Reaction of 1,2-dibromoethane with primary amines: formation of N , N ′-disubstituted ethylenediamines RNH–CH 2 CH 2 –NHR and homologous polyamines RNH–[CH 2 CH 2 NR] n –H
摘要:
The reaction of primary amines RNH2 (R: Me, Et, iPr, tBu and Ph) with 1,2-dibromoethane gave N,N'-disubstituted ethylenediamines R-NH-CH2CH2-NH-R (1) in yields ranging from 10% (1a; R=Me) to 70% (1d, R=tBu; 1e, R=Ph). Piperazines and N-substituted polyethyleneimines were identified (H-1 NMR, C-13 NMR and EI-MS) as side products of the reaction and isolated by fractional distillation. The piperazines 2 are formed in yields of 3-10% and can be separated from the diamines 1 in all cases, except for R=Me and Ph. The polyamine homologues RNH-[CH2CH2NR](n)-H (3-5) were isolated in yields ranging from 0.1% (n=4, R=iPr) to 14% (n=2, R=iPr). The yields of 1 increase with the size of the substituent R, no obvious trend exists for the yields of the side products. (C) 2003 Elsevier Ltd. All rights reserved.