Synthesis 2004(6): 851-856  
DOI: 10.1055/s-2004-816011
PAPER
© Georg Thieme Verlag Stuttgart · New York

Synthesis and Study of 1-Aryl-1H-4,5-dihydroimidazoles

Isabel Perillo*, M. Cristina Caterina, Julieta López, Alejandra Salerno
Departamento de Química Orgánica, Facultad de Farmacia y Bioquímica, Junín 956 (1113), Buenos Aires, Argentina
Fax: +541(1)49648250; e-Mail: iperillo@ffyb.uba.ar;
Further Information

Publication History

Received 13 January 2004
Publication Date:
15 March 2004 (online)

Abstract

An easy synthesis of 1-aryl-1H-4,5-dihydroimidazoles 1 by cyclocondensation of N-aryl-N′-formylethylenediamines 2 is described. Such precursors were synthesized by selective formylation of N-arylethylenediamines 3 with p-nitrophenyl formate. Cyclizations were performed using trimethylsilyl polyphosphate. Chemical properties of compounds 1, typical of amidine system, were studied. Reaction of 1 with methyl iodide leads to the corresponding 1-aryl-3-methyl-1H-4,5-dihydroimidazolium salts 5. Reduction of dihydroimidazoles 1 with sodium cyanoborohydride provides a convenient access to N-aryl-N′-methylethylenediamines 4.

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It is well known that N-1 and/or N-3 unsubstituted imidazolidines exhibit ring (imidazolidine)-chain (imine) tautomerism, [25] and usually both species can be spectroscopically identified.