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Vinyl type carbocations ArC+=CHX [X = CO2H, CO2Alk, C≡N, P(O)(OAlk)2] generated from alkyl 3-arylpropynoates and related compounds in fluorosulfonic acid at −75 to −20°C react with various benzene derivatives, following the mechanism of electrophilic substitution of hydrogen. A new procedure for the synthesis of alkyl 3,3-diarylpropenoates having various substituents in the aryl fragments has been developed on the basis of protonation of the triple bond in alkyl 3-arylpropynoates. [ABSTRACT FROM AUTHOR]

Nitration of phenylpropiolic acid derivatives ArC=CX (X=CN, CO2Me) in HSO3F at -75...-50°C afforded mononitro compounds, for instance,m-O2NC6H4C=CX. Vinyl type cations generated in HSO3F from methyl 3-arylpropiolates ArC+=CHCO2Me react along two pathways. The first among them results in formation of fluorosulfonates ArC(OSO2F)=CHCO2Me, and the second one after the attack of vinyl cation on the aryl moiety of the substrate affords a dimer that on nitration is converted into a nitro product with conserved triple bond. [ABSTRACT FROM AUTHOR]

Regio- and stereoselective oxidative dimerization of alkyl 3-arylpropynoates in the system CF3CO2H-CH2Cl2-PbO2 (1-30 h, 0-20°C) leads to dialkyl (E)-2,3-bis(arylcarbonyl)-2-butene-1,4-dioates withtransarrangement of the substituents at the double bond. [ABSTRACT FROM AUTHOR]

The article presents information on some processes that provide a simple synthetic route to various practically important compounds. For this purpose, researchers examined reactions of cation A with 2,3,5,6-tetramethylbenzenesulfonyl fluoride and acetonitrile. Researchers stated that such processes would provide a simple synthetic route to various practically important compounds. The yields of compounds IV and V differed considerably due to difference in electron-acceptor properties of the substituents in the aromatic substrates.

Examines a novel dimerization of methyl p-tolylpropynoate in fluorosulfonic acid with conservation of the triple bond. Formation of a relatively stable ion; Structure of isolated products; Inactivity of the triple bond in regioisomeric products II and III.

According to the 1H and 13C NMR data, 3-arylpropynoic acids and their esters XC6H n -C≡C-CO2R (R = H, Me, Et) having electron-withdrawing substituents in the benzene ring (X = NO2, CN, COMe, CO2Me) exist in HSO3F at −80 to 0°C as XC6H n -C≡C-C+(OH)OR ions. Derivatives with other substituents (X = H, F, Me, MeO) in HSO3F or CF3SO3H above −40°C undergo protonation at the acetylenic carbon atom neighboring to the acid group to give unstable vinyl-type XC6H n -C+=CH-CO2R cations which are then transformed into mixtures of stereoisomeric ( Z and E) fluorosulfonates or triflluoromethanesulfonates XC6H n -CY=CH-CO2R (Y = OSO2F, OSO2CF3), the E isomer prevailing. [ABSTRACT FROM AUTHOR]