The metal-free reaction of 5-(2-arylethenyl)-3-aryl-1,2,4-oxadiazoles with arenes in neat triflic acid (TfOH, CF3SO3H), both under thermal and microwave conditions, leads to 5-(2,2-diarylethyl)-3-aryl-1,2,4-oxadiazoles. The products are formed through the regioselective hydroarylation of the side chain carbon–carbon double bond of the starting oxadiazoles in yields up to 97%. According to NMR data and DFT calculations, N4,C-diprotonated forms of oxadiazoles are the electrophilic intermediates in this reaction.

No abstract

Reaction of CF3-propargyl alcohols with arenes under the action of HUSY zeolite CBV-720 at 100 °C for 1 h affords CF3-indenes.

Conjugated arylacetylenic ketones and aldehydes, propargyl-type alcohols, and arylacetylenes reacted with arenes in the presence of AlBr 3 or AlCl 3 as catalyst to give substituted indenes. 3-Arylpropynoic acids under analogous conditions gave rise to 3,3-diarylindan-1-ones, while the corresponding methyl esters were converted into methyl 3,3-diarylprop-2-enoates. The key intermediates in the transformations of acetylenic ketones and aldehydes and propargyl-type alcohols into indene derivatives are resonance-stabilized propargyl-allenyl cations -C≡C-C + ↔ -C + =C=C which reacted with one of the resonance structures to give isomeric indenes, depending on the substituent nature.

No abstract