source: Journal of Combinatorial Chemistry year: 2008 volume: 10 first page: 886 last page: 892 doi: 10.1021/cc800101k
Abstract: The cyclization of N,N'-dialkyl or diaryl ethane-1,2-diamines or propane-1,3-diamines with inorganic ammonium salts and orthoesters proceeds briskly under microwave irradiation to afford the corresponding imidazolinium or tetrahydropyrimidinium salts. The transformation is highly versatile and tolerates a wide range of substituents and counterions. It could be scaled up from 1 to 50 mmol without any difficulty. Because the workup is equally rapid and straightforward, this experimental procedure provides a fast and convenient access to an important class of heterocyclic compounds that have found numerous applications as N-heterocyclic carbene precursors, organocatalysts and ionic liquids.