One‐Step Access to Heteroatom‐Functionalized Imidazol(in)ium Salts

Abstract

Imidazolium salts have ubiquitous applications in energy research, catalysis, materials and medicinal sciences. Here, we report a new strategy for the synthesis of diverse heteroatom‐functionalized imidazolium and imidazolinium salts from easily available 1,4‐diaza‐1,3‐butadienes in one step. The strategy relies on a discovered family of unprecedented nucleophilic addition/cyclization reactions with trialkyl orthoformates and heteroatomic nucleophiles. To probe general areas of application, synthesized N‐heterocyclic carbene (NHC) precursors were feasible for direct metallation to give functionalized M/carbene complexes (M=Pd, Ni, Cu, Ag, Au), which were isolated in individual form. The utility of the chloromethyl function for the postmodification of the synthesized salts and Pd/carbene complexes was demonstrated. The obtained complexes and imidazolium salts demonstrated good activities in Pd‐ or Ni‐catalyzed model cross‐coupling and C−H activation reactions.

Diaza-1,3-butadienes as Useful Intermediate in Heterocycles Synthesis

“…Finally, the chloroalkyl substituted imidazolium salts 247 are the main products of the reaction of 244 with TMSCl when the diazadiene possesses identical alkyl groups on the carbon atoms of the diene backbone (R 1 = R 2 = Me). However, if the alkyls are different (R 1 = Et, R 2 = Me), a combination of three imidazolium salts, both isomeric chloroalkyl substituted salts 248 and 249 and vinyl substituted salts 250 , are obtained ( Scheme 59 ) [ 115 ].…”