Imidazolium‐dithiocarboxylate zwitterions catalysed ring‐opening additions of cyclopropenones

Abstract Imidazolium‐dithiocarboxylate zwitterions (NHC ⋅ CS 2 ), a novel organocatalyst that derived from N‐heterocyclic carbene (NHC), was used to activate cyclopropenones. Under the catalysis of 10 mol% NHC ⋅ CS 2, a range of phenols, alcohols, primary and secondary amines react with cyclopropenones to produce trisubstituted α , β ‐unsaturated esters and amides in 46–95% yield. More than 68 products, including 7 natural product derivatives have been synthesized through this method. Mechanism study showed NHC ⋅ CS 2 act as a Lewis base to activate the C=C double bond of cyclopropenones and trigger the ring‐opening reaction. HRMS analysis indicated the formation of the key adduct of NHC ⋅ CS 2 and cyclopropenone. More importantly, this study demonstrated completely different catalytic activity of NHC ⋅ CS 2 and NHC catalysts, the latter one cannot catalyse these reactions.