Synthesis of 5-arylacetylenyl-1,2,4-oxadiazoles and their transformations under superelectrophilic activation conditions

• Andrey I. Puzanov,
• Dmitry S. Ryabukhin,
• Anna S. Zalivatskaya,
• Dmitriy N. Zakusilo,
• Darya S. Mikson,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2021, 17, 2417–2424, doi:10.3762/bjoc.17.158

• the moment, there are no data on the preparation of 1,2,4-oxadiazoles containing a conjugated acetylenic substituent in the position 5 of the heterocyclic ring. Based on our previous works on the chemistry of 1,2,4-oxadiazoles in superacids [24][25], we undertook this study on further investigation of

• ], it was shown by means of NMR spectroscopy and DFT calculation that the protonation of these oxadiazoles in Brønsted superacids TfOH and FSO3H gave reactive N,C-diprotonated species. The protonation of oxadiazoles 1 takes place at the nitrogen N4 and the α-carbon of the side chain C=C bond. One would

• expect the formation of similar dications at the protonation of acetylenyloxadiazoles 3 in Brønsted superacids (see Table 1). Table 1 contains data on DFT calculations of cations Aa–d (N-protonated forms) and Ba–d (N,C-diprotonated forms) derived at the protonation of oxadiazoles 3a–d. Charge

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• for each isomer. In these reactions, we attribute no special effect due to microwaves. This has been a subject of some debate in the literature [37][38]. As we have demonstrated earlier, the microwave reactor simply provides a safe and reliable way to heat samples with superacids at temperatures well

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• superacids or coordination by a Lewis superacid to produce a di- (tri- or higher) cationic species, the study of superelectrophilic activation became a very active area of research [11][12][13]. The acid-catalyzed condensation of ketones and aldehydes with aromatic compounds is known as the hydroxyalkylation

Superelectrophilic carbocations: preparation and reactions of a substrate with six ionizable groups

• Sean H. Kennedy,
• Makafui Gasonoo and
• Douglas A. Klumpp

Beilstein J. Org. Chem. 2019, 15, 1515–1520, doi:10.3762/bjoc.15.153

• superelectrophilic reactivity [1][2][3][4][5]. Examples of superelectrophiles include the nitronium dication (1) and the acetylium dication (2, Scheme 1). Both of these species have been proposed as superelectrophilic intermediates in the reactions of nitronium (NO2+) and acetylium (CH3CO+) salts in superacids. In

Metal-free hydroarylation of the side chain carbon–carbon double bond of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles in triflic acid

• Anna S. Zalivatskaya,
• Dmitry S. Ryabukhin,
• Marina V. Tarasenko,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya,
• Elena V. Grinenko,
• Ludmila V. Osetrova,
• Eugeniy R. Kofanov and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2017, 13, 883–894, doi:10.3762/bjoc.13.89

• investigation of their properties are of ongoing interest in chemistry and medicine. Based on our previous works on reactions of cinnamides [24] and 5-styryl-2H-tetrazoles [25] with arenes under superelectrophilic activation with Brønsted or Lewis superacids, we turned our attention towards the hydroarylation

• metals Pt [28], Au [29], Ru [30], Rh [31][32][33], Ni [34], Pd [35], and Pd/Ag [36]. However, a metal-free hydroarylation variant of C=C bonds under the action of Brønsted or Lewis superacids has been developed [37][38] and we were able to extend the scope of this reaction [24][25]. The expected reaction

• species D. Thus, the NMR data reveal that the protonation of 5-styryl-substituted 1,2,4-oxadiazoles in superacids results in the formation of their relatively stable N4-protonated forms. However, these species do not react with aromatic π-nucleophiles (vide infra). Most probably, those reactive

Superelectrophilic activation of 5-hydroxymethylfurfural and 2,5-diformylfuran: organic synthesis based on biomass-derived products

• Dmitry S. Ryabukhin,
• Dmitry N. Zakusilo,
• Mikhail O. Kompanets,
• Anton A.Tarakanov,
• Irina A. Boyarskaya,
• Tatiana O. Artamonova,
• Mikhail A. Khohodorkovskiy,
• Iosyp O. Opeida and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2016, 12, 2125–2135, doi:10.3762/bjoc.12.202

• 5-HMF and 2,5-DFF were characterized by NMR spectroscopy in TfOH and studied by DFT calculations. These reactions show possibilities of organic synthesis based on biomass-derived 5-HMF and 2,5-DFF. Keywords: 2,5-diformylfuran; Friedel–Crafts reaction; 5-hydroxymethylfurfural; superacids; zeolites

• -derived products. Superelectrophilic activation is the generation of highly reactive di-, tri- (or even higher) cationic species by protonation and protosolvation of organic molecules with low nucleophilic Brønsted superacids, such as CF3SO3H (TfOH) or FSO3H [32]. The same activation may be achieved with

• and Lewis superacids. Previously superelectrophilic activation of aldehyde groups was achieved for heteroaromatic aldehydes [34][35][36][37], substituted benzaldehydes and o-phthalic dicarboxaldehyde [38]. Based on these findings, one would expect the activation of an aldehyde group of 5-HMF and 2,5

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

• rearrangement of aliphatic hydroperoxides proceeds quite readily in concentrated H2SO4 [318] or superacids [319] (Scheme 52). This is associated with higher resistance of these compounds toward acid-catalyzed rearrangements compared with benzylic or allylic hydroperoxides. For example, aliphatic hydroperoxides

Reactions of N,3-diarylpropiolamides with arenes under superelectrophilic activation: synthesis of 4,4-diaryl-3,4-dihydroquinolin-2(1H)-ones and their derivatives

• Larisa Yu. Gurskaya,
• Diana S. Belyanskaya,
• Dmitry S. Ryabukhin,
• Denis I. Nilov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2016, 12, 950–956, doi:10.3762/bjoc.12.93

• superelectrophilic activation of the N-formyl group by TfOH in the reaction with benzene resulted in the formation of N-(diphenylmethyl)-substituted dihydroquinolinones. Keywords: alkynes; quinolinones; Friedel–Crafts reactions; superacids; superelectrophilic activation; Introduction Quinoline derivatives are a

• ][12][13][14], we continued to develop some methods for the syntheses of quinoline derivatives. Previously we showed, just in a few examples, that some 3-aryl-N-(aryl)propiolamides reacted with benzene under the action of Brønsted or Lewis superacids affording 4-aryl-4-phenyl-3,4-dihydroquinolin-2(1H

• Discussion The protonation of alkynamides 1 on both the oxygen atom of the amide group and a carbon atom of the acetylene bond in superacids or coordination of these basic centers with strong Lewis acids leads to the formation of dications A that are considered as superelectrophiles [15] (Scheme 1). These

Gold(I)-catalysed one-pot synthesis of chromans using allylic alcohols and phenols

• Eloi Coutant,
• Paul C. Young,
• Graeme Barker and
• Ai-Lan Lee

Beilstein J. Org. Chem. 2013, 9, 1797–1806, doi:10.3762/bjoc.9.209

• dehydrative coupling strategy) [15][16]. To this end, the use of molybdenum catalyst CpMoCl(CO)3 together with an oxidant, o-chloranil, has been documented to catalyse the reaction of allylic alcohols with phenols to form chromans [17][18]. Strong and superacids have also been utilised in the synthesis of

Molecular rearrangements of superelectrophiles

• Douglas A. Klumpp

Beilstein J. Org. Chem. 2011, 7, 346–363, doi:10.3762/bjoc.7.45

• become more widely appreciated and it is shown to involve both Brønsted and Lewis acids [8]. Moreover, superelectrophiles have been utilized in many synthetic conversions. While these reactions are often carried out in superacids, less acidic media (CF3CO2H, H2SO4, BF3·H2O, and solid acids) have also

• Olah and coworkers some of which involve superelectrophiles [27]. In the presence of Brønsted superacids, ozone is protonated and the resulting ion (O3H+) is a highly reactive electrophilic species, capable of inserting into C–C and C–H σ-bonds in alkanes or alkyl groups. With another ionizable group

• coworkers studied this reaction by low temperature NMR and showed clean conversion of hydrazobenzene to the stable ion 119 in FSO3H-SO3 at –78 °C [34]. Jacquesy and coworkers have examined the chemistry of natural products in superacids and found several unusual rearrangements of multiply-protonated species