Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• activity in electrocatalytic HER [123]. Although free base corrole ligands demonstrated activity in HER, they were unstable in trifluoroacetic acid (TFA), a common proton source, leading to rapid degradation during catalysis. Subsequently, the same group introduced metal-free xanthene-bridged biscorroles

Efficient one-step synthesis of diarylacetic acids by electrochemical direct carboxylation of diarylmethanol compounds in DMSO

• Hisanori Senboku and
• Mizuki Hayama

Beilstein J. Org. Chem. 2024, 20, 2392–2400, doi:10.3762/bjoc.20.203

• xanthenol (1k) provided xanthene-9-carboxylic acid (2k) in an excellent yield of 90%. Phenyl(thiophen-2-yl)acetic acid (2l) could also be synthesized in an excellent yield of 92% yield by electrochemical carboxylation of phenyl(thiophen-2-yl)methanol (1l). Although a wide range of substrates was shown to be

• synthesized from 1,1-diphenylethanol (1i) and phenyl(thiophen-2-yl)methanol (1l), respectively, in one step by this electrochemical method. Notably, synthesis of xanthene-9-carboxylic acid (2k) and dibenzocycloheptene-5-carbocylic acid 2j was conducted with excellent yield. Direct substitution of a hydroxy by

• )phenylacetic acid (2e) [32], bis(4-methylphenyl)acetic acid (2f) [30][32], bis(4-methoxyphenyl)acetic acid (2g) [30][33], (4-hydroxyphenyl)phenylacetic acid (2h) [34], 2,2-diphenylpropaoic acid (2i) [35], 10,11-dihydro-5H-dibenzo[a,d]cycloheptene-5-carboxylic acid (2j) [30], 9H-xanthene-9-carboxylic acid (2k

Unravelling a trichloroacetic acid-catalyzed cascade access to benzo[f]chromeno[2,3-h]quinoxalinoporphyrins

• Chandra Sekhar Tekuri,
• Pargat Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2023, 19, 1216–1224, doi:10.3762/bjoc.19.89

• contruction of periphery-modified porphyrinoids [30][31][32][33][34][35][36][37][38][39][40][41], we thought to assemble benzo[f]chromeno[2,3-h]quinoxalinoporphyrins by incorporating porphyrin, quinoxaline and xanthene scaffolds in a single molecular framework using a multicomponent synthetic strategy. The

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• enabling controlled bond activations [45]. Regarding the reductive C–C arylation, the application of the xanthene dye rhodamine 6G (Rh-6G) as a catalyst for the reduction of heteroarenes bearing two or three bromine atoms (e.g., 6) under irradiation with green light (λ = 530 nm) gave monosubstituted

• while the C(sp2)–Br bond remained untouched. Subsequent irradiation with blue light gave the sequentially substituted products 9c and 9d. As with PDI, the xanthene dye rhodamine 6G (Rh-6G) can undergo reductive quenching upon excitation with green or blue light (Figure 5C). Considering that Rh-6G

Strategies in the synthesis of dibenzo[b,f]heteropines

• David I. H. Maier,
• Barend C. B. Bezuidenhoudt and
• Charlene Marais

Beilstein J. Org. Chem. 2023, 19, 700–718, doi:10.3762/bjoc.19.51

• (Scheme 7). Several azepine 30 and oxepine 31 examples were prepared in good yield from the respective acridane (26) and xanthene (27) derivatives. As an alternative to the thermal Wagner–Meerwin rearrangement (Scheme 5 and Scheme 6), which requires elevated temperatures, Stopka et al. [46] used mild

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

• Tulay Yildiz Irem Bastas Hatice Baspinar Kucuk Istanbul University-Cerrahpaşa, Department of Chemistry, Istanbul, Avcilar, 34320, Turkey 10.3762/bjoc.17.142 Abstract In this work, new derivatives (substituted 9-methyl-9-arylxanthenes) of xanthene compounds (5a–l) of possible biological

• significance were synthesized by developing a new synthesis method. In order to obtain xanthene derivatives, the original alkene compounds to be used as the starting materials were synthesized in four steps using appropriate reactions. A cyclization reaction by intramolecular Friedel–Crafts alkylation was

• carried out in order to synthesize the desired xanthene derivatives using the alkenes as starting compounds. The intramolecular Friedel–Crafts reaction was catalyzed by trifluoroacetic acid (TFA) and provided some novel substituted 9-methyl-9-arylxanthenes with good yields at room temperature within 6–24

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

• expected products [76]. Sun and co-workers modified the method proposed by Singh. In 2011, they reported a method that employed molecular iodine as the catalyst, under microwave radiation as heat source, and obtained tetrahydrobenzo[a]xanthene-11-one and diazabenzo[a]anthracene-9,11-dione derivatives in

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

A review of asymmetric synthetic organic electrochemistry and electrocatalysis: concepts, applications, recent developments and future directions

• Munmun Ghosh,
• Valmik S. Shinde and
• Magnus Rueping

Beilstein J. Org. Chem. 2019, 15, 2710–2746, doi:10.3762/bjoc.15.264

• 115 with moderate enantioselectivity (Scheme 38). As shown in Scheme 39, the mechanism involved initial formation of radical cation 117 via anodic oxidation of enamine 116 (obtained from the condensation of 114 and 105'), which then coupled with xanthene radical 119 (Scheme 39). Finally, hydrolysis of

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• gave access to silicon rhodamines in poor to moderate yields, we wanted to improve these first valuable experimental results. Results: The preparation of the xanthene triflate was enhanced and several boron sources were screened to find the optimal coupling partner. After optimization of the palladium

• the Suzuki–Miyaura cross-coupling reaction gave access to silicon rhodamines with neutral (hetero)aromatic xanthene substituents (phenyl: 67%, respectively 73% brsm; thienyl: 91%) (even though the term ‘dihydrosilaanthracene’ is correct to name the Si-anthracene moiety, the term ‘Si-xanthene’ is

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• trends for both radiative and nonradiative decays still remain difficult to predict despite theoretical and experimental efforts of the past years [29]. Here we initially assume that, in analogy to BODIPY fluorophores [30], restricted rotation around the xanthene aryl bond should lead to an improved

• quantum yields up to 0.67. As described previously, azetidine substituents at the xanthene moiety of 5, 7, and 9 lead to an improved quantum yield and to a red shift in comparison to the N,N-dimethylaniline analogues 1, 3, and 4 (Table 1, entry 1 vs 5, 3 vs 7, and 4 vs 9). In contrast, the 4

• -fluoroazetidine moiety in 10 (“JF635”) causes a hypsochromic shift without affecting the high quantum yield compared to the azetidine analogue 9 (“JF646”) (Table 1, entry 9 vs 10). Comparing the phenyl substituted rhodamine 2 with its 2’-methyl substituted analogue 3, restricted rotation around the xanthene

Selective benzylic C–H monooxygenation mediated by iodine oxides

• Kelsey B. LaMartina,
• Haley K. Kuck,
• Linda S. Oglesbee,
• Asma Al-Odaini and
• Nicholas C. Boaz

Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55

• , it shows incompatibility with functional groups such as alkenes, phenols, phenyl ethers, and alcohols, which are readily oxidized. The dibenzylic C–H bonds of fluorene and xanthene were also able to be functionalized. Xanthene (4a) was over-oxidized to the ketone (xanthone, 5a) in 57% yield (Figure 3

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

• these catalysts for extensive reactions, including the synthesis of bis(indolyl)methane derivatives, β-amino carbonyl compounds, 14H-dibenzo[a,j]xanthene derivatives, 1,8-dioxodecahydroacridine derivatives, xanthene derivatives, pyrimido[4,5-b]quinoline derivatives, spiro-isatin derivatives, spiro

• [DISM][CCl3COO] (18) and [Dsim][CF3COO] (19) ILs were utilized as recyclable, efficient, and eco-benign catalysts for the three-component one-pot condensations towards a variety of 1,8-dioxodecahydroacridine derivatives 22 and 14H-dibenzo[a,j]xanthene derivatives 24 in short reaction times under solvent

• 2,2'-bipyridine 25 using the reaction of chlorosulfonic acid and 2,2'-bipyridine as well as its application for the synthesis of the various xanthene derivatives 24, 27, and 28 [41]. In another study, the sulfonated imidazole 26 was prepared via the dropwise addition of chlorosulfonic acid to a

Synthesis of new p-tert-butylcalix[4]arene-based polyammonium triazolyl amphiphiles and their binding with nucleoside phosphates

• Vladimir A. Burilov,
• Guzaliya A. Fatikhova,
• Mariya N. Dokuchaeva,
• Ramil I. Nugmanov,
• Diana A. Mironova,
• Pavel V. Dorovatovskii,
• Victor N. Khrustalev,
• Svetlana E. Solovieva and
• Igor S. Antipin

Beilstein J. Org. Chem. 2018, 14, 1980–1993, doi:10.3762/bjoc.14.173

• ratio of the intensities of the first and third bands (373 and 384 nm, respectively) in its emission spectrum [40]. EY, an anionic xanthene dye, also can be used for CAC determination as its absorption spectrum shows a shift of the maximum absorption wavelength (λmax) in the presence of micelles or

• hydrophobic interactions with hydrophobic regions of calixarene aggregates that are typical for xanthene dyes [41]. The length of the alkyl chains in 10a,b does not affect the complex stoichiometry. Compounds 12a,b at concentrations below the CAC form dye–calixarene complexes of 2:1 stoichiometry [(X2

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

Synthesis and spectroscopic properties of β-meso directly linked porphyrin–corrole hybrid compounds

• Baris Temelli and
• Hilal Kalkan

Beilstein J. Org. Chem. 2018, 14, 187–193, doi:10.3762/bjoc.14.13

• ) position of substitution (meso or β). So far, corrole macrocyles have been integrated into porphyrin conjugates via anthracene, biphenylene, xanthene, dibenzofuran [16][17][18][19][20], amide [21] and triazole [22][23] linkers. Despite the large number of studies on the synthesis of porphyrin–corrole

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• /bjoc.13.52 Abstract Eosin B (EoB) and eosin Y (EoY), two xanthene dye derivatives with photosensitizing ability were prepared in high purity through an improved synthetic route. The dyes were grafted to a 6-monoamino-β-cyclodextrin scaffold under mild reaction conditions through a stable amide linkage

• aqueous medium, which precludes any response to light excitation. Keywords: β-cyclodextrins; fluorescence; photodynamic therapy; photosensitizers; singlet oxygen; xanthene; Introduction Cyclodextrins (CDs) are cyclic oligosaccharides able to form host–guest inclusion complexes with drugs and this

• xanthene-type PSs in conjugation with CDs is very scarce. The reasons behind this fact are most probably the difficulties in selective CD functionalization and limitations in xanthene-dye modification. Xanthene dyes can be introduced into the CD scaffold most easily through an ester linkage between the

Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

New synthetic strategies for xanthene-dye-appended cyclodextrins

• Milo Malanga,
• Andras Darcsi,
• Mihaly Balint,
• Gabor Benkovics,
• Tamas Sohajda and
• Szabolcs Beni

Beilstein J. Org. Chem. 2016, 12, 537–548, doi:10.3762/bjoc.12.53

• University, Hlavova 8, 12843 Prague 2, Czech Republic 10.3762/bjoc.12.53 Abstract Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore

• can reversibly cyclize. In this context we report a green approach for the synthesis of switchable xanthene-dye-appended cyclodextrins based on the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). By using 6-monoamino-β-cyclodextrin and commercially available

• supramolecular assembly of the xanthene-dye-appended cyclodextrins were developed based on the set of data collected by the extensive NMR characterization. Keywords: DMT-MM; fluorescein; rhodamine; supramolecular assembly; Introduction Cyclodextrins (CDs) are cyclic oligosaccharides consisting of 6, 7 or 8

Synthesis and spectroscopic properties of β-triazoloporphyrin–xanthone dyads

• Dileep Kumar Singh and
• Mahendra Nath

Beilstein J. Org. Chem. 2015, 11, 1434–1440, doi:10.3762/bjoc.11.155

• diporphyrin analogues [20][28][29][30]. Xanthene-9H-ones are an important class of oxygen-containing heterocycles and are mainly found as secondary metabolites in higher plants and microorganisms. The naturally occurring and synthetic xanthones possess diverse pharmacological activities [31][32][33][34

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• diarylmethanes, acridine, xanthene, thioxanthene, etc. It was based on the generation of a benzotriazole-stabilized carbanion followed by oxidation of this carbanion by copper iodide to form a radical. Subsequent elimination of nitrogen followed by ring closure yielded phenanthridine (Scheme 2) [13][14]. In the

Organic synthesis using photoredox catalysis

• Axel G. Griesbeck

Beilstein J. Org. Chem. 2014, 10, 1097–1098, doi:10.3762/bjoc.10.107

• other Ru or Ir complexes) with strong MLCT transitions, organic dyes such as xanthene, porphyrine or phthalocyanine dyes (e.g., eosin Y), and colloidal semiconductor particles (e.g., TiO2) [1][2][3][4][5][6][7][8][9]. In addition, combinations of light-absorbing materials have been studied such as dye

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• larger scales. However, the recent pursuit of environmentally more benign photoactive catalysts has focused on much cheaper metal-free dyes. Several commercially available fluorescein and xanthene dyes have been successfully applied to photoredox reactions, including radical substitutions at α-amino, β

Synthesis of axially chiral gold complexes and their applications in asymmetric catalyses

• Yin-wei Sun,
• Qin Xu and
• Min Shi

Beilstein J. Org. Chem. 2013, 9, 2224–2232, doi:10.3762/bjoc.9.261

• [55]. Then, (S)-7 was obtained by treatment of (S)-6 with Tf2O and pyridine in DCM in 99% yield. The usage of dimethylbis(diphenylphosphino)xanthene (XantPhos) as a ligand and Pd2(dba)3 as a catalyst in the presence of Cs2CO3, facilitated the reaction of (S)-7 with benzylamine in toluene to give the

Surfactant catalyzed convenient and greener synthesis of tetrahydrobenzo[a]xanthene-11-ones at ambient temperature

• Pravin V. Shinde,
• Amol H. Kategaonkar,
• Bapurao B. Shingate and
• Murlidhar S. Shingare

Beilstein J. Org. Chem. 2011, 7, 53–58, doi:10.3762/bjoc.7.9

• ]xanthen-11-one using tetradecyltrimethylammonium bromide (TTAB) at room temperature in water is described. Keywords: green chemistry; in-water synthesis; surfactant; tetradecyltrimethylammonium bromide (TTAB); xanthene; Introduction The development of novel synthetic methodologies to facilitate the

• biodynamic heterocycles and their synthesis has received much attention especially in the field of medicinal/pharmaceutical chemistry due to their wide range of biological/pharmacological activities, e.g., antibacterial [6], anti-inflammatory [7] and antiviral [8]. Some xanthene based compounds have found

• application as antagonists for inhibiting the action of zoxalamine and in photodynamic therapy [9][10]. In addition, their derivatives can be used as dyes [11][12], pH sensitive fluorescent materials for the visualization of biomolecular assemblies [13] and in laser technologies [14][15]. Among the xanthene