RSC Advances
Paper
which was separated, washed with hexane (2 6 5 mL) and
vacuum-dried (in some cases additional purification by
column chromatography over silica gel, using a methanol/
K. Lorenz, J. Manley, B. A. Pearlman, A. Wells, A. Zaks and
T. Y. Zhang, Green Chem., 2007, 9, 411.
4 For recent reviews covering innovative approaches for
amide bond formation see: (a) C. L. Allen and J. M.
J. Williams, Chem. Soc. Rev., 2011, 40, 3405; (b) V.
R. Pattabiraman and J. W. Bode, Nature, 2011, 480, 471;
2 2
CH Cl mixture as the eluent, was needed). The identities of
the resulting primary amides 2a–ae were assessed by compar-
1
13
1
ison of their H and C{ H} NMR spectroscopic data with
those reported in the literature, and by their fragmentation in
GC/MSD.
(
c) R. Garc ´ı a-Alvarez, P. Crochet and V. Cadierno, Green
´
Chem., 2013, 15, 46.
5
6
This method is complementary to the catalytic amidation
of aldehydes with amines which proved particularly useful
for the preparation of secondary and tertiary amides. For a
specific review on this reaction, see: K. Ekoue-Kovi and
C. Wolf, Chem.–Eur. J., 2008, 14, 6302.
General procedure for the ruthenium-catalyzed conversion of
aldehydes into primary amides using NH OH(aq) solution
2
Under a nitrogen atmosphere, the corresponding aldehyde (1
mmol), hydroxylamine (50 wt% solution in water; 80 mL, 1.3
mmol), 3 mL of water (a water/methanol mixture (10 : 1 v/v) in
(a) D. Gnanamgari and R. H. Crabtree, Organometallics,
2009, 28, 922; (b) J. F. Hull, S. T. Hilton and R. H. Crabtree,
the case of aldehyde 1ae), and the ruthenium(II) catalyst
Inorg. Chim. Acta, 2010, 363, 1243; (c) N. Raja, M. U. Raja
and R. Ramesh, Inorg. Chem. Commun., 2012, 19, 51; (d) R.
N. Prabhu and R. Ramesh, RSC Adv., 2012, 2, 4515.
R. R. Gowda and D. Chakraborty, Eur. J. Org. Chem., 2011,
6
[
RuCl
2
(g -C
6
Me
6
){P(NMe
2
)
3
}] (0.025 g, 0.05 mmol; 5 mol%)
were introduced into a teflon-capped sealed-tube and the
reaction mixture stirred at 100 uC for 7–24 h. After this time,
the hot mixture was passed through a filter paper, allowed to
reach room temperature, and subsequently stored in freezer at
7
8
2226.
(a) H. Fujiwara, Y. Ogasawara, K. Yamaguchi and
N. Mizuno, Angew. Chem., Int. Ed., 2007, 46, 5202; (b)
H. Fujiwara, Y. Ogasawara, M. Kotani, K. Yamaguchi and
N. Mizuno, Chem.–Asian J., 2008, 3, 1715.
2
20 uC for 10 h. This led to the crystallization of the
corresponding primary amide, which was separated, washed
with hexane (2 6 5 mL) and vacuum-dried (in some cases
additional purification by column chromatography over silica
gel, using a methanol/CH Cl mixture as the eluent, was
9 N. A. Owston, A. J. Parker and J. M. J. Williams, Org. Lett.,
2007, 9, 73.
2
2
needed).
10 M. A. Ali and T. Punniyamurthy, Adv. Synth. Catal., 2010,
3
52, 288.
1 (a) N. C. Ganguly, S. Roy and P. Mondal, Tetrahedron Lett.,
012, 53, 1413; (b) A. Mart ´ı nez-Asensio, M. Yus and D.
1
2
Acknowledgements
J. Ram o´ n, Tetrahedron, 2012, 68, 3948.
Financial support from the Ministerio de Econom ´ı a
Competitividad of Spain (Projects CTQ2010-14796/BQU and
CSD2007-00006) is gratefully acknowledged.
y
1
1
1
2 C. L. Allen, C. Burel and J. M. J. Williams, Tetrahedron Lett.,
2
010, 51, 2724.
3 B. K. Allam and K. N. Singh, Tetrahedron Lett., 2011, 52,
851.
5
4 The use of a glycerol-based carbon catalyst and silica
chloride both in organic media, has also been recently
described: (a) K. Ramesh, S. N. Murthy, K. Karnakar, K. H.
V. Reddy, Y. V. D. Nageswar, M. Vijay, B. L. A. P. Devi and R.
B. N. Prasad, Tetrahedron Lett., 2012, 53, 2636; (b) B. Datta
and M. A. Pasha, Bull. Korean Chem. Soc., 2012, 33, 2129.
5 For leading books covering this field see: (a) C. J. Li and T.
H. Chan, Comprehensive Organic Reactions in Aqueous
Media, John Wiley & Sons, New Jersey, 2007; (b) Organic
Reactions in Water Principles, Strategies and Applications, ed.
U. M. Lindstrom, Blackwell Publishing Ltd., Oxford, 2007;
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(a) See for example: Methoden Org. Chem. (Houben Weyl),
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