Cycloaddition of zirconacyclopentadiene with 2-bromoacrylate, 2-bromoacrylaldehyde, and 3-bromofuran-2,5-dione in the presence of cucl: A new pathway for the formation of benzene derivatives and isobenzofuran-1,3-dione

Article abstract of DOI:10.1080/00397910903007053

Reaction of zirconacyclopentadienes with 2-bromoalkenes in the presence of CuCl afforded multisubstituted benzene derivatives. The reactions of 2-bromoacrylate and 2-bromo-3-phenylacrylaldehyde afforded penta-and hexasubstituted benzenes in good yields. The reaction of 3-bromofuran-2,5-dione with zirconacyclopentadienes gave isobenzofuran-1,3-diones in good yields. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910903007053

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Cycloaddition of Zirconacyclopentadiene
with 2-Bromoacrylate, 2-
Bromoacrylaldehyde, and 3-
Bromofuran-2,5-dione in the Presence
of CuCl: A New Pathway for the
Formation of Benzene Derivatives and
Isobenzofuran-1,3-dione
Chao Chen a , Xiaoyu Yan a & Chanjuan Xi a
a Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical
Biology (Ministry of Education), Department of Chemistry , Tsinghua
University , Beijing, China
Published online: 03 Feb 2010.
To cite this article: Chao Chen , Xiaoyu Yan & Chanjuan Xi (2010) Cycloaddition of
Zirconacyclopentadiene with 2-Bromoacrylate, 2-Bromoacrylaldehyde, and 3-Bromofuran-2,5-
dione in the Presence of CuCl: A New Pathway for the Formation of Benzene Derivatives
and Isobenzofuran-1,3-dione, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 40:4, 570-579, DOI: 10.1080/00397910903007053
To link to this article: http://dx.doi.org/10.1080/00397910903007053
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Synthetic Communications1, 40: 570–579, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903007053
CYCLOADDITION OF ZIRCONACYCLOPENTADIENE WITH
2-BROMOACRYLATE, 2-BROMOACRYLALDEHYDE, AND
3-BROMOFURAN-2,5-DIONE IN THE PRESENCE OF CuCl:
A NEW PATHWAY FOR THE FORMATION OF BENZENE
DERIVATIVES AND ISOBENZOFURAN-1,3-DIONE
Chao Chen, Xiaoyu Yan, and Chanjuan Xi
Key Laboratory of Bioorganic Phosphorus Chemistry and Chemical Biology
(Ministry of Education), Department of Chemistry, Tsinghua University,
Beijing, China
Reaction of zirconacyclopentadienes with 2-bromoalkenes in the presence of CuCl afforded
multisubstituted benzene derivatives. The reactions of 2-bromoacrylate and 2-bromo-3-
phenylacrylaldehyde afforded penta- and hexasubstituted benzenes in good yields. The
reaction of 3-bromofuran-2,5-dione with zirconacyclopentadienes gave isobenzofuran-1,3-
diones in good yields.
Keywords: 2-Bromoacrylaldehyde; 2-bromoacrylate; 3-bromofuran-2,5-dione; cuprous chloride; zirco-
nacyclopentadiene
INTRODUCTION
Transformation of metallacycles to carbocyclic compounds is of general syn-
thetic interest, and special attention has been devoted to the preparation of benzene
derivatives. In this regard, zirconacyclopentadienes, which can be easily prepared by
reductive coupling of two alkynes on zirconocene(II) species[1–6] and can participate
in a number of organic reactions,[7,8] are especially attractive. Takahashi et al. have
reported several reactions of zirconacyclopentadienes with various alkynes, afford-
ing benzene derivatives in good yields.[9–11] These reactions have opened new avenues
for highly selective one-pot formation of benzene derivatives by coupling three dif-
ferent alkynes. Alternatively, reactions of zirconacyclopentadienes with other simple
and readily available substrates for the formation of benzene derivatives in a new
pathway remain to be developed. Herein, we report the reaction of zirconacyclopen-
tadienes with 2-bromoacrylate, 2-bromoacrylaldehyde, and 3-bromofuran-2,5-dione
in the presence of CuCl. This reaction provided a new method for the preparation of
benzene derivatives and isobenzofuran-1,3-dione (Scheme 1).
Received January 10, 2009.
Address correspondence to Chanjuan Xi, Key Laboratory of Bioorganic Phosphorus Chemistry
and Chemical Biology (Ministry of Education), Department of Chemistry, Tsinghua University, Beijing
100084, China. E-mail: cjxi@tsinghua.edu.cn
570

CYCLOADDITION OF ZIRCONACYCLOPENTADIENE
571
Scheme 1. Reaction of zirconacyclopentadiene with bromoethylene derivative.
RESULTS AND DISCUSSION
Reaction of zirconacyclopentadienes with 3-iodopropenoate and 3-iodocycloe-
nones in the presence of CuCl afforded cyclopentadienes and spirocyclic
compounds.[12,13] In this case, the reaction proceeded through a cross-coupling–
conjugate addition reaction sequence. Analogously, the reaction of zirconacyclopen-
tadiene with 2-bromoacrylate in the presence of CuCl was envisioned to be given
cyclohexdiene through cross-coupling–conjugate addition reaction in sequence.
However, it is interesting that reaction of zirconacyclopentadiene 1a with 2 equiv.
of ethyl 2-bromoacrylate 2a in the presence of 2 equiv. of CuCl took place at
50ꢀC in 12 h. Only benzene derivative 3a was obtained in 63% isolated yield rather
than the expected cyclohexadiene 4a (Scheme 2). At first, we tested the reaction of
zirconacyclopentadiene 1a with 1 equiv. of 2-bromoacrylate 2a in the presence of
2 equiv. of CuCl at 50ꢀC for 12 h. About 50% of starting 1a remained. Addition
of 2 equiv. of 2-bromoacrylate 2a to this mixture consumed essentially all of 1a.
The best yield of the benzene derivative was obtained when zirconacyclopentadiene
1a and 2-bromoacrylate 2a were in 1:2 ratio at 50ꢀC for 12 h.
Examination of 1:2 reaction mixture based on the reaction of zirconacyclopen-
tadiene 1a with 2 equiv. of butyl 2-bromoacrylate 2c in the presence of 2 equiv. of
Scheme 2. Reaction of zirconacyclopentadiene with fethyl 2-bromoacrylate.

572
C. CHEN, X. YAN, AND C. XI
Scheme 3. Reaction of zirconacyclopentadiene with butyl 2-bromoacrylate.
CuCl gave the benzene derivative 3c in 67% isolated yield together with nearly 1
equiv. of butyl acrylate (Scheme 3). This has provided a possible explanation for
the requirement for 2 equiv. of 2-bromoacrylate.
Further reaction with 2-bromo-3-phenylacrylaldehyde 2d under the identical con-
ditions afforded hexasubstituted benzene 3d in 66% isolated yield (Scheme 4). The
structure of 3d was unequivocally confirmed by single-crystal analysis (Fig. 1). (Crystal
data for compound 3d: C21H26O, MW ¼ 294.42, monoclinic, space group P21=n,
˚
˚
˚
R1 ¼ 0.0602, wR2 ¼ 0.1048, a ¼ 9.0946(17) A, b ¼ 9.0952(16) A, c ¼ 22.213(4) A,
3
ꢀ
ꢀ
ꢀ
˚
a ¼ 90 , b ¼ 97.408(16) , c ¼ 90 , V ¼ 1822.0(6) A , T ¼ 295 ꢁ 2 K, Z ¼ 4.)
The results concerning the formation of benzene derivatives are presented in
Table 1. Generally, various zirconacyclopentadienes, including monocyclic and
Scheme 4. Reaction of zirconacyclopentadiene with 2-bromo-3-phenylacrylaldehyde.
Figure 1. Structure of 3d.

CYCLOADDITION OF ZIRCONACYCLOPENTADIENE
573
Table 1. Cycloaddition
2-bromo-phenylacrylaldehyde
reactions
of
zirconacyclopentadienes
Time (h)
with
2-bromoacrylate
and
Zirconacyclopentadiene
Substrate
Product
Yield (%)a
12
12
12
2
70 (63)
55 (48)
75 (67)
75 (66)
12
67 (57)
12
64 (52)
67 (57)
2
(Continued )

574
C. CHEN, X. YAN, AND C. XI
Table 1. Continued
Zirconacyclopentadiene
Substrate
Time (h)
Product
Yield (%)a
–– (46)
12
2
72 (65)
aGC yields; isolated yields are given in parentheses.
bicyclic zirconacyclopentadienes bearing alkyl or aryl substituents, could react with
2a, 2b, 2c, and 2d in the presence of CuCl. In all cases, the corresponding products
were obtained in good yields.
Furthermore, when 3-bromofuran-2,5-dione 2e was applied, the reaction under
the identical conditions gave isobenzofuran-1,3-dione 5 (Scheme 5). In all cases, the
corresponding products were obtained in good yields. Results are summarized in
Table 2. The structure of 5a was also confirmed by single-crystal analysis (Fig. 2).
(Crystal data for compound 5a: C16H20O3, MW ¼ 260.32, monoclinic, space group
˚
˚
C2=c, R1 ¼ 0.0382, wR2 ¼ 0.0705, a ¼ 14.363(3) A, b ¼ 12.634(3) A, c ¼ 7.8445(17)
3
ꢀ
ꢀ
ꢀ
˚
˚
A, a ¼ 90 , b ¼ 102.948(19) , c ¼ 90 , V ¼ 1387.3(5) A , T ¼ 295 ꢁ 2 K, Z ¼ 4.)
With these results, we propose the following reaction mechanism (Scheme 6).
In the first step, the transmetallation of the Zr-C bond in zirconacyclopentadiene
to the Cu-C bond affords bis(cuprate) 6,[14] which reacts with 2-bromoacrylate via
Diels–Alder reaction to give the intermediate 7. Then, elimination of CuBr affords
cyclohexadiene derivative 8. Finally, elimination of the CuH drives the formation
of aromatic ring 3. The CuH reacts with the second molecular 2-bromoacrylate to
form acrylate and CuBr.
Scheme 5. Reaction of zirconacyclopentadiene with 3-bromofuran-2,5-dione.

CYCLOADDITION OF ZIRCONACYCLOPENTADIENE
575
Table 2. Cycloaddition reactions of zirconacyclopentadienes with
3-bromofuran-2,5-dione
Zirconacyclopentadine
Product
Yield (%)a
80 (74)
87 (82)
82 (76)
aGC yields; isolated yields are given in parentheses.
In summary, we have reported a new and simple method to synthesize penta-
and hexasubstituted benzenes from two alkynes and 2-bromoalkene via zircona-
cyclopentadienes in the presence of CuCl.
Figure 2. Structure of 5a.

576
C. CHEN, X. YAN, AND C. XI
Scheme 6. Proposed reaction mechanism.
EXPERIMENTAL SECTION
General
All reactions were carried out in a predried Schlenk tube and under nitrogen
with slightly positive pressure. Unless otherwise noted, all starting materials were
commercially available and were used without further purification. Methyl 2-bromo-
acrylate, ethyl 2-bromoacrylate, butyl 2-bromoacrylate, 2-bromo-3-phenylacrylalde-
hyde, and 3-bromofuran-2,5-dione were prepared according to the procedure
reported in the literature.[15,16] Tetrahydrofuran (THF) was refluxed and distilled
from sodium and benzophenone under a nitrogen atmosphere. Gas Chromato-
graphic (GC) analysis was performed on a gas chromatograph (Shimadzu
GC-14A) equipped with a flame ionization detector using a fused silica capillary
column (CBP1-M25-025) and Shimadzu CR6A-Chromatopac integrator. GC yields
1
were determined using suitable hydrocarbons as internal standards. H NMR and
13C NMR spectra were recorded on a Joel 300 NMR spectrometer with CDCl3
as the solvent and tetramethylsilane (TMS) as internal standard. Flash-column
chromatography was performed using silica gel (200–300 mesh).
Representative Procedure for the Preparation of Ethyl
2,3,4,5-Tetraethylbenzoate (3a)
n-BuLi (1.6 M in hexane, 2.4 mmol) at ꢂ78ꢀC was added to a solution of
Cp2ZrCl2 (1.2 mmol, 0.352 g) in THF (5.0 mL), and the mixture was stirred for
1 h. After addition of 3-hexyne (2.0 mmol, 228 mL), the mixture was warmed to room
temperature and stirred for 1 h. Before CuCl (2.0 mmol, 196 mg) was added, the
mixture was cooled to 0ꢀC using an ice bath and maintained at this temperature
for 5 min. Ethyl 2-bromoacrylate (2.0 mmol, 270 mL) was added to the mixture.
The mixture was warmed up to 50ꢀC, kept for 12 h, and quenched with 3 N HCl.
Then, aqueous layers were extracted with 15 mL of Et2O five times. The combined
organic layers were dried over Na2SO4. The solvent was evaporated, and the product

CYCLOADDITION OF ZIRCONACYCLOPENTADIENE
577
was purified by column chromatography with petroleum ether=diethyl ether 20=1 as
1
elution to afford the target compound as a light yellow liquid (165 mg, 63%). H
NMR (300 MHz, CDCl3, Me4Si) d 1.13–1.26 (m, 12H), 1.38 (t, J ¼ 7.2 Hz, 3H),
2.61–2.75 (m, 6H), 2.88 (q, J ¼ 7.5 Hz, 2H), 4.32 (q, J ¼ 7.2 Hz, 2H), 7.42 (s, 1H);
13C NMR (75 MHz, CDCl3, Me4Si) d 15.42, 15.35, 15.53, 15.84, 16.22, 21.79,
22.18, 22.99, 25.71, 60.71, 127.91, 129.29, 139.59, 140.20, 141.00, 143.97, 169.30.
Calcd. for C17H26O2 262.1933; found 262.1929.
Selected Data
Methyl 2,3,4,5-tetraethylbenzoate (3b). A light yellow liquid (119 mg,
1
isolated yield 48%). H NMR (300 MHz, CDCl3, Me4Si) d 1.15–1.26 (m, 12H),
2.62–2.74 (m, 6H), 2.91 (q, J ¼ 7.5 Hz, 2H), 3.87 (s, 3H), 7.45 (s, 1H); 13C NMR
(75 MHz, CDCl3, Me4Si) d 15.91, 15.98, 16.02, 16.53, 22.35, 22.74, 23.70, 26.17,
52.05, 128.34, 128.89, 139.95, 141.01, 141.75, 144.50, 169.72. Calcd. for C16H24O2
248.1776; found 248.1779.
Butyl 2,3,4,5-tetraethylbenzoate (3c). A light yellow liquid (195 mg,
1
isolated yield 67%). H NMR (300 MHz, CDCl3, Me4Si) d 0.97 (t, J ¼ 7.5 Hz, 3H),
1.12–1.26 (m, 12H), 1.41–1.48 (m, 2H), 1.65–1.1.74 (m, 2H), 2.60–2.74 (m, 6H),
2.91 (q, J ¼ 7.5 Hz, 2H), 4.26 (t, J ¼ 7.5 Hz, 2H), 7.42 (s, 1H); 13C NMR (75 MHz,
CDCl3, Me4Si) d 13.8, 15.3, 15.4, 15.8, 16.2, 19.4, 21.8, 22.2, 23.0, 25.7, 30.9, 64.7,
128.0, 130.5, 139.6, 140.3, 141.0, 144.0, 169.5. Calcd. for C19H30O2 290.2246; found
290.2249.
3,4,5,6-Tetraethylbiphenyl-2-carbaldehyde (3d). A light yellow liquid
1
(195 mg, isolated 66%). H NMR (300 MHz, CDCl3, Me4Si) d 0.91–1.04 (m, 6H),
1.20–1.25 (m, 6H), 2.39–2.45 (m, 2H), 2.74–2.81 (m, 4H), 2.95–3.00 (m, 2H),
7.21–7.23 (m, 2H), 7.34–7.39 (m, 3H), 9.69 (s, 1H); 13C NMR (75 MHz, CDCl3,
Me4Si) d 15.52, 15.67, 15.97, 16.05, 21.42, 21.96, 22.63, 22.80, 127.16, 127.97,
130.08, 132.03, 138.66, 138.95, 140.83, 144.42, 145.72, 195.50. Calcd. for C21H26O
294.1984; found 294.1980.
Ethyl 2,3,4,5-tetrapropylbenzoate (3e). A light yellow liquid (181 mg,
1
isolated yield 57%). H NMR (300 MHz, CDCl3, Me4Si) d 0.98–1.08 (m, 12H),
1.38 (t, J ¼ 7.2 Hz, 3H), 1.49–1.69 (m, 8H), 2.53–2.78 (m, 6H), 2.81 (q, J ¼ 8.1 Hz,
2H), 4.32 (q, J ¼ 7.2 Hz, 2H), 7.40 (s, 1H); 13C NMR (75 MHz, CDCl3, Me4Si)
d 14.81, 14.88, 15.00, 15.04, 15.08, 24.60, 24.67, 24.96, 25.35, 31.61, 31.89, 32.19,
35.23, 60.69, 128.61, 129.12, 138.26, 138.98, 140.10, 142.90, 169.36. Calcd. for
C21H34O2 318.2559; found 318.2563.
Methyl 2,3,4,5-tetrapropylbenzoate (3f). A light yellow liquid (158 mg, iso-
lated yield 52%). 1H NMR (300 MHz, CDCl3, Me4Si) d 0.96–1.06 (m, 12H),
1.25–1.37 (m, 8H), 2.56–2.60 (m, 6H), 2.80–2.83 (m, 2H), 3.85 (s, 3H), 7.42 (s, 1H);
13C NMR (75 MHz, CDCl3, Me4Si) d 13.97, 14.37, 14.82, 14.97, 24.50, 24.55, 24.87,
25.26, 31.83, 32.07, 32.45, 35.13, 51.76, 128.44, 128.73, 138.17, 139.33, 140.11,
143.08, 169.51. Calcd. for C20H32O2 304.2402; found 304.2402.

578
C. CHEN, X. YAN, AND C. XI
3,4,5,6-Tetrapropylbiphenyl-2-carbaldehyde (3g). A light yellow solid
1
(200 mg, isolated 57%). H NMR (300 MHz, CDCl3, Me4Si) d 0.78 (t, J ¼ 7.2 Hz,
3H), 1.10–1.18 (m, 9H), 1.36–1.44 (m, 2H), 1.64–1.66 (m, 6H), 2.36–2.41 (m, 2H),
2.74–2.76 (m, 4H), 2.97–3.00 (m, 2H), 7.25–7.27 (m, 2H), 7.37–7.42 (m, 3H), 9.78
(s, 1H); 13C NMR (75 MHz, CDCl3, Me4Si) d 14.70, 14.88, 15.05, 15.12, 24.72,
24.82, 24.89, 25.32, 31.32, 32.15, 32.68, 127.16, 127.96, 128.22, 130.09, 132.12,
137.55, 139.06, 139.73, 139.80, 144.37, 144.57, 195.41. Calcd. for C25H34O
350.2610; found 350.2615.
Ethyl 2,3,4,5-tetraphenylbenzoate (3h). A light yellow solid (118 mg,
1
isolated yield 26%). H NMR (300 MHz, CDCl3, Me4Si) d 0.96 (t, J ¼ 7.2 Hz, 3H),
4.07 (q, J ¼ 7.2 Hz, 2H), 6.77–6.95 (m, 10H), 7.07–7.19 (m, 10H), 7.93 (s, 1H);
13C NMR (75 MHz, CDCl3, Me4Si) d 13.79, 61.10, 125.78, 126.07, 126.44, 126.67,
126.85, 127.12, 127.26, 127.79, 129.96, 131.23, 131.38, 132.21, 139.35, 139.45,
140.10, 140.21, 141.09, 142.36, 143.08, 168.90. Calcd. for C33H26O2 454.1933; found
454.1938.
1,4-Diethyl-3-phenyl-5,6,7,8-tetrahydronaphthalene-2-carbaldehyde (3i). A
light yellow solid (190 mg, isolated yield 65%). 1H NMR (300 MHz, CDCl3, Me4Si) d
0.94 (t, J ¼ 7.5 Hz, 3H), 1.23 (t, J ¼ 7.5 Hz, 3H), 1.85–1.88 (m, 4H), 2.41 (q,
J ¼ 7.5 Hz, 2H), 2.85–2.90 (m, 4H), 2.97 (q, J ¼ 7.5 Hz, 2H), 7.21–7.25 (m, 2H),
7.37–7.42 (m, 3H), 9.73 (s, 1H); 13C NMR (75 MHz, CDCl3, Me4Si) d 14.39,
14.78, 21.86, 22.34, 22.77, 22.99, 26.47, 27.84, 127.33, 128.17, 130.20, 131.47,
136.23, 138.75, 138.95, 141.22, 141.35, 143.44, 195.64. Calcd. for C21H24O
292.1827; found 292.1830.
4,5,6,7-Tetraethylisobenzofuran-1,3-dione (5a). White solid (192 mg,
1
isolated 74%). H NMR (300 MHz, CDCl3, Me4Si) d 1.16–1.21 (m, 12H), 2.78 (q,
J ¼ 7.5 Hz, 4H), 3.05 (q, J ¼ 7.2 Hz, 4H); 13C NMR (75 MHz, CDCl3, Me4Si)
d 15.27, 15.44, 21.33, 22.21, 126.40, 142.93, 150.17, 163.41. Calcd. for C16H20O3
260.1412; found 260.1412.
4,5,6,7-Tetrapropylisobenzofuran-1,3-dione (5b). White solid (249 mg,
1
isolated yield 65%). H NMR (300 MHz, CDCl3, Me4Si) d 1.00–1.10 (m, 12H),
1.47–1.58 (m, 8H), 2.66–2.71 (m, 4H), 2.96–3.01 (m, 4H); 13C NMR (75 MHz,
CDCl3, Me4Si) d 14.58, 14.91, 24.64, 24.76, 30.19, 31.72, 126.50, 141.49, 149.06,
163.50. Calcd. for C20H28O2 316.2038; found 316.2034.
4,9-Diethyl-5,6,7,8-tetrahydronaphtho[2,3-c]furan-1,3-dione (5c). A light
1
yellow liquid (196 mg, isolated yield 76%) H NMR (300 MHz, CDCl3, Me4Si) d
1.12 (t, J ¼ 7.5 Hz, 6H), 1.82 (b, 4H), 2.84 (b, 4H), 3.03 (q, J ¼ 7.5 Hz, 4H);
13C NMR (75 MHz, CDCl3, Me4Si) d 13.90, 20.67, 21.98, 26.87, 125.07, 142.86,
145.41, 163.52. Calcd. for C16H18O3 258.1256; found 258.1253.
ACKNOWLEDGMENT
We thank the National Natural Science Foundation of China (20172032,
20872076) for supporting this work.

CYCLOADDITION OF ZIRCONACYCLOPENTADIENE
579
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