Reactions of trifluoromethyl-substituted arylacetylenes with arenes in superacids

Friedel–Crafts Alkylation of Arenes with 2-Halogeno-2-CF3-styrenes under Superacidic Conditions. Access to Trifluoromethylated Ethanes and Ethenes

“…The configuration of the Z - and E -isomers of 3 can be figured out by means of 1 H NMR. The signal of the vinyl proton in E -isomers 3 is low field shifted compared to the same signal in the Z -isomer . On the basis of these spectral regularities, we could elucidate the stereochemistry of Z / E -alkenes 3 and, consequently, resolve the structures of diastereomers 2 , D1 and D2.…”

“…Compounds 3a – p were obtained and characterized by ourselves previously, except for 3c , 3f , 3q (see their properties below).…”

“…On the basis of our preliminary communication and recent publications on reactions of CF 3 -alkynes, CF 3 CO-alkenes, and CF 3 -allyl alcohols in acids, we undertook a special study on reactions of CF 3 -styrenes bearing at the double bond an additional halogen atom under superelectrophilic activation.…”

Alkenylation of Arenes and Heteroarenes with Alkynes

“…Protonation of CF 3 -alkynes 533 in TfOH or FSO 3 H gives vinyl cations 534 , which are able to effectively alkenylate a range of arenes (benzene and alkyl-, methoxy-, and halogen-substituted arenes), affording alkenes 535 (Scheme ). , However, under superacidic reaction conditions, the latter alkenes are protonated to form tertiary carbocations 536 . These species are extremely stable in TfOH even at room temperature and were fully characterized by means of NMR. , Finally, upon quenching the reaction solution, cations 536 are either deprotonated or hydrated to afford E / Z- alkenes 535 or alcohols 537 , respectively.…”

“… , However, under superacidic reaction conditions, the latter alkenes are protonated to form tertiary carbocations 536 . These species are extremely stable in TfOH even at room temperature and were fully characterized by means of NMR. , Finally, upon quenching the reaction solution, cations 536 are either deprotonated or hydrated to afford E / Z- alkenes 535 or alcohols 537 , respectively. Quenching with anhydrous MeCN or MeOH/MeONa gave alkenes 535 only.…”