Electroreductive coupling of 2-acylbenzoates with α,β-unsaturated carbonyl compounds: density functional theory study on product selectivity

• Naoki Kise and
• Toshihiko Sakurai

Beilstein J. Org. Chem. 2022, 18, 956–962, doi:10.3762/bjoc.18.95

• -dihydronaphthalene-1,4-diones (Scheme 1) [5]. In addition, we disclosed that the electroreduction of phthalimides with α,β-unsaturated carbonyl compounds under the same conditions and subsequent treatment with trifluoroacetic acid (TFA) produced 3- and 2-substituted 4-aminonaphthalen-1-ols (Scheme 2) [6]. In this

Synthetic strategies for the preparation of γ-phostams: 1,2-azaphospholidine 2-oxides and 1,2-azaphospholine 2-oxides

• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 889–915, doi:10.3762/bjoc.18.90

• -methylphenol (DTBMP)), trifluoroacetic acid (TFA), and 4-methylbenzenesulfonic acid (TsOH) as the proton donors. The results indicated that the less bulky methanol, more bulky DTBMP, more sterically hindered and acidic TsOH show certain regio- and stereoselectivities, which also depended upon the steric

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• very small amount of trifluoroacetic acid (TFA). As shown in Figure 6c, the PL spectra in solution were dominated by the amount of TFA. At the appropriate ratio, the solution-processed device with compound 7 as single emission layer generated broadband white light emission under EL process (see Figure

Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• )2-bb-DSS), from which the TMS group could easily be removed by trifluoroacetic acid and replaced by bromine [27]. Another isomer of DSS, diseleno[3,2-b:2′,3′-d]selenophene (tt-DSS) has been successively synthesized from selenophene [28][29]. Among the limited fused aromatic compounds containing

New synthesis of a late-stage tetracyclic key intermediate of lumateperone

• Mátyás Milen,
• Bálint Nyulasi,
• Tamás Nagy,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2022, 18, 653–659, doi:10.3762/bjoc.18.66

• to the hydrazine derivative 4, followed by a Fischer indole synthesis with ethyl 4-oxopiperidine-1-carboxylate (5) provided tetracyclic compound 6. Its reduction with sodium cyanoborohydride in trifluoroacetic acid (TFA) to cis-indoline derivative (±)-7, followed by N-methylation [(±)-8] and

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• -workers [46]. They reacted the amine axle 11 with the axially chiral macrocycle (rac)-12 in a mixture of dichloromethane and trifluoroacetic acid in order to generate the pseudorotaxane (rac)-13. Then, an isocyanate stopper was added for the formation of the [2]rotaxane (rac)-14 in a yield of 42%. The X

Menadione: a platform and a target to valuable compounds synthesis

• Acácio S. de Souza,
• Ruan Carlos B. Ribeiro,
• Dora C. S. Costa,
• Fernanda P. Pauli,
• David R. Pinho,
• Matheus G. de Moraes,
• Fernando de C. da Silva,
• Luana da S. M. Forezi and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 381–419, doi:10.3762/bjoc.18.43

• in Scheme 17 below the optimized reaction conditions are shown for the synthesis of compounds 62 and 64 (Scheme 17) [110]. In 2019, Sultan and co-workers described a methodology for the synthesis of quinone derivatives using a combination of potassium persulfate, trifluoroacetic acid (TFA), and blue

• menadione (10) in trifluoroacetic acid under ethanol reflux conditions (Scheme 26) to synthesize acylhydrazones 81 in 63–91% yield. In view of the different structures that compounds 81a–e could adopt, after analysis by 2D NMR-NOESY spectra, it was found that all products were obtained as E-geometrical

Amamistatins isolated from Nocardia altamirensis

• Till Steinmetz,
• Wolf Hiller and
• Markus Nett

Beilstein J. Org. Chem. 2022, 18, 360–367, doi:10.3762/bjoc.18.40

• supplemented with 0.1% (v/v) trifluoroacetic acid. The gradient conditions were as follows: from 40% methanol to 70% in 5 minutes followed by an increase to 90% in 20 minutes, kept at 90% for 10 minutes. The flow rate was set to 10 mL/min. The elution of compounds was monitored with a diode array detector

• . Again, CAS active fractions were collected. For the final purification step, a Nucleodur C18 Isis column (250 × 10 mm, 5 μm, Macherey-Nagel) was used with a linear gradient from 25% to 90% acetonitrile in water + 0.1% (v/v) trifluoroacetic acid over a period of 30 min. The flow rate was set to 6 mL/min

Regioselective synthesis of methyl 5-(N-Boc-cycloaminyl)-1,2-oxazole-4-carboxylates as new amino acid-like building blocks

• Jolita Bruzgulienė,
• Greta Račkauskienė,
• Aurimas Bieliauskas,
• Vaida Milišiūnaitė,
• Miglė Dagilienė,
• Gita Matulevičiūtė,
• Vytas Martynaitis,
• Sonata Krikštolaitytė,
• Frank A. Sløk and
• Algirdas Šačkus

Beilstein J. Org. Chem. 2022, 18, 102–109, doi:10.3762/bjoc.18.11

• and 4g with trifluoroacetic acid. Removal of the Boc protection in the presence of CF3COOH in dichloromethane yielded trifluoroacetates 6a and 6b as white solids (Scheme 4). A single crystal of 6b was prepared via recrystallization from dichloromethane for X-ray diffraction analysis [48]. The

Synthesis of new pyrazolo[1,2,3]triazines by cyclative cleavage of pyrazolyltriazenes

• Nicolai Wippert,
• Martin Nieger,
• Claudine Herlan,
• Nicole Jung and
• Stefan Bräse

Beilstein J. Org. Chem. 2021, 17, 2773–2780, doi:10.3762/bjoc.17.187

• , failed under similar procedures. Abbreviations TFA, trifluoroacetic acid; DMSO, dimethyl sulfoxide; THF, tetrahydrofuran, TLC, thin-layer chromatography, LC–MS, liquid chromatography/mass spectrometry. Structural differences of several known (2–4) and so far unknown (5 and 6) pyrazolo[3,4-d][1,2,3]-3H

N-Sulfinylpyrrolidine-containing ureas and thioureas as bifunctional organocatalysts

• Viera Poláčková,
• Dominika Krištofíková,
• Boglárka Némethová,
• Renata Górová,
• Mária Mečiarová and
• Radovan Šebesta

Beilstein J. Org. Chem. 2021, 17, 2629–2641, doi:10.3762/bjoc.17.176

• concomitant formation of the urea or thiourea moiety, respectively. The corresponding N-Boc-protected precursors of the desired catalysts, 5a and 5b, were obtained in low to good yields. The removal of the Boc-protecting group with trifluoroacetic acid afforded the desired N-sulfinylthioureas (S,R)- and (S,S

Recent advances in organocatalytic asymmetric aza-Michael reactions of amines and amides

• Pratibha Sharma,
• Raakhi Gupta and
• Raj K. Bansal

Beilstein J. Org. Chem. 2021, 17, 2585–2610, doi:10.3762/bjoc.17.173

• 12 in good yields (75–95%) with up to 99% ee. Several sulfonic acids and carboxylic acids were tested as co-catalysts and trifluoroacetic acid (TFA) was found to give the best results [28]. Here the role of the co-catalyst is to assist in the formation of the iminium intermediate (Table 2) [29]. It

• -catalysts and trifluoroacetic acid and diphenyl hydrogenphosphate (DPP) were found to give the best results [30]. Cheng et al. reported an intramolecular 6-exo-trig aza-MR of hydroxylamine-derived enone 15 for the synthesis of chiral 3-substituted 1,2-oxazinanes 16. The catalyst 11 was used in this case

Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones

• Robin Klintworth,
• Garreth L. Morgans,
• Stefania M. Scalzullo,
• Charles B. de Koning,
• Willem A. L. van Otterlo and
• Joseph P. Michael

Beilstein J. Org. Chem. 2021, 17, 2543–2552, doi:10.3762/bjoc.17.170

• 15a was heated in capped tubes under microwave conditions [35][36][37] for 10 minutes in solvents such as ethanol (100 °C), xylene (150 °C) or N,N-dimethylformamide (150 °C) (Table 1, entries 3–5). Dissolution in neat protic or Lewis acids (e.g., hydrochloric acid, trifluoroacetic acid

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

• side afforded 6-membered chromene derivatives 75 but no thiochromene derivatives were observed [76]. Compound 75 on refluxing with trifluoroacetic acid isomerized to form exocyclic trans-compound 76. It was reported that 1,4-di(arylthiol)-2-butyne derivatives only afforded usual Hg(II)-salt-mediated

Synthesis of O⁶-alkylated preQ₁ derivatives

• Laurin Flemmich,
• Sarah Moreno and
• Ronald Micura

Beilstein J. Org. Chem. 2021, 17, 2295–2301, doi:10.3762/bjoc.17.147

• 6. Finally, the auxiliary functions were cleaved using trifluoroacetic acid (TFA) in dichloromethane and the target compound 2, m6preQ1, was isolated as TFA salt. The here established path to synthesize m6preQ1 offers high flexibility with respect to the O6 substituent. We demonstrate this by

• & 112.6 (C(arom, DMTr)), 74.5 (CAr3(DMTr)), 70.3 (CAr3(DMTr)), 55.3 (H3CO(DMTr)), 53.4 (H3CO(6)), 38.9 (H2CC(7)) ppm; ESIMS (m/z): [M + H]+ calcd, 798.3650; found, 798.3629. O6-Methyl preQ1 (trifluoroacetate salt) (2). Compound 6 (120 mg, 150 µmol) was dissolved in 500 µL dichloromethane. Trifluoroacetic

• acid (60 µL, 0.75 mmol) and 10 µL water were added. After 45 minutes the reaction was quenched by the addition of 100 µL methanol. Afterwards the solvents were removed in vacuo. The residue was triturated five times with dichloromethane and dried on high vacuum to give 35 mg of compound 2 (76%) as a

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

• 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

• hours. As a result, an alkene compound was used for activation with TFA in the synthesis of xanthene through intramolecular Friedel–Crafts alkylation for the first time. Keywords: alkene activation; intramolecular Friedel–Crafts alkylation; trifluoroacetic acid; xanthene; Introduction The interest in

• Brønsted acids and Lewis acids as catalysts (Table 1) to develop an intramolecular FCA protocol with activating alkenes effectively and economically in order to obtain some originally substituted arylxanthenes under mild conditions for the first time. We found that, among these acids, trifluoroacetic acid

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• , Fukutomi, and Nakayama [19] reported the synthesis of what they described as ‘true polyazulene’ through a cationic polymerization reaction. Their protocol involved heating the trifluoroacetic acid (TFA) solution of azulene (1) followed by treatment with triethylamine to obtain a brown polymeric product

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

• -dibromo-2,5-dimethylbenzene (101), with subsequent Suzuki cross-coupling of compound 102 with potassium vinyltrifluoroborate, removal of the N-Boc protecting group of 103 with trifluoroacetic acid, and borylative cyclization of precursor aminostyrene 104 [58]. Sparr’s research group developed the 1,5

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

• , laxative, and diuretic activities [97]. Trifluoroacetic acid was used as an additive, being suggested to avoid oxidation of the amine moiety by the formation of the corresponding ammonium salt. Similar conditions have been reported for an alternative synthesis of both enantiomers of the antitumor

Iodine-catalyzed electrophilic substitution of indoles: Synthesis of (un)symmetrical diindolylmethanes with a quaternary carbon center

• Thanigaimalai Pillaiyar,
• Masoud Sedaghati,
• Andhika B. Mahardhika,
• Lukas L. Wendt and
• Christa E. Müller

Beilstein J. Org. Chem. 2021, 17, 1464–1475, doi:10.3762/bjoc.17.102

• ]. However, synthetic methods for efficient synthesis of unsymmetrical 3,3'-DIMs with a quaternary carbon center, including trifluoromethyl-substituted 3,3'-DIMs, are still rare. Sasaki et al. reported the reaction of trifluoromethyl(indolyl)phenylmethanols with indoles in the presence of trifluoroacetic

• acid (TFA) and CHCl3 (Figure 2) [36]. Very recently, Ling et al. reported the same reaction in the presence of Ga(OTf)3 in acetonitrile (Figure 2) [37]. Although these methods are certainly useful, they have several undeniable drawbacks, including the use of heavy-metal catalysts and the necessity of

Double-headed nucleosides: Synthesis and applications

• Vineet Verma,
• Jyotirmoy Maity,
• Vipin K. Maikhuri,
• Ritika Sharma,
• Himal K. Ganguly and
• Ashok K. Prasad

Beilstein J. Org. Chem. 2021, 17, 1392–1439, doi:10.3762/bjoc.17.98

• -6-ynofuranoses 88a,b The ʟ-ido- and ᴅ-gluco precursors 88a,b were reacted with trifluoroacetic acid followed by acetic anhydride to afford the 1,2,3,5-tetra-O-acetyl nucleoside analogs 89a and 89b, respectively. Montgomery and Hewson base coupling reaction [60] of 1,2,3,5-tetra-O-acetyl nucleoside

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

• ]. The reaction that took 24 hours to run to completion in batch, reached 100% conversion after just 20 minutes in flow (Scheme 1). The Swern oxidation under trifluoroacetic acid-promoted conditions is often problematic due the formation of side products. In batch, benzaldehyde (17) was formed in 49

Beyond ribose and phosphate: Selected nucleic acid modifications for structure–function investigations and therapeutic applications

• Christopher Liczner,
• Kieran Duke,
• Gabrielle Juneau,
• Martin Egli and
• Christopher J. Wilds

Beilstein J. Org. Chem. 2021, 17, 908–931, doi:10.3762/bjoc.17.76

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

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

• that electron transfer is accompanied by proton transfer in the process (Scheme 43). In 2020, Stephenson and colleagues [14] employed 2-methoxynaphthalene (124) and acylated ethyl isonicotinate N-oxide obtained from 125 and trifluoroacetic acid anhydride to form EDA complexes for the preparation of