Protonation of Diarylacetylenes in Superacid HSO₃F and Their Oxidation in the HSO₃F/PbO₂ System: One‐Pot Synthesis of Polysubstituted Naphthalenes

Abstract

In the superacid HSO3F, diarylacetylenes bearing one electron‐withdrawing group (NO2, CN, COMe, CO2Me) in each arene ring form stable ions, protonated at these groups. Oxidation of such diarylacetylenes in the HSO3F/PbO2 system at –75 to –50 °C over 2–2.5 h, followed by quenching of the reaction mixture with hydrochloric (or hydrobromic) acid at –60 to 25 °C, resulted in the formation of (E,E)‐1,4‐dichloro (or dibromo)‐1,2,3,4‐tetraarylbuta‐1,3‐dienes. These butadienes spontaneously undergo electrocyclic transformation into polysubstituted naphthalenes at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Bis-Rhodamines Bridged with a Diazoketone Linker: Synthesis, Structure, and Photolysis

“…However, under all of these conditions, hydration of acetylenes 7a – c was sluggish. With HSO 3 F (magic acid), 11 Nafion NR50, Nafion 117, or p -toluenesulfonic acid, ketones did not form at all. Only by using great excess of water, trifluormethanesulfonic (TfOH, reagent), and propionic (solvent) acids at 140 °C, we managed to detect the formation of regioisomeric ketones ( Scheme 4 ).…”

“…26 Photolysis of the solutions containing aqueous HEPES buffer provided complex mixtures with diphenylacetic acid (13) as one of the main products (Figure S1). Irradiation in the presence of aqueous HCOONH 4 was found to be "cleaner" (Figure 2) and resulted in the formation of diphenylacetic acid Unlike azibenzil (11) and benzil ( 14), amide 16 did not display the absorption maximum at about 320 nm. The composition of amide 16 was confirmed by HRMS data obtained for the reaction mixture (see Figure S2).…”

Oxidation of aromatic compounds: XVII. Oxidative cross-dimerization of diarylacetylenes in the system CF3CO2H-CH2Cl2-PbO2. Characteristic of cation-radicals of diarylacetylenes by cyclic voltammetry and ESR spectroscopy

“…The properties of compounds I, VII, X, XIII, XVI, XVII, XXIII, XXIV, XXVI, XXVII are published in [2], of compound II, in [3], of compound XXVIII, in [7].…”

“…It was shown by ESR spectroscopy that the primary intermediates in these reactions were diarylacetylene cationradicals [7]. The extension of the synthetic potential of these reaction consists in the oxidation of mixtures of various diarylacetylenes for the preparation of products of their mixed (cross-) oxidative dimerization.…”

“…The oxidation of diarylacetylenes with the lead dioxide in various acids (CF 3 CO 2 H [2][3][4], HF [5], HSO 3 F [6,7]) gives products of the oxidative dimerization, (Z)-(cis)-1,2,3,4-tetraarylbut-2-ene-1,4-diones (unsaturated γ-diketones) Ar(ArCO)C=C(COAr)Ar, (E,E)-1,2,3,4-tetraaryl-1,4-difluoro(or dichloro)butadienes (Ar) XC=C(Ar)-(Ar)C=CX(Ar) (X = F, Cl) formed as a result of the closure of a new carbon-carbon bond through the acetylene carbon atoms of the diarylacetylenes. It was shown by ESR spectroscopy that the primary intermediates in these reactions were diarylacetylene cationradicals [7].…”