Received: 20 November 2016
Revised: 23 December 2016
Accepted: 31 December 2016
F U L L PA P E R
Mild and eco‐friendly chemoselective acylation of amines in
aqueous medium using a green, superparamagnetic, recoverable
†
nanocatalyst
Maryam Kazemi Miraki
| Elahe Yazdani | Leila Ghandi | Kobra Azizi | Akbar Heydari
Chemistry Department, Tarbiat Modares
University, PO Box 14155‐4838,
Tehran, Iran
Copper‐grafted guanidine acetic acid‐modified magnetite nanoparticles
(
Fe O @GAA‐Cu(II)) as a green, superparamagnetic and recoverable nanocatalyst
3
4
is found to promote quantitative N‐acylation of various amines in a very short time
with an equimolar amount of thioacetic acid in water at room temperature. This
method is found to be highly selective for amines and not sensitive to other func-
tional groups. Mild reaction condition, high selectivity, efficiency, simple workup
and excellent yields are some of the major advantages of the procedure.
Correspondence
Akbar Heydari, Chemistry Department,
Tarbiat Modares University, PO Box
1
†This article is dedicated to memory of
Khalil Motaharniya
KEYWORDS
heterogeneous catalyst, magnetic nanoparticles, N‐acylation reaction, organocatalyst
1
| INTRODUCTION
anhydrides react rapidly with water and alcohols leading to
the corresponding acids and esters, respectively. The selec-
Acylation of amines is a basic and important reaction in
organic chemistry. Many pharmacological molecules possess
tive acylation of amines in the presence of other functional
groups is a rather difficult process. Numerous strategies
including the direct and metal‐mediated condensation of
[1]
at least one amide bond. N‐Acyl derivatives of amines are
used for the synthesis of amides and their derivatives, as
starting materials for various transformations and for
protecting ─NH and ─OH group functionality in multi‐step
[
7]
unactivated carboxylic acids and amines, acylation through
[
8]
N‐acyl DBN tetraphenyl borate salts, mercury‐ and ruthe-
[
9]
nium‐catalysed Beckman rearrangements,
oxidative
[
2]
[10]
syntheses. Several methods for acylation have been devel-
amidation,
triazole‐ and imidazole‐mediated acyl transfer
and acylation through acylbenzotriazoles
[
11]
[12]
oped including: (a) direct reaction of an amine and an acid,
reactions
(
b) reaction of a readily available acid derivative (e.g. simple
have been developed to circumvent the inherent problems.
These reactions suffer from some drawbacks such as the
requirement of more expensive reagents, relatively harsh
reaction conditions and long reaction times. Thus, there is
still a great need to find various alternative reagents for acyl-
ation of amines.
methyl ester) with an amine, (c) formation of an activated car-
bonyl compound (e.g. acid chloride, anhydride or active
ester) followed by condensation with an amine and (d) one‐
pot reaction of a carboxylic acid with an amine in which a
[
3]
coupling reagent activates the acid component in situ.
[4]
Among various synthetic protocols, N‐acylation reaction
is commonly carried out with acetic anhydride or acetyl chlo-
ride in the presence of either acidic or basic catalysts under
various conditions. However, there are a number of prob-
lems associated with N‐acylation reactions using acyl chlo-
rides and acid anhydrides. For example, anhydrides can
form imides as side products when reacted with primary
In contrast to carboxylic acids, thioacids have been of
considerable interest due to their unique reactivity and selec-
[
13–17]
tivity in amide bond formations. Various authors
have
[
5]
reported elegant methods for N‐acylation of amines in pep-
[
18]
tide synthesis. In 2013, Gopi and co‐workers
used
copper(II) acetate as a catalyst for acylation of amines. But
this methodology suffers from using a large amount of cata-
lyst and cumbersome procedures for separation of the
resulting product. Filtration and expensive ultracentrifugation
[
6]
amines, while reactions of acyl chlorides with amines can
be highly exothermic. In addition, many acid chlorides and
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