Synthesis of New Imidazolidine and Tetrahydropyrimidine Derivatives

Synthesis of new imidazolidine and tetrahydropyrimidine derivatives 3a, b and 4a–c as cyclic 1,3-diamines under two reaction conditions (A and B) is described. Under reaction conditions-A, a suspension of (E)-2-cyano-2-(oxazolidin-2-ylidene)ethanethioamide 1 (1 eq.) and diaminoalkanes 2a–e (2 eq.) in absolute ethanol is heated under reflux for 16–22？h to afford 3a, b and 4a–c. Alternatively, under reaction conditions-B, a solution of thioamide 1 (1 eq.) in diaminoalkanes 2a–e (3 eq.) is stirred under solvent-free conditions at room temperature for 3 days to give desired products. Reaction conditions-A for having higher yields, shorter reaction times, and required less diamines is more effective than reaction conditions-B. Oxazolidine ring opening is observed by reacting compound 1 with all of the diamines 2a–e, but the thioamide group only reacts with nonbulky diamines 2a, b. The chemical structures of novel compounds were confirmed by 1H NMR, 13C NMR, elemental analysis, and FT-IR spectrometry. 1. Introduction Imidazolidines (tetrahydroimidazoles) are important building blocks in biologically active compounds [1] and carriers of pharmacologically active carbonyl compounds [2]. They have been reported to have important biological activities including, for example, 2-[(arylmethoxy) imino]imidazolidines as potential α-adrenergic receptor agonist [3], bisimidazolidines and 1,3-disubstituted imidazolidines as antimicrobial [4], 5-(4-chloro or fluoro-benzylidene-3-(4-nitrebenzyl)-4-thioxo-imidazolidin-2-one as antiparasitic [5], sulfonyliminoimidazolidines as oral hypoglycaemic [6], imidazolidin-2,4-diones, 2-thioxoimidazolidin-4-ones, 5-cycloalkylidene-hydantoins, and 5-cycloalkylidene-thiohydantoins as antiarrhythmic and anticonvulsant [7, 8], 1,3-dibenzyl-2-arylimidazolidine as anti-inflammatory [9], N,N′-di-aryl-methyl-2-(4-diethylamino phenyl) tetrahydroimidazoles and N,N′-di-4-diethylamino benzyl-2-(aryl) tetrahydroimidazoles as analgesic [10]. They have also been utilized as a versatile template for the synthesis of compounds with potential cyclooxygenase-2 inhibition activity [11] and termed as a promising group of NSAIDs with potential anti-inflammatory activities [9]. The pyrimidine fragment is present in various biologically active compounds, many of which have been found to be used in medical practice [12, 13]. Recently, much attention has been paid to derivatives of pyrimidine, including their hydrogenation products. This class of compounds displays wide ranges of biological and pharmacological properties such as anti-inflammatory [14],