Synthesis and structure of planar chiral ferroceno[d]pyridazinones, the first representatives of a novel class of fused metallocenes

Article abstract of DOI:10.1016/j.jorganchem.2011.01.032

A series of planar chiral ferroceno[d]pyridazinones was prepared by hydrazine-mediated cyclisations of (S_p)-2-formylferrocenoyl fluoride obtained in two steps from (2S,4S)-4-(methoxymethyl)-2-ferrocenyl-1,3-dioxane. Further derivatives based on the novel heterocyclic scaffold were resulted by means of the facile N-alkylation reactions carried out on the easily accessible fused product derived from the hydrazine-mediated cyclisation. Upon treatment with hydrazine (S_p)-2-formylferroce carboxylic acid, the precursor of the acid fluoride with enhanced reactivity, afforded a dimeric azine avoiding cyclisation. The spectacular difference between the experimentally observed reactivity of the bifunctional formylferrocenes was disclosed by comparative DFT analysis of the assumed hydrazone- and hydrazide intermediates with different values of LUMO energy associated with different conformation. The structures of the new compounds were established by IR and NMR spectroscopy, including HMQC, HMBC and DNOE measurements.

Full text of DOI:10.1016/j.jorganchem.2011.01.032

Journal of Organometallic Chemistry 696 (2011) 1626e1631
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis and structure of planar chiral ferroceno[d]pyridazinones, the first
representatives of a novel class of fused metallocenes
*
Á. Gyömöre, A. Csámpai
Institute of Chemistry, Eötvös Loránd University, P.O. Box 32, H-1518 Budapest 112, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of planar chiral ferroceno[d]pyridazinones was prepared by hydrazine-mediated cyclisations of
(Sp)-2-formylferrocenoyl fluoride obtained in two steps from (2S,4S)-4-(methoxymethyl)-2-ferrocenyl-
1,3-dioxane. Further derivatives based on the novel heterocyclic scaffold were resulted by means of the
facile N-alkylation reactions carried out on the easily accessible fused product derived from the hydra-
zine-mediated cyclisation. Upon treatment with hydrazine (Sp)-2-formylferroce carboxylic acid, the
precursor of the acid fluoride with enhanced reactivity, afforded a dimeric azine avoiding cyclisation.
The spectacular difference between the experimentally observed reactivity of the bifunctional for-
mylferrocenes was disclosed by comparative DFT analysis of the assumed hydrazone- and hydrazide
intermediates with different values of LUMO energy associated with different conformation. The
structures of the new compounds were established by IR and NMR spectroscopy, including HMQC, HMBC
and DNOE measurements.
Received 7 January 2011
Received in revised form
19 January 2011
Accepted 25 January 2011
Keywords:
Condensed ferrocene
Pyridazine
Planar chirality
DFT modelling
NMR spectroscopy
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
2. Results and discussion
During the last decades the chemistry of ferrocenes has attrac-
ted remarkable attention due to their wide range of interest in
material sciences, catalysis and biological assays [1]. Besides these
applications the sandwich complexes have also been shown
different biological activities and were also used in therapy [2].
Earlier, our group have synthesized and characterized different
ferrocene-containing heterocycles of potential and e in a few cases
[3e] - proved biological activity, including ferrocenyl-pyrazoles-
and pyrazolines-, condensed 1,2,4-triazoles- [3], imidazoles- [4],
diazepines- [5], oxazoles- [6], dihydropyrimidines [7], quinolines
[8] and pyridazines [9]. On the other hand, according to the liter-
ature a wide variety of heterocyclic scaffolds possess valuable
pharmaceutic properties including anticancer effects [10], however
much less attention has been paid to the chemistry of ferroceno-
condensed heterocycles offering the possibility to introduce planar
chirality into the molecule [11]. Prompted by this fact, in the frame
of our ongoing research on ferrocene-containing heterocyclic
compounds to be tested in in vitro assays we targeted the prepa-
ration of the first representatives of ferroceno[d]pyridazines, a new
class of heterocyclic ring system of potential biological relevance.
2.1. Synthesis of ferroceno[d]pyridazinones
First chiral ferrocenyl dioxane 1 was prepared from for-
myferrocene in two steps according to the protocol described by
Kagan et al. [12] which was then transformed into carboxylic acid 2
by directed diastereoselective lithiation [12] followed by carbox-
ylation (Scheme 1). We envisaged the hydrazine-mediated cycli-
sation of 2 to obtain ferroceno[d]pyridazione 5a which can be
considered as the precursor of a variety of N-alkylated derivatives.
Contrary to our expectations the reaction conducted in refluxing
ethanol afforded dimer 3 in good yield (82%) without being
contaminated by pyridazinone product. When a five-fold excess of
hydrazine hydrate was used as reagent 3 could again be isolated
from the reaction mixture. This observation is in accord with the
facile hydrazine-mediated conversion of formylferrocene yielding
dimmer azine [13]. Employing the same conditions ring closure of 2
was also attempted with methyl- and (2-hydroxyethyl)-hydrazine,
respectively, but the reactions gave undefined decomposition
products. Since the carboxyl group seemed to be deactivated by the
highly electron-releasing ferrocene moiety [14], 2 was converted
into acid fluoride 4 by treatment with cyanuricfluoride and
pyridine in DCM [15]. To our pleasure 4 could be isolated in
unexpectedly high yield (85%) which was converted into the first
targeted ferroceno[d]pyridazinone 5a in good yield (77%) on
short treatment (10 min) with hydrazine hydrate in dry THF at
* Corresponding author.
E-mail address: csampai@chem.elte.hu (A. Csámpai).
0022-328X/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2011.01.032

Á. Gyömöre, A. Csámpai / Journal of Organometallic Chemistry 696 (2011) 1626e1631
1.) t-BuLi / Et2O, rt, 1 h, Ar
1627
O
N
2
N2H4.H2O / EtOH
reflux, 2 h, Ar
2.) CO , 20 oC, 20 min.
–
3.) 2M2HCl, rt, 12 h
CHO
3
O
H
CO2H
CO2H
OMe
1
Fe
2 (52%)
Fe
Fe
Cyanuricfluoride
Pyridine, DCM,
rt, 1.5 h, Ar
3 (82%)
1
R3
4'
4-R3-PhNHNH2 / EtOH
reflux, 2 h, Ar
CHO
COF
Fe
1'
2'
N
N
H
3
2
PhCH2NHNH2.HCl,
H
4 (85%)
NH2NHR1 / THF
rt, 10 min, Ar
NaH / THF
1
CO2H
Fe
rt, 10 min, Ar
(E)-6a R3=H (64%)
(E)-6b R3=NO2 (86%)
1
N
N
N
7
6
BrCH2R2 or 2-(BrCH2)C5H4N.HBr
NaH / THF, rt, 12 h, Ar
R1
4
N
CH2R2
Fe
Fe
O
O
from 5a
5a R1=H (77%)
5e R2=Ph (31% from 4; 42% from 5a)
5f R2=CO2Et (45%)
5b R1=Me (44%)
5c R1=(CH2)2OH (34%)
5d R1=(CH2)2CN (14%)
5g R2=2-pyridyl (64%)
Scheme 1. Synthesis and subsequent transformations of planar chiral bifunctional ferrocenes including the synthesis of ferrocenopyridazinones.
room temperature. The reactions employing alkylhydrazine-type
reagents gave the corresponding N3-alkylated pyridazinones 5bee
in substantially lower yields (14e44%) which could not be
increased by employing prolonged reaction time (1 h) and elevated
temperature (50e60 ꢀC) due to the formation of the mixture of
undefined tarry materials. On the other hand, the N-alkylation
reactions of the easily accessible 5a with bezylbromide, 2-bromo-
methylpyridine and ethyl bromoacetate (5a/5eeg: Scheme 1)
carried out under basic conditions (NaH/THF) at room temperature
demonstrated an alternative synthetic route to versatile products
containing the novel metallocene scaffold.
pronounced deactivating effect of the ferrocene moiety on the
electrophilic centre, reflected by the calculated data of 8, is at least
partly compensated by the fluorine atom in 9.
Since the cyclisations of type 4/5 can also be assumed to
proceed in a competitive manner via primary N-acylation followed
by condensation with the formyl group hydrazide 10, the inter-
mediate of the reaction of 4 effected by hydrazine hydrate, was also
subjected to DFT analysis (Fig. 1). Suggesting its facile ring closure
the LUMO energy and the NH2eCO distance obtained for the
optimized structure are in line with the same parameters calcu-
lated for hydrazones 7e9.
Attempted cyclisations of 4 with phenylhydrazine and 4-nitro-
phenylhydrazine, respectively, carried out in THF at room temper-
ature led also to the formation of complex mixtures. Employing the
same reagents in refluxing ethanol 2 afforded hydrazones (E)-6a,b
(Scheme 1) which e on prolonged heating in the different mixtures
of EtOH and AcOH e underwent decomposition reactions.
2.3. Structure determination of the novel compounds
The spectroscopic data listed in the Experimental Part are
consistent with the structures of 2, 3, 4, 5aeg and (E)-6a,b only the
following remarks are necessary.
2.2. Comparative theoretical study on the structure and reactivity
of the possible intermediates involved in the cyclisation reactions
Both 1H and 13C NMR spectra taken of 2 in DMSO-d6 solution
point to the presence of formyl- and carboxyl groups excluding the
detectable formation of the cyclic hydroxylacton isomer.
Interestingly, in CDCl3 solution 4 proved stable enough to be
subjected to longer NMR measurements. In its 13C NMR spectrum
a considerable split of the line of the carbonyl group directly
attached to fluorine (1JC-F ¼ 336.3 Hz) was detected, while the
doublets of the C1 and C2 signals point to weaker interactions with
the fluorine atom (2JC-F ¼ 72.4 Hz and 3JC-F ¼ 4.6 Hz, respectively).
As the consequence of planar chirality the diastereotopic
protons of the CH2 group attached directly to N3 atom in 5beg
produce separated signals.
Prompted by the fact that in pure organic chemistry 2-for-
mylbenzoic acid and related bifunctional precursors can easily be
converted into condensed pyridazinones on the effect of hydrazines
[16], we undertook DFT modelling [17] to interpret the reluctance
of 2 and the enhanced reactivity of 4 to undergo analogous heter-
ocyclisation. The optimized global minimum structures of three
hydrazones with (Z) configuration 7, 8 and 9, the assumed inter-
mediates of the hydrazine-mediated cyclisation reactions of
2-formylbenzoic acid, 2 and 4 (Fig. 1), were obtained by B3LYP
calculations [18] using 6e31 G(d) basis set [19]. The energy values
of LUMO characterising the reactivity of the carbonyl group are in
good correlation with the crucial NH2eCO distance and the
above-mentioned preparative observations suggesting that the
The characteristic cross peak due to the 3J coupling between the
NH proton and C4a atom detected in the 1H-13C-HMBC spectrum of
5a indicates the condensation of the pyridazinone ring to the
ferrocene moiety.

1628
Á. Gyömöre, A. Csámpai / Journal of Organometallic Chemistry 696 (2011) 1626e1631
Fig. 1. Optimized structures with characteristic NH2eCO distance and ELUMO of hydrazones (Z)-7ꢂ9 and hydrazide 10 (for the sake of unique, comparable appearance the enantiomeric
form is represented), the assumed intermediates of the heterocyclisations of 2-formylbenzoic acid, 2 and 4.
The (E) configuration at the C]N bond in 6a,b was unambigu-
ously evidenced by the mutual NOE’s (6e9%) detected between the
NH and CH protons.
For 5aeg the assignment of the skeletal protons is based on
NOE’s (4e6%) detected for the proton pairs H1/H7, H7/H6 and
H6/H5.
(
15N) MHz, with the deuterium signal of the solvent as the lock and
TMS as internal standard (1H, 13C) and NH3(liq) as external refer-
ence (15N). The 15N NMR chemical shifts were obtained and
assigned from the 1He15N HMBC spectra. DEPT spectra were run in
a standard manner, using only a
Q
¼ 135ꢀ pulse to separate the CH/
CH3 and CH2 lines phased “up” and “down”, respectively. The
2D-COSY, HSQC, HMBC and DIFFNOE spectra were obtained by
using the standard Bruker pulse programs. All calculations were
carried out with the Gaussian 03 suite of programs [21]. Optimized
structures are available from the authors.
In the 1H-15N HMBC spectra of 5aeg the H1 signal gives corre-
lation with the signals of N2- and N3 atoms discernible at
320 ꢁ 2 ppm and 180 ꢁ 3 ppm, respectively, unambiguously sug-
gesting the presence of adjacent imino- and lactam groups. Both N2
and N3 signals are also correlated with the protons of the CH3- or
CH2 group directly attached to N3 (in 5beg). In the spectrum of 5a
the correlation between nuclei H3 and N3 appears as a satellite
signal reflecting a coupling constant of 95 Hz (1JN-H).
4.1. (Sp)-2-Formylferrocene-1-carboxylic acid (2)
In a dry Schlenk tube a solution of acetal 1 (6.32 g, 20 mmol) in
dry degassed diethylether (90 mL) was treated with a pentane
solution of t-butyllithium (1.7 M, 15.1 mL, 22 mmol) at ꢂ78 ꢀC for
10 min. The reaction mixture was allowed to warm up to rt., stirred
for 1 h and cooled down to ꢂ20 ꢀC. At this temperature dry CO2 gas
was introduced into the resulted orange suspension for 20 min to
produce the precipitate of the lithium carboxylate salt. After the
addition of 2 M HCl (30 mL) containing SnCl2 (1 g) the solution was
allowed to warm up to rt., stirred for overnight and the organic
phase was separated. The aqueous phase was extracted with EtOAc
(3 ꢃ 40 mL). The combined organic phase was washed with water
(3 ꢃ 40 mL), dried over Na2SO4, and evaporated. The oily residue
was subjected to flash column chromatography on silica first using
DCM-MeOH (80:1) as eluent to produce a fraction containing an
undefined mixture. On repeated elution with DCM-MeOH 30:1 two
bands developed on the standing phase. Evaporation of the first
band gave recovered formylferrocene (0.770 g, 18%). The residue
obtained by the evaporation of the second fraction was triturated
with petroleum ether 40/70, filtered off and dried to give the
product as a dark orange solid. Yield: 2.713 g (52%); mp.: 94e95 ꢀC
Due to the enhanced delocalisation of the lone pair from the NH
group towards the nitro substituent transmitted by the phenyl ring,
the corresponding signal is downfield shifted in (E)-6b (153 ppm)
relative to that measured for (E)-6a (142 ppm).
3. Conclusion
By extending the groups of hydrazine reagents and alkylating
agents the reported syntheses of the first representatives of planar
chiral ferroceno[d]pyridazinones based on 2-formylferrocene-
carbonyl fluoride might open up expedient ways to a wide variety
of novel metallocene derivatives of potential biological interest.
Alkylation with multifunctional reagents can be followed by further
transformations resulting in novel molecular libraries of diverse
structures. The easily accessible 2-formylferrocenecarbonyl fluo-
ride of which preparation is described in this contribution can be
considered as the precursor of a range of metallocene scaffolds with
planar chirality. The structure-reactivity relationship disclosed for
the hydrazone- and hydrazide intermediates by DFT modelling can
also be taken into account to set up procedures for related cycli-
sation reactions targeting the synthesis of further fused ferrocenes.
(decomp.); [
a]
25: þ24.5ꢀ (EtOH); IR (cmꢂ1): w3300e2500, 1708,
D
1625, 1454, 1213, 1174, 701; 1H NMR (DMSO-d6): 10.05 (s, 1H, CH]
O); 5.14 (br s, 1H, H3); 5.02 (br s, 1H, H4); 4.91 (br s, 1H, H5); 4.37 (s,
h
5-C5H5); 13C NMR (DMSO-d6): 194.3 (CH]O); 172.3 (CO2H);
4. Experimental
5H,
80.3 (C2); 77.1 (C3); 75.2 (C1); 74.9 (C4); 72.2 (
h
5-C5H5); 71.8 (C5);
All chemicals were obtained from commercially available sour-
ces (Aldrich, Fluka) and e except for THF e used without further
purification. THF was purified by subsequent distillations from
LiAlH4 and sodium benzophenone. Melting points (uncorrected)
were determined with a Boethius microstage. Merck Kieselgel
(230e400 mesh, 60 Ǻ) and alumina (Brockmann I grade, approx.
150 mesh, 58 Ǻ, activated neutral) were used for flash column
chromatography. The IR spectra were run by ATR (Attenuated Total
Reflectance) method [20] on a Bruker IFS-55 FT-spectrometer
controlled by Opus 3.0 software. Optical rotations were measured
with a Zeiss Polamat A polarimeter. The 1H and 13C NMR spectra
were recorded in DMSO-d6 or CDCl3 solution in 5 mm tubes at RT,
on a Bruker DRX-500 spectrometer at 500 (1H), 125 (13C) and 50
Anal. Calcd. for C12H10FeO3 (258.05): C: 55.85; H: 3.91; Found: C:
55.71; H: 4.03%.
4.2. General procedure for the reactions of 2 with hydrazines
(Sp)-2-Formylferrocenecarboxylic acid (0.516 g, 2 mmol) and the
corresponding hydrazine (2.2 mmol) were dissolved in ethanol
(20 mL) and the solution refluxed for 2 h under Ar. After evapora-
tion of the solvent and addition of water (10 mL) and a few drops of
acetic acid the residue was extracted with DCM. The organic layer
was dried over Na2SO4 and evaporated to obtain a solid which was
crystallized with petrolether 40/70 and dried to give the product.

Á. Gyömöre, A. Csámpai / Journal of Organometallic Chemistry 696 (2011) 1626e1631
1629
4.2.1. (Sp,Sp)-1,2-Bis-(2-carboxyferrocenylmethylydene)
4.4. General procedure for the reactions of 4 with hydrazines:
preparation of 5aed
hydrazine (3)
Red powder. Yield: 0.420 g (82%). mp.: 200e202 ꢀC (decomp.);
[
a]
25: þ41.3ꢀ (DMF/EtOH 2/1); IR (cmꢂ1): w3200e2800, 1664,1613,
(Sp)-2-Formylferrocenecarbonyl fluoride (0.774 g, 3 mmol) and
the corresponding hydrazine (4 mmol) were dissolved in dry THF
(10 mL) and the solution was stirred for 10 min at r.t. Following this
period the dark red solid precipitated from the reaction mixtures
resulted by the reactions of 4 with hydrazine hydrate and meth-
ylhydrazine, respectively, were extracted with DCM (2 ꢃ10 mL)
(5a) or with EtOAc (2 ꢃ10 mL) (5b). The The DCM solution of 5a
was filtered through cellit. After the evaporation of the solutions of
5a and 5b, respectively, the residue was triturated with petroleum
ether 40/70, filtered off and dried to obtain the product. The reac-
tion mixtures resulted by the reactions of 4 with 2-hydrazinoe-
thanol hydrazine and 3-hydrazinopropionitrile, respectively, were
evaporated to dryness and the oily residues were subjected to
column chromatography on neutral alumina using DCM as eluent.
The residue obtained by the evaporation of the orange band was
triturated with petroleum ether 40/70, filtered off and dried to give
the product.
D
1464, 1234, 1082, 825,742; 1H NMR (DMSO-d6): 9.05 (s, 1H, CH]N);
5.11 (br s, 1H, H3); 5.02 (br s, 1H, H5); 4.74 (br s, 1H, H4); 4.32 (s, 5H,
h
5-C5H5); 13C NMR (DMSO-d6): 172.7 (CO2H); 161.9 (CH]N); 79.6
(C4); 75.0 (C5); 73.5 (C3); 72.0 (h N
5-C5H5); 71.5 (C5); 70.9 (C2); 15
NMR (DMSO-d6): 329 (CH]N); Anal. Calcd. for C24H20Fe2O4
(512.12): C: 55.29; H: 3.94; N: 5.47; Found: C: 55.13; H: 3.98; N:
5.51%.
4.2.2. (Sp)-(E)-2-(2-carboxyferrocenylmethylydene)-1-
phenylhydrazine[(E)-6a]
Dark orange powder. Yield: 0.446 g (64%). mp.: 93e94 ꢀC
(decomp.); [
a
]
25: ꢂ12.0ꢀ (DMSO); IR (cmꢂ1): w3100e2700, 1679,
D
1599, 1494, 1287, 1257, 1171, 1000, 820, 747, 691; 1H NMR (DMSO-
d6): 12.53 (br s, 1H, CO2H); 10.22 (s, 1H, NH); 8.35 (s, 1H, CH]N);
7.14 (t, 3J ¼ 7.3 Hz, 2H, H3050); 6.94 (d, 3J ¼ 7.3 Hz, 2H, H2060); 6.65 (t,
3J ¼ 7.3 Hz, 1H, H40); 5.01 (br s, 1H, H3); 4.81 (br s, 1H, H5); 4.54 (br
s, 1H, H4); 4.17 (s, 5H, h
5-C5H5); 13C NMR (DMSO-d6): 173.4 (CO2H);
146.8 (CH]N); 136.9 (C10); 129.9 (C3050); 119.0 (C40); 112.5 (C2060);
4.4.1. (Sp)-Ferroceno[d]pyridazin-4(3H)-one (5a)
84.1 (C2); 72.6 (C4); 71.7 (C5); 71.4 (
h
5-C5H5); 70.1 (C1); 69.3 (C3);
Reddish orange powder. Yield: 0.587 g (77%); mp.: 157e160 ꢀC
25
15N NMR (DMSO-d6): 324 (CH]N); 142 (NH); Anal. Calcd. for
C18H16FeN2O2 (348.18): C: 62.09; H: 4.63; N: 8.05; Found: C: 61.98;
H: 4.68; N: 8.11%.
(decomp.);
[
a
]
D
:
þ60.5ꢀ (DMF-EtOH 3:2); IR (cmꢂ1):
w3200e2800, 1642, 1474, 1407, 1174, 1106, 841, 591; 1H NMR
(DMSO-d6): 11.16 (s, 1H, NH); 8.16 (s, 1H, H1); 5.13 (br s, 1H, H5);
5.02 (br s, 1H, H7); 4.58 (br s, 1H, H6); 4.12 (s, 5H,
NMR (DMSO-d6):167.1 (C4); 141.2 (C1); 79.7 (C7a); 74.5 (C4a); 74.1
(C6); 67.0 (C7); 66.7 (C5); 70.7 (
5-C5H5); 15N NMR (DMSO-d6): 323
h
5-C5H5); 13C
4.2.3. (Sp)-(E)-2-(2-carboxyferrocenylmethylydene)-1-(4-
nitrophenyl)hydrazine[(E)-6b]
h
Dark red powder. Yield: 0.676 g (86%). mp.: 210e212 ꢀC
(N2); 183 (N3); Anal. Calcd. for C12H10FeN2O (254.07): C: 56.73; H:
3.97; N: 11.03; Found: C: 56.88; H: 4.08; N: 8.03%.
(decomp.); [
a
]
25: þ37.2ꢀ (DMSO); IR (cmꢂ1): 3260, w3200e2800,
D
1670, 1593, 1300, 1273, 1172, 1108, 1070, 1000, 835, 748; 1H NMR
(DMSO-d6): 12.59 (br s, 1H, CO2H); 11.27 (s, 1H, NH); 8.61 (s, 1H,
CH]N); 8.12 (d, 3J ¼ 8.8 Hz, 2H, H3050); 7.08 (br d, 3J ¼ 8.8 Hz, 2H,
H2060); 5.11 (br s, 1H, H3); 4.93 (br s, 1H, H5); 4.69 (br s, 1H, H4);
4.4.2. (Sp)-3-Methylferroceno[d]pyridazin-4(3H)-one (5b)
Orange powder. Yield: 0.354
g
(44%); mp.: 101e103 ꢀC
(decomp.); [
a
]
D
25: þ50.4ꢀ (DMF-EtOH 1:1); IR (cmꢂ1): 2953, 2922,
4.26 (s, 5H,
(C10); 143.1 (CH]N); 138.7 (C40); 127.1 (C3050); 111.7 (C2060); 82.2
(C2); 73.4 (C5); 72.5 (C4); 71.7 (
5-C5H5); 71.2 (C1); 69.5 (C3); 15N
h
5-C5H5); 13C NMR (DMSO-d6): 173.3 (CO2H); 151.4
2853, 1649, 1444, 1409, 1342, 1102, 828, 598; 1H NMR (CDCl3): 8.04
(s,1H, H1); 5.24 (br s,1H, H5); 4.79 (br s,1H, H7); 4.44 (br s,1H, H6);
h
4.10 (s, 5H,
140.7 (C1); 79.1 (C7a); 74.8 (C4a); 73.9 (C6); 67.0 (C7); 65.8 (C5);
70.4 (
5-C5H5); 38.6 (NCH3); 15N NMR (CDCl3): 322 (N2); 177 (N3);
h
5-C5H5); 3.69 (NCH3); 13C NMR (CDCl3): 166.4 (C4);
NMR (DMSO-d6): 370 (NO2); 315 (CH]N); 153 (NH); Anal. Calcd.
for C18H15FeN3O4 (393.17): C: 54.99; H: 3.85; N: 10.69; Found: C:
55.04; H: 3.78; N: 10.81%.
h
Anal. Calcd. for C13H12FeN2O (268.09): C: 58.24; H: 4.51; N: 10.45;
Found: C: 58.28; H: 4.44; N: 10.32%.
4.4.3. (Sp)-3-(2-hydroxyethyl)ferroceno[d]pyridazin-4(3H)-one
4.3. (Sp)-2-formylferrocenoyl fluoride (4)
(5c)
Orange powder. Yield: 0.286
(decomp.); [
g
(32%); mp.: 105e107 ꢀC
(Sp)-2-Formylferrocene-1-carboxylic acid (2) (2.581 g, 10 mmol)
was dissolved in dry DCM (50 mL). To this solution pyridine
(1.650 mL) and cyanuride fluoride (3.605 mL) were added at 0 ꢀC.
After a few minutes the cooling bath was removed and the
mixture was stirred at rt for 90 min under Ar. After addition of
crushed ice the resulted suspension was filtered, the organic phase
was separated, washed with cold water (3 ꢃ 50 mL), dried over
Na2SO4, filtered and evaporated. After a few minutes the dark oily
residue solidified. The dark orange airstable crystals were
collected and dried in vacuum exicator over P2O5 overnight at rt.
(The product can be stored in PE flask at rt. practically without
decomposition.) Yield: 2.211 g (85%); mp.: 113e114 ꢀC (decomp.);
a
]
25: þ63.7ꢀ (DMF-EtOH 1:1); IR (cmꢂ1): 3350, 3085,
D
2951, 2865, 1622, 1580, 1444, 1409, 1346, 1140, 1105, 815, 590; 1H
NMR (DMSO-d6): 8.21 (s, 1H, H1); 5.16 (br s, 1H, H5); 5.02 (br s, 1H,
H7); 4.71 (br s, 1H, OH); 4.59 (br s, 1H, H6); 4.20 (m, 1H, NCHAHB);
4.13 (s, 5H,
h
5-C5H5); 3.94 (m, 1H, NCHAHB); 3.68 (t, 3J ¼ 5.9 Hz, 2H,
CH2OH); 13C NMR (DMSO-d6): 165.8 (C4); 141.2 (C1); 79.3 (C7a);
74.7 (C4a); 74.5 (C6); 67.1 (C7); 66.9 (C5); 70.9 (h
5-C5H5); 59.6
(CH2OH); 51.8 (NCH2); 15N NMR (CDCl3): 320 (N2); 178 (N3); Anal.
Calcd. for C14H14FeN2O2 (298.12): C: 56.40; H: 4.73; N: 9.40; Found:
C: 56.48; H: 4.70; N: 9.34%.
4.4.4. (Sp)-3-(2-cyanoethyl)ferroceno[d]pyridazin-4(3H)-one (5d)
Red powder. Yield: 0.129 g (14%); mp.: 117e120 ꢀC (decomp.);
[
a]
25: þ34.8ꢀ (acetone); IR (cmꢂ1): 1789, 1670, 1418, 1274, 1207,
D
951, 857, 774; 1H NMR (CDCl3): 10.49 (s, 1H, CH]O); 5.34 (br s, 1H,
[
a
]
25: þ77.2ꢀ (DMF-EtOH 1:1); IR (cmꢂ1): 2950, 2923, 2247, 1665,
D
H5); 5.18 (br s, 1H, H4); 4.96 (br s, 1H, H3); 4.44 (s, 5H,
h
5-C5H5);
1451,1368,1335,1304,1118,1104, 815, 785; 1H NMR (CDCl3): 8.14 (s,
1H, H1); 5.36 (br s, 1H, H5); 4.87 (br s, 1H, H7); 4.58 (m, 1H,
13C NMR (CDCl3): 193.3 (CH]O); 162.1 (d, 1JC-F ¼ 336.3 Hz, COF);
80.9 (d, 3JC-F ¼ 4.6 Hz, C2); 77.4 (C4); 76.1 (C3); 74.3 (br s, C5); 72.8
NCHAHB); 4.54 (br s, 1H, H6); 4.24 (m, 1H, NCHAHB); 4.18 (s, 5H, h5
-
(
h
5-C5H5); 65.8 (d, 2JC-F ¼ 72.4 Hz, C1); Anal. Calcd. for C12H9FFeO2
C5H5); 2.97 (t, 3J ¼ 5.9 Hz, 2H, CH2CN); 13C NMR (CDCl3): 166.5 (C4);
(260.04): C: 55.43; H: 3.49; Found: C: 55.48; H: 3.58%.
142.0 (C1); 118.0 (CN); 78.7 (C7a); 74.3 (C6); 74.1 (C4a); 67.4 (C7);

1630
Á. Gyömöre, A. Csámpai / Journal of Organometallic Chemistry 696 (2011) 1626e1631
66.4 (C5); 70.8 (
h
5-C5H5); 45.8 (NCH2); 17.5 (CH2CN); Anal. Calcd.
4.7. (2-Pyridylmethyl)ferroceno[d]pyridazin-4(3H)-one (5g)
for C15H13FeN3O (307.13): C: 58.66; H: 4.27; N: 13.68; Found: C:
58.64; H: 4.34; N: 13.74%.
Sodium hydride (0.120 g, 60% in mineral oil) (3 mmol) washed
with dry n-hexane three times was suspended in dry THF (5 mL). To
this suspension the solution of 5a (0.250 g, 1 mmol in 7 mL of dry
THF) was added dropwise at 0 ꢀC over a period of ca. 30 min. At this
temperature 2-bromomethylpyridine hydrobromide (0.385 g,
1.5 mmol) was added to the resulted deep red mixture which was
then allowed to warm up slowly to rt., and stirred for 12 h. The
workup of the reaction mixture described in Section 4.6 afforded
the product as deep red powder. Yield: 0.221 g, (64%); mp.:
4.5. Preparation of (Sp)-3-benzylferroceno[d]pyridazin-4(3H)-one
(5e)
Sodium hydride (0.140 g, 60% in mineral oil) (3.5 mmol)
washed with dry n-hexane three times was suspended in dry THF
(10 mL). To this suspension bezylhydrazine hydrochloride (0.555 g,
3.5 mmol) and (Sp)-2-formylferrocenecarbonyl fluoride (0.774 g,
3 mmol) were added in this sequence. The resulted mixture was
stirred for 10 min at room temperature and evaporated to dryness.
The residue was chromatographed on neutral alumina using DCM-
MeOH (80:1) as eluent. The reddish orange band was collected
and evaporated to obtain an orange thick oil which solidified on
trituration with petroleum ether 40/70. The suspension was
filtered off and dried to give 5e as an orange powder. Yield:
126e128 ꢀC (decomp.); [
a]
25: þ51.9ꢀ (DMSO); IR (cmꢂ1): 3091,
D
1661, 1591, 1435, 1345, 1335, 1108, 1028, 827, 752; 1H NMR (CDCl3):
8.62 (br s, 1H, H60, py); 8.17 (s, 1H, H1); 7.68 (t, 3J ¼ 7.1 Hz, 1H, H40,
py); 7.39 (br s, 1H, H40, py); 7.22 (br s, 1H, H30, py); 5.64 (d,
2J ¼ 15.2 Hz, 1H, NCHAHB); 5.32 (d, 2J ¼ 15.2 Hz, 1H, NCHAHB); 5.29
(br s, 1H, H5); 4.85 (br s, 1H, H7); 4.51 (br s, 1H, H6); 4.14 (s, 5H, h5
-
C5H5); 13C NMR (CDCl3): 166.6 (C4); 157.5 (C20, py); 149.6 (C60, py);
141.3 (C1); 137.2 (C40, py); 123.0 (C3050, two coalesced lines as
evidenced by 1He13C HSQC); 79.2 (C7a); 74.7 (C6); 74.0 (C4a); 67.3
0.320 g, (31%); mp.: 93e95 ꢀC (decomp.); [
a
]
25: ꢂ12.4ꢀ (DMSO); IR
D
(cmꢂ1): 2956, 2923, 2858, 1657, 1581, 1493, 1447, 1330, 1105, 1001,
820, 736; 697; 1H NMR (CDCl3): 8.13 (s, 1H, H1); 7.51 (d,
(C7); 66.2 (C5); 70.6 (h
5-C5H5); 55.5 (NCH2); 15N NMR (CDCl3): 328
(N10, py); 321 (N2); 178 (N3); Anal. Calcd. for C18H15FeN3O (345.18):
C: 62.63; H: 4.38; N: 12.17; Found: C: 62.57; H: 4.46; N: 12.14%.
3
3J ¼ 7.3 Hz, 2H, H2060); 7.42 (t, J ¼ 7.3 Hz, 1H, H40); 7.35 (t,
3J ¼ 7.3 Hz, 2H, H3050); 5.52 (d, 2J ¼ 14.8 Hz, 1H, NCHAHB); 5.29 (br
s, 1H, H5); 5.12 (d, 2J ¼ 14.8 Hz, 1H, NCHAHB); 4.84 (br s, 1H, H7);
Acknowledgements
4.50 (br s, 1H, H6); 4.01 (s, 5H, h
5-C5H5); 13C NMR (CDCl3): 166.1
(C4); 141.2 (C1); 138.2 (C10); 129.0 (C3050); 128.9 (C2060); 128.0
(C40); 79.0 (C7a); 74.9 (C6); 74.0 (C4a); 67.3 (C7); 66.0 (C5); 70.5
This work was financially supported by the Hungarian Scientific
Research Fund (OTKA K-68887) and the European Union and the
European Social Fund (grant agreement no. TÁMOP 4.2.1/B-09/
KMR-2010-0003).
(h
5-C5H5); 53.9 (NCH2); 15N NMR (CDCl3): 321 (N2); 178 (N3);
Anal. Calcd. for C19H16FeN2O (344.19): C: 66.30; H: 4.69; N: 8.14;
Found: C: 66.44; H: 4.56; N: 8.06%.
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D
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