Cyanosilylation of Aldehydes Catalyzed by Iron(III) Arylhydrazone-β-Diketone Complexes

Article abstract of DOI:10.1071/CH17595

Two known iron(iii) complexes, [Fe(H2O)3(L1)]·xH2O (x≤4 (1), 5 (2)) and [Fe(H2O)3(L2)]·3H2O (3), bearing the basic forms of 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (H3L1) and 3-(2-(2,4-dioxopentan-3-y

Full text of DOI:10.1071/CH17595

CSIRO PUBLISHING
Aust. J. Chem. 2018, 71, 190–194
Communication
https://doi.org/10.1071/CH17595
Cyanosilylation of Aldehydes Catalyzed by Iron(III)
Arylhydrazone-b-Diketone Complexes
A B H
, ,
B
C
Atash V. Gurbanov,
Abel M. Maharramov, Fedor I. Zubkov,
D E
,
F G
,
Alexander M. Saifutdinov,
and Firudin I. Guseinov
A
Centro de Qu´ımica Estrutural, Instituto Superior Te´cnico, Universidade de Lisboa,
Avenue Rovisco Pais, 1049–001 Lisbon, Portugal.
B
Organic Chemistry Department, Baku State University, Z. Xalilov Street 23,
Az 1148 Baku, Azerbaijan.
C
Organic Chemistry Department, Faculty of Science, Peoples’ Friendship University of
Russia (RUDN University), 6 Miklukho-Maklaya Street, 117198 Moscow,
Russian Federation.
D
Kazan National Research Technological University, Karl Marx Street 68, 420015
Kazan, Republic of Tatarstan, Russian Federation.
E
Institute for Chemistry and Biology, Immanuel Kant Baltic Federal University,
Universitetskaya Street, 236000 Kaliningrad, Russian Federation.
National University of Science and Technology (MISIS), Moscow Leninsky Prospect 4,
119049 Moscow, Russian Federation.
F
G
Zelinskiy Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky
Prospect 47, 119991 Moscow, Russian Federation.
H
Corresponding author. Email: organik10@hotmail.com
Two known iron(III) complexes, [Fe(H2O)3(L1)]ꢀxH2O (x ¼ 4 (1), 5 (2)) and [Fe(H2O)3(L2)]ꢀ3H2O (3), bearing the basic
forms of 5-chloro-3-(2-(4,4-dimethyl-2,6-dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonic acid (H3L1) and
3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-hydroxy-5-nitrobenzenesulfonic acid (H3L2), were prepared and used as
homogeneous catalysts for cyanosilylation of a variety of aldehydes with trimethylsilyl cyanide leading to the
corresponding cyanohydrin trimethylsilyl ethers. High yield (up to 98 %) was observed in the reaction catalyzed by 3
at room temperature in methanol.
Manuscript received: 19 November 2017.
Manuscript accepted: 1 February 2018.
Published online: 20 February 2018.
Introduction
reaction conditions, different metal–AHAMC complexes can be
prepared.[2] In solution, in comparison with other metal ions
(Cu2þ, UO22þ, Ni2þ, Co2þ, Zn2þ, Cd2þ, Mn2þ, Ca2þ, and
Mg2þ), iron(III) forms the most stable complexes with AHAMC
ligands,[3] and three FeIII-AHAMC complexes were isolated in
the solid state and structurally characterized (Chart 1).[4,5] Those
complexes were successfully applied as the catalysts for per-
oxidative oxidation of cycloalkanes[4] and for C–C coupling
between nitroethane and various aldehydes (Henry reaction).[5]
Arylhydrazones of active methylene compounds (hereafter
denoted as AHAMC) have attracted much attention owing to
their high synthetic potential for organic synthesis.[1] Moreover,
metal complexes of AHAMC ligands have been found to pos-
sess a wide variety of useful properties.[2] The modification of
the aromatic and/or active methylene fragments of AHAMC
strongly influences their coordination, catalytic, and other
properties.[2] Thus, depending on the substituent and on the
H2O
H2O
H2O
OH2
O
H2O
OH2
O
H3C
H2
C
O
O
H3C
Fe
N
SO3
C
C
Fe
N
C
C
SO3
C
H3C
H2C
O
3H2O
xH2O
N
C
N
C
O
CH3
NO2
Cl
x ϭ 4 (1), 5 (2)
3
Chart 1. Schematic representations of known FeIII-AHAMC complexes 1–3.[4,5]
Journal compilation Ó CSIRO 2018
www.publish.csiro.au/journals/ajc

Iron(III) Complexes in Cyanosilylation Reaction
191
R
Catalyst
Table 1. Selection of catalyst for the cyanosilylation of benzaldehyde
with TMSCN
R
CHO
ϩ
N
C
SiMe3
N
C
O
SiMe3
Reaction conditions: solvent (2 mL), TMSCN (0.6 mmol) and benzaldehyde
(0.4 mmol), in air at room temperature, 24-h reaction time
Scheme 1. Cyanosilylation of aldehydes.
Entry
Catalyst
Amount of catalyst Solvent ConversionA [%]
[mol-%]
In the present work, we report the use of these known FeIII-
AHAMC (Chart 1)[4,5] as homogeneous catalysts for the cya-
nosilylation of aliphatic and aromatic aldehydes with tri-
methylsilyl cyanide (TMSCN) to yield cyanohydrin
trimethylsilyl ethers (Scheme 1).
1
1
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
–
–
–
–
THF
41.4
41.7
42.3
47.7
47.7
48.1
78.9
79.0
83.9
14.7
15.1
15.9
16.0
27.2
27.9
65.2
20.0
14.0
14.4
24.7
2
2
THF
3
3
THF
4
1
CH2Cl2
CH2Cl2
CH2Cl2
MeOH
MeOH
MeOH
THF
5
2
Owing to the versatile transformations of cyanohydrin tri-
methylsilyl ethers to chiral carboxylic acids, ketones, amines,
etc., great efforts havebeen devoted to theC–C coupling reaction
(cyanosilylation reaction) between aldehydes and TMSCN to
produce cyanohydrin trimethylsilyl ethers (Scheme 1).[6] Both
types of catalysts (organocatalysts and metal complexes) have
been used in this reaction, for example, N-methylmorpholine
N-oxide,[7] P(RNCH2CH2)N,[8] 1,1,3,3-tetramethylguanidine,[9]
tetraethylammonium 2-(N-hydroxycarbamoyl)benzoate[10] and
N-heterocyclic carbenes,[11,12] as well as metal catalysts
such as Cu(CF3SO3)2,[13] ZnI2,[14] KCN:18-crown-6,[15]
Yb(OTf)3,[16,17] Yb(CN)3,[18] LiCl and LiClO4,[19–21] R2SnCl2
and Sn-montmorillonite,[22,23] MgBr2ꢀEt2O,[24] Zr(KPO4)2,[25]
CsF,[26,27] VO(OTf)2,[28] InBr3,[29] NbF5,[30] Fe(Cp)2PF6,[31]
CuII hydrazone complexes,[32–34] lead(II)-3-aminopyrazine-2-
carboxylate,[35] supported ionic liquids,[36] lanthanide-contain-
ing polyoxometalate-intercalated layered double-hydroxides,[37]
and metal organic frameworks (MOFs).[38–43] Among the metal
catalysts, iron compounds have also received attention in recent
years,[44–47] but there are no reports on the application of
FeIII-AHAMC in this reaction.
6
3
7
1
8
2
9
3
10
11
12
13
14
15
16
17B
18
19
20
H3L1
H3L2
THF
H3L1
CH2Cl2
CH2Cl2
MeOH
MeOH
MeOH
–
H3L2
H3L1
H3L2
FeCl3ꢀ6H2O
–
–
–
–
THF
CH2Cl2
MeOH
ADetermined by 1H NMR analysis of crude products.
BEntries 17–20 were adapted from ref. [34a].
at room temperature (Table 1). The experimental results show
that the solvent has an important effect on the reaction. Owing to
the poor solubility of catalysts in CH2Cl2 and DMF, the yield of
cyanohydrin trimethylsilyl ether, i.e. 2-phenyl-2-((trimethyl-
silyl)oxy)acetonitrile is lower (entry 6, up to 48 %) in compar-
ison with MeOH (entry 9, up to 84 %). However, the reaction
without catalyst (Table 1, entry 17) resulted in only 20 % con-
version of benzaldehyde. Compound 3 showed the highest
activity (Table 1, entry 9) in MeOH, and optimization of the
reaction conditions (reaction time, amount of catalyst and
temperature) was carried out in a model benzaldehyde–TMSCN
system with 3 as the catalyst in this solvent (Table 2). As shown
in Table 2, the reaction was complete after 4 h (Table 2, entry 5)
and 5 mol-% of 3 was found to be sufficient to obtain the
maximum conversion (entry 11). Temperature variation (in the
15–558C range) had only a small effect on the conversion
(entries 13–17) and hence room temperature was typically used.
To further explore the general applicability of 3 to the
catalysis of the cyanosilylation reaction, a family of aliphatic
aldehydes as well as benzaldehyde derivatives with para elec-
tron-withdrawing (–Br, –Cl, and –NO2) and donating (–N(Me)2,
–OMe, and –Me) groups were selected as substrates in the
following reactions (Table 3). The length of alkyl chains of
the aliphatic aldehydes has a slight effect on the yield of the
corresponding cyanohydrin trimethylsilyl ethers (90.0–99.1 %,
entries 1 and 2, Table 3). The benzaldehyde derivatives
bearing para electron-withdrawing groups were converted into
the corresponding cyanosilylation products in high yields
(84.2–88.1 %, entries 7–9), whereas when the benzaldehyde
derivatives with para electron-donating groups were used
as the substrates, the corresponding product yield clearly
decreased under the same conditions (entries 3–5). This can be
explained by the nature of the substituents, as the para
Experimental
Materials and Instrumentation
All the chemicals were obtained from commercial sources
(Aldrich) and used as received. 5-Chloro-3-(2-(4,4-dimethyl-2,6-
dioxocyclohexylidene)hydrazinyl)-2-hydroxybenzenesulfonic
acid (H3L1), 3-(2-(2,4-dioxopentan-3-ylidene)hydrazinyl)-2-
hydroxy-5-nitrobenzenesulfonic acid (H3L2), 1, 2, and 3 were
synthesized according to the reported procedures.[4,5] 1H NMR
spectra were recorded at room temperature on a Bruker Avance
II þ 300 (UltraShieldTM Magnet) spectrometer operating at
300.130 MHz for protons. The chemical shift (ppm) is reported
using tetramethylsilane as the internal reference. The reference
values used for deuterated chloroform (CDCl3) were 7.26 and
77.00 ppm for 1H and 13C NMR spectra respectively.
Catalytic Activity Studies
The solvent (THF, CH2Cl2 or anhydrous MeOH; 2 mL) was
added toa flask thatcontainedthe catalyst(1, 2, or3) (1–9 mol-%)
and aldehyde (0.4mmol); the solution was stirred continuously
and the progress of the reaction was followed by TLC. The crude
reaction mixture was characterized by 1H NMR. The conversion
into products was determined by 1H NMR.[32–34,48–50]
Results and Discussion
Compounds 1, 2, 3, H3L1, H3L2, and FeCl3ꢀ6H2O were tested as
homogeneous catalysts for the cyanosilylation reaction of
benzaldehyde (as a test compound) with TMSCN in protic
(methanol) and aprotic (1,2-dichloromethane and THF) solvents

192
A. V. Gurbanov et al.
Table 2. Evaluation of reaction conditions of cyanosilylation of benz-
aldehyde with TMSCN catalyzed by 3
We compared the results of the cyanosilylation of benzalde-
hyde with TMSCN with other reported catalysts. Thus, catalyst
3 has several advantages in comparison with the other reported
ones; for example, a ZnII system provided a low yield (30 %) and
required a low temperature (08C),[51] a CuII system also provided
a low yield (27 %), and required a long reaction time (48 h) and
high temperature (408C),[52] a TiIV system required a long
reaction time (48 h) and low temperature (ꢁ208C),[53] and an
AlIII one required a long reaction time (18 or 96 h) and a low
temperature of ꢁ50 or ꢁ408C.[54,55]
Reaction conditions: MeOH (2 mL), TMSCN (0.6 mmol) and benzaldehyde
(0.4 mmol), in air
Entry
Time
[h]
Amount of catalyst
[mol-%]
Temperature
ConversionA
[%]
[8C]
1
0.5
1
2
3
4
5
4
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
1
2
3
4
5
6
5
5
5
5
5
25
25
25
25
25
25
25
25
25
25
25
25
15
25
35
45
55
66.4
72.6
77.7
81.5
83.9
83.9
53.2
65.6
74.7
81.4
83.9
83.9
76.9
83.9
84.2
84.7
85.0
2
3
4
5
Conclusions
6
A variety of cyanohydrin ethers were readily prepared from
aliphatic and aromatic aldehydes with TMSCN under the
influence of a catalytic amount of 3 in a convenient one-pot
procedure. Attractive features of the method include the cheap,
easily prepared catalyst and low catalyst loading.
7
8
9
10
11
12
13
14
15
16
17
Supplementary Material
1H and 13C NMR data for isolated compounds are available on
the Journal’s website.
Conflicts of Interest
ADetermined by 1H NMR analysis of crude products (see Experimental
section).
The authors declare no conflicts of interest.
Acknowledgements
The authors are grateful to the Fundac¸a˜o para a Cieˆncia e a Tecnologia (FCT)
(project UID/QUI/00100/2013), Portugal, for financial support. The publi-
cation was also prepared with the support of the ‘RUDN University Program
5–100’. Firudin I. Guseinov is grateful to the Russian Science Foundation for
grant no. 14-50-00126. The authors thank the Portuguese NMR Network
(IST-UL Centre) for access to the NMR facility.
Table 3. Addition of TMSCN to various aldehydes catalysed by 3 in
methanol
Reaction conditions: 5 mol-% of catalyst 3, MeOH (2 mL), TMSCN
(0.6 mmol) and aldehyde (0.4 mmol); reaction time: 4 h
Entry
Substrate
ConversionA
[%]
Isolated
yieldB
[%]
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99.2
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