Tandem diazotization/cyclization approach for the synthesis of a fused 1,2,3-triazinone-furazan/furoxan heterocyclic system

• Yuri A. Sidunets,
• Valeriya G. Melekhina and
• Leonid L. Fershtat

Beilstein J. Org. Chem. 2024, 20, 2342–2348, doi:10.3762/bjoc.20.200

• obtained using NaNO2 in an AcOH + MeSO3H [1:1] solution (Table 1, entry 7). Organic solvents (CH2Cl2, MeCN) were not applied due to a known rapid decomposition of the generated (1,2,5-oxadiazolyl)diazonium salts [42]. The optimized conditions were applied for the preparation of [1,2,5]oxadiazolo[3,4-d

Green and sustainable approaches for the Friedel–Crafts reaction between aldehydes and indoles

• Periklis X. Kolagkis,
• Eirini M. Galathri and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2024, 20, 379–426, doi:10.3762/bjoc.20.36

• , such as camphorsulfonic acid (CSA) [44], diammonium hydrogen phosphate (DAHP) [45], Amberlyst 15 [46], P2O5/MeSO3H [47], p-sulfonic acid calix[4]arene [48], xanthan sulfuric acid (XSA) [49], H5PW10V2O40/pyridino-santa barbara amorphous-15 (SBA-15) [50], TiO2-SO42− [51][52], humic acid [53] or Lewis

Catalyzed and uncatalyzed procedures for the syntheses of isomeric covalent multi-indolyl hetero non-metallides: an account

• Ranadeep Talukdar

Beilstein J. Org. Chem. 2021, 17, 2102–2122, doi:10.3762/bjoc.17.137

• , which possess AhR affinity [93]. Janosik presented a synthesis of such selenopyrans 132 via the bis(indol-2-yl)selanes 131 [73]. Treating these compounds with orthoformate esters in the presence of the Brønsted acid MeSO3H led to the target selenopyrans (Scheme 17b). The methylated analogs of 132

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

• 138. Then, an oxidative cyclization of 138 in the presence of FeCl3 afforded dibenzo[a,c]anthracenes 139a and 139b in moderate yields (58–68%). On the other hand, they obtained dibenzo[a,c]anthracenes 139c–e in low to moderate yields (15–54%) when they used DDQ/MeSO3H instead of FeCl3 [66]. In a study

• substituted anthraquinone derivatives 191 from phthalic anhydride (164) and several arenes 190 by using a combined system of AlCl3 and MeSO3H (Scheme 44) [80]. Arenes 190 containing electron-donating groups yielded the anthraquinone derivatives 191a–c in very good yields (80–93%). On the other hand, reactions

• 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

Preparation of 2-phospholene oxides by the isomerization of 3-phospholene oxides

• Péter Bagi,
• Réka Herbay,
• Nikolett Péczka,
• Zoltán Mucsi,
• István Timári and
• György Keglevich

Beilstein J. Org. Chem. 2020, 16, 818–832, doi:10.3762/bjoc.16.75

• to decomposition caused by the vigorous reaction conditions. Based on this promising preliminary result with MeSO3H, the effect of both the reaction temperature and the reaction time was investigated. It was found that complete isomerization to the 2-phospholene oxide derivative 4a could not be

• reached with MeSO3H at 25 °C even after prolonged reaction times. Setting the reaction temperature to 50 °C and the reaction time to 60 h seemed to be the reasonable choice, as nearly the same isomeric composition (96:4) could be achieved as at 160 °C, but with significantly increased yield (up to 81

• conditions via the formation of chlorophospholenium salts (Scheme 1, route I), or using MeSO3H or Cs2CO3 (Scheme 1, routes II or III). These results were compared with those obtained for the 1-phenyl-3-methyl-3-phospholene oxide (1a). Scheme 1 shows that, considering all reaction pathways, the highest extent

N-(1-Phenylethyl)aziridine-2-carboxylate esters in the synthesis of biologically relevant compounds

• Iwona E. Głowacka,
• Aleksandra Trocha,
• Andrzej E. Wróblewski and
• Dorota G. Piotrowska

Beilstein J. Org. Chem. 2019, 15, 1722–1757, doi:10.3762/bjoc.15.168

Studies towards the synthesis of hyperireflexolide A

• G. Hari Mangeswara Rao

Beilstein J. Org. Chem. 2018, 14, 2106–2111, doi:10.3762/bjoc.14.185

• reported from our laboratory the synthesis of γ-lactone-fused cyclopentane derivative 5 from the respective Diels–Alder adduct in 5 steps with an overall yield of 29% [32]. Hydrolysis of dimethyl ketal 5 with MeSO3H in 1,2-DCE furnished γ-lactone-fused cyclopentanone 6 in 97% yield. Cyclopentanone 6 exists

Solvent-free and room temperature synthesis of 3-arylquinolines from different anilines and styrene oxide in the presence of Al₂O₃/MeSO₃H

• Hashem Sharghi,
• Mahdi Aberi,
• Mohsen Khataminejad and
• Pezhman Shiri

Beilstein J. Org. Chem. 2017, 13, 1977–1981, doi:10.3762/bjoc.13.193

• been developed in the presence of Al2O3/MeSO3H via one-pot reaction of anilines and styrene oxide. This methodology provides very rapid access to 3-arylquinolines in good to excellent yields under solvent-free conditions at room temperature in air. Keywords: 3-arylquinolines; Al2O3; MeSO3H; one-pot

• MeSO3H has been previously used as an effective and mild reagent for organic transformations [14]. In continuation of our studies to develop new synthetic methods for heterocycles [15][16][17][18][19], herein, we disclose a novel route to the synthesis of 3-arylquinolines from aniline derivatives and

• optimized conditions for the synthesis of quinolines, the reaction of 3,4-dimethylaniline (1, 1.0 mmol) and styrene oxide (2, 2.0 mmol) in an open atmosphere was chosen as a model reaction (Table 1). Control experiments showed that in the absence of Al2O3 and MeSO3H, no quinoline 3a was observed (Table 1

Chemoselective O-acylation of hydroxyamino acids and amino alcohols under acidic reaction conditions: History, scope and applications

• Tor E. Kristensen

Beilstein J. Org. Chem. 2015, 11, 446–468, doi:10.3762/bjoc.11.51

• hydroxyamino acids in the form of methanesulfonic acid (MeSO3H) was identified. In 1977, chemists in India had reported that L-tyrosine, hydroxy-L-proline, L-serine, DL-serine and DL-threonine could all be chemoselectively O-acetylated overnight in high chemical yields with acetic anhydride in glacial acetic

• acyl chlorides in MeSO3H (Scheme 6) [34]. After acylation of hydroxyproline at the >10 g scale in MeSO3H overnight at room temperature, the product was separated as the (usually oily) methanesulfonate salt by addition of Et2O. The salts were neutralized with aqueous NH3, and the free O-acylhydroxyamino

• acids were recrystallized from suitable solvents such as acetone, lower alcohols and H2O. Acylation reactions in MeSO3H are more vigorous and exothermic than in CF3CO2H since MeSO3H (pKa ≈ −2) is a stronger acid than CF3CO2H (pKa ≈ 0.5). Their densities are the same (1.48 g/mL at 25 °C), but the melting

An efficient access to the synthesis of novel 12-phenylbenzo[6,7]oxepino[3,4-b]quinolin-13(6H)-one derivatives

• Wentao Gao,
• Guihai Lin,
• Yang Li,
• Xiyue Tao,
• Rui Liu and
• Lianjie Sun

Beilstein J. Org. Chem. 2012, 8, 1849–1857, doi:10.3762/bjoc.8.213

• alternative route would be desirable. Recently, the Eaton’s reagent, a mixture of P2O5 and MeSO3H [43], has gained wide application as an advantageous medium for cyclization reactions [44], and we have also reported the serendipitous discovery of its excellent performance in these types of transformations [32

Efficient, highly diastereoselective MS 4 Å-promoted one-pot, three-component synthesis of 2,6-disubstituted-4-tosyloxytetrahydropyrans via Prins cyclization

• Naseem Ahmed and
• Naveen Kumar Konduru

Beilstein J. Org. Chem. 2012, 8, 177–185, doi:10.3762/bjoc.8.19

• , MeSO3H [13], Sc(OTf)3 [14], O3ReOSiPh3 [15], TMSBr [16] – or with Lewis acid catalysts such as AlCl3 [17], InCl3 [18][19], TiCl4, HBF4·OEt2 [20], InBr3 [21], TiBr4 [22], Fe(III) compounds [23], BF3·OEt2 [24], polymer supported [25], microwave accelerated with BiCl3 [26], and Pd0/SnII mediated by a three