A mild stereo- and enantiospecific conversion of 2,3-diaryl-substituted oxiranes into 2,2-dimethyl-1,3-dioxolanes by an acetone/amberlyst 15 system

Article abstract of DOI:10.1002/ejoc.200600034

Amberlyst 15 is an efficient catalyst for the reaction of aryl-substituted oxiranes with acetone to prepare 2,2-dimethyl-1,3-dioxolanes in high yields. trans-2,3-Diaryloxiranes afford trans-acetonides enantiospecifically at room temperature, and the use of enantiopure 2,3-diaryloxiranes results in no loss of stereochemical integrity in the resulting trans-acetonides. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejoc.200600034

FULL PAPER
DOI: 10.1002/ejoc.200600034
A Mild Stereo- and Enantiospecific Conversion of 2,3-Diaryl-Substituted
Oxiranes into 2,2-Dimethyl-1,3-Dioxolanes by an Acetone/Amberlyst 15
System
Arlette Solladié-Cavallo,[a] Elias Choucair,[a] Milan Balaz,[a] Paolo Lupattelli,*[b]
Carlo Bonini,[b] and Nadia Di Blasio[b]
Keywords: Acetonides / Amberlyst 15 / Enantioselectivity / Oxygen heterocycles
Amberlyst 15 is an efficient catalyst for the reaction of aryl-
substituted oxiranes with acetone to prepare 2,2-dimethyl-
1,3-dioxolanes in high yields. trans-2,3-Diaryloxiranes afford
trans-acetonides enantiospecifically at room temperature,
and the use of enantiopure 2,3-diaryloxiranes results in no
loss of stereochemical integrity in the resulting trans-aceto-
nides.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
lead invariably to meso-acetonides as the main reaction
product (Scheme 1).
Introduction
The 2,2-dimethyl-1,3-dioxolane (acetonide) group is a
widely used protecting group for vicinal diols. The prepara-
tion of acetonides usually involves the reaction of the diol
with acetone, 2,2-dimethoxypropane, or 2-methoxypropene
under acidic conditions.[1]
The direct conversion of epoxides to the corresponding
acetonides has been described with the use of different
Lewis acid catalysts. Among the most recent catalysts, with
various degrees of success in terms of yield and selectivity,
are anhydrous SnCl2,[2] tin() tetraphenylporphyrin per-
chlorate,[3] 2,4,4,6-tetrabromo-2,5-cyclohexadienone,[4] bis-
muth() salts,[5] various titanium complexes,[6] [(C5Me5)-
Ir(NaMe)3],[7] RuCl3,[8] CH3ReO3,[9] Cu(OTf)2,[10,11]
Er(OTf)3,[12] BF3·Et2O,[13] LiBF4,[14] and heteropoly-
acids.[15] Many of these catalysts are strong Lewis acids and
are not suitable in the presence of other functional groups.
Heterogeneous catalysts, such as K-10 montmorillonite[16]
and various zeolites,[17] have also been studied in order to
find milder reaction conditions. However, examples with
2,3-disubstituted oxiranes bearing at least one aryl group
have been reported only occasionally. The conversion of ep-
oxides into acetonides by the above-mentioned systems usu-
ally occurs through a general SN2 mechanism, with inver-
sion of configuration at the oxiranyl carbon approached by
acetone. Thus, trans-symmetrical 2,3-disubstituted oxiranes
Scheme 1.
Herein we report the direct conversion of di- and
trisubstituted epoxides into 2,2-dimethyl-1,3-dioxolanes
(acetonides) by acetone in the presence of the acid resin
Amberlyst 15.
Results and Discussion
During our studies on metal halide promoted opening
reactions of diaryl epoxides,[18] we observed the formation
of a considerable amount (up to 30%) of by-products, along
with the expected halohydrins, when the reaction was per-
formed in acetone. These results prompted us to investigate
the acetone/Amberlyst 15 system as a reagent with a variety
of aryl epoxides (Scheme 2). The results are shown in
Table 1.
We started by studying the behavior of styrene oxide (1a)
in the presence of different amounts of Amberlyst 15, at
different reaction temperatures, and with acetone as the sol-
vent. We noted that although the acetonide could be
formed by the use of very small quantities of resin (20 mg/
mmol of substrate), the best results, in terms of yield and
reaction time, were obtained using a 220 mg/mmol ratio at
[a] Laboratoire de Stéréochimie Organométallique associé au
CNRS, ECPM/Université L. Pasteur,
25 rue Becquerel, 67087 Strasbourg, France
[b] Dipartimento di Chimica, Università degli studi della Basili-
cata,
Via N. Sauro 85, 85100 Potenza, Italy
E-mail: lupattelli@unibas.it
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
Eur. J. Org. Chem. 2006, 3007–3011
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3007

P. Lupattelli et al.
FULL PAPER
Scheme 2.
Scheme 3.
Table 1. Conversion of aryl epoxides into acetonides.
We first of all noted a slightly higher lability of the corre-
sponding 2,3-diaryl products due to the presence of acidic
traces, with respect to dioxolanes 2a and 2d, thus leading to
several by-products. However, after an initial neutralization
with NaHCO3 these by-products were almost totally avo-
ided. As can be seen, high yields of acetonides were ob-
tained after reasonable reaction times, with temperatures
ranging between 25 and –78 °C; only traces of by-product
were detected. At –78 °C, a higher amount of Amberlyst 15
was required to lead the reaction to completion (entry 6).
From the data shown in Table 2, it is clear that the tempera-
ture has a strong effect on the stereoselectivity of the reac-
Entry
1[a]
R1
R2 Time [h] cis-2[b] trans-2[b] 3[b]
1
2
3
4
1a
1b
1c
1d
H
CH3
Ph
H
H
H
12
12
1
82[c]
18
–
28[c]
13
38[c]
53
23[d]
18[e]
Ph
Ph
8
82[e]
[a] All reactions were performed with 220 mg of Amberlyst 15 per
millimol of substrate and in a 0.1  acetone solution of the sub-
strate at room temperature. [b] Determined by 1H NMR analysis
of the crude mixture. [c] 34% of the corresponding diols were de-
tected. [d] 11% of unidentified product. [e] Isolated yield.
room temperature. Under these conditions, the dioxolane tion. At room temperature, the corresponding acetonides
2a (R1 = R2 = H) was obtained in 82% yield, together with were obtained in high yield, with a cis/trans ratio of 2/3
an 18% yield of phenylacetaldehyde (entry 1). Triphenyloxi- (entry 1). Running the reaction at 40 °C, the trans/cis ratio
rane (1d) also gave a high yield of the corresponding aceto- of the products decreased slightly (4/3.6) and a considerable
nide 2d (entry 4).
amount of the aldehyde 3 was formed (24%). Upon lower-
In the case of trans-2,3-disubstituted oxiranes such as ing the temperature, the formation of the cis isomer in-
trans-β-methylstyrene (1b) and trans-stilbene (1c; entries 2 creased, and it became the major reaction product below
and 3, respectively), we noted an interesting stereoselec- –10 °C. While the formation of the cis-acetonide can be eas-
tivity towards trans-acetonides, with a clear retention of ily explained by a classical SN2 oxiranyl ring opening with
configuration at the oxiranyl carbon atoms.
inversion of configuration, the trans isomer implies the for-
In order to study the stereoselectivity of this transforma- mation of an acyclic cationic-type intermediate, which has
tion, the 2,3-disubstituted model trans-stilbene oxide (1c) already been suggested in the reactions with metal halides
was allowed to react under different conditions (Scheme 3). as nucleophiles.[19] Upon lowering the temperature, the for-
The most significant results of the effect of temperature on mation of the acyclic intermediate becomes slower, while
stereoselectivity of acetonide formation are collected in the SN2 opening with inversion of configuration becomes
Table 2.
more competitive.
Table 2. Conversion of trans-stilbene oxide (1c) into acetonides.
Entry[a]
Temp. [°C]
Time [h]
Conv.[b]
cis-2c [%][b]
trans-2c [%][b]
3 [%][b]
1
2
3
4
25
0
–10
–50
–78
–78
1
3
8
12
10.5
10.5
100
100
100
100
37
40
50
55
67
80
75
60
50
45
24
16
25
–
–
–
9
4
–
5
6[c]
100
[a] All reactions were performed with 300 mg of Amberlyst 15 per millimol of substrate and in 0.1  acetone solution of the substrate.
1
The workup was performed by neutralization with NaHCO3 s.s. [b] Determined by H NMR analysis on the crude mixture. [c] 660 mg
of Amberlyst 15 per millimol of substrate.
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Eur. J. Org. Chem. 2006, 3007–3011

Acetone/Amberlyst 15 as a Mild and Efficient Catalyst
FULL PAPER
This stereochemical outcome prompted us to submit op-
tically pure (R,R)-1c to the standard conditions at room
temperature (Scheme 4). No loss of stereochemical integrity
of the corresponding trans-acetonide was obtained, which
proved that no epimerization occurs during the oxiranyl
ring opening.[20] After easy chromatographic purification,
trans-(R,R)-acetonide 2c was obtained in good isolated
yield. This method represents the first direct enantioselec-
tive access to this acetonide from the parent epoxide.
Scheme 5. Synthesis of enantiopure ortho-substituted diaryl epox-
ides.
Once submitted to our standard conditions, the optically
active epoxides afforded the corresponding new (R,R) trans-
acetonides 5b and 7b in high yield with no loss of stereo-
chemical integrity (Scheme 6). The cis-acetonides were not
formed in these cases.
Scheme 4.
We then extended our procedure to racemic nonsymmet-
rical 2,3-diaryloxiranes, which can be easily prepared, in ra-
cemic form, by the reaction of benzylidene sulfur ylide, gen-
erated from the corresponding sulfonium salts under phase-
transfer conditions, with the appropriate aryl aldehyde.[19a]
ortho-Nitro and ortho-methoxy trans-epoxides 4 and 6 were
prepared in this way and submitted to our standard condi-
tions; both epoxides produced the corresponding aceto-
nides quantitatively, with a trans/cis ratio of between 4:1
and 10:1 (Scheme 4).
Scheme 6. Synthesis of enantiopure trans-acetonides.
In conclusion, these results show that Amberlyst 15 is an
efficient catalyst for the enantiospecific conversion of
mono- and diaryl-substituted epoxides directly to their 2,2-
dimethyl-1,3-dioxolane derivatives, which are useful inter-
mediates in the synthesis of functionalized diaryl glycols.
Nonracemic trans-epoxides 4 and 6[21] were prepared in
good yield and more than 99.5% ee (as determined by
HPLC) from the pure (R,R,R,SS)-(–)-sulfonium salt 8,[22]
commercial 2-nitro- and 2-methoxybenzaldehydes, and the
phosphazene base EtP2 [EtN=P(NMe2)2{N=P(NMe2)3}]
to generate the sulfur ylide (Scheme 5).
Experimental Section
1H and 13C NMR spectra were recorded at 300 (or 500) and 75 (or
125) MHz, respectively. Mass spectra were recorded with a Hew-
lett–Packard 6890 chromatograph equipped with a HP 5973 mass
detector. Commercially available reagents were used without fur-
ther purification. All reactions were monitored by TLC on silica
Eur. J. Org. Chem. 2006, 3007–3011
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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3009

P. Lupattelli et al.
FULL PAPER
gel-coated plates. Column chromatography was carried out using
60–240 mesh silica gel at atmospheric pressure.
2926, 1531, 1383, 1234, 1057, 757, 699. MS: m/z (%) 284 (2) [M –
15]+, 193 (9), 135 (100). C17H17NO4 (299.32): calcd. C 68.21, H
5.72, N 4.68; found C 68.1, H 5.6, N 4.6.
General Procedure. Preparation of 2,2-Dimethyl-4-phenyl-1,3-di-
oxolane (2a): Amberlyst 15 (220 mg) was added in one portion to
a solution of styrene oxide 1a (1 mmol) in acetone (10 mL) at room
temperature and the mixture was allowed to stir until the reaction
was complete (by TLC and GC analysis). The Amberlyst was fil-
tered off and NaHCO3 s.s. (10 mL) was poured into the solution.
The solvent was then evaporated and the aqueous layer was ex-
tracted with Et2O (3×10 mL). The combined organic layers were
dried with Na2SO4 and the solvent was removed. The crude prod-
trans-(4R,5R)-5b was obtained from (2R,3R)-4 in 80% isolated
yield [99.5% ee; HPLC Chiralcel OD, n-hexane/2-propanol 95:5,
0.5 mLmin–1, tR = 11.41 min. [α]2D5 = –6.0 (c = 2, CHCl3)] using
the same procedure.
cis-2,2-Dimethyl-4-(2-nitrophenyl)-5-phenyl-1,3-dioxolane (5a): (E)-
2-(2-Nitrophenyl)-3-phenyloxirane 4 (1 mmol), acetone (10 mL),
and Amberlyst 15 (300 mg) at room temperature yielded 5b
(59.8 mg; 20%) after chromatographic purification on silica gel (pe-
uct was purified by silica gel chromatography (n-hexane/Et2O, 4:1)
troleum ether/diethyl ether, 7:3) as
a
yellow oil. 1H NMR
1
to give 2a (146 mg; 82% yield) as a colorless oil whose H and 13
C
(300 MHz, CDCl3): δ = 1.28 (s, 6 H), 5.0 (d, 3J = 4.0 Hz, 1 H),
5.57 (d, 3J = 4.0 Hz, 1 H), 7.40 (m, 9 H) ppm. MS: m/z (%) 284
(2) [M – 15]+, 193 (9), 135 (100). C17H17NO4 (299.32): calcd. C
68.21, H 5.72, N 4.68; found C 68.1, H 5.6, N 4.6.
NMR spectra were identical to those reported in the literature.[2]
cis- and trans-2,2,5-Trimethyl-4-phenyl-1,3-dioxolanes (2b): Epoxide
1b (1 mmol), acetone (10 mL), and Amberlyst 15 (220 mg) at room
temperature yielded 2b (126 mg; 66%) together with 34% of the
corresponding 1-phenyl-1,2-propandiol. 1H NMR (300 MHz,
trans-4-(2-Methoxyphenyl)-2,2-dimethyl-5-phenyl-1,3-dioxolane
(7b): (E)-2-(2-Methoxyphenyl)-3-phenyloxirane 6 (1 mmol), ace-
tone (10 mL), and Amberlyst 15 (300 mg) at room temperature
yielded 7b (199 mg; 70%) after chromatographic purification on
3
CDCl3) of a 66:34 mixture with the diols: δ = 1.09 (d, J = 6.5 Hz,
3 H, cis, 28%), 1.29 (d, 3J = 6.0 Hz, 3 H, trans, 38%), 1.47 (s, 3 H,
cis, 28%), 1.52 (s, 3 H, trans, 38%), 1.56 (s, 3 H, trans, 38%), 1.64
(s, 3 H, cis, 28%), 3.86 (qd, 3J1 = 6.0, 3J2 = 8.5 Hz, 1 H, trans,
1
silica gel (petroleum ether/diethyl ether, 9:1) as a colorless oil. H
NMR (500 MHz, CDCl3): δ = 1.67 (s, 3 H), 1.68 (s, 3 H), 3.32 (s,
3
3
3
38%), 4.02 (qd, J1 = 6.5, J2 = 4.0 Hz, 1 H, cis, 28%), 4.47 (d, J
3
3
3 H), 4.77 (d, J = 8.0 Hz, 1 H), 5.27 (d, J = 8.0 Hz, 1 H), 6.75
(d, 3J = 8.0 Hz, 1 H), 7.02 (dd, 3J1 = 3J2 = 8.0 Hz, 1 H), 7.30 (m, 6
H), 7.59 (d, 3J = 8.0 Hz, 1 H) ppm. 13C NMR (125 MHz, CDCl3): δ
= 27.2, 54.8, 79.3, 84.7, 108.9, 110.6, 120.7, 125.2, 126.6, 126.8,
3
= 8.5 Hz, 1 H, trans, 38%), 4.69 (d, J = 4.0 Hz, 1 H, cis, 28%),
7.2–7.4 (m, 5 H) ppm.
trans-2,2-Dimethyl-4,5-diphenyl-1,3-dioxolane (2c): Epoxide 1c
(1 mmol), acetone (10 mL), and Amberlyst 15 (300 mg) at room
temperature yielded trans-2c (152 mg; 60%) after chromatographic
purification on silica gel (petroleum ether/diethyl ether, 9:1) as an
127.2, 127.7, 128.0, 129.0, 137.6, 157.2 ppm. IR (neat): ν = 2984,
˜
2931, 1495, 1251, 1055, 894, 754, 698. MS: m/z (%) 284 (1) [M+],
269 (2) [M – 15]+, 227 (10) [M – 57]+, 178 (100), 148 (99). C18H20O3
(284.35): calcd. C 76.03, H 7.09; found C 75.9, H 7.0.
1
oil. H NMR (500 MHz, CDCl3): δ = 1.69 (s, 6 H), 4.76 (s, 2 H),
7.30–7.50 (m, 10 H) ppm. 13C NMR (175 MHz, CDCl3): δ = 27.2,
85.4, 109.3, 126.7, 128.2, 128.4, 128.5, 130.2, 133.7, 136.7 ppm.
MS: m/z (%) 197 (6) [M – 57]+, 179 (7) [M – 75]+, 148 (100).
C17H18O2 (254.32): calcd. C 80.28, H 7.13; found C 80.1, H 7.2.
trans-(4R,5R)-7b was obtained from (2R,3R)-6 in 80% isolated
yield [99.5% ee; HPLC Chiralcel OJ, n-hexane/2-propanol 99:1,
0.5 mLmin–1, tR = 31.95 min. [α]2D5 = +13 (c = 0.4, CHCl3)] using
the same procedure.
trans-(4R,5R)-2c was obtained from (2R,3R)-1c[19b] in 60% yield
[99.5% ee;[20] [α]2D5 = +50 (c = 0.7, CHCl3)] using the same pro-
cedure.
cis-4-(2-Methoxyphenyl)-2,2-dimethyl-5-phenyl-1,3-dioxolane (7a):
This compound was isolated (28 mg, 10% yield) after chromato-
graphic purification on silica gel (petroleum ether/diethyl ether, 9:1)
cis-2,2-Dimethyl-4,5-diphenyl-1,3-dioxolane (2c): Epoxide 1c
(1 mmol), acetone (10 mL) and Amberlyst 15 (300 mg), at –78 °C,
yielded cis-2c (191 mg; 75%) after chromatographic purification on
silica gel (petroleum ether/diethyl ether = 9:1) as a colorless oil. 1H
NMR (300 MHz, CDCl3): δ = 1.62 (s, 3 H), 1.84 (s, 3 H), 5.53 (br.
s, 2 H), 6.90–7.20 (m, 10 H).
1
as a colorless oil. H NMR (500 MHz, CDCl3): δ = 1.61 (s, 3 H),
3
3
1.81 (s, 3 H), 3.61 (s, 3 H), 5.53 (d, J = 7.5 Hz, 1 H), 5.81 (d, J
= 7.5 Hz, 1 H), 6.47 (d, 3J = 8.0 Hz, 1 H), 6.76 (dd, 3J1 = J2
=
3
8.0 Hz, 1 H), 7.01 (m, 5 H), 7.29 (m, 2 H) ppm. 13C NMR
(125 MHz, CDCl3): δ = 24.2, 26.7, 54.6, 76.3, 81.07, 108.9, 119.8,
126.2, 126.6, 126.7, 126.9, 127.2, 127.4, 127.8, 138.3, 155.0 ppm.
2,2-Dimethyl-4,4-5-triphenyl-1,3-dioxolane (2d): Epoxide 1d
(1 mmol), acetone (10 mL), and Amberlyst 15 (220 mg) at room
temperature yielded 2d (271 mg; 82%) after chromatographic puri-
fication on silica gel (petroleum ether/diethyl ether, 9:1) as a white
solid (m.p. 113 °C from ethanol).[23] 1H NMR (300 MHz, CDCl3):
δ = 1.46 (s, 3 H), 1.83 (s, 3 H), 5.64 (s, 1 H), 7.0–7.50 (m, 15 H)
ppm.
Supporting Information (see also the footnote on the first page of
this article): Experimental procedures and characterization data for
epoxides (2R,3R)-4 and (2R,3R)-6. 1H and 13C NMR spectra of
compounds trans-2c, -5b, and -7b.
Acknowledgments
trans-2,2-Dimethyl-4-(2-nitrophenyl)-5-phenyl-1,3-dioxolane
(5b):
(E)-2-(2-Nitrophenyl)-3-phenyloxirane (1 mmol), acetone
4
We thank the University of Basilicata and the University “Louis
Pasteur” for financial support and the CNRS (France) for a three-
month position for P. L.
(10 mL) and Amberlyst 15 (300 mg) at room temperature yielded
5b (239 mg; 80%) after chromatographic purification on silica gel
(petroleum ether/diethyl ether, 7:3) as a colorless oil. 1H NMR
3
(300 MHz, CDCl3): δ = 1.70 (s, 6 H), 4.79 (d, J = 8.5 Hz, 1 H),
[1] T. W. Greene, P. Wuts, in Protective Groups in Organic Synthe-
sis, 3rd ed., John Wiley & Sons, New York, 1999, 207–210.
[2] J. R. Vyvyan, J. A. Meyer, K. D. Meyer, J. Org. Chem. 2003,
68, 9144–9147.
[3] S. Tangestaninejad, M. Habibi, V. Mirkhani, M. Moghadam,
J. Chem. Res. (S) 2001, 365–367.
3
5.49 (d, J = 8.5 Hz, 1 H), 7.21 (m, 2 H), 7.29 (m, 3 H), 7.46 (dd,
3
3
3
3J1 = J2 = 8.0 Hz, 1 H), 7.66 (dd, J1 = J2 = 8.0 Hz, 1 H), 7.73
(d, J = 8.0 Hz, 1 H), 7.82 (d, J = 8.0 Hz, 1 H) ppm. 13C NMR
3
3
(75 MHz, CDCl3): δ = 26.8, 27.2, 79.7, 85.8, 109.8, 124.3, 126.5,
128.6, 128.7, 128.8, 129.0, 131.0, 132.8, 135.5 ppm. IR (neat): ν =
˜
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Acetone/Amberlyst 15 as a Mild and Efficient Catalyst
FULL PAPER
[4] H. Firouzabadi, N. Iranpoor, H. Shaterian, Bull. Chem. Soc.
Jpn. 2002, 75, 2195–2205.
[5] I. Mohammadpoor-Baltork, A. Khosropour, H. Aliyan, Synth.
Commun. 2001, 31, 3411–3416.
[6] N. Iranpoor, B. Zeynizadeh, J. Chem. Res. (S) 1998, 466–467.
[7] R. Adams, T. Barnard, K. Brosius, J. Organomet. Chem. 1999,
582, 358–361.
[17] L. W. Zatorski, P. T. Wierzchowski, Catal. Lett. 1991, 10, 211–
214.
[18] A. Solladié-Cavallo, P. Lupattelli, C. Marsol, T. Isarno, C. Bon-
ini, L. Caruso, A. Maiorella, Eur. J. Org. Chem. 2002, 1439–
1444.
[19] a) A. Solladié-Cavallo, P. Lupattelli, C. Bonini, J. Org. Chem.
2005, 70, 1605–1611; b) P. Lupattelli, C. Bonini, L. Caruso, A.
Gambacorta, J. Org. Chem. 2003, 68, 3360–3363.
[20] The ee was measured by chiral HPLC analysis, see: C. Rosini,
S. Scamuzzi, M. Pisani Focati, P. Salvadori, J. Org. Chem. 1995,
60, 8289–8293.
[21] The (R,R) configurations of the epoxides were assigned on the
basis of the positive sign of their optical rotation, in analogy
with known epoxides: A. Solladié-Cavallo, M. Roje, T. Isarno,
V. Sunjic, V. Vinkovic, Eur. J. Org. Chem. 2000, 1077–1080.
[22] For the synthesis of 10 from (R,R,R)-oxathiane see: E. Vedejs,
D. A. Engler, M. J. Mullins, J. Org. Chem. 1977, 42, 3109–3113.
For the synthesis of (R,R,R)-oxathiane see: E. L. Eliel, J. E.
Lynch, F. Kume, S. V. Frye, Org. Synth. 1987, 65, 215–221.
[8] N. Iranpoor, F. Kazemi, Synth. Commun. 1998, 28, 3189–3193.
[9] Z. Zhu, J. Espenson, Organometallics 1997, 16, 3658–3663.
[10] S.-H. Lee, J.-C. Lee, M.-L. Li, N.-S. Kim, Bull. Korean Chem.
Soc. 2005, 26, 221–222.
[11] P. Krasik, M. Bohemien-Bernard, Q. Yu, Synlett 2005, 854–
856.
[12] A. Procopio, R. Dalpozzo, A. De Nino, L. Mariuolo, M.
Nardi, B. Russo, Adv. Synth. Catal. 2005, 347, 1447–1450.
[13] J. M. Concellón, J. R. Suárez, S. Garcia-Granda, M. R. Diaz,
Org. Lett. 2005, 7, 247–250.
[14] F. Kazemi, A. R. Kiasat, S. Ebrahimi, Synth. Commun. 2005,
35, 1441–1445.
[15] J.-Y. He, F. Gao, R.-M. Hua, Chin. J. Chem. 2005, 23, 1275– [23] D. H. R. Barton, P. D. Magnus, G. Smith, G. Streckert, D.
1277.
Zurr, J. Chem. Soc., Perkin Trans. 1 1972, 542–552.
Received: January 17, 2006
Published Online: May 3, 2006
[16] I. Busci, A. Meleg, A. Molnàr, M. Bartòk, J. Mol. Catal. 2001,
168, 47–52.
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