1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• naphthoquinones [40][41][42]. β-NQS preparation methods generally employ β-naphthol or 1-amino-β-naphthol as starting materials. The first procedure was developed by Witt [43] in the late 19th century when he prepared 1,2-naphthoquinone-4-sulfonic acid ammonium salt (16) in a 60–75% yield from 1-amino-β-naphthol

• -naphthoquinone-4-sulfonic acid sodium salt (β-NQSNa, 18) was very effective as a colorimetric indicator of blood amino acids. This compound came to be called Folin's reagent. To achieve 18 with adequate purity to be used in the tests, an elaborate large-scale synthetic route was developed. β-Naphthol (20) was

• transformed into α-nitroso-β-naphthol (17); then, in a single step, a sulfonic group was added, and the nitrous group was reduced, forming compound 15, which was transformed into β-NQSNa (18) after oxidation with nitric acid. Despite not knowing exactly the structure of the adduct, Folin speculated that the

Recent advances in the asymmetric phosphoric acid-catalyzed synthesis of axially chiral compounds

• Alemayehu Gashaw Woldegiorgis and
• Xufeng Lin

Beilstein J. Org. Chem. 2021, 17, 2729–2764, doi:10.3762/bjoc.17.185

• -naphthol (88) and allene-iminium intermediate I-24 to form axially chiral I-25, followed by rearomatization of the naphthol ring of I-25 and isomerization to I-26. Thereafter, CPA forms two hydrogen bonds with the two OH groups of I-26 to generate a carbocation and facilitates an intramolecular

• tetrasubstituted allenes with aryl substituents, the asymmetric synthesis of these scaffolds has received much attention. In 2020, Lu and co-workers carried out the enantioselective dehydrative γ-arylation of α-indolyl-α-trifluoromethylpropargyl alcohol 105 and 1-naphthol (106) or 2-naphthol (107) catalyzed by

• indole ring of the propargyl alcohol, the yield decreases, which could be due to steric effects. Since the chiral phosphoric acid catalysts can interact with these groups via double hydrogen bonds, control studies have shown that the free OH on naphthol/phenol and the NH groups on the α-indolyl-α

Transition-metal-free intramolecular Friedel–Crafts reaction by alkene activation: A method for the synthesis of some novel xanthene derivatives

• Tülay Yıldız,
• İrem Baştaş and
• Hatice Başpınar Küçük

Beilstein J. Org. Chem. 2021, 17, 2203–2208, doi:10.3762/bjoc.17.142

• of their important biological and fluorescent uses. To summarize the main syntheses of these studies: in particular, transition metal-catalyzed cascade benzylation–cyclization [17], cyclization of polycyclic aryl triflate esters [18], reaction of β-naphthol and aldehydes [19][20] or inter- or

Recent advances in the syntheses of anthracene derivatives

• Giovanni S. Baviera and
• Paulo M. Donate

Beilstein J. Org. Chem. 2021, 17, 2028–2050, doi:10.3762/bjoc.17.131

• synthesize tetrahydrobenzo[a]xanthene-11-ones 184 and diazabenzo[a]anthracene-9,11-dione derivatives 185 in good yields via a multicomponent reaction (Scheme 42) [76]. This methodology was based on the cyclocondensation of aromatic aldehydes 180, β-naphthol (181), and cyclic 1,3-dicarbonyl compounds 182 or

• -workers [77] provided better results. In a related approach, Estévez-Braun and co-workers synthesized dibenzo[a,h]anthracene-12,13-diones 188 from 2-hydroxy-1,4-naphthoquinone (186), β-naphthol (181), and aromatic aldehydes 187 through a multicomponent reaction that used InCl3 as catalyst under solvent

• multicomponent reactions employing 2-hydroxy-1,4-naphthoquinone (186), β-naphthol (181), and aromatic aldehydes. Synthesis of substituted anthraquinones catalyzed by an AlCl3/MeSO3H system. Palladium(II)-catalyzed/visible light-mediated synthesis of anthraquinones. [4 + 2] Anionic annulation reaction for the

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

• methods include V2O5 and VO(acac)2 used for the alkylation of 2-naphthol and nitrogen-containing heteroaromatic moieties containing N-methylmorpholine-N-oxide, tetrahydroisoquinolines, and N,N-dimethylacetamide [107][108][109][110][111][112][113]. The mechanisms involving oxidation of the amine mediated

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

• the phenol hydroxy group in the transition state. This assumption could also explain the high o-selectivity obtained in the fluorinations of naphthol, phenylurethane, and trimethylsilyl ether of phenol, and the exclusive 6-selectivity observed in the fluorination of conjugated enol triisopropylsilyl

A comprehensive review of flow chemistry techniques tailored to the flavours and fragrances industries

• Guido Gambacorta,
• James S. Sharley and
• Ian R. Baxendale

Beilstein J. Org. Chem. 2021, 17, 1181–1312, doi:10.3762/bjoc.17.90

Microwave-assisted multicomponent reactions in heterocyclic chemistry and mechanistic aspects

• Shivani Gulati,
• Stephy Elza John and
• Nagula Shankaraiah

Beilstein J. Org. Chem. 2021, 17, 819–865, doi:10.3762/bjoc.17.71

• ] reported the potential of naphthopyrans as non-purine xanthine oxidase inhibitors. They explored a silicated fluoroboric acid-catalyzed three-component cycloaddition involving acyclic 1,3-diketones 54, β-naphthol (55) and aldehyde 5 for the synthesis of substituted naphthopyrans 56 under microwave

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• the dearomatization of β-naphthol promoted by visible light via intermolecular charge transfer (Scheme 29). In this method, β-naphthol anion 87 (β-naphthol 85 formed in the presence of base) is employed as electron donor to form EDA complex with electron acceptor perfluoroalkyl iodide 28. Single

Valorisation of plastic waste via metal-catalysed depolymerisation

• Francesca Liguori,
• Carmen Moreno-Marrodán and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2021, 17, 589–621, doi:10.3762/bjoc.17.53

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• pH-responsive nano-assemblies with switchable size and structure are formed by the association of a photoacid, anthocyanidin, and a linear polyelectrolyte in aqueous solution. Specifically, anionic disulfonated naphthol derivatives, neutral hydroxyflavylium, and cationic poly(allylamine) are used as

• molecules in aqueous solution. The building blocks pelargonidin chloride (Flavy), 1-naphthol-3,6-disulfonate (1N36S), and poly(allylamine) are depicted in Scheme 2. The aim was to exploit the photoacid's unique capability to undergo photoinduced intermolecular excited state proton transfer reactions, both

• quaternary amines with hydroxy groups is not common but has been observed [90][91][92]. The electrostatic interaction of naphthol-based molecule ions are known to be at least of ΔH = −50 kJ/mol [32]. This suggests that here not only one charge interacts, instead, for ΔH3 it has to be between three charges

Synthesis of aryl 2-bromo-2-chloro-1,1-difluoroethyl ethers through the base-mediated reaction between phenols and halothane

• Yukiko Karuo,
• Ayaka Kametani,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2021, 17, 89–96, doi:10.3762/bjoc.17.9

• corresponding products in comparably high yields (Table 2, entries 7–9). Also, 1-naphthol (1k) was compatible with the reaction conditions giving the product 2k in a good yield of 85% (Table 2, entry 10). As shown in entries 11–13 (Table 2), o-iodophenol (1l) and the alkenyl-substituted phenols 1m and 1n, all

Stereoselective Biginelli-like reaction catalyzed by a chiral phosphoric acid bearing two hydroxy groups

• Xiaoyun Hu,
• Jianxin Guo,
• Cui Wang,
• Rui Zhang and
• Victor Borovkov

Beilstein J. Org. Chem. 2020, 16, 1875–1880, doi:10.3762/bjoc.16.155

• described the efficient asymmetric Biginelli reaction with a chiral ytterbium catalyst to provide excellent enantioselectivities up to >99% ee [12]. Later, Gong reported the first organocatalytic Biginelli reaction using 1,1'-bi-2-naphthol (BINOL) derived chiral phosphoric acids as catalysts, furnishing the

Oxime radicals: generation, properties and application in organic synthesis

• Igor B. Krylov,
• Stanislav A. Paveliev,
• Alexander S. Budnikov and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2020, 16, 1234–1276, doi:10.3762/bjoc.16.107

• -iminooxycyclohexadienones 28a,b (Scheme 12). Phenol (29) and 1-naphthol (30) were transformed into 4,4-bisoximes 31 and 32, respectively (Scheme 12) [35][78]. Imines 37–40 were obtained with good yields by the reaction of di-tert-butyliminoxyl radicals with primary and secondary amines 33–36 for several hours at room

Copper-catalyzed enantioselective conjugate reduction of α,β-unsaturated esters with chiral phenol–carbene ligands

• Shohei Mimura,
• Sho Mizushima,
• Yohei Shimizu and
• Masaya Sawamura

Beilstein J. Org. Chem. 2020, 16, 537–543, doi:10.3762/bjoc.16.50

• ). Thus, the hydroxy group of L1 was essential for the enantioselectivity by the catalyst. When the mesityl group of L1 was changed to a bulkier 2-Me-4,6-Cy2-C6H2 group in L4, the enantioselectivity was markedly improved to 90% ee, with a high yield (97%, Table 1, entry 4). A naphthol substituent on the

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• -dimensional displays [22], information storage systems [23], molecular photoswitches [24], etc. Among a series of chiral scaffolds for CPL emitting molecules, axially chiral 1,1’-bi-2-naphthol (BINOL) has been frequently adopted for the core structure owing to the availability of both enantiomers as well as

• ’-binaphthyl backbone as precursors for the dehydrogenative coupling reaction (Scheme 2). In general, functionalization of the BINOL hydroxy groups should be performed at temperatures below 80 °C to prevent racemization [40][41]. 6,6’-Di-tert-butyl-1,1’-bi-2-naphthol (1) was treated with 2,6-difluoropyridine

The reaction of arylmethyl isocyanides and arylmethylamines with xanthate esters: a facile and unexpected synthesis of carbamothioates

• Narasimhamurthy Rajeev,
• Toreshettahally R. Swaroop,
• Ahmad I. Alrawashdeh,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Seegehalli M. Anil,
• Kuppalli R. Kiran,
• Chandra,
• Paris E. Georghiou,
• Kanchugarakoppal S. Rangappa and
• Maralinganadoddi P. Sadashiva

Beilstein J. Org. Chem. 2020, 16, 159–167, doi:10.3762/bjoc.16.18

• ], iron nanoparticle-catalyzed reactions of 2-naphthol with benzaldehyde and some of its derivatives with thiourea [22], isothiocyanato oxindoles with ketones [23], ammonium isothiocyanates with chalcones [24], and α-isothiocyanato esters with α-keto amides [25]. Among the synthetic methods available for

Carbazole-functionalized hyper-cross-linked polymers for CO₂ uptake based on Friedel–Crafts polymerization on 9-phenylcarbazole

• Dandan Fang,
• Xiaodong Li,
• Meishuai Zou,
• Xiaoyan Guo and
• Aijuan Zhang

Beilstein J. Org. Chem. 2019, 15, 2856–2863, doi:10.3762/bjoc.15.279

• ]. FDA was first used as cross-linker to knit aromatic building blocks [15]. Researchers used this method to knit triptycenes [16], triphenylphosphine [4], benzimidazole, 1,3,5-triphenylbenzene [17], carbazole [18], naphthol-based monomers [10] etc. with FDA to obtain various HCPs, which exhibited

2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes

• Li-Li Wang,
• Yi-Kuan Tu,
• Huan Yao and
• Wei Jiang

Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146

• interesting new binding properties. During the last six years, our group have developed a series of naphthol-based macrocyclic receptors [24][25][26][27][28][29]. Of them, oxatub[4]arene [30][31] and zorb[4]arene [32][33] show multiple conformations due to the flipping of naphthalenes and thus resulted in a

DABCO- and DBU-promoted one-pot reaction of N-sulfonyl ketimines with Morita–Baylis–Hillman carbonates: a sequential approach to (2-hydroxyaryl)nicotinate derivatives

• Soumitra Guin,
• Raman Gupta,
• Debashis Majee and
• Sampak Samanta

Beilstein J. Org. Chem. 2018, 14, 2771–2778, doi:10.3762/bjoc.14.254

• better yields than the former one. By this C–C/C–N bonds forming procedure, N-sulfonyl ketimine derived from a bulky α-naphthol moiety was found to be a suitable coupling reagent, leading to the corresponding α-naphthol-substituted nicotinate derivatives 5ea and 5ee in 71% and 74% yields, respectively

An overview on recent advances in the synthesis of sulfonated organic materials, sulfonated silica materials, and sulfonated carbon materials and their catalytic applications in chemical processes

• Hashem Sharghi,
• Pezhman Shiri and
• Mahdi Aberi

Beilstein J. Org. Chem. 2018, 14, 2745–2770, doi:10.3762/bjoc.14.253

• -acenaphthenequinone derivatives, tetrahydrobenzo[a]xanthenone derivatives, tetrahydrobenzo[a]acridinone derivatives, 1-amidoalkyl-2-naphthol derivatives, 2H-indazolo[2,1-b]phthalazine-1,6,11(13H)trione derivatives, quinoline derivatives, bis-coumarin derivatives, 2H-indazolo[2,1-b]phthalazinetrione derivatives

• and 37 from active carbonyl compounds (e.g., isatins 32, acenaphthoquinone (33), and aldehydes 38), a variety of C–H activated acids (cyclohexane-1,3-dione (20a), 5,5-dimethylcyclohexane-1,3-dione (20b), 2-naphthol (23), ethyl acetoacetate (34a), 4-hydroxycoumarin (34b), triacetic acid lactone (34c

• ), and 1-naphthol (34d)), and malononitrile (35) in water at 90 °C. Isatin (32) and acenaphthenequinone (33) were reacted with C–H activated acids 20a,b, 23, and 34a–c and malononitrile (35) to form the corresponding spiro-isatin derivatives 36 and spiro-acenaphthenequinone derivatives 37 under mild and

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• respect, the key building block 29 was derived by employing a sequential O-allylation and CR, then again O-allylation, and CR [35] starting with a commercially available 6-bromo-2-naphthol (27). Subsequently, the diallyl derivative 29 was exposed to G-II catalyst 2 to deliver a ring-closure product 30 (83

• an important role as cosmetics and as pharmaceutical ingredients. Therefore, we conceived a simple approach, where the SM coupling and RCM were employed as critical steps [42][43]. Our journey begin with O-allylation of β-naphthol 76 by using allyl bromide (28) to give O-allyl derivative 77. Then

Synthesis of spirocyclic scaffolds using hypervalent iodine reagents

• Fateh V. Singh,
• Priyanka B. Kole,
• Saeesh R. Mangaonkar and
• Samata E. Shetgaonkar

Beilstein J. Org. Chem. 2018, 14, 1778–1805, doi:10.3762/bjoc.14.152

• and its efficient utilization in the spirocyclization of naphthols containing carboxylic acids. 1-Naphthol-2-propionic acids 37 were cyclized to corresponding spirolactone derivatives 39 using chiral-8,8’-diiodonaphthyl reagent 38 as precatalyst, mCPBA as an oxidant in chloroform at low temperature

• compound 136 was achieved in 87% yield by the reaction of PIDA (15) with the naphthol derivative 135 in trifluoroethanol at room temperature. Additionally, synthesized compound 136 was used as key intermediate in the total synthesis of natural products 137 and 138 (Scheme 50). Additionally, more analogues

• pathway for the synthesis of the naturally occurring antibiotic platensimycin (154) which is isolated from Streptomyces platensis. In this report, 6-methoxy-1,4-naphthoquinone-4-ethylene ketal (153) was synthesized by intermolecular oxidative cyclization of 7-methoxy-α-naphthol (152) with ethylene glycol

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

• Alberto Spinella,
• Marco Russo,
• Antonella Di Vincenzo,
• Delia Chillura Martino and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127

• (bromocresol green, 8), a bis-indole (indigo carmine, 9) and a naphthalene-bis-diazoic (naphthol blue-black, 10), in order to evaluate the outcome of molecular size, shape and electric charge. Dyes can be considered suitable and easily detectable models of pollutants [43][44][45][46][47], for the removal of

Synthesis of chiral 3-substituted 3-amino-2-oxindoles through enantioselective catalytic nucleophilic additions to isatin imines

• Hélène Pellissier

Beilstein J. Org. Chem. 2018, 14, 1349–1369, doi:10.3762/bjoc.14.114

• 43 in good to high yields (78–99%) and uniformly excellent enantioselectivities (94–99% ee) regardless of the electronic character of the aromatic rings of the isatin and 1-naphthol and the position of their substituent (R1 and R2). Moreover, comparable excellent yields (90–97%) and

• were tolerated, giving good results in most cases. The best enantioselectivity (99% ee) was achieved in the reaction of 3-methoxy-substituted 2-naphthol whereas the lowest one (75% ee) was obtained in the reaction of an N-methylisatin imine (R2 = H, R3 = Me) with unsubstituted 2-naphthol (R1 = H). It