TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 43 (2002) 3975–3976
Silica gel induced cleavage of aziridines by aromatic amines
under solvent free conditions
R. Vijaya Anand, Ghanshyam Pandey and Vinod K. Singh*
Department of Chemistry, Indian Institute of Technology, Kanpur 208 016, India
Received 25 March 2002; accepted 12 April 2002
Abstract—A variety of aziridines were opened in an efficient manner with aromatic amines using silica gel under solvent free
conditions. © 2002 Elsevier Science Ltd. All rights reserved.
Ring opening of aziridines with nucleophiles is an
important transformation in organic synthesis and it
is usually carried out by means of Lewis acids.1,2 If
the nucleophiles are amines, the products become
diamines which are a synthetically important class of
compounds. Recently, the ring opening of aziridines
by amines has been reported in the presence of ytter-
bium triflate,2a,2b copper(II) and tin(II) triflates2c in an
appropriate solvent. However, there is no report in
the literature where this type of aziridine cleavage has
been achieved using silica gel under solvent free con-
ditions. In this paper we report, for the first time, the
opening of aziridines with aromatic amines with silica
gel under solvent free conditions.
lated yield was not high (32%, entry 3). An unusual
feature of this reaction is that only aromatic amines
opened the aziridines. Aliphatic amines such as
diethylamine, n-butylamine, benzylamine and pyrro-
lidine failed to react with aziridines at room tempera-
ture. When entry 1 was repeated with a mixture of
aniline and benzylamine (1:1 ratio; 1.2 mmol of each
amine), only the diamine 1a was obtained in 81%
yield. Aniline reacted with the aziridine, but benzy-
lamine remained unreacted. This observation indi-
cated that the methodology will be very useful for the
preferential cleavage of aziridines by aromatic amines.
The present methodology for solvent-free cleavage of
aziridines by aromatic amines over aliphatic amines
should find application in organic synthesis, and to
the best of our knowledge, is unprecedented in the
literature.
A variety of aziridines were synthesized from the cor-
responding amino alcohols3 in one step using MsCl
(1.1 equiv.) and Et3N (2.5 equiv.) in pyridine (as sol-
vent) at room temperature and then subjected to the
cleavage reaction with amines by means of silica gel.
In most cases, a high yield of the ring-opened
product was obtained (Table 1). In the cases of
acyclic terminal aziridines (entries 19 and 20), the
reaction was highly regioselective as only one product
was isolated. It was observed that if a solvent such as
ether was used, the cleavage of the aziridine became
sluggish, and even after 2 days the reaction was not
complete (50–60% conversion). An important feature
of the reaction was that the highly deactivated amine
such as p-nitroaniline also reacted, although the iso-
General procedure: A mixture of an aziridine (1
mmol), an aromatic amine (1.2 mmol) and silica gel
(500 mg; activated at 120°C under vacuum for 6 h)
was taken in a 5 mL R.B. flask and the solid shaken
till the reaction was complete (disappearance of
aziridine spot on TLC plate). The silica gel–reaction
mixture was loaded onto a small silica gel column
and eluted with ethyl acetate–petroleum ether to
afford the pure diamines.4
Acknowledgements
We thank the CSIR (Government of India) for fund-
ing our research and a senior research fellowship to
R.V.A.
* Corresponding author. Fax: 91-512-597436; e-mail: vinodks@
iitk.ac.in
0040-4039/02/$ - see front matter © 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(02)00727-X
Anand, R. Vijaya
