Synthesis of ferrocenyl-β-enamino ketones: A search of ferrocenylpyrido[2,3-d]pyrimidines using a Ni(CN)2/NaOH/KCN system as catalytic precursor

Article abstract of DOI:10.1016/j.jorganchem.2009.07.017

New ferrocenyl-β-enamino ketones (1-6), were obtained from 6-amino-1,3-dimethyluracil and several ferrocenyl-α-ketoalkynes via MeNH^- anion in a monophasic aqueous system containing Ni(CN)₂/CO/NaOH/H₂O/KCN are described. A

Full text of DOI:10.1016/j.jorganchem.2009.07.017

Journal of Organometallic Chemistry 694 (2009) 3823–3827
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of ferrocenyl-b-enamino ketones: A search of ferrocenylpyrido[2,3-d]py-
rimidines using a Ni(CN)2/NaOH/KCN system as catalytic precursor
Ivonne Arellano a, Pankaj Sharma a, Armando Cabrera a, Diego Pérez a, José L. Arias b, Noé Rosas a,
*
a Instituto de Química, Universidad Nacional Autónoma de México, 04510 México DF, Mexico
b Departamento de Química, Facultad de Estudios Superiores Cuautitlán, Universidad Nacional Autónoma de México, Cuautitlán Izcalli, Edo. de México, 54700 México, Mexico
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 June 2009
Received in revised form 7 July 2009
Accepted 8 July 2009
Available online 31 August 2009
New ferrocenyl-b-enamino ketones (1–6), were obtained from 6-amino-1,3-dimethyluracil and several
ferrocenyl-a
-ketoalkynes via MeNHꢀ anion in a monophasic aqueous system containing Ni(CN)2/CO/
NaOH/H2O/KCN are described. A mechanism for obtaining of b-enamino ketones is suggested.
Ó 2009 Elsevier B.V. All rights reserved.
Keywords:
Ferrocenyl-b-enamino ketones
Pyrido[2,3-d]pyrimidines
Aqueous catalytic system
Nickel
1. Introduction
3095 cmꢀ1 can be attributed to the stretching vibration of the
hydrogen bonded enamine N–H group. This band appears at a low-
b-Enamino ketones are versatile synthetic intermediates for the
synthesis of several natural products [1], -aminoalcohols [2] and
er frequency as a consequence of N–HꢁꢁꢁO@C intramolecular inter-
action. A similar observation has been reported earlier [10]. In
these compounds the N–H stretching vibration appears at lower
frequency due to the presence of electron donor ferrocenyl moiety
at the nucleophilic side of the compounds in comparison to the
N–H vibration observed for similar ferrocenyl enaminones
(3203 cmꢀ1) where the ferrocenyl moiety is at the electrophilic
side [10]. IR spectrum of compound (1) in CHCl3 shows C@O vibra-
c
different heterocyclic compounds such as pyridones, pyrimidones,
pyranones, isoquinolines [3], and present interesting pharmacolog-
ical properties such as anticonvulsants and are pharmacophores
for other several drugs [4]. These b-enamino ketones can be syn-
thesized in variety of ways [3b] and the most common method in-
cludes the condensation of amines with b-dicarbonyl compounds
under homogeneous or heterogeneous catalytic conditions [5].
Though variety of b-enamino ketones are reported in literature,
ferrocenyl-b-enamino ketone, where the ferrocenyl group is linked
to the nucleophilic side of the molecule, is unknown. On the other
hand ferrocenyl group has been widely used in the design or rede-
sign of drugs that can result favorable changes in their biological
activities [6–9]. In view of the above it is worth while to prepare
some new ferrocenyl-b-enamino ketones.
tion at 1592 cmꢀ1, suggesting the presence of
a,b unsaturated car-
bonyl system. In the mass spectra of all the compounds, molecular
ion peaks are observed along with the loss of cyclopentadienyl
fragment [M-65]+ which corresponds to base peak in the fragmen-
tation pattern. 1H NMR spectra of all the compounds present sim-
ilar chemical shifts pattern for ferrocenyl group. In all the
compounds
a
singlet appearing at ꢂ11.85 ppm and doublet
appearing at ꢂ3.13 ppm can be assigned to the aminic protons.
The appearance of NH proton at higher chemical shift is due to
the presence of intramolecular H-bonding. This observation also
confirms the absence of the imine form in these compounds. The
absence of two sets of signals in IR and NMR spectra for these com-
pounds confirms the existence of only enamino configuration, con-
trary to the doubling of signals observed earlier in similar
compounds [10]. In the 13C NMR spectra of all these compounds
a signal at 186–187 ppm can be assigned to the carbonyl group.
In the case of 1-p-methoxy-phenyl-3-methylamino-3-ferroce-
nyl-2-propenone (1), the molecular structure was unambiguously
established by X-ray crystallography and exists as Z–s–Z configura-
2. Results and discussion
New ferrocenyl-b-enamino ketones obtained in this work
(Table 1) are characterized by various physicochemical techniques.
In the IR spectra of all the synthesized ferrocenyl-b-enamino ke-
tones, C@O and C@C vibrations are observed. A weak band at
* Corresponding author. Tel.: +52 56224556; fax: +52 56162203.
E-mail address: noe@servidor.unam.mx (N. Rosas).
0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2009.07.017

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I. Arellano et al. / Journal of Organometallic Chemistry 694 (2009) 3823–3827
Table 1
Ferrocenyl b-enamino ketones.
Entry
1
Ferrocenyl-
a
-ketoalkynes
Uracil
Ferrocenyl-b-enamino ketones
Yield %
75
Me
O
6-Amino-1,3-dimethyluracil
NH
NH
NH
Fc
O
Fe
OMe
OMe
O
Me
2
6-Amino-1,3-dimethyluracil
74
Fc
O
Fe
OMe
MeO
OMe
MeO
O
Me
3
4
6-Amino-1,3-dimethyluracil
6-Amino-1,3-dimethyluracil
80
72
Fc
O
Fe
O
Me
NH
Fc
O
Fe
O
Me
5
6
6-Amino-1,3-dimethyluracil
6-Amino-1,3-dipropyluracil
78
72
NH
Fc
O
Fe
O
Pr
NH
Fc
O
Fe
OMe
OMe
Reaction conditions: Time 15 min; temperature 55 °C; Ni(CN)2/CO/5N NaOH/KCN; yielding 7-ferrocenyl-2,4-dioxopyrido[2,3-d]pyrimidines <5%.
No reaction without (NiCN)2/CO/KCN for 24 h. at 55 °C. Fc = Ferrocenyl group.
tion as shown in Fig. 1. Crystal data and selected bond lengths and
angles for 1 are given in Table 2 and 3, respectively. The compound
is monomeric and crystallizes in the space group P21 with Flack
parameter ꢀ0.041(18). This compound crystallizes with two inde-
pendent molecules per asymmetric unit and presents an intramo-
lecular NꢀHꢁꢁꢁO@C hydrogen bond. The C@CꢀC@O atoms are
planar and the bond lengths indicate electron delocalization.
C(3)–C(10) bond is a typical sp2–sp2 single bond, suggesting that
the cyclopentadienyl ring is not involved in the conjugation.
Previously our group has reported that at room temperature in
the presence of a nickel catalytic system viz Ni(CN)2/CO/KCN/
55 °C, an anionic specie MeNHꢀ is formed by the decomposition
of 6-amino-1,3-dimethyluracil which is facilitated by the another
anionic catalytic specie [Ni(CN)4]ꢀ4, obtaining the corresponding
ferrocenyl-b-enamino ketones as is shown in Scheme 1. Ferroce-
nylpyrido[2,3-d]pyrimidines were also obtained but in very low
yields (5%) at this temperature. But in the absence of Ni(CN)2, CO
and KCN catalytic system, no reaction occurred even after 24 h.
A plausible two steps pathway can be envisaged for the prepa-
ration of ferrocenyl-b-enamino ketones.
The first step involves the retrocondensation of 6-amino-1,3-
dimethyluracil affording N,N0-dimethylurea and cyanoacetate ion
[12] (Scheme 2). The second step involves a nucleophilic attack
of [Ni(CN)4]ꢀ4, formed in situ in basic media, on the N,N0-dimethyl-
urea, affording the methylamide MeNHꢀ [13]. This anion after the
NaOH, reaction of ferrocenyl-a-ketoalkynes and 6-amino-1,3 dim-
ethyluracil yield 7-ferrocenyl-2,4-dioxopyrido[2,3-d]pyrimidines
[11]. But in this work, increasing the temperature from 25° at

I. Arellano et al. / Journal of Organometallic Chemistry 694 (2009) 3823–3827
3825
Fig. 1. ORTEP diagram of 1-p-methoxy-phenyl-3-methylamino-3-ferrocenyl-2-propenone (1).
Table 2
Crystallographic data for compounds (1).
Parameter
Compound (1)
Parameter
Compound (1)
Empirical formula
Formula weight
Crystal color
Crystal system
Space group
Crystal size (mm)
a (Å)
C21H21FeNO2
375.24
Red prism
Monoclinic
P21
0.34 ꢃ 0.13 ꢃ 0.03
11.4202(13)
8.813(1)
17.962(2)
90
Z
4
DCalc (Mg/m3)
1.400
0.860
k (mmꢀ1
2
Reflections collected
Independent reflections
Rint
R1 [I > 2r(I)]
wR2
Goodness-of-fit (GOF)
Flacks parameter
Max/min
)
H
(o)
1.81–25.35
14 810
6486
0.0708
0.0560
0.0801
0.808
b (Å)
c (Å)
a
(°)
b (°)
(°)
V (Å3)
99.912(2)
90
1780.9(3)
ꢀ0.041(18)
c
D
q
(e Åꢀ3
)
0.577/ꢀ0.321
O
R
H
O
R1
N
R
O
O
N
R
Ni(CN)2/H2O/KCN/CO
NaOH (5N)/55 ºC/
N
N
+ Fc
NH2
Fc
O
+
R1
N
R
15 min
O
N
R
<5%
Fc
R1
>70%
Fc= Ferrocenyl
1 R= Me, R1= p-methoxyphenyl
2 R= Me, R1= 3,5-dimethoxyphenyl
3 R= Me, R1= m-tolyl
4 R= Me, R1= p-ethylphenyl
5 R= Me, R1= Phenyl
6 R= n-Pr, R1= p-methoxyphenyl
Scheme 1.
O
Me
O
O
N
retrocondensation
NC
+
[Ni(CN)4]-4/NaOH/H2O
MeHN
NHMe
O
O
N
NH2
Me
Scheme 2.

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I. Arellano et al. / Journal of Organometallic Chemistry 694 (2009) 3823–3827
and data reduction) and SHELXTL were used for solution and refine-
ment of the structure.
O
[Ni(CO)x(CN)y]-z
carbonylated nickel
species
NaOH/H2O/CO
2 MeNH
+
Me
Me
+
N
H
N
H
3.3. 1-p-Methoxyphenyl-3-methylamino-3-ferrocenyl-2-propenone
(1)
[Ni(CN)4]-4
Me
H
N
The product was obtained as described in the general procedure
as an orange solid (75%); Empirical formula: C21H21NO2Fe; mp.
123 °C; IR (CHCl3 solution, selected, cmꢀ1) 1326 (OMe), 1592
(C@O), 3095 (N–H); Mass spectrum EI: m/z (%) = 375 (66) [M]+,
310 (100) [M–cp]+; 1H NMR (300 MHz, CDCl3, d in ppm) 3.13 (d,
3H, J = 5.5 Hz, NCH3), 3.86 (s, 3H, OMe), 4.23 (s, 5H, cp-ring), 4.42
(t, 2H, J = 1.9 Hz, cp-ring), 4.61 (t, 2H, J = 1.9 Hz, ring-cp), 6.18 (s,
1H, C@CH), 6.94 (d, 2H, J = 8.5 Hz, 3,5-phenyl), 7.89 (d, 2H,
J = 8.8 Hz, 2,6-phenyl), 11.80 (s, 1H, NH); 13C NMR (75 MHz, CDCl3,
d in ppm) 31.7 (CH3N), 55.4 (p-OCH3-phenyl), 69.7, 70.3, 70.4, 79.3
(C, cp-ring), 92.6 (C@C–CO), 113.5 (2C, 3,5-phenyl), 128.5 (1C, 1-
phenyl), 133.8 (2C, 2,6-phenyl), 161.5 (1C, 4-phenyl), 166.9
(C@C), 185.8 (C@O).
O
MeNH
Fc
Fc
O
R1
R1
Scheme 3.
Table 3
Selected bond length (Å) and selected bond angles (o) for the compounds (1).
Angles (°)
Bond length (Å)
O(1)–C(1)–C(2)
N(1)–C(3)–C(2)
C(3)–C(2)–C(1)
O(3)–C(22)–C(23)
N(2)–C(24)–C(23)
C(24)–C(23)–C(22)
C(2)–C(3)–C(10)
C(23)–C(24)–C(31)
121.4(6)
120.1(5)
125.8(6)
120.3(6)
118.5(5)
126.5(5)
118.7(5)
120.2(5)
O(1)–C(1)
C(1)–C(2)
C(2)–C(3)
C(3)–N(1)
O(3)–C(22)
C(22)–C(23)
C(23)–C(24)
C(24)–N(2)
1.286(6)
1.404(7)
1.382(7)
1.322(7)
1.262(6)
1.442(7)
1.387(7)
1.343(6)
3.4. 1-3,5-Dimethoxyphenyl-3-methylamino-3-ferrocenyl-2-
propenone (2)
The product was obtained as described in the general procedure
as an orange solid (74%); Empirical formula: C22H23NO3Fe; mp.
140 °C; IR (CHCl3 solution, selected, cmꢀ1) 1320 (OMe), 1548
(C@C), 1592 (C@O), 3092 (N–H); Mass spectrum EI: m/z (%) = 405
(54) [M]+, 340 (100) [M–cp]+; 1H NMR (300 MHz, CDCl3, d in
ppm) 3.15 (d, 3H, J = 5.5 Hz, NCH3), 3.85 (s, 6H, OMe), 4.24 (s, 5H,
cp-ring), 4.43 (t, 2H, J = 1.9 Hz, cp-ring), 4.61 (t, 2H, J = 1.9 Hz,
ring-cp), 6.16 (s, 1H, C@CH), 6.55 (t, 1H, J = 2.3 Hz, 4-phenyl),
7.07 (d, 2H, J = 2.2 Hz, 2,6-phenyl), 11.87 (s, 1H, NH); 13C NMR
(75 MHz, CDCl3, d in ppm) 31.8 (CH3N), 55.6 (3,5-OCH3-phenyl),
69.9, 70.3, 70.4, 78.7 (C, cp-ring), 93.2 (C@C–CO), 102.7 (1C, 4-phe-
nyl), 104.7 (2C, 2,6-phenyl), 143.5 (1C, 1-phenyl), 160.7 (2C, 3,5-
phenyl), 167.8 (C@C), 185.9 (C@O).
1,2-addition to ferrocenyl-
enamino ketones (Scheme 3).
a-ketoalkynes yields the ferrocenyl-b-
In order to confirm that alkylamide ion is the nucleophilic spe-
cie is formed in the second step, the reaction is carried out using 6-
amino-1,3-dipropyluracil, instead of 6-amino-1,3-dimethyluracil
with 1-p-methoxy-phenyl-3-ferrocenyl-propynone yielding 1-p-
methoxy-phenyl-3-propylamino-3-ferrocenyl-2-propenone, (entry
6, Table 1).
In summary, we found a new one pot method to prepare ferr-
ocenyl-b-enamino ketones from 6-amino-1,3-disustituted uracil
derivatives and several ferrocenyl-a-ketoalkynes, these reactions
can be performed in water with mild conditions in the presence
3.5. 1-m-Methylphenyl-3-methylamino-3-ferrocenyl-2-propenone (3)
of Ni catalyst.
The product was obtained as described in the general procedure
as an orange solid (80%); Empirical formula: C21H21NOFe; mp.
71 °C; IR (CHCl3 solution, selected, cmꢀ1) 1322 (OMe), 1592
(C@O), 3044 (N–H); Mass spectrum EI: m/z (%) = 359 (56) [M]+,
294 (100) [M–cp]+; 1H NMR (300 MHz, CDCl3, d in ppm) 2.41 (s,
3H, CH3), 3.14 (d, 3H, J = 5.8 Hz, NCH3), 4.23 (s, 5H cp-ring), 4.42
(t, 2H, J = 1.9 Hz, cp-ring), 4.61 (t, 2H, J = 1.9 Hz, ring-cp), 6.19 (s,
1H, C@CH), 7.24 (d, 2H, J = 6.6 Hz, 4-phenyl), 7.32 (t, 2H,
J = 7.4 Hz, 5-phenyl), 7.70 (d, 1H, J = 7.6 Hz, 6-phenyl), 7.73 (s, 1H,
2-phenyl), 11.90 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, d in ppm)
21.7 (m-CH3-Phenyl), 31.8 (CH3N), 69.9, 70.3, 70.4, 78.9 (C, cp-
ring), 93.2 (C@C–CO), 123.9 (1C, 6-phenyl), 127.6 (1C, 5-phenyl),
128.2 (1C, 2-phenyl), 131.1 (1C, 4-phenyl), 137.9 (1C, 1-phenyl),
141.2 (1C, 3-phenyl), 167.5 (C@C), 186.8 (C@O).
3. Experimental
3.1. General procedure
A 5 N NaOH solution (25 mL) was saturated by slowly bubbling
CO at room temperature for 30 min. To the solution was then
added 2 mmol of Ni(CN)2ꢁ4H2O and stirred under a CO atmosphere
until a pale yellow solution was obtained. Addition of 15 mmol of
KCN resulted in a color change to orange. The 6-amino-1,3-disusti-
tuted uracil (5 mmol) and the ferrocenyl-a-ketoalkynes [6]
(5 mmol) were added keeping the temperature at 55 °C, the mix-
ture was stirred for 15 min. The evolution of the reaction was fol-
lowed by TLC. The reaction products were quantified in a Hewlett
Packard 5870 until the end of reaction. After the usual workup the
products were purified by crystallization.
3.6. 1-p-Ethylphenyl-3-methylamino-3-ferrocenyl-2-propenone (4)
The product was obtained as described in the general procedure
as an orange solid (72%); Empirical formula: C22H23NOFe; mp.
50 °C; IR (CHCl3 solution, selected, cmꢀ1) 1324 (OMe), 1539
(C@C), 1592 (C@O); Mass spectrum EI: m/z (%) = 373 (45) [M]+,
308 (100) [M–cp]+; 1H NMR (300 MHz, CDCl3, d in ppm) 1.26 (t,
3H, J = 7.5 Hz, CH2CH3), 2.70 (c, 2H, J = 15.1 Hz, CH2CH3), 3.13 (d,
3H, J = 5.5 Hz, NCH3), 4.23 (s, 5H, ring-cp), 4.42 (t, 2H, J = 1.9 Hz,
ring-cp), 4.61 (t, 2H, J = 1.9 Hz, ring-cp), 6.20 (s, 1H, C@CH), 7.26
(d, 2H, J = 8.0 Hz, 3,5-phenyl), 7.83 (d, 2H, J = 8.3 Hz, 2,6-phenyl),
11.86 (s, 1H, NH); 13C NMR (75 MHz, CDCl3, d in ppm) 15.49
3.2. X-ray crystallography
The X-ray intensity data were measured at 298 K on a Bruker
Smart APEX CCD-based X-ray diffractometer using a monochroma-
tized Mo Ka radiation (Ka 0.71073 Å). The detector was placed at a
distance of 4.837 cm from the crystal. Analysis of the data showed
negligible decays during data collections. An analytical face in-
dexed absorption correction was applied. Crystal structure was re-
fined by full-matrix least squares. SMART software (data collection

I. Arellano et al. / Journal of Organometallic Chemistry 694 (2009) 3823–3827
3827
(CH2CH3), 28.84 (CH3N), 31.79 (CH2CH3), 69.8, 70.3, 70.4, 79.3 (C,
Acknowledgements
cp-ring), 92.9 (C@C–CO), 126.9 (2C, 3,5-phenyl), 127.8 (2C, 2,6-
phenyl), 138.6 (1C, 1-phenyl), 146.9 (1C, 4-phenyl), 167.2 (C@C),
186.6 (C@O).
We thank to Dirección General de Asuntos del Personal Acadé-
mico, DGAPA, Universidad Nacional Autónoma de México UNAM,
for financial support. Project No. IN 204507-3.
3.7. 1-Phenyl-3-methylamino-3-ferrocenyl-2-propenone (5)
The product was obtained as described in the general procedure
as an orange solid (78%); Empirical formula: C20H19NOFe; mp.
53 °C; IR (CHCl3 solution, selected, cmꢀ1) 1591 (C@C), 1545
(C@O), 3089 (N–H); Mass spectrum EI: m/z (%) = 345 (71) [M]+,
280 (100) [M–cp]+; 1H NMR (300 MHz, CDCl3, d in ppm) 3.15 (d,
3H, J = 5.2 Hz, NCH3), 4.24 (s, 5H, cp-ring), 4.43 (t, 2H, J = 1.9 Hz,
cp-ring), 4.62 (t, 2H, J = 1.9 Hz, ring-cp), 6.20 (s, 1H, C@CH), 7.43
(t, 3H, J = 3.3 Hz, phenyl), 7.90 (dd, 2H, J = 6.6 Hz, phenyl), 11.90
(s, 1H, NH); 13C NMR (75 MHz, CDCl3, d in ppm) 31.8 (CH3N),
69.6, 70.1, 70.6, 78.8 (C, cp-ring), 92.9 (C@C–CO), 126.7, 126.9,
128.2, 128.4, 131.0, 141.2 (C-phenyl), 167.6 (C@C), 186.5 (C@O).
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2009.07.017.
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3.8. 1-p-Methoxy-phenyl-3-prophylamino-3-ferrocenyl-2-propenone
(6)
The product was obtained as described in the general procedure
as an orange solid (72%); Empirical formula: C23H25NO2Fe; mp.
43 °C; IR (CHCl3 solution, selected, cmꢀ1
)
2926 (C@C),
1592(C@O); Mass spectrum EI: m/z (%) = 403 (48) [M]+, 338 (100)
[M–cp]+; 1H NMR (300 MHz, CDCl3, d in ppm) 1.00 (t, 3H,
J = 11.1 Hz, CH2CH2CH3), 1.66 (sex, 2H, J = 10.7 Hz, CH2CH2CH3),
3.44 (c, 2H, J = 19.3 Hz, NCH2CH2CH3), 3.86 (s, 3H, OMe), 4.23 (s,
5H cp-ring), 4.40 (t, 2H, J = 2.8 Hz, cp-ring), 4.58 (t, 2H, J = 2.7 Hz,
ring-cp), 6.18 (s, 1H, C@CH), 6.94 (d, 2H, J = 8.8 Hz, 3,5-phenyl),
7.90 (d, 2H, J = 8.8 Hz, 2,6-phenyl), 11.85 (s, 1H, NH). 13C NMR
(75 MHz, CDCl3,
d
in ppm) 11.7 (CH3CH2CH2N), 24.1
[11] I. Arellano, P. Sharma, J.L. Arias, A. Toscano, A. Cabrera, N. Rosas, J. Mol. Catal. A:
Chem. 266 (2007) 294.
[12] I. Devi, P. Bhuyan, Tetrahedron Lett. 46 (2005) 5727.
[13] A.M. Barrios, S.J. Lippard, Inorg. Chem. 40 (2001) 1250.
(CH3CH2CH2N), 46.7 (CH3CH2CH2N), 55.4 (p-OCH3-phenyl), 69.6,
70.3, 70.4, 79.7 (C, cp-ring), 92.5 (C@C–CO), 113.5 (2C, 3,5-phenyl),
128.5 (C, 1-phenyl), 128.6 (2C, 2,6-phenyl), 161.4 (1C, 4-phenyl),
166.1 (C@C), 184.2 (C@O).