COMMUNICATION
Efficient Co(II) heterogeneously catalysed synthesis of a-aminonitriles at
room temperature via Strecker-type reactions†
Fatemeh Rajabi,*a Sara Ghiassianb and Mohammad Reza Saidi*b
Received 27th April 2010, Accepted 7th June 2010
First published as an Advance Article on the web 21st June 2010
DOI: 10.1039/c0gc00047g
An environmentally friendly and highly active mesoporous
Co(II) complex on mesoporous SBA-15 material could be
used as an easily recoverable catalyst for the synthesis of
a-aminonitriles from a wide range of aldehydes/ketones
and primary or secondary amines with good to excellent
conversions yields at room temperature under solventless
conditions. The catalyst can be recovered by simple filtra-
tion and could be reused at least 10 times without loss of
catalytic activity.
using ketones is still highly challenging (and even not feasible) for
less reactive ketones.7–9,11 Zhang et al. have recently reported an
efficient Brønsted acid catalysed ketone, amine and trimethylsilyl
cyanide (TMSCN) Strecker type reaction, using phosphoric acid
derived catalysts.7 Good to excellent yields of products were
obtained using simple ketones as substrates in the reaction.
However, the protocol suffered from important drawbacks
including the use of high catalyst loadings (10 mol%) of a catalyst
that needs to be recovered by flash chromatography and long re-
action time (typically 24–48 h). Other extensively reported Lewis
acid and base catalysts6–10 often required high catalyst loadings,
some of them are difficult to separate, or recovered and recycles.
The use of ketimines as substrates in Strecker-type cyanation
reactions has been restricted to a few selected examples, and
mostly related to asymmetric processes,8,9 due to their inferior
electrophilic character compared to aldimine counterparts, thus
remaining a significant challenge in organic chemistry.9
Our aim was to develop more efficient and environmentally
friendly catalytic processes. Recently we have reported the
application of a simple and efficient Co(II) complex supported
on mesoporous SBA-15 (Scheme 1) in a wide range of impor-
tant reactions including aerobic oxidations,12 chemoselective
deprotection of acetates,13 acetylation of alcohols14 and C-
heteroatom bond forming reactions.15 This hybrid Co/SBA-
15 catalyst, featuring advantages from both heterogeneous and
homogeneous systems, was found to be highly active and
selective in the reported organic transformations with low
catalyst loadings, offering a versatile and greener approach to
more efficient heterogeneous catalytic process.
Introduction
a-Aminonitriles constitute a major class of naturally occurring
compounds of great interest due to their useful biological
activities and their interconversion to important a-aminoacids
(via facile hydrolysis). They also have been widely used as the
essential building blocks of peptides and proteins synthesis. Nu-
merous synthetic methods have been developed for the synthesis
of a-aminonitriles over a century due to the significance and
prevalence of this class of compounds.1–3
The Strecker reaction represents one of the most direct and ap-
pealing approaches for the preparation of such a-aminonitriles.
The process originally involved the addition of ammonia and
hydrogen cyanide to acetaldehyde and subsequent hydrolysis
of adduct to give alanine, an important aminoacid.4 However,
classical protocols of the Strecker reaction are sometimes of
limited synthetic potential as they often involve harsh condi-
tions, or substrate limitations with side products. With the aim
of developing a milder and more convenient approach towards
the construction of a-aminonitriles, significant advances have
been reported for this important process over the past few years.
These have been mostly related to the optimisation of reaction
conditions and the use of more challenging substrates including
natural products,5 the design of novel and more efficient catalytic
systems6,7 as well as the development of asymmetric Strecker
syntheses.8,9
Scheme 1 Structure of the supported Co(II) catalyst.12–15
The Strecker reaction with aldehydes has been extensively
studied using a wide range of homogeneous and heterogeneous
catalysts.6–10 However, the three-component Strecker reaction
Aiming to bridge the gap between the use of such versatile het-
erogeneous catalysts and the transformation of ever challenging
organic substrates for efficiency-improved catalytic processes,
herein we report a simple, eco-friendly and most convenient
synthetic pathway towards a-aminonitriles from a variety of
aldehydes, ketimines and ketiminium salts using Co/SBA-15 as
catalyst at room temperature. To the best of our knowledge, this
is the first example for the synthesis of a-aminonitriles from
ketiminium salts as substrates.
aDepartment of Science, Payame Noor Univesity, P. O. Box 878, Qazvin,
Iran. E-mail: f_rajabi@pnu.ac.ir; Fax: +98 28 1334 4081; Tel: +98 28
1333 6366
bDepartment of Chemistry, Sharif University of Technology, P. O. Box
11465-9516, Tehran, Iran. E-mail: saidi@sharif.edu; Fax: +98 21 6601
2983; Tel: +98 21 6600 5718
† Electronic supplementary information (ESI) available: Experimental
and spectral data. See DOI: 10.1039/c0gc00047g
This journal is
The Royal Society of Chemistry 2010
Green Chem., 2010, 12, 1349–1352 | 1349
©