Synthesis of new unsymmetrical 4,5-dihydroxy-2-imidazolidinones. Dynamic NMR spectroscopic study of the prototropic tautomerism in 1-(2-benzimidazolyl)- 3-phenyl-4,5-dihydroxy-2-imidazolidinone

Abstract

The acid-catalyzed cyclocondensation in refluxing acetonitrile of aqueous glyoxal with N-heteroaryl-N′-phenylureas 4a-f (heteroaryl = 2-thiazolyl, 2-pyrimidinyl, 2-pyrazinyl, 2-pyridinyl, 3-pyridinyl and 2-benzimidazolyl) led to the formation of the corresponding 1-heteroaryl-3-phenyl-4,5-dihydroxy-2- imidazolidinones 5a-f. All the products were characterized by elemental and spectroscopic analyses. The free-energy barrier etermined by dynamic NMR studies to be 81 ± 2 KJ mol-1. © 2006 by MDPI.