Iron powder and tin/tin chloride as new reducing agents of Meerwein arylation reaction with unexpected recycling to anilines

Article abstract of DOI:10.1080/00397911.2019.1704786

Simple and rapid route for Meerwein arylation reaction using iron powder or a mixture of tin/tin chloride has been developed. In the presence of iron powder, different aryl diazonium salts reacted with methyl vinyl ketone, acrylates, and isopropenyl acetate. Production of oximes was detected as the main product with acrylates or in a mixture with β-aryl methyl ketones in the case of methyl vinyl ketone. The in situ produced HNO₂ from an excess of NaNO₂/HCl was trapped by alkyl aryl radical to form oximes in the E configuration form. The presence of tin/tin chloride mixture in the reaction of the aryl diazonium salts with methyl vinyl ketone produced Michael products along with β-aryl methyl ketones. The predicted α-aryl methyl ketones from the reaction of isopropenyl acetate with the diazotized anilines were obtained using iron or tin/tin chloride mixture.

Full text of DOI:10.1080/00397911.2019.1704786

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Iron powder and tin/tin chloride as new reducing
agents of Meerwein arylation reaction with
unexpected recycling to anilines
Ahmed B. Abdelwahab, Eslam R. El-Sawy & Gilbert Kirsch
To cite this article: Ahmed B. Abdelwahab, Eslam R. El-Sawy & Gilbert Kirsch (2020)
Iron powder and tin/tin chloride as new reducing agents of Meerwein arylation reaction
with unexpected recycling to anilines , Synthetic Communications, 50:4, 526-538, DOI:
10.1080/00397911.2019.1704786
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2020, VOL. 50, NO. 4, 526–538
https://doi.org/10.1080/00397911.2019.1704786
Iron powder and tin/tin chloride as new reducing agents of
Meerwein arylation reaction with unexpected recycling
to anilines
a,b
a
Ahmed B. Abdelwahaba,b,c , Eslam R. El-Sawy , and Gilbert Kirsch
ꢀ
ꢀ
a
b
ꢀ
ꢀ
Laboratoire Lorrain de Chimie Moleculaire (L.2.C.M.), Universite de Lorraine, Metz, France; Chemistry
of Natural Compounds Department, National Research Centre, Dokki-Cairo, Egypt; Plant Advanced
c
ꢁ
Technologies (PAT), Vandoeuvre-les-Nancy, France
ABSTRACT
ARTICLE HISTORY
Received 16 October 2019
Simple and rapid route for Meerwein arylation reaction using iron
powder or a mixture of tin/tin chloride has been developed. In the
presence of iron powder, different aryl diazonium salts reacted with
methyl vinyl ketone, acrylates, and isopropenyl acetate. Production
of oximes was detected as the main product with acrylates or in a
mixture with b-aryl methyl ketones in the case of methyl vinyl
ketone. The in situ produced HNO2 from an excess of NaNO2/HCl
was trapped by alkyl aryl radical to form oximes in the E configur-
ation form. The presence of tin/tin chloride mixture in the reaction
of the aryl diazonium salts with methyl vinyl ketone produced
Michael products along with b-aryl methyl ketones. The predicted
a-aryl methyl ketones from the reaction of isopropenyl acetate with
the diazotized anilines were obtained using iron or tin/tin chloride
mixture.
KEYWORDS
Diazonium salt; iron
powder; Meerwein
arylation; radical reaction;
reducing agent; tin;
tin chloride
GRAPHICAL ABSTRACT
Introduction
The C–C bond formation is a critical step of great importance in organic synthesis. As
an alternative to expensive coupling chemistry, the Meerwein arylation reaction is a
highly efficient methodology for this synthesis. Meerwein arylation reaction was
ꢀ
Laboratoire Lorrain de Chimie Moleculaire (L.2.C.M.),
CONTACT Gilbert Kirsch
gilbert.kirsch@univ-lorraine.fr
ꢀ
Universite de Lorraine, 1 Boulevard Arago, Metz 57070, France.
ꢀ
These authors have contributed equally to this work.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

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reported firstly in 1939.[1] It is a simple pathway of furnishing the C-C bond by a reac-
tion between aryl radical and an alkene. The aryl radical is developed by the reduction
of diazonium salt using mostly transitional metal salts.[2,3]
Copper salts are the classical and the most employed reducing agent for Meerwein
arylation.[4–12] Recently, in 2019, copper(I) was used in its nano form to catalyze
Meerwein arylation.[13] Additionally, titanium (III) chloride was used for varieties of
activated olefins.[14–16] Besides, silver salt in combination with fluoride sources catalyzed
the transformation of styrenes to fluorinated compounds.[17] One of the commonly
used metal salts is Fe2þ in the form of sulfate for the reaction between functionalized or
non-functionalized olefins and the arenediazonium salts.[18–21] FeSO4 was described also
to be used in a combination with TiCl3 for synthesizing 1,4-diarylpyrazole deriva-
tives.[22] Additionally, in 2012, iron complex ferrocene (Cp2Fe) was the solvent-soluble
mediator to perform the arylation of ethyl vinyl ether to arylated acetaldehyde by con-
tinuous flow synthesis technique.[23]
As an effort to exclude the use of transitional metals, metal-free Meerwein arylation was
performed using basic catalysis with activated[24] and non-activated olefins.[25] Also, perox-
ides,[26] iodide,[27,28] and phenanthroline[28] are considered examples of catalysts replacing
the transitional metals[28]. On the other hand, radical photocatalyzed Meerwein arylation in
the presence of metal complexes has been developed rapidly in the last years.[29–32]
Among all, the reducing agents used for Meerwein arylation and were mentioned
previously, the Fe powder or the tin in its elemental or oxidized form has not been
recorded before. The importance of Meerwein arylation motivated us to check the
reactivity of the Fe powder as well as the tin/tin chloride mixture as reducing agents for
expanding the panel of Meerwein’s catalysts.
Results and discussion
Following the purpose of present work, the iron powder was investigated as a reducing
agent for the reaction of substituted phenyl diazonium salts with activated olefins,
namely methyl vinyl ketone and acrylates. We considered the Fe powder as an ideal
reducing agent since it is abundant, inexpensive, nontoxic and easily discarded metal.
Thus, we began our study with the reaction of p-chlorophenyl diazonium salt 1a, that
prepared in situ by HCl and NaNO2 with two equivalent of methyl vinyl ketone in acet-
one-H2O as a solvent and in the presence of iron powder (2 equiv.). The reaction mix-
ture was extracted with ethyl acetate and purified using column chromatography. The
purified fractions showed the b-aryl methyl ketone 2a which is usually obtained under
Meerwein arylation condition[2,14,16] in 40% yield along with a solidified one 3a in 19%
yield. The separated solid was purified by the crystallization process and then became a
challenge to be identified.
Compound 3a was crystallized from cyclohexane as colorless crystals and was
assigned the molecular formula C10H10ClNO2 as a result of its molecular ion
[M þ Na]þ peak at 234.0319 in the HRESI-MS. Its 1H NMR spectrum (400 MHz,
DMSO) revealed two singlet signals at dH 3.67 and 2.25 which attributed to the pres-
ence of (3H, CH3) and (2H, CH2), respectively with no conjugation with each other,
besides, a singlet signal at dH 12.52 that attributed to the presence of OH. The 13C

528
A. B. ABDELWAHAB ET AL.
Scheme 1. Formation of oximes by NO gas efflux for recycling NO wastes.
Table 1. Optimizing reaction conditions mediated by iron powder.
Yield (%)
Entry
Diazotizing agent
NaNO2/HCl
Atmosphere
Solvent
DMF–H2O
H2O
DMF/AcOH–H2O
Acetone–H2O
Acetone–H2O
Acetone–H2O
Acetone–H2O
2a
3a
1
2
3
4
5
6
7
N2
N2
N2
N2
0
0
38
41
40
0
0
0
13
11
19
0
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl/HBF4
tBuONO
Open-air
Open-air
Open-air
0
0
NMR (100 MHz, CDCl3) spectrum showed one resonance corresponding to one car-
bonyl group (dC 196.3), along with one resonance at (dC 158.1) which confirm the pres-
ence of (C¼N) group. Besides the rest of the aromatic carbons (dC 134.6, 132.3, 130.6
(2 carbons), 128.5 (2 carbons)), as well as the methylene (dC 27.6) and the methyl group
at (dC 25.3), respectively.
The NMR and mass spectroscopic analysis of compound 3a suggested a possible similar-
ity to previously prepared oximes by nitric oxide gas efflux through a proposed technique by
C. de Salas for recycling NO wastes.[33,34] They developed a technique for denitrification of
the industrial wastes through Meerweein arylation catalyzed by FeSO4 7H2O or Fe(II)-
EDTA complex in DMSO-H2O as a solvent and metal-free in some cases[33,34] (Scheme 1).
In which, the arenediazonium tetrafluoroborates reacted with different alkenes including
acrylic acid, acrylates, acrylamide, styrenes, allyl acetate, and vinyl cyanide to produce collec-
tions of oximes of E and E/Z mixtures[33,34] (Scheme 1).
Based on the above evidence the structure of compound 3a was assigned as (E)-4-(4-
chlorophenyl)-3-(hydroxyimino)butan-2-one (Table 1).
The use of Fe powder in the present work was established after several trials of reac-
tion optimization including different parameters: solvent, atmosphere, and diazonium
salt (Table 1). The p-chlorophenyl diazonium salt was prepared by NaNO2/HCl and the
product was accessible in this case. The p-chlorophenyl diazonium salt using t-BuONO
as well as p-chlorophenyl diazonium tetrafluoroborate were prepared with no products
in the alkylation step.

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Table 2. The reaction of methyl vinyl ketone with arenediazonium salts.
β-aryl methyl
ketones 2
Yield
(%)
Yield
(%)
Entry
β-aryl methyl
ketones 2
Yield
(%)
Yield
(%)
Entry
Oximes 3
Oximes 3
24
19
31
20
59
7
30
52
49
12
25
30
Regarding the atmosphere, the inert gas was initially applied following the typical
Meerwein arylation technique,[2,14,16] and we found that the yield was not affected when
we switched to open air. On the other hand, the reaction was notably sensitive to the
solvent change. Acetone-H2O mixture seemed to be the most suitable solvent. Whereas,
DMF-H2O did not afford a good vehicle for performing the reaction and no product
was collected. Acetic acid offered suitable media even though the drawback of being sol-
idified at 0 ꢁC which was encountered by using AcOH-DMF. Finally, acetone has the
advantage of being an easy-evaporation solvent, and thus the acetone-H2O mixture was
designated as a solvent of choice.
After having optimized the reaction conditions we screened different anilines 1b–1k
to react with methyl vinyl ketone (Table 2). The results were identical to those obtained
for compound 3a.
During the progress of our practical work, we tried the reaction of ethyl and benzyl
acrylates with the p-chlorophenyl diazonium salt employing the previous conditions of
preparing 2a–2k (Scheme 2). The reaction gave the suggested oximes as pure and basic
products without any traces of the classical products of Meerwein arylation.
The structures of 4a and 4b were clarified based on their elemental analyses and
spectral data. The obtained results indicated the formation of oximes. For further con-
firmation of the structure as well as identification of the type of oxime isomer, a crystal
of 4b was prepared and submitted to X-ray (Figure 1, CCDC 1864773). The oxime was
recognized as the E isomer, which matched with the proposed results for 3a–3i.

530
A. B. ABDELWAHAB ET AL.
Scheme 2. The reaction of p-chlorophenyl diazonium salt with ethyl acrylate and benzyl acrylate.
Figure 1. ORTEP structure of 4b. CCDC 1864773 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre,
12 Union Road, Cambridge CB2 1EZ, UK; fax: þ44 1223 336033.
Our procedure presented a pathway to prepare the oximes by the excessive NaNO2/
HCl rather than nitric oxide gas in C. de Salas condition.[33,34] It is noteworthy to men-
tion that, the compound 4a was obtained as colorless crystal (m.p. 97–9 ꢁC) in contrast
to the physical state which reported for it as brown oil.[33]
The suggested mechanism for the formation of b-aryl ketones via the use of iron
powder is depicted in Scheme 3. The radical I is generated by oxidation of Fe to Feþ2
.
The double bond on the functionalized olefin contributes to forming a C-C bond. Then
the intermediate II is stabilized by the second oxidation of Feþ2 to Feþ3. Finally, the
acidic media supplies a proton in a-position of the linear chain of phenylbutanone
derivatives to yield the classical Meerwein arylation product 2b.
Regarding the formation of oximes, the pathway is supposedly proceeded by trapping
of the intermediate (II) by the nitrite (HNO2); generated from the excess of NaNO2/
HCl to give (III), which is consequently stabilized by further oxidation of Feþ2 to Feþ3
and withdraws a proton from HCl in the media to release FeCl3. The final step is
accomplished by loss of water to provide the oxime 3b. It was interesting to observe the
color gradient of the reaction medium from the light green to the dark green, which
confirms the oxidation of the Fe powder during radicals formation to ferrous chloride;
Feþ2 and then ferric chloride; Feþ3
.

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Scheme 3. Proposed mechanism for the formation of b-aryl methyl ketones and oxime via the
reaction between the diazonium salt and methyl vinyl ketone using iron metal.
Table 3. Optimizing reaction conditions mediated by tin/tin chloride mixture.
Yield (%)
Entry
Diazotizing agent
NaNO2/HCl
Reducing agent
Solvent
2a
3a
5a
1
2
3
4
5
6
7
Tin
DMF–AcOH–H2O
DMF–AcOH–H2O
DMF–AcOH–H2O
Acetone–H2O
AcOH–H2O
Acetone–AcOH–H2O
DMF–AcOH
0
0
40
0
0
0
0
0
0
0
0
0
0
27
0
0
0
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl
NaNO2/HCl/HBF4
Tin chloride
Tin/Tin chloride
Tin/Tin chloride
Tin/Tin chloride
Tin/Tin chloride
Tin/Tin chloride
Traces
Traces
0
0
To test another possibility in this study, tin/tin chloride mixture was investigated as a
reducing agent for the reaction of the corresponding aryl diazonium salts of 1a–1k with
methyl vinyl ketone. It’s known that tin-metal and tin chloride is operative reducing
agents under acidic conditions.[35] The reaction was performed according to the typical
method previously reported for iron powder using a stoichiometric amount of tin: tin
chloride. Many combinations of tin/tin chloride and solvents were examined to optimize
the reaction in order to obtain the desired Meerwien product 3a. It was found that the
exclusive usage of tin or tin chloride didn’t help in giving results. Moreover, the add-
ition of AcOH was found very crucial to accomplish the reaction. Switching solvents
between DMF and acetone were found to affect the yields and the outputs of the reac-
tion in the favor of DMF as overall results (Table 3).

532
A. B. ABDELWAHAB ET AL.
Table 4. The percentage of recovered anilines.
Anilines
% of recovery
1a
1b
1c
1d
1e
1g
1h
43
46
22
64
Traces
0
0
In the case of p-chlorophenyl and p-bromophenyl diazonium salts, the classical
Meerwien arylation products 2a (20%) and 2c (9%) were identified along with the pro-
duction of amines 5a and 5c in 27% and 20% yields, respectively. In contrast to the rest
of anilines, the classical Meerwien arylation products were obtained as main products
with 1b, 1g, 1h, 1j, and 1k in 17–37% yields, whereas, the oximes 3c and 3g in 21%
and 12% yields were detected along with 2c and 2g, experimental part.
The structures of 5a and 5c were confirmed based on their elemental analysis and
1
spectral data. The H NMR spectral data of 5a and 5c were in total agreement with the
previous work to be Michael products.[36]
The unexpected results of 5a and 5c have been proposed as a result of the return of
corresponding anilines 1a and 1c. Hereafter the anilines 1a and 1c reacted with the
unsaturated olefin to produce the corresponding Michael products 5a and 5c.
The total output of the reaction of methyl vinyl ketone with aryl diazonium salts that
mediated by tin/tin chloride mixture was very low. Augmenting the number of equiva-
lents of methyl vinyl ketone didn’t help in the yield enhancement.
The anilines restoring impacted by the presence of tin/tin chloride mixture was tested
for all the aryl diazonium salts under study via excluding the olefin from the reaction
media to verify the capability of recovering the corresponding anilines after being com-
pletely transformed to diazonium salts.
Thus, diazonium salts were prepared by the well-known procedure and precipitated
by HBF4.[37] The solution was tested by TLC to assure the absence of the original ani-
lines. All conditions of Michael adduct production were reestablished without adding
the olefin. Iron powder, as well as tin/tin chloride, was deployed to recover the anilines.
It was noticed that tin/tin chloride mixture is the reagent that has the capability to
transform the radical back to the corresponding anilines. Additionally, the results
showed that not all the tested aryl diazonium salts could be restored to their original
form (Table 4). The recovering of anilines from their diazonium salts was fairly
reported in the literature under a basic condition.[38]
To widen the scope of our research, we used isopropenyl acetate which was employed
by C. Molinaro and his coworker to synthesize a-aryl methyl ketones.[24] We applied the
previous conditions of the iron powder as well as the tin/tin chloride mixture to investi-
gate their influence on the final products. The reaction behavior was found to follow the
same manner of C. Molinaro and produced the expected a-aryl methyl ketones (Table 5).
In the case where the tin/tin chloride mixture is used, we elevated the amount of iso-
propenyl acetate to 10 equivalents, to help raise the reported product from low to mod-
erate (Table 5). Increasing the number of equivalents of isopropenyl acetate didn’t help
in the yield enhancement with the Fe powder.

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Table 5. The reaction of isopropenyl acetate with aryl diazonium salts.
Entry
α-aryl methyl
ketones
Yield %
Entry
α-aryl methyl
ketones
Yield %
Fe
Sn/SnCl2
Fe
Sn/SnCl2
powder
mixture
powder
mixture
36
51
69
26
44
55
29
18
36
29
47
0
35
37
45
27
28
38
54
56
19
42
Conclusion
We reported here new reducing agents of Meerwein arylation reaction using the iron
powder or the tin/tin chloride mixture for the first time. Although iron element was
used widely as Fe(II) in the salt of sulfate, it has never been used as iron powder. It was
observed that the reaction of aryl diazonium salts with vinyl methyl ketone produced a
mixture of b-aryl ketones and E isomer of oximes in most cases. While the reaction
with ethyl and benzyl acrylates led to the formation of the oxime in E configuration
form as main products. Moreover, the presence of the tin/tin chloride mixture in such
reaction of the diazotized anilines with methyl vinyl ketone produced Michael products
in a mixture with b-aryl methyl ketones. On the other side, the reaction of aryl diazo-
nium salts with isopropenyl acetate led to the formation of the corresponding a-aryl
methyl ketones under the action of the iron powder or the tin/tin chloride mixture. In
summary, despite the advancements of the reported Meerwein arylation methods. The
development route of this reaction using the iron powder or the tin/tin chloride mixture
seems to be simple, cheap, rapid process, and could be run feasibly on the open air
without the need for inert gas.

534
A. B. ABDELWAHAB ET AL.
Experimental
General information
All solvents and reagents were purchased from commercial sources. Melting points were
determined with a Bu€chi 530 digital melting point apparatus and are uncorrected.
Elemental analyses were performed on CHNS-O analyzer (Perkin-Elmer, USA) and
were found within 0.4% of the theoretical values.1H and 13C NMR spectra were meas-
ured with a Bruker Avance spectrometer (Bruker, Germany) at 400 and 100 MHz,
respectively, using TMS as the internal standard. Hydrogen coupling patterns are
described as singlet (s), doublet (d), triplet (t), quartet (q) and multiplet (m). Chemical
shifts were defined as parts per million (ppm) relative to the solvent peak. High-
resolution mass spectra were measured with a MICROTOF-Q ESI/QqTOF (Bruker
Daltonics, Germany). Column chromatography was performed using silica gel (60 M,
0.04–0.063 mm) with a proper eluent system. Thin-layer chromatography (TLC) was
performed using silica gel plates (POLYGRAM SILG/UV254, 0.20 mm), which were
visualized under UV light (254 nm) and by spraying using (vanillin/H2SO4/ethanol)
mixture. The ketone spot was stained by green color while the oximes were showed as
pale yellow after spraying. All reagents and solvents were of commercial grade. Iron
metal powder, tin granular and tin chloride (Sigma-Aldrich Chemie GmbH, Export
Department Eschenstr.5 82024 Taufkirchen, Germany)
Procedures
General procedure for the preparation of 2a–k, 3a–i, 4a,b, and 6a–k using
iron element
To a suspension of aniline 1a–k (7.8 mmol) in HCl (10 ml, 6 N), a solution of NaNO2
(1.4 g, 20.3 mmol) in water (5 ml) was added slowly over 30 min at 0 ꢁC. Meanwhile, in
a two-necked round flask, fitted with condenser and gas bubbler, olefin (15.6 mmol)
was dissolved in acetone (20 ml). The diazonium salt solution was added slowly to the
stirred olefin solution through a septum by syringe. After complete addition, the iron
powder (0.88 g, 15.6 mmol) was added to the reaction mixture 2–3 times. The reaction
mixture was stirred at 0 ꢁC until the N2 evolving ceased, then the reaction mixture was
removed from the ice and the stirring was continued at r.t. for another 30 min to 1 h.
After the reaction accomplished, the reaction mixture was quenched by water and ice
and extracted by ethyl acetate. The products were obtained in pure form after purifica-
tion by silica gel column chromatography using different eluent systems. The oximes
were recrystallized from a proper solvent.
Characterization of compounds 2a–2k
4-Phenylbutan-2-one (2b)[39]
Purified by column chromatography using (DCM–MeOH, 99:1) as yellow oil; yield:
1
iron: 24%, 0.27 g, tin: 26%, 0.15 g; H NMR (400 MHz, CDCl3) d ¼ 7.33–7.27 (m, 2H),
7.26–7.17 (m, 3H), 2.92 (t, J ¼ 8 Hz, 2H), 2.79 (t, J ¼ 8 Hz, 2H), 2.16 (s, 3H).

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Characterization of compounds 3a–3i
(E)-3-(Hydroxyimino)-4-phenylbutan-2-one (3b)
Purified by column chromatography using (DCM–MeOH, 99:1) Rf ¼ 0.33 and the
obtained solid recrystallized from (MeOH–H2O, 1:1) as yellow crystals; m.p. 82–4 ꢁC;
1
yield: 17%, 0.23 g; H NMR (400 MHz, DMSO) d ¼ 12.45 (s, 1H), 7.20–7.13 (m, 2H),
7.09 (t, J ¼ 6.5 Hz, 3H), 3.68 (s, 2H), 2.26 (s, 3H); 13C NMR (100 MHz, CDCl3)
d ¼ 196.7, 158.5, 136.2, 129.2, 128.4, 126.4, 28.27, 25.40; HRMS (ESI): m/z [M þ Na]þ
calcd for C10H11NO2Na: 200.0682; found: 200.0698; Anal. Calcd for C10H11NO2: C,
67.78; H, 6.26; N, 7.90. Found: C, 68.22; H, 6.15; N, 7.95.
Characterization of compounds 4a and 4b
Ethyl (E)-3-(4-chlorophenyl)-2-(hydroxyimino)propanoate (4a)[33,34]
Purified by column chromatography using (cyclohexane–EtOAc, 4:1) Rf¼0.25 as color-
1
less crystals; yield: 47%, 0.89 g; H NMR (400 MHz, DMSO) d ¼ 12.53 (s, 1H), 7.34 (d,
J ¼ 8.6 Hz, 2H), 7.21 (d, J ¼ 8.6 Hz, 2H), 4.18 (q, J ¼ 7.1 Hz, 2H), 3.82 (s, 2H), 1.21 (t,
J ¼ 7.1 Hz, 3H).
Characterization of compounds 5a and 5c
4-((4-chlorophenyl)amino)butan-2-one (5a)[36]
Purified by column chromatography using (cyclohexane–EtOAc, 4:1) Rf ¼ 0.25 and the
1
obtained solid is white crystals; yield: 27%, 0.2 g; H NMR (400 MHz, CDCl3) d ¼ 7.04
(d, J ¼ 8 Hz, 2H), 6.45 (d, J ¼ 8 Hz, 2H), 3.94 (s, 1H), 3.31 (t, J ¼ 6.1 Hz, 2H), 2.66 (t,
J ¼ 6.0 Hz, 2H), 2.10 (s, 3H).
The experimental part and spectroscopic data for compounds are available in
supplementary files.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was supported by the French and Egyptian governments through a co-financed fellow-
ship granted by the French Embassy in Egypt (Institut Franc¸ais d’Egypte) and the Science and
Technology Development Fund (STDF). Additionally, Plant Advanced Technologies (PAT) is a
private company of research. It financed the project of post-doc of A.B Abdelwahab during this
work was carried out.
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