furan-4,9-dione2-Substituted Naphtho[2,3-b]furan-4,9-dione

4,9-Dimethoxynaphtho[2,3-b]furan 9 was obtained in 91% yield via the reductive methylation of naphtho[2,3-b]furan-4,9-dione 2 . After treatment of 9 with butyllithium, the mixture was allowed to react with N,N-dimethylacetamide, followed by oxidization with cerium(IV) diammonium nitrate to give 2-acetylnaphtho[2,3-b]furan-4,9-dione 1 . 2-Formylnaphtho[2,3-b]furan-4,9-dione 13 and 2-trimethylsilyl-naphtho[2,3-b]furan-4,9-dione 14 were also obtained from 9 by a similar method. The halodesilylations of 14 easily gave 2-iodonaphtho[2,3-b]furan-4,9-dione 16 , 2-bromonaphtho[2,3-b]furan-4,9-dione 17 , and 2-chloronaphtho[2,3-b]furan-4,9-dione 18 in 82%, and 93% and 83% yield, respectively. Furthermore, the nitrodesilylation of 14 gave 2-nitronaphtho[2,3-b]furan-4,9-dione 3 in 77% yield.     

DABCO-catalyzed three-component reaction for the synthesis of naphtho[2,3-b]thiophene-4,9-diones

An efficient synthesis of naphtho[2,3-b]thiophene-4,9-diones has been developed via DABCO-catalyzed three-component reaction of 1,4-naphthoquinone derivatives, α,β-unsaturated ketones and hydrated sodium sulfide. The reaction is initiated by sequential Michael additions of sodium sulfide to α,β-unsaturated ketone and of generated anion to 1,4-naphthoquinone derivative, followed by intramolecular oxidative cyclization and aromatization. Various functional groups in the α,β-unsaturated ketones survive under the reaction conditions and naphtho[2,3-b]thiophene-4,9-diones are generated in good yields.     

A short-step synthesis of naphtho[2,3-b]furan-4,9-dione

Phthalic anhydride in THF was added to 3-lithiofuran 2 in THF to give 3,3-di-(3-furyl)-1,3-dihy-droisobenzofuran-1-one 4 . On the other hand, 2 in THF was added to phthalic anhydride in THF to give 2-(3-furanoyl)benzoic acid 3 by the inverse addition method. Further, the parent naphtho[2,3-b]furan-4,9-dione 1 was obtained from the reaction of 3 with two equimolar amounts of LDA.     

Room temperature cyclization of arylpropiolic acid anhydride: Synthesis of naphtho[2,3-c]furan-1,3-dione derivatives

Cyclic anhydrides such as naphtho[2,3-c]furan-1,3-dione derivatives were synthesized from the reaction of arylpropiolic acids and 2-chloro-4,6-dimethoxy-1,3,5-triazine in the presence of N-methylmorpholine at room temperature. This mild condition provided the naphtho[2,3-c]furan-1,3-dione derivatives in good yields. Spectroscopic analysis suggested that the formation of arylpropiolate is the rate-determining step.     

Isofuranonaphthoquinones from ventilago maderaspatana: Crystal structure of ventilone-C

From the root bark of Ventilago maderaspatana (Rhamnaceae) five isofuranonaphthoquinones have been isolated. Ventilone-A is 4,9-dihydro-5,8-dihydroxy-6,7-methylenedioxy-1-methylnaphtho[2,3-c] furan-4,9-dione and B is the 5-methyl ether. Ventilone-C has the structure 1,3,4,9-tetrahydro-8-hydroxy-5-methoxy-6, 7-methylenedioxy-1-methylnaphtho[2,3-c]furan-4,9-dione, D is the isomeric 8-methyl ether, and E is the 5,8-dimethyl ether. Structures were determined by spectroscopic methods, and X-ray crystallographic analysis of ventilone-C.     

Synthesis of derivatives of naphtho[2,3-b]furan-4,9-dione

The reaction of 2,3-dichloro-1,4-naphthoquinone with ketoenols has been studied. A series of substituted naphtho[2,3-b]furan-4,9-quinones has been synthesized and some of their reactions have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 867–870, July, 1970.     

Structure Determination of New Isomeric Naphtho[2,3-b]furan-4,9-diones from Tabebuia avellanedae by the selective-INEPT technique

Beside the known naphthoquinones, dehydro-α-lapachone ( 17 ) and lapachol ( 20 ), four new naphtho[2,3-b]-furan-4,9-diones, i.e. the 2-acetyl-5-hydroxy. 2-acetyl-8-hydroxy. (?)-5-hydroxy-2-(1′-hydroxyethyl), and (±)-8-hydroxy-2-(1′-hydroxyethyl) derivatives 16, 15, 12 , and 13 , respectively, and the new compound benzo[b]furan-6-carboxaldehyde ( 8 ) have been isolated from a CHCl₃ extract of the inner stem bark of Tabebuia avellanedae LORENTZ ex GRISEB ., together with four known naphthofurandiones, a dihydroisocoumarin derivative, (?)–6-hydroxymellein, and five benzoic-acid and three benzaldehyde derivatives which have not been reported previously from this plant. Structure determination of the isomeric 5- and 8-hydroxynaphtho[2,3?b]furan-4,9-diones was carried out unambiguously by a combination of selective-INEPT experiments and X-ray crystallographic analysis.     

Synthesis of C-2 Unsubstituted Furanonaphthoquinones

Four C-2 unsubstituted naphtho[2,3-b]furan-4,9-quinones were prepared via the corresponding phthalides obtained by directed ortho-metalation-based route.     

New ‘2-phenylnaphthalene’-mediated synthesis of benzo[b]naphtho[2,3-d]furan-6,11-diones and 6-oxa-benzo[a]anthracene-5,7,12-triones: first total synthesis of 6-oxa-benzo[a]anthracen-5-ones

We describe here a novel synthesis of benzo[b]naphtho[2,3-d]furan-6,11-diones based on the heteroannulation of 2-(2-bromophenyl)-3-hydroxy-1,4-naphthoquinones. The naphthoquinones were prepared from 3-(2-bromophenyl)naphthalen-2-ols, which were obtained by intramolecular aldol condensation of 2-[3-(2-bromophenyl)-2-oxo-propyl]benzaldehydes. Alternatively, benzo[b]naphtho[2,3-d]furan-6,11-diones were obtained more directly and efficiently by cyclization of 3-(2-bromophenyl)naphthalen-2-ols to benzo[b]naphtho[2,3-d]furans and oxidation of the resulting compounds. Furthermore, the first 6-oxabenzo[a]anthracen-5-one described was similarly obtained from 2-[3-(2-formylphenyl)-2-oxopropyl]benzoic acid and oxidized to 6-oxa-benzo[a]anthracene-5,7,12-trione.     

A facile synthesis of 2-acetylnaphtho[2,3-b]furan-4,9-dione

Reaction of the parent naphtho[2,3-b]furan-4,9-dione 2 with various electrophilic reagents was difficult, and only nitration of 2 gave small amounts of 2-nitronaphtho[2,3-b]furan-4,9-dione 4 . Then 2-acetylnaphtho[2,3-b]furan-4,9-dione 1 was not obtained by the acetylation of 2 . On the other hand, compound 1 that is isolated from Tabebuia Cassinoides and has cytotoxic activity, was obtained from 3-lithiofuran in five steps.     

Synthesis of benzo[f]isoindole-4,9-diones

A synthesis of benzo[f]isoindole-4,9-diones 1 is presented starting from the reaction of 2,3-bis(bromomethyl)-1,4-dimethoxynaphthalene 15 with primary amines affording 2,3-bis(aminomethyl)-1,4-dimethoxynaphthalenes 14, which could be converted by CAN-mediated oxidation in one step to benzo[f]isoindole-4,9-diones 1. An alternative synthesis of benzo[f]isoindole-4,9-diones 1 starts from 2,3-bis(bromomethyl)-1,4-naphthoquinone 9 via 2,3-dihydrobenzo[f]isoindoles 10 which spontaneously oxidize.     

A D-A copolymer of dithienosilole and a new acceptor unit of naphtho[2,3-c]thiophene-4,9-dione for efficient polymer solar cells

A strong electron-withdrawing unit, naphtho[2,3-c]thiophene-4,9-dione, was copolymerized with dithienosilole to get a D-A copolymer, PDTSNTDO, with a narrow bandgap and lower-lying HOMO level. The PCE of the PDTSNTDO-based device reached 5.21%, with a high open circuit voltage of 0.88 V.     

Green synthesis of naphtho[2,3-f]quinolin-13-one and naphtho[2,3-a]acridin-1(2H)-one derivatives catalyzed by heteropoly acid supported montmorillonite K-10 clay

Herein, synthesis of a series of naphtho[2,3-f]quinolin-13-one and naphtho[2,3-a]acridin-1(2H)-one derivatives directly by one-pot multi-component reaction of 1,3-dicarbonyl compounds (1,3-indanedione/1,3-cyclohexanedione), 2-aminoantharacene/2-naphthylamine and various substituted aldehydes under solvent-free conditions using heteropoly-11-molybdo-1-vanadophosphoric acid supported on montmorillonite K-10 clay catalyst (10% PVMoK-10) is reported. The successful formation of naphtho[2,3-f]quinolin-13-one and naphtho[2,3-a]acridin-1(2H)-one derivatives was confirmed by various spectroscopic techniques. This study offers a green approach for the synthesis of novel quinolinone derivatives.     

An efficient three-component reaction involving [3 + 1 + 1] furannulation leading to furanonaphthoquinones in water

An efficient and clean green synthesis of highly substituted linear naphtho[2,3-b]-furan-4,9-dione derivatives, starting from 2-hydroxy-1,4-naphthoquinone, alkyl isocyanides and a variety of aldehydes, is described. This new method provides the first example of an efficient regioselective synthetic method for the synthesis of linear naphtho[2,3-b]-furan-4,9-dione ring systems by formation of three bonds. This [3 + 1 + 1] furannulation strategy affords furanonaphthoquinones in moderate to high yields, using water as a cheap, non-toxic, environmentally friendly solvent, in a one-step reaction, without the need of complicated work-up procedures.     

Studies on quinones. Part 37. Synthesis and biological activity of o-aminoester functionalised benzo- and naphtho[2,3-b]thiophenequinones

The synthesis of 3-amino-2-methoxycarbonyl-4,7-dimethoxybenzo[b]thiophene (5) and benzothieno[3,2-d][1,3]oxazin 15 from 3,6-dimethoxy-2-nitrobenzaldehyde (1) is reported. Benzo[b]thiophene-4,7-quinones 9 and 10 were prepared in good yields by oxidative deprotection of the corresponding dimethoxybenzothiophenes 8 and 7. Cycloaddition reaction of quinone 8 with 1-(E)-trimethylsilyloxy-1,3-butadiene followed by acid-induced aromatization provides access to naphtho[2,3-b]thiophene-4,9-quinone 13 and 14. The in vitro activity of the new quinones against Leishmania amazonensis and human-T-cell leukemia virus type 1 (HTLV-1) is reported.     

Investigation of quinones

Naphtho[2,3-f]quinoxaline-7,12-diones add a molecule of benzenesulfinic acid to give 5-phenylsulfonyl-7, 12-dihydroxynaphtho[2,3-f]quinoxalines. The latter are oxidized to 5-phenylsulfonyl-substituted quinones, which add a molecule of benzenesulfinic acid to the oxygen atoms of the quinone grouping to give the O⁷-benzenesulfonate of 5-phenylsulfonyl-7, 12-dihydroxynaphtho[2,3-f]quinoxaline. The protonated form of naphtho[2,3-f]quinoxa-line-7, 12-dione, which is stabilized by an intramolecular hydrogen bond, as confirmed by the anomalously high basicity of angular naphtho[2,3-f]quinoxaline-7,12-dione as compared with its linear isomer, which is inert in reactions with benzenesulfinic acid, undergoes reaction.     

Deep eutectic solvent-mediated expedient multicomponent synthesis of oxazine scaffolds

A simple, efficient, and eco-friendly protocol for the synthesis of 1,3-oxazine derivatives, viz. 7-aryl-7,8-dihydro-6H-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-e][1,3]oxazines and 3-aryl-3,4-dihydro-2H- naphtho[2,3-e][1,3]oxazine-5,10-diones, involving one-pot multicomponent condensation reaction of various amines and formaldehyde with sesamol/2-hydroxy-1,4-naphthoquinone, respectively, catalyzed by a choline chloride–oxalic acid deep eutectic solvent has been developed. The method offers several advantages, including mild reaction conditions, simple operating procedure, recyclable and biodegradable catalyst, short reaction times, and excellent yields of the target products.