from diethyl oxalate with primary amines in three-steps involving LiAlH4 reduction of

the corresponding oxamides to unsymmetrical N,N'-disubstituted-1,2-ethanediamines and

condensation with formaldehyde. [86S657] Perillo et al. [00JHC57] recently prepared 1-

benzyl-3-arylimidazolidines from formaldehyde and N-benzyl-N'-aryl-1,2-

ethanediamines, produced by BH3 reduction of the corresponding N-benzoyl-N'-aryl- 1,2-

ethanediamines. [98SC1625]

 R1 and R2 alkyll or aryl) groups are generally introduced when N,N'-disubstituted-

1,2-ethanediamines are prepared in the protocols mentioned above. However, the

methods limit the efficiency and the productivity for preparation of a wide variety of

imidazolidines. N-Substituted benzotriazoles have been reported as useful synthetic

precursors due to the easy replacement of the benzotriazole group as a leaving group via

nucleophilic substitution, elimination, reduction, cyclization, etc.[98CR409] We now

report a simple and efficient way to prepare novel unsymmetrical imidazolidines, and

optically active imidazolidines in good to excellent yields and extend this methodology to

the preparation of 2,3-dihydro-1H-benzimidazoles using benzotriazole as a synthetic

auxiliary.

 SBt Bt
 R1-N N-R2 \,N Ny
 H H HCHO RMgX 2.3
 S2.3
 2.2 (R1 = R2) Bt = benzotriazolyl
 RlN N-R2
 HHO 2.1 "HCHO
 H 4 steps
 SArl-N NYPh
 2O0 O H H
 PhN R2 2.6, Y = H2
 H H EtO OEt BH3 E 2.6, Y = H2
 2.4 2.5 2.7, Y = C=O

Scheme 2-1. Previously reported methods for imidazolidines