CF₃-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry

• Anthony J. Fernandes,
• Armen Panossian,
• Bastien Michelet,
• Agnès Martin-Mingot,
• Frédéric R. Leroux and
• Sébastien Thibaudeau

Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32

• long been investigated. This review highlights recent and past reports focusing on their study and potential in modern synthetic transformations. Keywords: carbocation; organic synthesis; superelectrophile; trifluoromethyl; Introduction Carbocations are pivotal intermediates in organic chemistry, and

• of dicationic superelectrophile 160. Again, due to charge repulsions as well as due to the strong electron-withdrawing effect of the CF3 group, the positive charge adjacent to the CF3 group is highly delocalized within the phenyl ring, and arylation occurs regioselectively at the para-position

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

• superelectrophile. These two kinds of species may react with benzene leading to products of the transformation of the carbonyl group into a diphenylmethyl one (Figure 2) [19]. To the best of our knowledge, no data on the generation of superelectrophilic species from carbonyl-substituted benzimidazoles and their

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

• proposed involving tetra-, penta-, or hexacationic species. Keywords: cation; Friedel–Crafts; heterocycle; superacid; superelectrophile; Introduction During the 1970s and 80s, Olah and co-workers described the novel chemistry of highly-charged organic cationic species. This work lead to the concept of

Nucleophilic dearomatization of 4-aza-6-nitrobenzofuroxan by CH acids in the synthesis of pharmacology-oriented compounds

• Alexey M. Starosotnikov,
• Dmitry V. Shkaev,
• Maxim A. Bastrakov,
• Ivan V. Fedyanin,
• Svyatoslav A. Shevelev and
• Igor L. Dalinger

Beilstein J. Org. Chem. 2017, 13, 2854–2861, doi:10.3762/bjoc.13.277

• -dinitrobenzofuroxan (DNBF) another reaction pathway was observed. DNBF react with β-diketones and even monoketones in DMSO solution to give carbon-bonded σ-adducts in the absence of any added base [15] (Scheme 2). However, DNBF is a typical superelectrophile [16], it reacts very easily with water or methanol without

Molecular rearrangements of superelectrophiles

• Douglas A. Klumpp

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

• ; superelectrophile; Introduction The Knorr cyclization is a classical method for preparing quinol-2-ones from β-ketoamides [1]. In 1964, Staskin published a report describing his studies of the Knorr cyclization and noted that the conversion works best with more than 1.0 equiv of Brønsted or Lewis acids [2]. To

• generate a protosolvated superelectrophile (2 or 3, Scheme 1). Protosolvation of the acetyl cation produces an electrophile with increasing dicationic character and consequently superelectrophilic reactivity. Since Olah’s proposal of superelectrophilic activation, the role of dicationic intermediates has

• example, 2-oxazolines were shown [14] to form products with arenes and a mechanism was proposed involving ring opening of the superelectrophile (13, Scheme 2). The ring opening step effectively separates the positive charge centers, as the superelectrophile isomerizes from a 1,3-dication 13 to a 1,5