Nitration of phenylpropiolic acid derivatives in HSO3F and reactions of vinyl type cations formed therefrom.

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]