Synthesis and Synthetic Applications of 1-Aryl-2-alkyl-4,5-dihydro-1<i>H</i>-imidazoles

Abstract

Abstract An easy synthesis of 1-aryl-2-alkyl-4,5-dihydro-1H-imidazoles 1 by cyclo-condensation of N-acyl-N′-arylethylenediamines 2 is described. Such precursors were synthesized by aminolysis of the corresponding N-(2-bromoethyl)amides 3. Cyclizations were performed using trimethylsilyl polyphosphate as a mild dehydrating agent, under microwave irradiation. Chemical properties of 1-aryl-2-alkyl-4,5-dihydro-1H-imidazoles, typical of the amidine system, were studied. Reduction of dihydroimidazoles with sodium cyanoborohydride leads regiospecifically to N-alkyl-N′-arylethylenediamines 4, and nucleophilic attack to methyl iodide leads to the corresponding 1-aryl-2-alkyl-3-methyl-4,5-dihydro-1H-imidazolium salts 5. Keywords: Alkylationamidinescyclization4,5-dihydro-1H-imidazolesheterocyclesreductions ACKNOWLEDGMENTS This work was financially supported by the Universidad de Buenos Aires and Agencia Nacional de Promoción Científica y Tecnológica. The collaboration of María de los Angeles Ramirez is also gratefully acknowledged.