Carbenoid Etherifications catalyzed by "green" silver nanoparticles and iron-copper nanoparticles

Article abstract of DOI:10.2174/157017812799303971

Etherfication products were obtained from sodium salts of p-toluenesulfonylhydrazones in alcohol solutions at reflux temperature on treatment with catalytic amounts of iron-copper nanoparticles, and silver nanoparticles, which were prepared from Camellia

Full text of DOI:10.2174/157017812799303971

2
Letters in Organic Chemistry, 2012, 9, 2-6
Carbenoid Etherifications Catalyzed by “Green” Silver Nanoparticles and
Iron-Copper Nanoparticles
Marco A. García1, Ángel García-Muñoz1, Josué A. Peña1, Jessica Trujillo-Reyes1, Raul A. Morales-
Luckie1, Miguel Avalos-Borja2, Alfredo R. Vilchis-Nestor1, Víctor Sánchez-Mendieta1, David
Corona1 and Erick Cuevas-Yañez*,1
1Centro Conjunto de Investigación en Química Sustentable UAEM-UNAM. Carretera Toluca-Atlacomulco Km 14.5,
Toluca, Estado de México, 5200, Mexico
2Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México. Km. 107 Carretera Tijuana-
Ensenada, Baja California, 22800, Mexico
Received May 15, 2011: Revised August 19, 2011: Accepted August 19, 2011
Abstract: Etherfication products were obtained from sodium salts of p-toluenesulfonylhydrazones in alcohol solutions at
reflux temperature on treatment with catalytic amounts of iron-copper nanoparticles, and silver nanoparticles, which were
prepared from Camellia sinensis natural extracts.
Keywords: Carbenoids, ethers, nanoparticles, p-toluensulfonyl hydrazones.
Carbene and carbenoid intermediates are useful synthetic
tools which have diversified the field of transformations in
Organic Chemistry. However, the number of sources of
carbenoids is limited, depending mainly on a relatively small
range of diazocarbonyl compounds and some rhodium and
copper catalysts [1]. Recently, the groups of Aggarwal [2-5],
Barluenga and Valdés [6-8], Cheung [9] and our group [10]
have described carbenoid reactions through in situ diazo
group generation under mild conditions using p-
toluenesulfonylhydrazones as starting materials.
isopropyl ether formation, most of the reactions showed
another product which was identified as the corresponding
azine and, in some cases, was the major product.
Ph
Ph
1) iPrONa / iPrOH /reflux
2) Agnano / iPrOH /reflux
O
NNHTs
Ph
Ph
2
1
Scheme 1. Synthesis of ether 2 from tosylhydrazone 1.
On the other hand, nanoparticles represent a novel source
of catalysts with applications in many chemical processes.
For example, Sudrik and coworkers reported the use of silver
nanoclusters in the Wolff rearrangement of several
diazoketones for carboxylic acid homologations [11-13].
Motivated by these preceding reports, we started to
investigate the use of alternative sources of diazo compounds
and nanoparticle catalysts in carbenoid reactions.
In
a
model
study,
benzophenone p-toluene
sulfonylhydrazone 1 was reacted with a slight excess of
sodium isopropoxide, and the resulting sodium salt was
treated at isopropanol reflux temperature with catalytic
amounts of silver nanoparticles (Fig. 1), which in turn were
prepared from an adaptation of a silver nitrate bioreduction
using natural extracts of Camellia sinensis (“green tea”)
[14]. After column chromatography purification, the reaction
afforded the isopropyl ether 2 in 55% yield (Scheme 1).
Fig. (1). TEM Micrograph of Ag nanoparticles obtained from
bioreduction with Camellia sinesis, scale bar: 5000 nm.
In order to explore the reaction scope, several
tosylhidrazones were reacted under similar conditions and
the results are presented in Table 1. In addition to the
On the other hand, a novel kind of iron-copper
nanoparticles which were first used in waste water treatment
(Fig. 2) [15], was tested as carbenoid insertion catalyst in
this study. Initially, experiments were made in order to find
optimal catalytic concentrations. The best conditions were
obtained using a 10 mg catalyst / mmol tosilhydrazone ratio
(Table 2), giving isopropyl ether 2 in 78 % yield.
*Address correspondence to this author at the Centro Conjunto de
Investigación en Química Sustentable UAEM-UNAM. Carretera Toluca-
Atlacomulco Km 14.5, Toluca, Estado de México, 5200, Mexico; Tel: +52
722 276 66 10 ext. 7734; Fax: +52 722 217 51 09;
E-mail: ecuevasy@uaemex.mx
© 2012 Bentham Science Publishers
1875-6255/12 $58.00+.00

Carbenoid Etherifications Catalyzed by “Green” Silver Nanoparticles
Letters in Organic Chemistry, 2012, Vol. 9, No. 1
3
Table 1. Carbenoid insertions using silver nanoparticles
1) iPrONa
iPrOH /reflux
R1
R2
R1
R2
R2
R1
+
O
N
N
NNHTs
R1
R2
2) Agnano
iPrOH /reflux
Entry
R1
R2
% ispropyl ether
% azine
1
2
3
4
5
Ph
CH3
H
Ph
55
65
67
10
68
22
18
15
30
20
3-(1-PhSO2C4H3N)
4-PhC6H4
H
2,4,5-CH3OC6H2
2,6-ClC6H3
H
To the best of our knowledge, this is the first example
about the use of nanoparticles as catalysts in carbenoid
intermolecular insertions. These results display an alternative
methodology to prepare sterically hindered ethers from p-
toluenesulfonylhydrazones and nanosized catalysts, which
complement and extend the results of Barluenga-Valdes [8]
and Chandrasekhar [18]. In addition, all the ethers described
herein are useful points of departure enroute to novel
bioactives molecules and gasoline additives [19], with
promising applications in this last area.
EXPERIMENTAL
The starting materials were purchased from Aldrich
Chemical Co. and were used without further purification.
Solvents were distilled before use. Silica plates of 0.20 mm
thickness were used for thin layer chromatography. Melting
points were determined with a Fisher-Johns melting point
apparatus and they are uncorrected. 1H and 13C NMR spectra
were recorded using a Bruker AVANCE 300, the chemical
shifts (ꢀ) are given in ppm relative to TMS as an internal
standard (0.00). For analytical purposes the mass spectra
were recorded on a JEOL JMS-5X 10217 in the EI mode, 70
eV, 200oC via direct inlet probe. Only the molecular and
parent ions (m/z) are reported. IR spectra were recorded on a
Nicolet Magna 55-X FT instrument. TEM studies were
Fig. (2). TEM Micrograph of Fe-Cu nanoparticles, scale bar: 5nm.
This catalytic system was extended to some
tosylhydrazones using diverse alcohols, obtaining the
corresponding ethers in moderate-good yields (Table 3).
Although the azine formation mechanism is not clear,
this probably occurs through a diazoalkane oxidation-
dimerization step, such as Sharma [16], Shechter and co-
workers [17] have previously described.
Table 2. Effect of Catalyst Concentration in Carbenoid Insertion
1) iPrONa
iPrOH /reflux
Ph
Ph
Ph
Ph
Ph
Ph
Ph
+
O
N
N
NNHTs
2) Fe-Cuano
iPrOH /reflux
Ph
3
2
Entry
mg catalyst/mmol hydrazone
Time (h)
% ispropyl ether
% azine
1
2
3
4
5
6
3
105
70
24
24
12
5
35
50
78
78
45
35
60
35
20
20
35
35
5
10
12
15
20

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Letters in Organic Chemistry, 2012, Vol. 9, No. 1
García et al.
Table 3. Carbenoid Insertions Using Iron-Copper Nanoparticles
1) R3ONa
R1
R2
R1
R2
R2
R1
R1
R3OH /reflux
R3
N
N
+
O
NNHTs
R2
2) Fe-Cunano
R3OH /reflux
Entry
R1
R2
R3
% ispropyl ether
% azine
1
2
3
4
5
6
7
8
9
Ph
Ph
Ph
H
Ph
iPr
Me
Et
78
65
70
70
54
62
75
50
78
20
23
15
35
23
20
15
25
12
Ph
Ph
2,6-ClC6H3
2,6-ClC6H3
2,6-ClC6H3
2,4,5-CH3OC6H2
2,4,5-CH3OC6H2
2,4,5-CH3OC6H2
iPr
nBu
Et
H
H
H
iPr
Me
Et
H
H
performed on
microscope, operated at accelerating voltage of 200 kV.
a
JEM-100CX transmission electron
vacuo. Purification by column chromatography (SiO2,
hexane/AcOEt 9:1) afforded the isopropyl ether and azine
according to Table 1.
The silver iron-copper nanoparticles were provided by
the Advanced Materials Laboratory from Universidad
Autónoma del Estado de Mexico and they were prepared
using the method described by Sanchez-Mendieta and
coworkers [10, 11].
Isopropoxydiphenylmethane (entry 1, Table 1, and entry 1,
Table 3)
Colorless oil. IR (KBr, cm-1) 1599, 1355. 1H NMR (500
MHz, CDCl3) ꢀ 1.20 (d, 6H), 3.64 (h, 1H), 5.47 (s, 1H), 7.25
(m, 10H). 13C NMR (125 MHz, CDCl3) ꢀ 22.2, 69.0, 80.4,
126.2, 127.1, 128.2, 142.4. MS [EI+] m/z (%) 226 [M]+ (6),
167 [M-C3H7O] (99), 149 [M-C6H5]+ (100). HRMS (EI+):
for C16H18O calcd. 226.1348, found 226.1351.
Preparation of Silver Nanoparticles
Camellia sinensis (“Green tea”) Extract Preparation
A conventional green tea bag (lagg’s), containing 1.5g of
the dried plant, was boiled in 100 ml of 2-propanol during 1
minute. The resulting extract was filtered and used for
further experiments.
1-Benzenesulfonyl-3-(1-isopropoxy-ethyl)pyrrole (entry 2,
Table 1)
Colorless oil. IR (KBr, cm-1) 3432, 3138, 2972, 1177. 1H-
NMR (500 MHz, CDCl3) ꢀ ppm: 1.49 (d, 3H), 1.10 (d, 3H),
1.34 (d, 3H), 3.51 (h, 1H), 4,42 (q, 1H), 6.28 (dd, 1H), 7.03
(m, 1H), 7.11 (m, 1H), 7.44-7.63 (m, 3H), 7.82-7.87 (m,
2H). 13C-NMR (125 MHz, CDCl3) ꢀ ppm: 21.8, 22.8, 22.9,
68.1, 68.6, 112.5, 117.56, 121.2, 126.7, 129.2, 132.8, 133.7,
139. MS [EI+] m/z (%) 293 [M]+ (5), 236 [M-C4H9]+ (100).
HRMS (EI+): for C15H19NO3S calcd. 293.1086, found
293.1089.
Synthesis of silver nanoparticles using Camellia sinensis
(“Green tea”) extract in 2-propanol
Aliquots of this extract (2 mL) were added to a 10-3
M
solution of AgNO3 in 2-propanol (5 mL). The final volume
was adjusted to 10 mL with 2-propanol. The reaction
mixture was stirred at room temperature for 24 h. The silver
nanoparticles were used without additional purification.
4-(Isopropoxy-phenyl-methyl)biphenyl. (entry 3, Table 1)
1
IR (KBr, cm-1) 1460, 1170. H-NMR (500 MHz, CDCl3)
Carbenoid Etherifications Using Silver Nanoparticles
ꢀ ppm: 1.22 (d, 3H), 1.25 (d, 3H), 3.7 (m, 1H), 5.53 (s, 1H),
7.20 (m, 14H). 13C-NMR (125 MHz, CDCl3) ꢀ ppm: 22.2,
22.3, 69.1, 80.2, 127.0, 127.3, 127.4, 128.3, 128.4, 128.6,
128.9, 129.2, 140.1, 140.9, 142.0, 142.8. MS [EI+] m/z (%)
302 [M]+ (61), 243 [M-C3H2O]+ (100). HRMS (EI+): for
C22H22O calcd. 302.1671, found 302.1675.
Typical Procedure
Sodium (0.080 g, 3.5mmol) was added to anhydrous
isopropanol (10 mL), and the resulting mixture was stirred at
50ºC under a nitrogen atmosphere for 1 h to dissolve the
sodium completely. The solution was cooled to room
temperature and
a
solution of the corresponding
1-Isopropoxymethyl-2,4,5-trimethoxy-benzene (entry 4,
Table 1, and entry 7, Table 3)
Colorless oil. IR (KBr, cm-1) 2957, 1603, 1347. 1H-NMR
(500 MHz, CDCl3) ꢀ: 1.21 (d, 6H), 3.67 (h, 1H), 3.81 (s,
3H), 3.84 (s, 3H), 3.85 (s, 3H), 4.58 (s, 2H), 6.56 (s, 1H),
tosylhidrazone (3.2 mmol) in isopropanol (10 mL) was
added. The reaction mixture was stirred at 50ºC for 2 h and a
suspension of silver nanoparticles (2 mL of a 10-2 M solution
in isopropanol) was added. The resulting reaction mixture
was stirred at reflux temperature for 12 h. The mixture was
cooled to room temperature and the solvent was removed in

Carbenoid Etherifications Catalyzed by “Green” Silver Nanoparticles
Letters in Organic Chemistry, 2012, Vol. 9, No. 1
5
6.93 (s, 1H). 13C-NMR (125 MHz, CDCl3) ꢀ: 22.2, 22.3,
56.1, 56.3, 56.4, 65.6, 69.1, 97.4, 113.2, 118.36, 142.9,
148.9, 151.5. MS [EI+] m/z (%) 240 [M]+ (20) 225 [M -
CH3]+ (100) HRMS (EI+): for C13H20O4 calcd. 240.1362,
found 240.1367.
[M]+ (10), 135 [M-C6H5]+ (100). HRMS (EI+): for C14H14O
calcd. 212.1201, found 212.1208.
2-Butoxymethyl-1,3-dichlorobenzene (entry 5, Table 3)
Colorless oil. IR (KBr, cm-1) 2958, 1603, 1345. 1H-NMR
(500 MHz, CDCl3) ꢀ: 0.97 (t, 2H), 1.29-1.65 (m, 4H), 3.59
(t, 2H), 4.95 (s, 2H), 7.11-7.67 (m, 3H). 13C-NMR (125
MHz, CDCl3) ꢀ: 13.9, 19.1, 31.8, 70.9, 76.7, 126.9, 129.8,
133.6, 135.6, 138.9. MS [EI+] m/z (%) 232 [M]+ (50) 189
[M- C3H7] (100). HRMS (EI+): for C11H14Cl2O calcd.
232.0422, found 232.0426.
1,3-Dichloro-2-isopropoxymethylbenzene (entry 5, Table 1,
and entry 4, Table 3)
Colorless oil. IR (KBr, cm-1) 2959, 1603, 1345. 1H-NMR
(500 MHz, CDCl3) ꢀ ppm: 1.44 (d, 6H), 3.84-3.97 (m, 1H),
5.73 (s, 2H), 7.43-7.62 (m, 3H). 13C-NMR (125 MHz,
CDCl3) ꢀ ppm: 22.5, 69.2, 76.9, 127.3, 127.4, 129.1, 143.2.
MS [EI+] m/z (%) 218 [M]+ (100). HRMS (EI+): for
C10H12Cl2O calcd. 218.0265, found 218.0268.
1,3-Dichloro-2-ethoxymethyl-benzene (entry 6, Table 3)
Colorless oil. IR (KBr, cm-1) 2958, 1603, 1345. 1H-NMR
(500 MHz, CDCl3) ꢀ: 1.16 (t, 2H), 4.09 (q, 2H), 4.98 (s, 2H),
7.11-7.67 (m, 3H). 13C-NMR (125 MHz, CDCl3) ꢀ: 14.1,
56.4, 69.9, 126.9, 129.8, 133.6, 135.6, 138.9. MS [EI+] m/z
(%) 204 [M]+ (50) 189 [M- CH3]+ (100). HRMS (EI+): for
C11H14Cl2O calcd. 204.0109, found 204.0110.
Preparation of Iron-Copper Nanoparticles
.
A solution of FeSO4 7H2O (2.30 g; 7.5 mmol) in H2O
.
(750 mL) was added to solution of CuSO4 5H2O (0.69 g; 2.5
mmol) in H2O (250 mL). The resulting mixture was stirred
with mechanical stirring (300 rpm) at room temperature. A
solution of 0.5 M NaOH was added dropwise to pH=7.
When pH was adjusted, a solution of NaBH4 (0.757 g; 20
mmol) in H2O (100 mL) was added, a vigorous evolution of
hydrogen occurred, and the resulting dark mixture was
stirred at room temperature for 15 min. The mixture was
filtered, and the precipitate was washed successively with
water and acetone. The nanoparticles were dried in vacuo at
room temperature for 24 h.
1,2,4-Trimethoxy-5-methoxymethyl-benzene (entry 8, Table
3)
Colorless oil. IR (KBr, cm-1) 2957, 1603, 1347. 1H-NMR
(500 MHz, CDCl3) ꢀ: 3.81 (s, 3H), 3.84 (s, 3H), 3.85 (m,
6H), 4.55 (s, 2H), 6.56 (s, 1H), 6.93 (s, 1H). 13C-NMR (125
MHz, CDCl3) ꢀ: 56.1, 56.2, 56.3, 56.4, 65.6, 66.9, 97.4,
113.2, 118.36, 142.9, 148.9, 151.5. MS [EI+] m/z (%) 212
[M]+ (40) 181 [M- CH3O]+ (100) HRMS (EI+): for
C11H16O4 calcd. 212.1049, found 212.1046.
1-Ethoxymethyl-2,4,5-trimethoxy-benzene (entry 9, Table
3)
Carbenoid
Etherifications
using
Iron-Copper
Colorless oil. IR (KBr, cm-1) 2957, 1603, 1347. 1H-NMR
(500 MHz, CDCl3) ꢀ: 1.21- (t, 3H), 3.51 (q, 2H), 3.81 (s,
3H), 3.84 (s, 3H), 3.85 (s, 3H), 4.51 (s, 2H), 6.51 (s, 1H),
6.92 (s, 1H). 13C-NMR (125 MHz, CDCl3) ꢀ: 15.2, 56.1,
56.3, 56.4, 65.6, 66.9, 97.4, 113.2, 118.36, 142.9, 148.9,
151.5. MS [EI+] m/z (%) 226 [M]+ (50) 211 [M- CH3]+
(100) HRMS (EI+): for C12H18O4 calcd. 226.1205, found
226.1206.
Nanoparticles
Typical Procedure
Sodium (0.080 g, 3.5mmol) was added to the
corresponding anhydrous alcohol (10 mL), and the resulting
mixture was stirred at 50ºC under a nitrogen atmosphere for
1 h to dissolve the sodium completely. The solution was
cooled to room temperature and a solution of the appropriate
tosylhydrazone (3.2 mmol) in alcohol( 10 mL) was added.
The reaction mixture was stirred at 50ºC for 2 h and iron-
copper nanoparticles (0.01g) were added. The resulting
reaction mixture was stirred at reflux temperature for 12 h.
The mixture was cooled to room temperature and the solvent
was removed in vacuo. Purification by column
chromatography (SiO2, hexane/AcOEt 9:1) afforded the
corresponding ethers and azines according to table 3.
ACKNOWLEDGEMENTS
Financial support from SIEA-UAEMEX is gratefully
acknowledged. The authors would like to thank Signa, S.A.
de C.V. for some graciously donated solvents and reagents,
and M. C. Nieves Zavala for the technical support.
Methoxydiphenylmethane (entry 2, Table 3)
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Nanocluster Redox-Couple-Promoted Nonclassical Electron