Efficient hydration of nitriles to amides catalysed by sodium nitrate modified fluorapatite

Article abstract of DOI:10.1016/S0040-4039(03)00872-4

The selective hydration of several nitriles to amides have been carried out in water without organic solvent in presence of sodium nitrate modified synthetic fluorapatite in heterogeneous media. The yields obtained are generally high.

Full text of DOI:10.1016/S0040-4039(03)00872-4

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 4031–4033
Efficient hydration of nitriles to amides catalysed by sodium
nitrate modified fluorapatite
a
a
a
a
Abderrahim Solhy, Abdellatif Smahi, Hanane El Badaoui, Brahim Elaabar,
a
a
a,
b
Abderrahim Amoukal, Abdellatif Tikad, Sa ¨ı d Sebti * and D. J. Macquarrie
a
Laboratoire de Chimie Organique Appliqu e´ e et Catalyse, Universit e´ Hassan II, Facult e´ des Sciences Ben M’Sik B.P. 7955,
0702 Casablanca, Morocco
2
b
Department of Chemistry, University of York, Heslington, York YO10 5DD, UK
Received 26 March 2003; accepted 1 April 2003
Abstract—The selective hydration of several nitriles to amides have been carried out in water without organic solvent in presence
of sodium nitrate modified synthetic fluorapatite in heterogeneous media. The yields obtained are generally high. © 2003 Elsevier
Science Ltd. All rights reserved.
Nitriles hydration is an important method to synthesise
amides. Commonly this reaction is carried out using a
strong acid or base. However under these conditions
the carboxylic acid is formed as a by-product. To
enhance the selectivity of the amides synthesis, several
1
catalysts or reagents have been used as cobalt, palla-
Scheme 1.
2
3
4
dium, rhodium, sodium percarbonate, hydrogen per-
5
6
7
9
oxide,
potassium
sodium perborate,
trimethylsilanolate
chloromethylsilane,
8
The fluorapatites have been prepared by reaction
between diammonium phosphate, calcium nitrate and
ammonium fluoride in presence of ammonia (Scheme 2)
and
others.
1
0
Biotransformations were also used in this synthesis.
More interestingly, the use of a heterogeneous process
enhances the selectivity in this reaction. The advantage
of this methodology is well known as the environmen-
tally friendly chemistry. Few examples of heterogeneous
catalysts have been used in the nitriles hydration as
16
as described previously. The FAP obtained was cal-
cined at 900°C before use. The structure of this catalyst
was confirmed by X-ray diffraction, infrared spectra
and chemical analysis. The surface area of calcined
FAP was determined by the BET method and found to
1
1
12
13
14
KF/Al O , resines, amberlyst, MnO /SiO , and
2
3
2
2
2
−1
15
be S=15.4 m g . The total pore volume was calcu-
KF/natural phosphate. On the other hand, we have
demonstrated that the synthetic fluorapatite (FAP) can
be used as a new heterogeneous catalyst in organic
synthesis in the the liquid phase. FAP modified with
sodium nitrate has been also used as a catalyst for
3
−1
lated by the BJH method (V =0.058 cm g ).
T
The modified FAP has been prepared by impregnation
of the FAP with a solution of sodium nitrate (NaNO3/
FAP=1/2 w/w) followed by calcination at 900°C. The
surface area of the new catalyst Na/FAP was deter-
1
6
17
Knoevenagel condensation.
In this work, we wish to describe an efficient selective
hydration of nitriles by Na/FAP catalyst in heteroge-
neous media in water (Scheme 1).
Keywords: nitriles hydration; amides synthesis; reaction in water;
heterogeneous catalysis; fluorapatite; sodium nitrate.
*
Corresponding author. Tel.: +212-6146-4819; fax: +212-2224-9672;
e-mail: saidsebti@yahoo.fr
Scheme 2.
0
040-4039/03/$ - see front matter © 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)00872-4

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032
A. Solhy et al. / Tetrahedron Letters 44 (2003) 4031–4033
Table 1. Hydration of nitriles to amides catalysed by FAP and Na/FAP
2
−1
mined by the BET method as 5.4 m g and the total
estimated by the adsorption of phenol at 0.44 and 0.57
mmol g (2 h), respectively, using GC analysis.
3
−1
pore volume obtained by the BJH method is 0.0032 cm
−
1
g . The infrared spectra are run at 150°C under vac-
uum. The spectrum of dried FAP doped with sodium
nitrate seems to be a simple combination of nitrate and
phosphates bands. It is worth noting that in spectra of
both FAP and doped, no hydroxyls bands are observed
in the range of 3000–4000 cm . The calcined material
has a very interesting set of peaks for OH groups at
high frequency (3710 and 3639 cm ) and a broad peak
at around 1460 cm . All these peaks are in the spec-
trum of Ca(OH) when heated to 300°C to remove
some water. Therefore, it seems that the active species
in CaOH type unit, maybe formed by reaction of NaO
species with Ca centres. The XPS indicates a very small
amount of carbon in both dried and calcined materials,
so we can rule out a significant amount of CaCO in
the samples. The XRD patterns of calcined Na/FAP
showed the apparition of new phases, so the CaO phase
2q=32.2; 37.5 and 54.0) is clearly identified. Two new
phases are probably CaNaPO4 and Na Ca (PO ) F
obtained by an exchange of sodium with calcium. No
crystalline phases of Na O and CaF were observed.
The hydration of nitriles 1 to amides 2 was carried out
in water at 100°C using 2.5 mmol of nitrile and 0.1 g of
the catalyst. The work-up included the addition of
ethanol, filtration to separate the catalyst and evapora-
tion. The products obtained were purified by washing
−
1
1
13
with hexane and identified by H, C NMR and IR
spectroscopy. First of all, we have tested the activity of
the FAP alone in this reaction. The yields of amides 2
after 24 h of reaction time are moderate for 2e and 2i–k
and poor for the others amides. In this reaction the
nitriles derivatives of pyridine ring are more reactive
than those of benzene. Thereafter we have used the
modified phosphate Na/FAP to carried out the hydra-
tion of nitriles. Firstly we have used various quantities
of water to optimise the synthetic conditions. Thus the
yields of isolated amide 2a were 42, 95, 89, 68 and 58%
using 1, 5, 10, 15 and 20 ml of water respectively. The
best conditions for this reaction were found to be 2.5
mmol of substrate, 0.1 g of Na/FAP and 5 ml of water,
which have been applied to synthesis several amides 2
as can be seen in Table 1. The yields obtained are
−
1
−
1
2
3
(
2
4
4 3
2
2
The basic properties of FAP and Na/FAP have been

A. Solhy et al. / Tetrahedron Letters 44 (2003) 4031–4033
4033
generally high. The nitriles with the pyridine ring 3i–k
are also more active than the benzene derivatives when
we use Na/FAP as catalyst. The nitrile 1h, with the
electron-donating methoxy group gave the lowest yield
2. Kaminskaia, N. V.; Kostic, N. M. J. Chem. Soc. Trans.
1996, 18, 3677.
3. Koffl-Bie Djoman, M. C.; Nalt Ajjou, A. Tetrahedron
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Synth. Commun. 1990, 20, 1445.
13
of amide. IR and C NMR spectra were utilised, in
1
addition to H NMR to confirm that, in this case, some
carboxylic acid is formed as a side product. However,
none of the other products showed any contamination
with acid.
5
. (a) Katrizky, A. R.; Pilarski, B.; Urogdi, L. Synthesis
989, 949; (b) Balicki, R.; Kaczmarek, L. Synth. Com-
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1
6
. Sharifi, A.; Mohsenzadeh, F.; Mojtahedi, M. M.; Saidi,
M. R.; Balalaie, S. Synth. Commun. 2001, 31, 431.
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In conclusion, we have prepared the sodium nitrate
modified synthetic fluorapatite and used it as an excel-
lent catalyst for the selective hydration of nitriles to
amides. This transformation has been applied to the
synthesis of several amides with good yields in environ-
mentally friendly water. Na/FAP can be used as a good
and versatile new catalyst for the selective hydration of
nitriles to amides.
7
8
9
3
119.
0. (a) Wang, M. X.; Lin, S. J. Tetrahedron Lett. 2001, 42,
925; (b) Klempier, N.; deRaadt, A.; Faber, K. Tetra-
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6
hedron Lett. 1991, 32, 341; (c) Mauger, J.; Nagasawa, T.;
Yamada, H. Tetrahedron 1989, 45, 1347.
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Acknowledgements
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999, 38, 974.
4. (a) Brueilles, P.; Leclerc, R.; Uguen, D. Tetrahedron Lett.
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Financial assistance of the ‘Minist e` re de l’Enseigement
Sup e´ rieur’ of Morocco (PROTARS, P2T3/59) is grate-
fully acknowledged. We thank also the ‘Office Ch e´ rifien
des Phosphates (OCP)’ and ‘Centre d’Etudes et de
Recherches sur les Phosphates Min e´ raux (CERPHOS)’
for their support. D.J.M. thanks the Royal Society for
a University Research Fellowship.
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