CHAPTER 2
 CONVENIENT SYNTHESIS OF UNSYMMETRICAL IMIDAZOLIDINES

 2.1 Introduction

 Imidazolidines have attracted attention due to their important role as building

blocks in the synthesis of biologically active compounds. [96JMC3483] [96EJP273]

[98B13893] [00CPB729] [93PR913] [94EJP223] [70JMC1212] [70JMC1215] Early

symmetrical imidazolidines prepared by condensation of N,N'-diaryl-1,2-ethanediamines

with formaldehyde were reported by Bischoff et al. [1898CB3248] in 1898 and by

Scholtz et al. [1901CB1504] in 1901. Since their work, preparation of other symmetrical

imidazolidines including 1,3-diarylimidazolidines [59LAC120] and 1,3-

dialkylimidazolidines from N,N'-dialkyl- 1,2-ethanediamines [49JOC952] was

demonstrated using the same methodology. Other methods were also reported: i) the

reduction of symmetrical cyclic ureas with LiA1H4, [86JOC2228] ii) reactions of 1,3,6,8-

tetraazatricyclo[4.4.1.13'8]dodecane with p-substituted phenols, [93SC2919] and iii) the

Mannich reaction of 1,2-ethanediamine, benzotriazole and formaldehyde followed by

nucleophilic substitutions with the Grignard reagents. [90JCS(P1)541]

 On the other hand, few syntheses of unsymmetrical N,N'-disubstituted

imidazolidines have been reported. Kliegel et al. demonstrated in 1977 that preparation of

1-phenyl-3-alkylimidazolidines by reactions of formaldehyde with N-alkyl-N'-phenyl-

1,2-ethanediamines previously prepared by the condensation of f-aminosulfonic acids

and primary amines. [77LAC956] Lambert synthesized unsymmetrical imidazolidines