Ortho-ester-substituted diaryliodonium salts enabled regioselective arylocyclization of naphthols toward 3,4-benzocoumarins

• Ke Jiang,
• Cheng Pan,
• Limin Wang,
• Hao-Yang Wang and
• Jianwei Han

Beilstein J. Org. Chem. 2024, 20, 841–851, doi:10.3762/bjoc.20.76

• of butylated hydroxytoluene (BHT) into the template reaction. Remarkably, we observed that the desired product was not formed, suggesting a radical pathway. Subsequently, we investigated the bond-formation sequence in the benzocyclization reaction. A possible intermediate of 3al’ was prepared and

• -oxyl; BHT = butylated hydroxytoluene. Optimization of reaction conditions.a Scope of naphthols and phenols for the synthesis of 3,4-benzocoumarins.a,b. Scope of ortho-ester-substituted diaryliodonium salts.a Supporting Information Supporting Information File 16: Experimental procedures, LC–MS spectra

Copper-promoted C5-selective bromination of 8-aminoquinoline amides with alkyl bromides

• Changdong Shao,
• Chen Ma,
• Li Li,
• Jingyi Liu,
• Yanan Shen,
• Chen Chen,
• Qionglin Yang,
• Tianyi Xu,
• Zhengsong Hu,
• Yuhe Kan and
• Tingting Zhang

Beilstein J. Org. Chem. 2024, 20, 155–161, doi:10.3762/bjoc.20.14

• indicated that both the acylamino and quinoline N motifs played a significant role. On the other hand, the stoichiometric amount of free radical inhibitors, including TEMPO and BHT, could not comprehensively suppress the reaction. Based on these experimental results and previous works [30][31][32], a

Lewis acid-promoted direct synthesis of isoxazole derivatives

• Dengxu Qiu,
• Chenhui Jiang,
• Pan Gao and
• Yu Yuan

Beilstein J. Org. Chem. 2023, 19, 1562–1567, doi:10.3762/bjoc.19.113

• . It was found that the desired product could be obtained in 87% yield (Scheme 4). Next, some control experiments were carried out to study the reaction mechanism. We found that the reaction of compound 3a could not be inhibited by TEMPO and BHT under the standard conditions. Therefore, it is assumed

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

DDQ in mechanochemical C–N coupling reactions

• Shyamal Kanti Bera,
• Rosalin Bhanja and
• Prasenjit Mal

Beilstein J. Org. Chem. 2022, 18, 639–646, doi:10.3762/bjoc.18.64

• performed radical trapping experiments using TEMPO and BHT in the reaction of substrate 1c (Figure 5a). Under the standard reaction conditions in the presence of TEMPO or BHT, the expected product 2c was formed in 66 and 72% yields. These results indicate that a radical pathway may not be involved in the

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

• cyclization was explored. As a radical mechanism appeared very likely, the standard reaction with aqueous TBHP was run in the presence of the radical quenchers TEMPO and BHT (4 equivalents respectively) in separate experiments. While trapping a radical species of interest in form of a TEMPO ester was

Access to highly substituted oxazoles by the reaction of α-azidochalcone with potassium thiocyanate

• Mysore Bhyrappa Harisha,
• Pandi Dhanalakshmi,
• Rajendran Suresh,
• Raju Ranjith Kumar and
• Shanmugam Muthusubramanian

Beilstein J. Org. Chem. 2020, 16, 2108–2118, doi:10.3762/bjoc.16.178

• , the reaction of 1m with potassium thiocyanate 2 under the optimal conditions in the presence of TEMPO furnished azirine and TEMPO, while the same reaction in the presence of BHT afforded the BHT-coupled thiocyanate product (SO-(2,6-di-tert-butyl-4-methylphenyl) (thioperoxocyanate)). These observations

Metal-free synthesis of phosphinoylchroman-4-ones via a radical phosphinoylation–cyclization cascade mediated by K₂S₂O₈

• Qiang Liu,
• Weibang Lu,
• Guanqun Xie and
• Xiaoxia Wang

Beilstein J. Org. Chem. 2020, 16, 1974–1982, doi:10.3762/bjoc.16.164

•  5). When the reaction was conducted in the presence of radical scavengers such as 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) and butylated hydroxytoluene (BHT), the reactions were completely shut down, which indicated that the reaction proceeds through a radical pathway [37][38][39][40][41]. Also

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

• was explained by the decrease of the O–H bond dissociation energy by the electron-donating substituent Y [35][79][80][81][82][83][84]. The result of these reactions depends on the phenol structure. 4-Methylphenol (27a) and 2,6-di-tert-butyl-4-methylphenol (BHT, 27b) gave 4-methyl-4

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• under mild reaction conditions to yield saturated ketones 410 and 411 in good to excellent yields. Hydrogen isotope labelling showed that water was likely the source of hydrogen since no reaction was observed under anhydrous conditions. By contrast, the addition of either TEMPO and BHT to the reaction

KOt-Bu-promoted selective ring-opening N-alkylation of 2-oxazolines to access 2-aminoethyl acetates and N-substituted thiazolidinones

• Qiao Lin,
• Shiling Zhang and
• Bin Li

Beilstein J. Org. Chem. 2020, 16, 492–501, doi:10.3762/bjoc.16.44

• involved in the reaction. Excellent yields of products 3a or 5a were obtained in the presence of the radical scavengers (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), stilbene, or butylated hydroxytoluene (BHT) in the reaction of benzyl bromide with 2-methyl-2-oxazoline or 2-(methylthio)-4,5

Room-temperature Pd/Ag direct arylation enabled by a radical pathway

• Amy L. Mayhugh and
• Christine K. Luscombe

Beilstein J. Org. Chem. 2020, 16, 384–390, doi:10.3762/bjoc.16.36

• reported for decarboxylative coupling between indole and 2-nitrobenzoic acids at 110 °C [18]. Under such conditions, silver carboxylates decompose to produce carbonyl and phenyl radicals, which could explain the origin of nitrobenzene incorporation [19][20]. When the radical trapping agent BHT was added to

• suppressed by the addition of TEMPO and BHT. Moreover, Ph-BHT was observed by GC–MS when BHT was added. Similar to the polymerization trials, coupling was inhibited when the standard conditions were run in the dark. Both the Ph-BHT adduct and continued poor reactivity in the dark provides growing evidence

• published results were replicated, then radical traps were introduced. In these cases, BHT completely eliminated the formation of product 12 and partially inhibited the conversion to product 13. In both cases the arene–BHT adduct was observed by GC–MS as shown in the inset of Scheme 4. While more extensive

Construction of trisubstituted chromone skeletons carrying electron-withdrawing groups via PhIO-mediated dehydrogenation and its application to the synthesis of frutinone A

• Qiao Li,
• Chen Zhuang,
• Donghua Wang,
• Wei Zhang,
• Rongxuan Jia,
• Fengxia Sun,
• Yilin Zhang and
• Yunfei Du

Beilstein J. Org. Chem. 2019, 15, 2958–2965, doi:10.3762/bjoc.15.291

• , method a). When another radical-trapping reagent, BHT, was used, the reaction gave 50% yield of the desired product 2a (Scheme 3, method b). Since the reaction was not greatly suppressed in both cases, we tentatively propose that this dehydrogenative oxidation reaction may undergo both radical and

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• or BHT under the standard conditions, and the reactions were suppressed by radical scavengers, which suggested that the reaction underwent a radical process. The proposed mechanism is depicted in Scheme 9. Initially, the CF3 radical 35 is generated from the Togni reagent II (30) under the action of

• cyclization under transition-metal free conditions. With the addition of a radical scavenger such as TEMPO or BHT, the reaction was suppressed remarkably. In the same year, Dai’s group also reported the ring-opening-initiated tandem cyclization of cyclopropanols 91 with acrylamides 122 or 2-isocyanobiphenyls

Assembly of fully substituted triazolochromenes via a novel multicomponent reaction or mechanochemical synthesis

• Robby Vroemans,
• Yenthel Verhaegen,
• My Tran Thi Dieu and
• Wim Dehaen

Beilstein J. Org. Chem. 2018, 14, 2689–2697, doi:10.3762/bjoc.14.246

• equivalent nitroalkene, 1.2 equivalents of salicylaldehyde and 0.1 equivalents of DABCO as catalyst in the first step at 40 °C, and 2 equivalents of benzyl azide, 2 equivalents of acetic acid, 0.3 equivalents of BHT as antioxidant, 4 Å MS and DMF under argon atmosphere at 120 °C in the second step. Crude NMR

• 4a–g. aReaction conditions for two-step one-pot procedure: 1. 1 (1.2 equiv), 2 (1 equiv), DABCO (0.1 equiv), 1.5 h, 40 °C; 2. 4 (2 equiv), acetic acid (2 equiv), BHT (0.3 equiv), 4 Å MS (50 mg), DMF (0.1 mL), 24 h, 120 °C. bReaction conditions for two-step one-pot procedure with solid

• reaction vial: 1. 1 (1.2 equiv), 2a (1 equiv), DABCO (0.1 equiv), 15 min, 30 Hz; 2. 4a (2 equiv), acetic acid (2 equiv), BHT (0.3 equiv), 4 Å MS (50 mg), DMF (2 mL), 24 h, 120 °C. bReaction time for the first step: 2 h. The overall isolated yields are given for 2 steps. Two-step reaction towards

Cobalt-catalyzed peri-selective alkoxylation of 1-naphthylamine derivatives

• Jiao-Na Han,
• Cong Du,
• Xinju Zhu,
• Zheng-Long Wang,
• Yue Zhu,
• Zhao-Yang Chu,
• Jun-Long Niu and
• Mao-Ping Song

Beilstein J. Org. Chem. 2018, 14, 2090–2097, doi:10.3762/bjoc.14.183

• , benzoquinone (BQ), suppressed the formation of product 3aa. When 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) or 2,6-di-tert-butyl-4-methylphenol (BHT) was added under the standard reaction conditions, a significantly reduced yield (39% or 23%) was obtained (Scheme 3, reaction 2). These facts suggest that a

One-pot preparation of 4-aryl-3-bromocoumarins from 4-aryl-2-propynoic acids with diaryliodonium salts, TBAB, and Na₂S₂O₈

• Teppei Sasaki,
• Katsuhiko Moriyama and
• Hideo Togo

Beilstein J. Org. Chem. 2018, 14, 345–353, doi:10.3762/bjoc.14.22

• the presence of 2,2,6,6-tetramethylpiperidine 1-oxyl radical (TEMPO, 2.0 equiv) or 2,6-di(tert-butyl-p-cresol (BHT, 3.0 equiv) at the second step under the same procedure and conditions, but 3-bromo-4-phenylcoumarin (3Aa) was not obtained at all in both reactions. Thus, the present bromocyclization of

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

A strategic approach to [6,6]-bicyclic lactones: application towards the CD fragment of DHβE

• Tue Heesgaard Jepsen,
• Emil Glibstrup,
• François Crestey,
• Anders A. Jensen and
• Jesper Langgaard Kristensen

Beilstein J. Org. Chem. 2017, 13, 988–994, doi:10.3762/bjoc.13.98

• 91% yield to furnish carboxylic acid 6. The subsequent 6π-electrocyclization performed in refluxing toluene in the presence of a catalytic amount of 2,6-di-tert-butyl-4-methylphenol (BHT) led to lactone 7 in 83% yield. The removal of the Ts-protecting group was initially attempted with SmI2 but

• , 0 °C. ii) NaH, DMF, 0 °C, then 3-buten-1-yl methanesulfonate, 100 °C. iii) n-BuLi, ClCO2Et, THF, −78 °C. iv) LiI, AcOH, 70 °C. v) PdCl2(PPh3)2, Ag2CO3, THF, rt. vi) LiOH, H2O, THF, rt. vii) BHT (cat.), PhMe, reflux. viii) SmI2. ix) Sodium naphthalenide, DME, −78 °C, then Boc2O, rt. x) TFA, DCM, rt

• , CH3CN, 50 °C; b) CbzCl, TEA, DCM, 0 °C to rt. v) LiHMDS, THF, −78 °C, 1 h, then ClCO2Et, −78 °C to rt. vi) LiHMDS, THF, −78 °C, 2 h, then ClCO2Et, −78 °C, 1 h. vii) LiI, AcOH, 70 °C. viii) PdCl2(PPh3)2, Ag2CO3, THF, 60 °C. ix) LiOH, H2O, THF, rt. x) BHT (cat.), PhMe, reflux. xi) Pd/C, H2, EtOAc or MeOH

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• natural antioxidants are flavonoids, anthocyanins and their glycosides. Huber and collaborators [18] revealed the inhibition of PUFA oxidation by quercetin and its 3-O-glucoside. They were as effective as butylated hydroxytoluene (BHT, a synthetic antioxidant) against the oxidation of DHA and methylated

• linolenic acid (MLN) in emulsion. Anthocyanins (as natural extracts) were effective at increasing the stability of salmon oil when incorporated in a hydroxypropyl methylcellulose matrix for obtaining fish oil packaging films [21]. The addition of BHT, propyl gallate and citric acid to the herring byproducts

Determination of formation constants and structural characterization of cyclodextrin inclusion complexes with two phenolic isomers: carvacrol and thymol

• Miriana Kfoury,
• David Landy,
• Steven Ruellan,
• Lizette Auezova,
• Hélène Greige-Gerges and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2016, 12, 29–42, doi:10.3762/bjoc.12.5

• antioxidants such as butylated hydroxytoluene (BHT) or butylated hydroxyanisole (BHA), suspected to be carcinogenic [13][14]. However, the major drawbacks for their use in food are their low aqueous solubility that limits their homogenous dispersion and their contact with pathogens [15], their susceptibility

Molecular-oxygen-promoted Cu-catalyzed oxidative direct amidation of nonactivated carboxylic acids with azoles

• Wen Ding,
• Shaoyu Mai and
• Qiuling Song

Beilstein J. Org. Chem. 2015, 11, 2158–2165, doi:10.3762/bjoc.11.233

• carboxylic acids. The reactions were totally inhibited by radical scavengers 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and BHT (2,6-di-tert-butyl-4-methylphenol), suggesting that a radical pathway might be involved in these transformations (Scheme 7). A careful look at the literature reveals that Cu(II

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• Table 1, that inhibition rate constants kA for all the dimers and monomers are of the same order of magnitude and manifest a moderate antioxidant capacity, comparable with those of butylated hydroxytoluene (BHT). In this model DL-α-tocopherol (11) exhibits two orders of magnitude higher antioxidant

Synthesis of a resin monomer-soluble polyrotaxane crosslinker containing cleavable end groups

• Ji-Hun Seo,
• Shino Nakagawa,
• Koichiro Hirata and
• Nobuhiko Yui

Beilstein J. Org. Chem. 2014, 10, 2623–2629, doi:10.3762/bjoc.10.274

• methacrylate hydrochloride, N,N’-carbonyldiimidazole, ethyl 4-(dimethylamino)benzoate (DMBE), 3,5-di-tert-butyl-4-hydroxytoluene (BHT) and 2-hydroxyethyl methacrylate were purchased from Sigma-Aldrich Chemical Co. (St. Louis, MO, USA). Urethane methacrylate (Art ResinTM) was purchased from Negami Chemical

• crosslinker (50 wt % C12-Bu12-MA12 PRX and 25 wt % UDMA) with 5 wt % (to total monomer mixture) of initiator mixture (camphorquinone 2 wt %, CMBE 2 wt %, BHT 1 wt %) was dissolved in 200 wt % acetone and cast in a 8 mm in diameter and 0.5 mm deep disk-type Teflon assembly mold and dried by air blowing. The