Oxidation of aromatic compounds: XVI. Radical cations derived from acetylenic compounds with electron-withdrawing groups: Reactions and ESR parameters

Synthesis of polyarylacetylenes by γ‐ray‐induced polymerization of terminal alkynes. Nanostructures of ortho‐substituted derivatives

“…The addition process and the subsequent propagation steps can occur by either attack of the cationic carbon (C1) or of the radicalic carbon (C2) to triple bonds. Steric reasons and the modest effects of the substituents with largely different electronic properties (CF 3 vs OMe) indicate radicalic CC bond forming steps, in agreement with studies on the reactivity of radical cations generated from acetylenic compounds 36. Attack of the radicalic species to either C1 or C2 of ArCCH corresponds to head to tail (HT) or head to head (HH) addition modes, respectively, and accounts for the different polymeric domains in the structure.…”

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

“…In the cation-radicals of diarylacetylenes with the singly occupied molecular orbital b 1 the acetylene bond transmits well the spin density between the aromatic rings and is essentially involved in its delocalization (Fig. 3) (see also the data of [1] on the characteristic by ESR of cation-radicals of acetylene compounds with electron-withdrawing groups). The presence of the spin density on the acetylene carbon atoms results in the formation of the new carbon-carbon bond Table 2.…”

“…However the now available experimental data are insuffi cient for distinguishing these two reaction routes (cf. with the data of [1] on reactions of cation-radicals of acetylene compounds with electron-withdrawing groups).…”

“…1 Oxidation of mixtures of diarylacetylenes I, II, VII, X, XIII, XVI, XVII in the system CF 3 CO 2 H-CH 2 Cl 2 -PbO 2 . To a solution of 0.43 ml of CF 3 CO 2 H in 4 ml of CH 2 Cl 2 was added while vigorous stirring at 0°C 1 mmol of each diarylacetylene.…”

Atom-economic synthesis of β-ketosulfones based on gold-catalyzed highly regioselective hydration of alkynylsulfones

“…27,28 Vasil'ev et al have reported the hydration of alkynylsulfones (4 examples, 40-80%) under the action of the excess of trifluoroacetic acid (5-7 equiv.). 29 The reaction occurs through the addition of the acid followed by hydrolysis of the intermediate ester; this process is not atom-economic.…”