A simple synthesis of ferrocenyl bis-amides by a Ugi four-component reaction

Article abstract of DOI:10.1016/j.jorganchem.2010.06.029

An efficient and simple synthesis of ferrocenyl bis-amides by the Ugi four-component reaction of ferrocenecarboxaldehyde, carboxylic acids, isocyanides and amines in methanol at room temperature is reported.

Full text of DOI:10.1016/j.jorganchem.2010.06.029

Journal of Organometallic Chemistry 695 (2010) 2320e2324
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
A simple synthesis of ferrocenyl bis-amides by a Ugi four-component reaction
*
Roya Akbarzadeh, Peiman Mirzaei, Ayoob Bazgir
Department of Chemistry, Shahid Beheshti University, G.C., P.O. Box 19396-4716, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
An efficient and simple synthesis of ferrocenyl bis-amides by the Ugi four-component reaction of fer-
rocenecarboxaldehyde, carboxylic acids, isocyanides and amines in methanol at room temperature is
reported.
Received 3 April 2010
Received in revised form
7 June 2010
Accepted 29 June 2010
Available online 6 July 2010
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Ferrocenecarboxaldehyde
Ugi reaction
Ferrocenyl bis-amide
Ferrocene
Isocyanide
1. Introduction
The reactions using ferrocenecarboxaldehyde as starting mate-
rial have recently attracted the interest of the synthetic community
Multi-component reactions have recently become one of the
favored methods to prepare pharmacologically relevant
compounds [1,2]. The Ugi four-component reaction (U-4CR) is the
known isocyanide-based multi-component reactions useful for
because the formation of different ferrocene derivatives can be
expected depending on the specific conditions and structure of the
building blocks [21e29].
Considering the above reports, the development of new and
simple synthetic methods for the efficient preparation of the new
ferrocene derivatives will be a beneficial and interesting challenge. In
this paper, we report an efficient synthesis of ferrocenyl bis-amides
by a Ugi four-component reaction using ferrocenecarboxaldehyde.
generation of molecular diversity [3]. In U-4CR (Fig. 1) an a-amido
carboxamide is formed from the reaction of an isocyanide,
a carboxylic acid, and an imine, which is normally formed in situ
from an aldehyde or ketone and an amine. Due to the great diver-
sity of products which can be obtained by this reaction, the U-4CR is
an important tool in combinatorial chemistry [4].
2. Results and discussion
Because ferrocene derivatives are characterized by their ability
to make metal-centred redox systems to generate oxidized or
reduced form of different properties they have been widely
employed in various fields such as: molecular recognition as
biosensors [5e9], in asymmetric catalysis [10], in polymer science
as redox active polymers and dendrimers [11], in nonlinear optics
[12], in synthesis of complex photochemical systems [13] and in
pharmacology [14]. Successful attempts of the synthesis of amino
acids bearing ferrocene moiety have been also performed [15e20].
Ferrocenyl amino acids found their application in food chemistry as
a possible substitute for phenylalanine in the commercial sweet-
ener aspartame [20].
We found that a mixture of ferrocenecarboxaldehyde 1, iso-
cyanides 2aed, carboxylic acids 3aec and amines 4aed in the
absence of any catalyst at room temperature in methanol for 24 h
afforded ferrocenyl bis-amides 5aej in good yields (Scheme 1). The
results are summarized in Table 1.
To the best of our knowledge, this new Ugi four-component
strategy provides the first example of an efficient synthesis of fer-
rocenyl bis-amide derivatives. This method, based on catalyst-free
reaction in methanol, is the most simple and convenient and would
be applicable for the synthesis of different types of ferrocenyl bis-
amides.
Compounds 5 are stable solids whose structures were estab-
lished by IR, 1H and 13C-NMR spectroscopy and elemental analysis.
The elucidation of the structure of 5 using IR, 1H and 13C-NMR
spectroscopic data is discussed with 5a as an example. The IR
* Corresponding author. Fax: þ98 21 22431661.
E-mail address: a_bazgir@sbu.ac.ir (A. Bazgir).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.06.029

R. Akbarzadeh et al. / Journal of Organometallic Chemistry 695 (2010) 2320e2324
2321
O
R4
N
Table 1
O
Synthesis of ferrocenyl bis-amides 5.
NH2
R4
NC
R2
COOH
R2
R3
U-4CR
+
+
Products 5
R
R0
R00
Yield
(%)
+
N
H
R3
R
R1
O
R
R1
Fig. 1. General description of U-4CR.
a
70
spectrum of 5a exhibited absorption bands due to carbonyl groups
of amides at 1672 and 1624 cmꢀ1 and the NH absorption of amide
group was observed at 3323 cmꢀ1. The 1H-NMR spectrum of 5a
b
c
60
75
consisted of multiplet signals for the cyclohexyl rings
(dH
1.17e1.88 ppm) and the NHeCH resonance (dH 3.69) and a sharp
singlet for the methine group (dH 6.04 ppm). A broad resonance (dH
8.23 ppm) was observed for the NH group and a multiplet signal for
the ferrocenyl hydrogens
hydrogens exhibited two broad resonances in the aromatic region
of the spectrum. In the 13C-NMR spectrum, the signals at
67.7,
(dH 3.93e4.17 ppm). The aromatic
d
¼
68.1, 69.2, 69.9 and 82.2 ppm was attributed to the carbon atoms of
the ferrocenyl system. The carbonyl groups of amides were visible
d
e
62
66
at
d
¼ 167.9 and 169.7 ppm and the methine carbon was observed at
d
¼ 60.2 ppm. The signal at
d
¼ 48.5 ppm was attributed to the
methine carbon atom of the cyclohexyl group.
Compound 5 apparently results from the formation of ferrocenyl
imine 6 (formed in situ by reaction of amine 4 and the ferrocene-
carboxaldehyde 1). Subsequent reaction of the imine 6 with the
isocyanides 2 and the carboxylic acids 3 gives intermediate 7, which
rearranges via an acyl transfer into the bis-amides 5 (Scheme 2).
Ferrocene derivatives containing heterocyclic systems have
attracted special attention in recent years [30e32]. Due to the
importance of ferrocenyl heterocyclic compounds, we used 2-
amino pyridine 8a and 2-amino-pyrimidine 8b as heterocyclic
amines in the reaction. This made it possible to synthesize new
ferrocenyl bis-amides containing pyridine and pyrimidine moiety
9a,b (Scheme 3).
f
74
g
73
72
When the indole-3-carboxylic acid 10 was selected as a hetero-
cyclic carboxylic acid (Scheme 4), the ferrocenyl bis-amide con-
taining indole moiety 11 was obtained in 68% yield.
h
3. Conclusion
In conclusion, we have described an efficient Ugi four-compo-
nent reaction for the synthesis of ferrocenyl bis-amide derivatives
under mild and neutral reaction conditions. This method has the
advantages of inexpensive reagents, simple operation and simple
experimental work up procedures.
i
j
CH3
51
45
4. Experimental
4.1. General
Melting points were measured on an Electrothermal 9100
apparatus and are uncorrected. IR spectra were recorded on
O
NHR
CHO
MeOH
Fe
+ R-NC + R'-COOH + R''-NH2
R''
N
Fe
r.t./ 24 h
O
R'
1
2a-c
3a-c
4a-d
5a-j
Scheme 1. Synthesis of ferrocenyl bis-amides 5.

2322
R. Akbarzadeh et al. / Journal of Organometallic Chemistry 695 (2010) 2320e2324
HeAr, 5H), 7.10 (bs, HeAr, 5H), 8.23 (bs, NH, 1H); 13C-NMR (DMSO-
d6, 75.47 MHz): 25.2, 25.7, 32.8, 32.9, 48.5, 60.2, 67.7, 68.1, 69.2,
d
69.9, 82.2, 127.0, 127.8, 127.9, 128.2, 129.3, 131.2, 137.2, 140.5, 167.9,
169.7. Anal. Calcd for C31H32FeN2O2: C, 71.54; H, 6.20; N, 5.38%.
Found: C, 71.41; H, 6.11; N, 5.29%.
4.3.2. Compound 5b
White powder (60%); mp 120e122 ꢁC; IR (KBr) nmax 3300 (NH),
Scheme 2. Mechanism of the reaction.
2918, 1689 (CO), 1622 (CO) cmꢀ1 1H-NMR (DMSO-d6, 300 MHz):
;
d
2.38 (bs, 2CH3, 6H), 4.17 (bs, CHfer, 9H), 6.62 (s, CH, 1H), 7.12 (bs,
HeAr, 13H), 8.56 (bs, NH, 1H). Anal. Calcd for C33H30FeN2O2: C,
73.07; H, 5.57; N, 5.16%. Found: C, 72.94; H, 5.50; N, 5.27%.
Due to very low solubility of the products 5b and 5c, we cannot
report the 13C-NMR data for these products.
a Shimadzu IR-470 spectrometer. 1H and 13C-NMR spectra were
recorded on a BRUKER DRX-300 AVANCE spectrometer at 300.13
and 75.47 MHz, respectively. Elemental analyses were performed
using a Heracus CHN-O-Rapid analyzer. Chemicals were purchased
from Fluka or Merck and used as received.
4.3.3. Compound 5c
Cream powder (75%); mp 185e186 ꢁC; IR (KBr) nmax 3320 (NH),
2936, 1674 (CO), 1631 (CO) cmꢀ1 1H-NMR (DMSO-d6, 300 MHz):
;
4.2. General procedure for the preparation of ferrocenyl bis-amides
5, 8 and 10
d
1.19e1.91 (m, 5 CH2 of cyclohexyl, 10H), 1.67 (s, CH3, 3H), 3.73 (bs,
CHeN of cyclohexyl, 1H), 3.89e4.32 (m, CHfer, 9H), 5.90 (s, CH, 1H),
6.68e6.99 (bs, HeAr, 4H), 7.07e7.15 (m, HeAr, 5H), 8.32 (bs, NH,
1H). Anal. Calcd for C32H34FeN2O2: C, 71.91; H, 6.41; N, 5.24%.
Found: C, 71.83; H, 6.34; N, 5.18%.
A mixture of ferrocenecarboxaldehyde (1 mmol), carboxylic acid
(1 mmol), isocyanide (1 mmol) and amine (1 mmol) in methanol
(3 mL) was stirred for 24 h (The progress of reaction was monitored
by TLC.). After completion of reaction, the reaction mixture was
filtered and the precipitate washed with ether (5 mL) to afford the
pure product.
4.3.4. Compound 5d
Yellow powder (62%); mp 118e120 ꢁC; IR (KBr) nmax 3309 (NH),
2919, 1688 (CO), 1629 (CO) cmꢀ1 1H-NMR (DMSO-d6, 300 MHz):
;
4.3. Spectral data for selected compounds
d 1.06e1.90 (m, 5 CH2 of cyclohexyl, 10H), 3.70 (bs, CHeN of
cyclohexyl, 1H), 4.05e4.20 (m, CHfer, 9H), 6.04 (s, CH, 1H), 6.98 (bs,
4.3.1. Compound 5a
HeAr, 4H), 7.11e717 (m, HeAr, 5H), 8.33 (d, J ¼ 8.4 Hz, NH, 1H); 13C-
Yellow powder (70%); mp 189e191 ꢁC; IR (KBr) nmax 3323 (NH),
NMR (DMSO-d6, 75.47 MHz): d 25.2, 25.7, 32.8, 32.9, 48.6, 60.1, 65.3,
2931, 1672 (CO), 1624 (CO) cmꢀ1
;
1H-NMR (DMSO-d6, 300 MHz):
67.8, 68.3, 69.3, 69.9, 82.0, 127.8, 128.1, 128.2, 129.6, 131.4, 133.0,
137.1, 139.6, 167.9, 169.5. Anal. Calcd for C31H31ClFeN2O2: C, 67.10; H,
5.63; N, 5.05%. Found: C, 67.19; H, 5.57; N, 5.13%.
d
1.17e1.88 (m, 5 CH2 of cyclohexyl, 10H), 3.69 (bs, CHeN of
cyclohexyl, 1H), 3.93e4.17 (m, CHfer, 9H), 6.04 (s, CH, 1H), 6.92 (bs,
O
NHCy
COOH
NC
NH2
CHO
MeOH
Fe
Heterocycle
+ Heterocycle
N
+
+
Fe
r.t./ 24 h
O
Ph
N
N
N
Heterocycle
:
9a 80%
9b 82%
8a
8b
Scheme 3. Synthesis of heterocyclic ferrocenyl bis-amides 9.
O
NHCy
NH2
NC
COOH
CHO
Ph
MeOH
N
Fe
Fe
+
+
+
r.t./ 24 h
O
N
H
NH
10
11
68%
Scheme 4. Synthesis of ferrocenyl bis-amide containing indole moiety 11.

R. Akbarzadeh et al. / Journal of Organometallic Chemistry 695 (2010) 2320e2324
2323
4.3.5. Compound 5e
300 MHz): d 1.15e1.74 (m, 5 CH2 of cyclohexyl,10H), 3.07 (bs, CHeN
Yellow powder (66%); mp 110e111 ꢁC; IR (KBr) nmax 3319 (NH),
of cyclohexyl, 1H), 4.01 (bs, CHfer, 5H), 4.31e4.96 (m, Hfer, 4H), 4.96
(s, CH, 1H), 6.81 (bs, HeAr, 1H), 7.09 (bs, HeAr, 1H), 740e7.95 (m,
HeAr, 7H), 8.22 (bs, NH, 1H); 13C-NMR (DMSO-d6, 75.47 MHz):
2921, 1691 (CO), 1632 (CO) cmꢀ1 1H-NMR (DMSO-d6, 300 MHz):
;
d
1.40 (s, 3CH3, 9H), 3.96e4.19 (m, CHfer, 9H), 6.05 (s, CH, 1H), 6.93
(bs, HeAr, 5H), 7.11e714 (m, HeAr, 5H), 7.86 (bs, NH, 1H); 13C-NMR
(DMSO-d6, 75.47 MHz): 28.9, 50.9, 60.7, 67.7, 68.0, 69.2, 69.8, 70.0,
d
25.2, 25.9, 34.1, 49.5, 56.8, 67.0, 68.4, 69.3, 80.1, 116.4, 123.4, 124.6,
d
128.9, 129.7, 131.3, 133.2, 135.6, 140.9, 165.5, 167.8. Anal. Calcd for
C30H31FeN3O2: C, 69.10; H, 5.99; N, 8.06%. Found: C, 68.99; H, 5.91;
N, 8.13%.
82.5, 127.0, 127.9, 128.0, 128.3, 129.3, 131.1, 137.3, 140.6, 168.4, 169.7.
Anal. Calcd for C29H30FeN2O2: C, 70.45; H, 6.12; N, 5.67%. Found: C,
70.33; H, 6.20; N, 5.74%.
Due to very low solubility of the products 5f and 5g, we cannot
4.3.12. Compound 9b
report the 13C-NMR data for these products.
Light brown powder (82%); mp 230 ꢁC (decomposed); IR (KBr)
nmax 3336 (NH), 2930, 1676 (CO), 1647 (CO) cmꢀ1; 1H-NMR (DMSO-
4.3.6. Compound 5f
d6, 300 MHz):
d 1.13e1.77 (m, 5 CH2 of cyclohexyl, 10H), 3.08 (bs,
Cream powder (74%); mp 115e117 ꢁC; IR (KBr) nmax 3323 (NH),
CHeN of cyclohexyl, 1H), 4.04 (bs, CHfer, 5H), 4.30e4.97 (m, Hfer
,
2919, 1699 (CO), 1636 (CO) cmꢀ1
;
1H-NMR (DMSO-d6, 300 MHz):
4H), 4.99 (s, CH, 1H), 6.80 (bs, HeAr, 1H), 7.07 (bs, HeAr, 1H),
742e7.97 (m, HeAr, 6H), 8.25 (bs, NH, 1H). Anal. Calcd for
C29H30FeN4O2: C, 66.67; H, 5.79; N, 10.72%. Found: C, 66.58; H, 5.71;
N, 10.81%.
d
1.08e1.93 (m, 5 CH2 of cyclohexyl, 10H), 3.62 (bs, CHeN of cyclo-
hexyl, 1H), 3.96e4.25 (m, CHfer, 9H), 6.04 (s, CH, 1H), 6.73e7.89 (m,
HeAr,12H), 8.16 (d, J ¼ 8.6 Hz, NH,1H). Anal. Calcd for C35H34FeN2O2:
C, 73.69; H, 6.01; N, 4.91%. Found: C, 73.79; H, 5.93; N, 4.80%.
Due to very low solubility of the product 9b, we cannot report
the 13C-NMR data for this product.
4.3.7. Compound 5g
Brown powder (73%); mp 146e148 ꢁC; IR (KBr) nmax 3334 (NH),
4.3.13. Compound 11
2931, 1699 (CO), 1638 (CO) cmꢀ1
d
;
1H-NMR (DMSO-d6, 300 MHz):
Cream powder (68%); mp 165e166 ꢁC; IR (KBr) nmax 3342 (NH),
1.30e1.90 (m, 5 CH2 of cyclohexyl, 10H), 3.71 (bs, CHeN of
3241 (NH), 2929, 1654 (CO), 1639 (CO) cmꢀ1 1H-NMR (DMSO-d6,
;
cyclohexyl, 1H), 3.94e4.18 (m, CHfer, 9H), 6.03 (s, CH, 1H), 6.95 (bs,
HeAr, 5H), 7.36 (bs, HeAr, 2H), 7.96 (bs, HeAr, 2H), 8.28 (bs, NH,
1H). Anal. Calcd for C31H31FeN3O4: C, 65.85; H, 5.53; N, 7.43%.
Found: C, 65.77; H, 5.47; N, 7.52%.
300 MHz): d 1.08e1.84 (m, 5 CH2 of cyclohexyl, 10H), 3.63 (bs,
CHeN of cyclohexyl, 1H), 3.89e4.13 (m, CHfer, 9H), 5.89 (s, CH, 1H),
6.88e7.29 (m, HeAr and CH, 10H), 8.09 (bs, NH, 1H), 10.77 (bs, NH,
1H); 13C-NMR (DMSO-d6, 75.47 MHz):
d 25.2, 25.7, 31.9, 32.7, 48.3,
59.3, 67.8, 67.9, 69.1, 69.9, 82.3, 108.8, 111.6, 118.5, 119.0, 121.2, 123.8,
127.5, 127.9, 128.3, 131.0, 136.4, 140.2, 168.1, 170.3. Anal. Calcd for
C32H32FeN4O2: C, 68.58; H, 5.75; N,10.00%. Found: C, 68.45; H, 5.65;
N, 9.89%.
4.3.8. Compound 5h
Orange powder (72%); mp 146e147 ꢁC; IR (KBr) nmax 3331 (NH),
2921, 1698 (CO), 1639 (CO) cmꢀ1 1H-NMR (DMSO-d6, 300 MHz):
;
d
1.41 (s, 3CH3, 9H), 3.96e4.21 (m, CHfer, 9H), 6.03 (s, CH, 1H), 6.94
(bs, HeAr, 5H), 7.34 (d, J ¼ 8.1 Hz, HeAr, 2H), 7.99 (d, J ¼ 8.1 Hz,
Acknowledgements
HeAr, 2H), 8.25 (bs, NH, 1H); 13C-NMR (DMSO-d6, 75.47 MHz):
d
28.9, 51.0, 60.8, 67.8, 68.1, 69.2, 69.7, 70.1, 82.1, 123.3, 127.6, 128.1,
We gratefully acknowledge financial support from the Research
Council of Shahid Beheshti, G.C., University.
129.3, 131.2, 139.6, 143.7, 147.4, 168.1, 168.3. Anal. Calcd for
C29H29FeN3O4: C, 64.57; H, 5.42; N, 7.79%. Found: C, 64.47; H, 5.49;
N, 7.68%.
References
4.3.9. Compound 5i
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Cream powder (51%); mp 213e215 ꢁC; IR (KBr) nmax 3320 (NH),
2934, 1676 (CO), 1632 (CO) cmꢀ1 1H-NMR (DMSO-d6, 300 MHz):
;
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d
1.16e1.85 (m, 5 CH2 of cyclohexyl, 10H), 1.59 (s, CH3, 3H), 3.62 (bs,
CHeN of cyclohexyl, 1H), 3.88e4.13 (m, CHfer, 9H), 5.82 (s, CH, 1H),
7.02e7.14 (m, HeAr, 5H), 8.17 (d, J ¼ 6.9 Hz, NH, 1H). 13C-NMR
(DMSO-d6, 75.47 MHz): d 23.5, 25.2, 25.7, 32.7, 32.8, 48.4, 60.4, 67.7,
67.9, 69.0, 69.8, 82.5, 127.8, 128.4, 130.9, 139.8, 168.0, 169.2. Anal.
Calcd for C26H30FeN2O2: C, 68.13; H, 6.60; N, 6.11%. Found: C, 68.23;
H, 6.65; N, 6.02%.
4.3.10. Compound 5j
Yellow powder (45%); mp 205 ꢁC (decomposed); IR (KBr) nmax
3323 (NH), 2930, 1671 (CO), 1631 (CO) cmꢀ1 1H-NMR (DMSO-d6,
;
300 MHz): 2.26 (s, CH3, 3H), 3.87e4.13 (m, CHfer, 9H), 4.72 and 5.03
(ABSystem, J ¼ 9.1 Hz, CH2), 6.17 (s, CH, 1H), 6.65 (bs, HeAr, 2H),
6.92 (bs, HeAr, 3H), 7.12 (bs, HeAr, 5H), 7.38 (bs, HeAr, 2H), 7.84
(bs, HeAr, 2H), 9.37 (bs, NH, 1H). Anal. Calcd for C33H30FeN2O2S: C,
65.35; H, 4.99; N, 4.62%. Found: C, 65.24; H, 4.91; N, 4.69%.
Due to very low solubility of the product 5j, we cannot report
the 13C-NMR data for this product.
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(2004) 1684e1690.
Orange powder (80%); mp 195 ꢁC (decomposed); IR (KBr) nmax
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1617e1622.

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ꢀ
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