Nanosized iron- or copper-catalyzed homocoupling of aryl, heteroaryl, benzyl, and alkenyl grignard reagents

Article abstract of DOI:10.1080/00397910802238726

Under very mild reaction conditions, iron or copper nanoparticles efficiently promoted the homocoupling of different Grignard reagents in tetrahydrofuran at room temperature. The nanosized iron or copper particles were generated in situ in a simple and economical way from commercially available FeCl2 or CuCl2, respectively, an excess of lithium powder, and a catalytic amount (5 mol%) of 4,4′-di-tert-butylbiphenyl (DTBB) as electron carrier. The reaction of a series of aryl, heteroaryl, benzyl, and alkenyl Grignard reagents in the presence of a substoichiometric amount of the iron or copper nanoparticles led to the formation of the corresponding homocoupling products in good yield. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802238726

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Nanosized Iron- or Copper-
Catalyzed Homocoupling of
Aryl, Heteroaryl, Benzyl, and
Alkenyl Grignard Reagents
Yanina Moglie a , Evangelina Mascaró a , Fabiana
Nador a , Cristian Vitale a & Gabriel Radivoy a
a Department of Chemistry, National University of
the South, Bahía Blanca, Argentina
Published online: 20 Oct 2008.
To cite this article: Yanina Moglie , Evangelina Mascaró , Fabiana Nador ,
Cristian Vitale & Gabriel Radivoy (2008): Nanosized Iron- or Copper-Catalyzed
Homocoupling of Aryl, Heteroaryl, Benzyl, and Alkenyl Grignard Reagents, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 38:22, 3861-3874
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Synthetic Communications1, 38: 3861–3874, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802238726
Nanosized Iron- or Copper-Catalyzed
Homocoupling of Aryl, Heteroaryl, Benzyl, and
Alkenyl Grignard Reagents
ꢀ
Yanina Moglie, Evangelina Mascaro, Fabiana Nador, Cristian Vitale,
and Gabriel Radivoy
Department of Chemistry, National University of the South,
´
Bahıa Blanca, Argentina
Abstract: Under very mild reaction conditions, iron or copper nanoparticles
efficiently promoted the homocoupling of different Grignard reagents in tetrahy-
drofuran at room temperature. The nanosized iron or copper particles were gen-
erated in situ in a simple and economical way from commercially available FeCl2
or CuCl2, respectively, an excess of lithium powder, and a catalytic amount
(5 mol%) of 4,40-di-tert-butylbiphenyl (DTBB) as electron carrier. The reaction
of a series of aryl, heteroaryl, benzyl, and alkenyl Grignard reagents in the
presence of a substoichiometric amount of the iron or copper nanoparticles led
to the formation of the corresponding homocoupling products in good yield.
Keywords: Copper nanoparticles, Grignard reagents, homocoupling, iron
nanoparticles
Transition metal–catalyzed coupling reactions of organohalogenated
compounds to form carbon–carbon bonds are one of the most powerful
tools in organic synthesis.[1] In the past decade, this methodology evolved
into a general and efficient route for the synthesis of many relevant
chemicals, materials, and bioactive compounds.[1,2] Among the different
transition metal–based reagents utilized in these coupling reactions,
Received February 29, 2008.
Address correspondence to Gabriel Radivoy, Departamento de Quımica,
´
Universidad Nacional del Sur, Avda. Alem 1255, 8000 Bahıa Blanca, Argentina.
E-mail: gradivoy@criba.edu.ar
´
3861

3862
Y. Moglie et al.
palladium and nickel complexes are by far the most widely studied,
mainly because of their selectivity, extensive applicable scope, and com-
patibility with many functional groups.[3] However, most of the palla-
dium- and nickel-based catalysts are expensive and involve the use of
toxic ligands such as phosphine compounds. Therefore, the development
of more convenient methodologies with respect to environmental and
economic considerations is still in demand. In this sense, the use of iron-
or copper-based catalysts is particularly attractive because both metals
are inexpensive, readily available, and very attractive regarding environ-
mental considerations. On the other hand, the previousor in situ transfor-
mation of the organohalogenated substrates into the corresponding
Grignard reagents is a valuable alternative because it allows the use of
a wide variety of metal reagents as catalysts.[4] Since the pioneering work
of Kochi et al.,[5] iron and copper salts emerged as very attractive
alternatives for the homo- and cross-coupling of Grignard reagents and
halogenated compounds.[6] In recent years, interest in the homocoupling
of vinyl, aryl, and heteroaryl organomagnesium reagents[4b,c,7,8c] has been
renewed mainly because these reactions provide an easy access to the
construction of a symmetrical di- or polyolefinic, aromatic or heteroaro-
matic backbone, with potential important applications in the field of
optical materials, molecular devices, and organic conductors.[9] Although
the homocoupling of Grignard reagents has been observed as a side
reaction by many authors dealing with metal-catalyzed cross-coupling
reactions, few reports appear in the literature concerning the selective
homocoupling of organomagnesium compounds by iron or copper cata-
lysis. Recently, Nagano and Hayashi[7a] and Cahiez et al.[4b] indepen-
dently reported the homocoupling of aryl Grignard reagents catalyzed
by iron trichloride in the presence of noxious 1,2-dihalogenalkanes.
Following that, Xu et al.[4c] described the homocoupling of in situ gener-
ated organomagnesium compounds derived from alkyl and aryl bromides
by using a combination of metallic magnesium and a catalytic amount of
iron salts, although no homocoupled products were obtained using aryl
chlorides as substrates. More recently, Cahiez et al.[7f] and Liu and Lei[7h]
reported the homocoupling of aryl Grignard reagents catalyzed by iron
trichloride using molecular oxygen or dry air as the oxidant. On the other
hand, to the best of our knowledge, the copper-mediated homocoupling
of Grignard reagents for the preparation of the corresponding symmetri-
cal coupled products was seldom reported before.[8]
In the past, we have been working on the reduction of different
organic functional groups using new reducing systems consisting of a
mixture of copper or iron hydrated salts (CuCl2 ꢀ 2H2O or FeCl2 ꢀ 4H2O,
O, respectively), an excess of lithium powder, and a catalytic amount of
an arene as electron carrier, in which the source of hydrogen is the salt

Homocoupling of Grignard Reagents
3863
crystallization water.[10,11] Our ongoing interest in exploring the synthetic
scope and applicability of these active-metal-based reactive combinations
prompted us to study the reactivity of the analogous copper- and iron-
based systems but using the corresponding anhydrous salts to be tested
in different coupling reactions. In a very recent communication,[12] we
have reported the efficiency of the FeCl2–Li–arene (cat.) system in the
reductive coupling of nitro-aromatics to directly afford the corresponding
azo-compounds in good yields. On the other hand, we found that the
active iron and copper generated by this methodology consisted of very
reactive, monodispersed spherical iron(0) or coper(0) nanoparticles.
Typical transmission electron microscopy (TEM) micrographs and sizes
distribution graphics for both iron and copper nanoparticles are depicted
in Figs. 1 and 2, respectively.
We report herein our results on a coupling methodology of various
organomagnesium compounds, including chlorides and bromides, that
leads to a simple and economic preparation of biaryls, biheteroaryls,
bibenzyls, and conjugated dienes, under very mild reaction conditions,
using a substoichiometric amount of iron(0) or copper(0) nanoparticles,
generated in situ from commercially available iron(II) chloride or
copper(II) chloride respectively, lithium, and a catalytic amount of
4,40-di-tert-butylbiphenyl (DTBB) as electron carrier.
Table 1 summarizes the results obtained for the reaction of a series of
aryl, heteroaryl, benzyl, and vinyl Grignard reagents (1.0 mmol) with a
mixture of iron(II) chloride (0.5 mmol) or copper(II) chloride (0.5 mmol),
an excess of lithium powder (1:8 molar ratio, referred to the iron or cop-
per salt), and a catalytic amount of DTBB (5.0 mol%) in tetrahydrofuran
at room temperature, which led to the corresponding homocoupling
Figure 1. TEM micrograph and size distribution graphic of iron nanoparticles.
The sizes were determined by measuring diameters of 200 nanoparticles randomly
selected on the TEM images.

3864
Y. Moglie et al.
Figure 2. TEM micrograph and size distribution graphic of copper nanoparticles.
The sizes were determined by measuring diameters of 200 nanoparticles randomly
selected on the TEM images.
products. Both phenylmagnesium chloride and bromide gave biphenyl in
excellent yield (Table 1, entries 1 and 2 respectively) either using iron(0)
or copper(0) nanoparticles. Similarly, p-methylphenylmagnesium
bromide rendered the corresponding 4,40-dimethylbiphenyl in good yield
(Table 1, entry 3). It is worth noting that for the iron-promoted homo-
coupling, the electronic properties of substituents attached to the aroma-
tic ring did not affect the coupling process. Substrates bearing strong
electron-releasing groups (Table 1, entry 4) or electron-withdrawing ones
(Table 1, entry 5) gave the symmetrically substituted biaryls in good
yield. However, the copper-based system showed a notably lower effi-
ciency for the coupling of aryl Grignard reagents having an electron-
withdrawing group on the aromatic ring (Table 1, entry 5), which is in
agreement with previous results published by Lee for the copper(II)
triflate–induced homocoupling of Grignard reagents.[8e] With regard to
the steric hindrance effect, substitution at the ortho positions of the aryl
Grignard reagents resulted in significantly lower yields of the homocou-
pling products with both iron- and copper-based coupling systems (Table 1,
entries 6 and 7). Interestingly, the coupling procedure was successfully
applied to heteroaromatic Grignard reagents such as 2-pyridylmagne-
sium bromide, 3-pyridylmagnesium bromide and 2-thienylmagnesium
bromide, which were efficiently converted into the corresponding biheter-
oaryl compounds in good yields (Table 1, entries 8, 9 and 10, respec-
tively). Under the same conditions, benzyl Grignard reagents afforded
the corresponding 1,2-diarylethanes in excellent yield (Table 1, entries 11
and 12, respectively), although other primary alkyl Grignard reagents
such as dodecylmagnesium bromide (Table 1, entry 13) gave very low con-
version to the desired tetracosane. Finally, it should be noted that both

Homocoupling of Grignard Reagents
3865
Table 1. Iron- or copper-catalyzed homocoupling of Grignard reagents
Yield (%)b
Reaction
Entry Grignard reagent time (h)a
Product
Fec Cud
1
2
3
4
4
3
85
88
77
82
80
73
4
5
3
5
84
80
79
66
6
7
8
65e
63e
10
54f
51f
8
4
75
72
(Continued )

3866
Y. Moglie et al.
Table 1. Continued
Yield (%)b
Fec Cud
Reaction
Entry Grignard reagent time (h)a
Product
9
4
78
70
10
11
3
2
85
81
75g
75g
12
2
81g
80g
13
8
8
20g
50i
16g
41i
14h
aAll reactions were performed using RMgX (1.0 mmol), FeCl2 or CuCl2
(0.5 mmol), Li (8.0 mmol), DTBB (0.1 mmol), THF, 20 ꢁC.
bAll products were > 95% pure (GLC); isolated yield after column chromato-
graphy (hexane-ethyl acetate), based on the starting material, unless otherwise
stated.
cReaction performed with the FeCl2-Li-DTBB(cat.) system.
dReaction performed with the CuCl2-Li-DTBB(cat.) system.
eA ca. 1:1 mixture of toluene and o-cresol was recovered as by-products.
fA ca. 1:1 mixture of naphthalene and 1-naphthol was recovered as by-
products.
gGLC yield based on the starting material.
hA 1:1 mixture of Z- and E-isomers was used.
iDiastereoisomeric ratio: E=E:E=Z ¼ 99:1, determined by GC-MS.

Homocoupling of Grignard Reagents
3867
iron- and copper-based coupling systems promoted the homocoupling of
alkenyl Grignard reagents in a highly stereoselective way. Thus, when the
previously described methodology was applied to a 1:1 mixture of (E)-
and (Z)-b-styrylmagnesium bromide, the corresponding (E,E)-1,4-diphe-
nylbutadiene was obtained as the main reaction product (ca. 99%),
although in low to moderate yield (Table 1, entry 14).
The presence of the iron or copper nanoparticles was demonstrated
to be essential by carrying out two blank experiments with p-methyl-
phenylmagnesium bromide as the starting material. Thus, without using
the mentioned nanoparticles, after workup of the reaction mixture, only
toluene and very low yields (10–15%) of the desired homocoupling
product were obtained after stirring for 12 h at room temperature.
In summary, we have developed two efficient iron- and copper-
catalyzed methodologies to perform the homocoupling of aryl-, hetero-
aryl-, benzyl-, and alkenylmagnesium chlorides and bromides, under mild
reaction conditions, based on the use of iron(0) or copper(0) nanoparti-
cles generated in a simple and economic way from commercially available
iron(II) chloride or copper(II) chloride, lithium, and a catalytic amount
of DTBB as electron carrier. It should be noted that the reactions were
highly stereoselective in the coupling of alkenyl Grignard reagents. We
are actively exploring new applications of these coupling systems to
cross-coupling reactions, and further study on the mechanistic aspects
is in progress.
EXPERIMENTAL
General Procedure
All moisture-sensitive reactions were carried out under a nitrogen atmo-
sphere. Anhydrous tetrahydrofuran was freshly distilled from sodium=
benzophenone ketyl. Other solvents used were treated prior to use by stan-
dard methods.[13] Anhydrous iron(II) chloride and copper(II) chloride
were commercially available (Aldrich). Column chromatography was per-
formed with Merck silica gel 60 (0.040–0.063 mm, 240–400 mesh). Thin-
layer chromatography (TLC) was performed on precoated silica gel plates
(Merck 60, F254, 0.25 mm). Nuclear magnetic resonance (NMR) spectra
were recorded on a Bruker ARX-300 spectrophotometer using CDCl3
as solvent and tetramethylsilane (TMS) as internal reference. Mass
spectra (EI) were obtained at 70 eV on a Hewlett Packard HP-5890 gas
chromatography–mass spectrometry (GC=MS) instrument equipped with
a HP-5972 selective mass detector. Infrared (FT-IR) spectra were
obtained on a Nicolet-Nexus spectrophotometer. The purity of volatile

3868
Y. Moglie et al.
compounds and the chromatographic analyses (GC) were determined
with a Shimadzu GC-9A instrument equipped with a flame-ionization
detector and a 2-m column (1.5% OV17 9A SUS Chrom 103 80=1000),
using nitrogen as carrier gas. TEM images of iron and copper nanoparti-
cles were recorded at the TEM service of the University of Alicante
(Spain) using a Jeol JEM2010 microscope equipped with a lanthanum
hexaboride filament and operated at an acceleration voltage of 200 kV.
Starting Grignard reagents showed in entries 1–7 and 10–14 (Table 1)
were prepared in dry diethyl ether from the corresponding commercially
available organic halides by the standard method.[14] Then 2- and
3-pyridylmagnesium chlorides were prepared according to the procedure
[15]
´
reported by Trecourt et al., by a bromine-magnesium exchange.
General Procedure for the Nanosized Iron- or Copper-Catalyzed
Homocoupling of Grignard Reagents
A mixture of FeCl2 (128 mg, 1.0 mmol) or CuCl2 (134 mg, 1.0 mmol),
lithium powder (56 mg, 8.0 mmol), and DTBB (27 mg, 0.1 mmol) in
THF (5 ml) was vigorously stirred at room temperature under a nitrogen
atmosphere. The reaction mixture, which was initially dark green, chan-
ged to black, thus indicating the formation of iron(0) or copper(0) nano-
particles respectively. Then, a solution of the Grignard reagent (2.0 mmol)
in ether (5 ml) was added. The reaction time was monitored by gas–liquid
chromatography (GLC). After total conversion of the starting material,
the resulting suspension was diluted with diethyl ether (10 ml) and 10%
HCl (10 ml). The organic layer was washed with water (10 ml), dried over
anhydrous sodium sulfate, and evaporated (15 torr). The resulting residue
was purified by column chromatography (silica gel; hexane=ethyl acet-
ate). All the products are known compounds and were fully characterized
by comparison of their physical and spectroscopic data with those of the
corresponding commercially available pure samples or literature data.
Data
Biphenyl[4c] (Entries 1 and 2)
White solid; mp 68–69 ꢁC; IR (KBr) n ¼ 3031, 1941, 1880, 1573, 1481,
1
1342, 1173, 1081, 902, 743, 702 cmꢂ1; H NMR (300 MHz, CDCl3) d:
7.34–7.46 (m, 6H), 7.59 (4H, d, J ¼ 8.1 Hz); 13C NMR (300 MHz, CDCl3)
d: 127.1, 127.2, 128.7, 141.2; MS (EI, 70 eV) m=z (%): 154 (100) [Mþ], 76
(15) [Mþ–C6H6].

Homocoupling of Grignard Reagents
3869
4,40-Dimethylbiphenyl[16] (Entry 3)
White solid; mp 118–120 ꢁC; IR (KBr) n ¼ 3015, 2923, 1600, 1481, 803,
723 cmꢂ1 1H NMR (300 MHz, CDCl3) d: 2.39 (6H, s), 7.24 (4H, d,
;
J ¼ 8.1 Hz), 7.48 (4H, d, J ¼ 8.1 Hz); 13C NMR (300 MHz, CDCl3) d;
21.3, 127.1, 129.7, 136.9, 138.5. MS (EI, 70 eV) m=z (%): 182 (100)
[Mþ], 181 (27), 167 (35), 166 (11), 165 (22).
4,40-Dimethoxybiphenyl[4c] (Entry 4)
White solid; mp 178–180 ꢁC; IR (KBr) n ¼ 1614, 1506, 1276, 1250, 1178,
1
1040, 1015, 825, 805 cmꢂ1; H NMR (300 MHz, CDCl3) d: 3.83 (6H, s),
6.95 (4H, d, J ¼ 9.1 Hz), 7.47 (4H, d, J ¼ 9.2 Hz); 13C NMR (300 MHz,
CDCl3) d: 55.4, 114.3, 127.5, 133.1, 158.8; MS (EI, 70 eV) m=z (%): 214
(100) [Mþ], 199 (85), 171 (26), 156 (10), 139 (10), 128 (15).
4,40-Bis(trifluoromethyl)biphenyl[17] (Entry 5)
White solid; mp 92–93 ꢁC; IR (KBr) n ¼ 1324, 1166, 1133, 1114, 1070,
1
829 cmꢂ1; H NMR (300 MHz, CDCl3) d: 7.71 (4H, d, J ¼ 8.8 Hz), 7.78
(4H, d, J ¼ 8.8 Hz); 13C NMR (300 MHz, CDCl3) d: 124.0 (2 ꢃ CF3, q,
J ¼ 272 Hz), 125.8 (4 ꢃ CCCF3, q, J ¼ 3.4 Hz), 127.6, 130.3 (2 ꢃ CCF3,
q, J ¼ 34.4 Hz), 143.2; MS (EI, 70 eV) m=z (%): 290 (100) [Mþ], 271
(35), 240 (10), 152 (28).
2,20-Dimethylbiphenyl[16] (Entry 6)
Colorless oil; bp 85–90 ꢁC=0.8 mm Hg; IR (film) n ¼ 3030, 2945, 1607,
1
1509, 1169, 1006, 725 cmꢂ1; H NMR (300 MHz, CDCl3) d: 2.10 (6H,
s), 7.24 (2H, d, J ¼ 7.4 Hz), 7.27 (2H, t, J ¼ 7.4 Hz), 7.32 (2H, t,
J ¼ 7.3 Hz), 7.41 (2H, d, J ¼ 7.3 Hz); 13C NMR (300 MHz, CDCl3) d:
19.8, 125.8, 127.1, 129.4, 129.9, 135.6, 141.6; MS (EI, 70 eV) m=z (%):
182 (68) [Mþ], 167 (100), 166 (23), 165 (48), 152 (22).
1,10-Binaphthyl[7f] (Entry 7)
White solid; mp 156–159 ꢁC; IR (Nujol) n ¼ 3050, 1585, 1506, 1215, 1117,
1
965, 805, 748, 683 cmꢂ1; H NMR (300 MHz, CDCl3) d: 7.24–7.30 (1H,
m), 7.42 (1H, d, J ¼ 8.2 Hz), 7.45–7.54 (2H, m), 7.60 (1H, t, J ¼ 7.6 Hz),
7.91–7.99 (2H, m); 13C NMR (300 MHz, CDCl3) d: 125.4 125.9, 126.3,

3870
Y. Moglie et al.
126.8, 128.0, 128.3, 128.5, 133.1, 133.8, 138.7; MS (EI, 70 eV) m=z (%):
254 (100) [Mþ], 253 (74), 252 (52), 250 (13), 126 (27).
2,20-Bipyridyl[18] (Entry 8)
Yellow solid, mp 70–73 ꢁC; IR (KBr) n ¼ 3086, 1580, 1557, 1463, 1416,
1
1261, 1041, 894, 760, 656 cmꢂ1; H NMR (300 MHz, CDCl3) d: 7.12–
7.15 (2H, m), 7.64–7.69 (2H, m), 8.47–8.50 (2H, m), 8.56–8.63 (2H, m);
13C NMR (300 MHz, CDCl3) d: 121.2, 123.8, 136.6, 149.2, 156.3; MS
(EI, 70 eV) m=z (%): 156 (100) [Mþ], 155 (34), 129 (18), 128 (19), 78
(18), 51 (15).
3,30-Bipyridyl[4c] (Entry 9)
Orange oil; IR (neat) n ¼ 3029, 1592, 1592, 1468, 1427, 1401, 1333, 1200,
1025, 997, 796, 714 cmꢂ1; 1H NMR (300 MHz, CDCl3) d: 7.38–7.45 (2H,
m), 7.89 (2H, ddd, J1 ¼ 7.8 Hz, J2 ¼ 2.3 Hz, J3 ¼ 1.8 Hz), 8.65 (2H, dd,
J1 ¼ 4.8 Hz, J2 ¼ 1.8 Hz), 8.85 (2H, d, J ¼ 2.3 Hz); 13C NMR (300 MHz,
CDCl3) d: 123.7, 133.0, 134.2, 147.9, 149.2; MS (EI, 70 eV) m=z (%) :
156 (100) [Mþ], 129 (11), 128 (10), 103 (09), 76 (10), 50 (08).
2,20-Bithiophene[19] (Entry 10)
White solid; mp 31–33 ꢁC; IR (neat) n ¼ 3053, 1593, 1497, 1391, 1131,
1
965, 853, 815, 740 cmꢂ1; H NMR (300 MHz, CDCl3) d: 7.00–7.03 (2H,
m), 7.17–7.22 (2H, m); 13C NMR (300 MHz, CDCl3) d: 123.7, 124.3,
127.7, 137.4; MS (EI, 70 eV) m=z (%) : 166 (100) [Mþ], 124 (11), 121 (28).
Bibenzyl[7f] (Entry 11)
White solid; mp 52–53 ꢁC; IR (KBr) n ¼ 3060, 3020, 2910, 2846, 1602,
1505, 1496, 694 cmꢂ1 1H NMR (300 MHz, CDCl3) d: 2.94 (4H, s),
;
7.20–7.25 (6H, m), 7.30–7.35 (4H, m); 13C NMR (300 MHz, CDCl3) d:
37.9, 125.9, 128.3, 128.5, 141.9; MS (EI, 70 eV) m=z(%): 182 (26) [Mþ],
91 (100), 65 (18).
4,40-Dimethylbibenzyl[20] (Entry 12)
White solid; mp 79–81 ꢁC; IR (KBr) n ¼ 3010, 2959, 2941, 1520, 1465,
816, 712 cmꢂ1; 1H NMR (300 MHz, CDCl3) d: 2.26 (6H, s), 2.81 (4H, s),

Homocoupling of Grignard Reagents
3871
6.93 (4H, s); 13C NMR (300 MHz, CDCl3) d: 19.9, 36.6, 127.3,
128.0, 137.2, 137.8; MS (EI, 70 eV) m=z (%): 210 (21) [Mþ], 195 (18),
105 (100).
E,E-1,4-Diphenylbutadiene[7f] (Entry 14)
White solid; mp 152–153 ꢁC; IR (KBr) n ¼ 3030, 3016, 1492, 1443, 1074,
1
998, 983, 985, 740, 691 cmꢂ1; H NMR (300 MHz, CDCl3) d: 6.66 (2H,
dd, J1 ¼ 12.0 Hz, J2 ¼ 2.9 Hz), 7.00 (2H, dd, J1 ¼ 12.0 Hz, J2 ¼ 2.9 Hz),
7.29–7.32 (2H, m), 7.38–7.41 (4H, m), 7.48–7.52 (4H, m); 13C NMR
(300 MHz, CDCl3) d: 126.6, 127.8, 128.8, 129.4, 132.8, 137.5; MS (EI,
70 eV) m=z (%): 206 (100) [Mþ], 191 (35), 178 (14), 165 (10), 128 (33),
115 (11), 91 (45).
ACKNOWLEDGMENTS
This work was generously supported by Consejo Nacional de Investiga-
´
´
ciones Cientıficas y Tecnicas (CONICET) (Project PIP 5104) and
SGCyT-UNS (Project PGI 24=Q026) from Argentina. Y. M. and E.
M. also thank CONICET for doctoral fellowships, and F. N. is thankful
´
to Secretarıa General de Ciencia y Tecnologıa–Universidad Nacional del
Sur (SGCyT-UNS) for a student fellowship. The authors gratefully
´
ꢀ
´
acknowledge the Servicios Tecnicos de Investigacion of the University
of Alicante (Spain) for TEM analysis.
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