Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• . Šindelář and Lizal [36] also presented the synthesis of hybrid macrocycles containing glycoluril and aromatic units. In 2014, Keinan et al. [37] reported a series of macrocycles, consisting of alternating urea or thiourea and phenol units, namely, multifarenes. Hitherto, multifarenes and their derivatives

Selective sulfonylation and isonitrilation of para-quinone methides employing TosMIC as a source of sulfonyl group or isonitrile group

• Chuanhua Qu,
• Run Huang,
• Yong Li,
• Tong Liu,
• Yuan Chen and
• Guiting Song

Beilstein J. Org. Chem. 2021, 17, 2822–2831, doi:10.3762/bjoc.17.193

• reactions [35][36][37][38][39], etc. In this context, the electron-rich aryl(phenol)methane isonitrile may be a new active unit, which can be seen from the previous case of p-QMs type reaction [40][41][42][43][44][45][46][47][48][49][50][51] and the above-mentioned properties of isocyanide. Herein, we

• reaction without adding bases, and unexpectedly found Ag salts could catalyze the 1,6-conjugate addition of TosMIC (2a) and p-QM 1a to provide aryl(phenol)methane isonitrile 4a under base-free conditions (Table 1, entries 6–8). When the silver salt was removed from the reaction conditions, the reaction did

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• , according to Temel and co-workers who studied a similar scaffold, namely, 4-bromo-2-((quinoline-8-yl)methyl)phenol [27], no imine–hemiaminal tautomer peak transition was observed for the Schiff bases 3. In general, there were slightly significant changes in the transitions according to the changes in the

• -Methyl-4-(trifluoromethyl)quinolin-6-yl)imino)methyl)phenol (3aa): Yellow solid, yield 20%; mp 129–132 °C; 1H NMR (400 MHz, CDCl3) δ 12.98 (s, 1H, OH), 8.72 (s, 1H, CH=N), 8.15 (d, J = 8.9 Hz, 1H, H-8), 7.85 (bs, J = 2.1 Hz, 1H, H-5), 7.74 (dd, J = 9.0, 2.3 Hz, 1H, H-7), 7.61 (s, 1H, H-3), 7.48–7.39 (m

• ]+ calcd for C18H14F3N2O, 331.1053; found, 331.1037. (E)-2-(((2-Phenyl-4-(trifluoromethyl)quinolin-6-yl)imino)methyl)phenol (3ba): Yellow solid, yield 90%; mp 183–186 °C; 1H NMR (600 MHz, CDCl3) δ 12.96 (s, 1H, OH), 8.71 (s, 1H, CH=N), 8.27 (d, J = 8.9 Hz, 1H, H-8), 8.20–8.14 (m, 3H, Ph, H-3), 7.87 (bs, 1H

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

• afforded products 46 in moderate to good yields (50–97%), excellent diastereoselectivities (>95:5 dr), and high enantioselectivities (91:9 to 98:2 er, Scheme 15). The control experiments showed that the N–H group in naphthylindoles, the OH group in phenol, and the carboxylate group in azodicarboxylate play

• 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

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• utilization of the ethoxycarbonyl group for phenol protection. The main objective of this concept was, that after successful N-acyl-Pictet–Spengler cyclization two remaining pairs of transformations might be performed in one single transformation each: route A comprises reduction with lithium alanate, and

• should lead to an N-methyl group and to reductive cleavage of the carbonate-protected phenol(s); route B is based on treatment with an alkyllithium compound [26], which should remove all ethoxycarbonyl groups and provide N-nor analogues of the products obtained in route A (Figure 3). The required

• control) gave the desired racemic N-ethoxycarbonyl-1-benzyltetrahydroisoquinolines 5a–h with intact ethoxycarbonyl protection of the phenolic groups (Table 2). Simultaneous phenol deprotection and reduction of the carbamate group (route A) to an N-methyl group was accomplished by lithium alanate reduction

Synthesis of highly substituted fluorenones via metal-free TBHP-promoted oxidative cyclization of 2-(aminomethyl)biphenyls. Application to the total synthesis of nobilone

• Ilya A. P. Jourjine,
• Lukas Zeisel,
• Jürgen Krauß and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2668–2679, doi:10.3762/bjoc.17.181

• reaction to give the hydroxyfluorenone 10t (Scheme 6) was unsuccessful, suggesting that here TBHP chemoselectively reacts with the phenolic group to generate non-identifiable products. In order to provide an access to phenolic fluorenones as well, some commonly used phenol protecting groups were tested

• -radical reagents [62]. An extremely poor yield was further obtained with methylenedioxy substrate 15p. Our application of this new protocol to the first total synthesis of the natural product nobilone (1d) is depicted in Scheme 7. The commercially available phenol 16 was TBS-protected to give compound 17

• Suzuki cross-coupling reactions, followed by reduction or reductive amination. The oxidative cyclization conditions are compatible with many functional groups on the aromatic rings (methoxy, chloro, cyano, nitro, and phenol protecting groups like TBS and SEM – but not benzyl and methylenedioxy

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds

• Sumana Mandal,
• Raju D. Chaudhari and
• Goutam Biswas

Beilstein J. Org. Chem. 2021, 17, 2348–2376, doi:10.3762/bjoc.17.153

• frameworks from various tosylanilinoallyl acetals. 4H-Chromene derivatives were also synthesized starting from phenol derivatives (Scheme 38). Cyclization involving alkynes (-C≡C-) Marson et al. had developed the synthesis of substituted furans 133a–c promoted by catalytic use of Hg(II) salt through

Synthesis of phenanthridines via a novel photochemically-mediated cyclization and application to the synthesis of triphaeridine

• Songeziwe Ntsimango,
• Kennedy J. Ngwira,
• Moira L. Bode and
• Charles B. de Koning

Beilstein J. Org. Chem. 2021, 17, 2340–2347, doi:10.3762/bjoc.17.152

• with O-phenylhydroxylamine as reagent were not successful and only resulted in the formation of the benzonitriles 16a, 16c and 16e. Presumably, the oximes were formed but were unstable and the facile elimination of phenol took place to liberate the benzonitriles. Finally, the use of this methodology

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

• synthesized the novel unactivated alkenes 4a–l containing three aryl groups as the starting materials. The synthesis of 4a is demonstrated in Scheme 1. First, 2-phenoxybenzaldehyde (1a) was synthesized by coupling reaction of phenol with commercial 2-fluorobenzaldehyde. This reaction was carried out with very

• Büchi Melting Point B-540 apparatus. Scope of substrates for intramolecular FCA by activation of 4a–l and their isolated yields. aConditions: 4a–l (0.1 mmol) and TFA (10 mol %) in dry CH2Cl2 (1 mL) were stirred at room temperature for 1–24 hours. bYield of isolated product. Synthesis of 4a: (i) phenol

Preparation of mono-substituted malonic acid half oxyesters (SMAHOs)

• Tania Xavier,
• Sylvie Condon,
• Christophe Pichon,
• Erwan Le Gall and
• Marc Presset

Beilstein J. Org. Chem. 2021, 17, 2085–2094, doi:10.3762/bjoc.17.135

• . SMAHOs bearing classical ester groups could be obtained in moderate yields (iPr: 51%; Bn: 53%; allyl: 52%) and the use of less nucleophilic alcohols such as t-BuOH, 2,2,2-trifluoroethanol, (−)-menthol, and phenol led to decreased yields (37%, 34%, 28%, and 17%, respectively). More functionalized alcohols

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

• biologically active molecules (22 and 23) (Scheme 9A) [92]. Interestingly, the same conditions could be used for benzene hydroxylation to obtain phenol but were ineffective with benzene rings bearing either electron-donating or electron-withdrawing substituents. Notably, the catalyst could be reused five times

• reaction suggested it goes through a radical pathway. Similar to the oxidation of alkanes to give alcohols and carbonyl compounds, vanadium complexes have been reported to mediate the hydroxylation of arenes, including the obtaining of phenol from benzene. However, most mechanistic studies provided

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

• -4j < unsubstituted 4a < 3,5-diCl 4t < 2,6-diCl 4r < pentachloro 4v, in good agreement with the decreasing order of the pKa values of the pyridines. For example, in order to fluorinate phenol, triMe 5-4j needed heating at 100 °C in a haloalkane solvent for 24 h, whereas pentachloro 5-4v required only

• aromatics such as phenol, cresol, and naphthalene were fluorinated in chloroform at 22 °C (Scheme 18). The N-F imide reagent 7-1a fluorinated the sodium salt of diethyl 1-methylmalonate at −10 °C to give the corresponding fluoro product in high yield (96%). Later (1991 and 1992), the same laboratory

• shown in Scheme 40, the 18-2 pyridinium series proved to be effective fluorinating agents for a wide range of substrates. Moreover, an extremely high ortho-selectivity was observed in the fluorination of phenol. This could be attributed to a hydrogen-bonding interaction between the sulfonate anion and

A recent overview on the synthesis of 1,4,5-trisubstituted 1,2,3-triazoles

• Pezhman Shiri,
• Ali Mohammad Amani and
• Thomas Mayer-Gall

Beilstein J. Org. Chem. 2021, 17, 1600–1628, doi:10.3762/bjoc.17.114

• -triazole-based phenol or alcohol coordinates to the Pd center to form complex 158. Then, the electrophilic palladation of the 1,2,3-triazole ring occurs to achieve Pd(II) intermediate 159. Isocyanide migrates to 159 to obtain the seven‐ or eight‐membered palladium cycle 160. The reductive elimination of

Breaking paracyclophane: the unexpected formation of non-symmetric disubstituted nitro[2.2]metaparacyclophanes

• Suraj Patel,
• Tyson N. Dais,
• Paul G. Plieger and
• Gareth J. Rowlands

Beilstein J. Org. Chem. 2021, 17, 1518–1526, doi:10.3762/bjoc.17.109

• pathway involves electrophilic addition para to the phenol to form the ipso-substituted nitro 12 compound. Subsequent rearrangement of the nitro species 12 to the nitrito dienone 13, by homolysis and recombination of the radical pair, is followed by hydrolysis to furnish alcohol 6 [70]. Addition of the

Co-crystallization of an organic solid and a tetraaryladamantane at room temperature

• Fabian Rami,
• Jan Nowak,
• Felix Krupp,
• Wolfgang Frey and
• Clemens Richert

Beilstein J. Org. Chem. 2021, 17, 1476–1480, doi:10.3762/bjoc.17.103

• as guest molecules. Here we report the co-crystal structures of phenol, which is solid at room temperature, with both 1,3,5,7-tetrakis(2,4-dimethoxyphenyl)adamantane (TDA) and 1,3,5,7-tetrakis(2,4-diethoxyphenyl)adamantane (TEO). The co-crystals were obtained from solutions in dichloromethane by slow

• configuration [18]. One limitation of the EnOC method was that the guest compound to be encapsulated had to be a liquid, so that it could act as solvent for the TAA, which would rapidly crystallize upon cooling of a hot, saturated solution. Here we report two co-crystal structures of TAAs with phenol, obtained

• by crystallization at room temperature, using dichloromethane as solvent. Results We opted for a benzene derivative for our first foray into organic solids to be encapsulated in TAA crystals, because a number of benzene derivatives have been found in EnOCs in the past [13][14][15]. Phenol was

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

• hue dependent on the structure of the phenol. The mechanism of many color reactions popular in the 19th century is rather complex, and the one involved in the Schiff test of aldehyde is still not completely clear, despite the relevance in medical histology [22]. The report by Schiff on the Guareschi

• chloroform–phenol reaction attracted the attention of Karl Reimer (1845–1883) and Ferdinand Tiemann (1848–1899), who set out to investigate the chemistry involved in the color formation, eventually discovering the phenol formylation that bears their name [6]. The Guareschi reaction, then extensively applied

• to the identification of pharmaceutical phenols by Sigmund Lustgarten, is carried out under anhydrous conditions, either on an alkaline salt of the phenol or by adding solid KOH or NaOH to a chloroform solution of the phenol [5][21]. Reimer and Tiemann discovered that, in the presence of water, the

Recent advances in palladium-catalysed asymmetric 1,4–additions of arylboronic acids to conjugated enones and chromones

• Jan Bartáček,
• Jan Svoboda,
• Martin Kocúrik,
• Jaroslav Pochobradský,
• Alexander Čegan,
• Miloš Sedlák and
• Jiří Váňa

Beilstein J. Org. Chem. 2021, 17, 1048–1085, doi:10.3762/bjoc.17.84

• was chosen DMF, although the use of polar aprotic solvents usually leads to products of the oxidative Heck reaction. The authors noticed a significant reduction of Pd(II) to Pd(0) (by secondary processes such as oxidative homocoupling or oxidation of boronic acid to the corresponding phenol). The Pd(0

Application of the Meerwein reaction of 1,4-benzoquinone to a metal-free synthesis of benzofuropyridine analogues

• Rashmi Singh,
• Tomas Horsten,
• Rashmi Prakash,
• Swapan Dey and
• Wim Dehaen

Beilstein J. Org. Chem. 2021, 17, 977–982, doi:10.3762/bjoc.17.79

• spectrum of 15 showed two apparent singlets separately at δH 7.86 and δH 8.35, which confirmed that the hydrogen atoms of the phenol ring had a para-relationship. The 1H NMR spectrum of compound 14 was similar to that of compound 15 concerning the pyridine part. However, two separate doublet signals

Metal-free glycosylation with glycosyl fluorides in liquid SO₂

• Krista Gulbe,
• Jevgeņija Lugiņina,
• Edijs Jansons,
• Artis Kinens and
• Māris Turks

Beilstein J. Org. Chem. 2021, 17, 964–976, doi:10.3762/bjoc.17.78

• -glycosides to demonstrate the scope of acceptors compatible with our glycosylation conditions (Scheme 1). Most of the primary alcohols (2a, 2d–3f) were glycosylated in high yields (up to 91%). In the case of less reactive secondary alcohols (2b, 2h, 2j, 2k) and phenol (2l) better yields were obtained when

• 3.0 equiv of nucleophile were used. For example, the yield of mannoside 3l was increased from 34% to 79% when the amount of phenol (2l) was changed from 1.0 to 3.0 equiv. Similar reactivity relationships were observed in a series of thiols (2c, 2m–p), but the glycosylation yields comparing to the

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• phenol-tethered alkenyl alcohol 310 and o-aminobenzaldehyde 311 using chiral phosphoric acids (Scheme 72) [114]. Diverse functionalized trans-fused pyranotetrahydroquinoline derivatives 312 were synthesized in excellent yield and selectivity (up to 99% yield and 99% ee). List et al. reported a chiral

Enhanced target cell specificity and uptake of lipid nanoparticles using RNA aptamers and peptides

• Roslyn M. Ray,
• Anders Højgaard Hansen,
• Maria Taskova,
• Bernhard Jandl,
• Jonas Hansen,
• Citra Soemardy,
• Kevin V. Morris and
• Kira Astakhova

Beilstein J. Org. Chem. 2021, 17, 891–907, doi:10.3762/bjoc.17.75

• removal of the side-chain protecting groups was achieved by using trifluoroacetic acid (TFA)/phenol/water/triisopropylsilane (TIPS) 88:5:5:2 (3 × 60 min). After cleavage, the remaining resin was extracted with DCM (2 × 10 min). All DCM extracts and TFA cleavages were combined, and the resulting mixture

Synthesis of bis(aryloxy)fluoromethanes using a heterodihalocarbene strategy

• Carl Recsei and
• Yaniv Barda

Beilstein J. Org. Chem. 2021, 17, 813–818, doi:10.3762/bjoc.17.70

• (difluoromethoxy)arenes, while the reaction with dichlorocarbene gives salicylaldehydes via hydrolysis of an ortho-dichloromethylphenol: the Reimer–Tiemann reaction. The literature, other than this single reference with pentafluorophenol [6], is bereft of references to the capture of heterodihalocarbenes by phenol

• limitations that we had encountered in terms of yield and regioselectivity were presumably specific to the ambident nucleophile 6. We considered that a different ambident nucleophile, a phenol, might also give unusual selectivity for production of a bis(aryloxy)fluoromethane over a Reimer–Tiemann formylation

• aldehydes were present, and that unreacted phenol comprised a further 26% of the mass balance. Thus, the reactivity of fluorobromocarbene in this case mirrored the tendency of difluorocarbene to react with phenoxides to form dihalomethyl phenyl ethers, rather than forming aldehydes as with dichlorocarbene

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

• them in view of their great significance in organic synthesis. In 2018, Miyake and colleagues [50] found a protocol for the preparation of (Z)-2-iodovinyl phenyl ether 168 by utilizing ethynylbenziodoxol(on)e (EBX) 167 and phenol derivative 166 (Scheme 59). Due to the lack of significant electronic

• effects of phenol, a variety of phenols, including electron-donor and electron-withdrawing groups, were been converted into corresponding 2-iodovinyl phenyl ethers in moderate to excellent yield with high regio- and stereoselectivities. According to the analysis of the mechanism (Scheme 60), a molecule of

• phenol anion is first added to the alkyne group of an EBX, forming electron acceptor 169, which causes the destabilization of the C–I bond. Then, electron acceptor 169 forms an EDA complex with phenol anion, along with light-promoted electron transfer occurring. Thereby, the C–I bond and the I–O bond

Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• and the p-quinone methides part was reduced to phenol. After the phenolic part of 13a,b was oxidized to p-quinone methides with PIFA, 14a and 14b were synthesized in 87% and 91% yields, respectively. Moreover, by submitting 13a,b to reductive conditions in presence of Zn, the pyridazine part of 13a,b

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

• developed, using a solvent or molecular hydrogen as cleaving agents [81]. The main solvolytic process include: hydrolysis (water) alcoholysis (methanol, ethanol, 1-butanol, 2-ethyl-1-hexanol, phenol) glycolysis (ethylene glycol (EG), 1,2-propanediol (PD), 1,3- and 1,4-butanediol (BD)), diethylene glycol