Palladium-catalyzed tandem reaction of yne-propargylic carbonates with boronic acids: A simple method for the synthesis of fused aromatic rings through allene-mediated electrocyclization

Article abstract of DOI:10.1002/chem.200400573

The palladium-catalyzed tandem reactions of yne-propargylic carbonates with aryl boronic acids, 2-furyl boronic acid, and 2-thiopheneboronic acid, followed by 6π-electrocyclization to give fused ring aromatic products such as naphthalene, benzofuran, and

Full text of DOI:10.1002/chem.200400573

FULL PAPER
Palladium-Catalyzed Tandem Reaction of Yne–Propargylic Carbonates with
Boronic Acids: A Simple Method for the Synthesis of Fused Aromatic Rings
through Allene-Mediated Electrocyclization
Feng Wang,[a] Xiaofeng Tong,[a] Jiang Cheng,[b] and Zhaoguo Zhang*[a]
Abstract: The palladium-catalyzed
tandem reactions of yne–propargylic
carbonates with aryl boronic acids, 2-
furyl boronic acid, and 2-thiophenebor-
onic acid, followed by 6p-electrocycli-
zation to give fused ring aromatic prod-
ucts such as naphthalene, benzofuran,
and benzothiophene derivatives are re-
alized. Screening of the reaction condi-
tions revealed that the combination of
[Pd(PPh3)4] in THF gave the best re-
sults in terms of reactivity and product
yields in the reaction of yne–propargyl-
ic carbonates with phenylboronic acid.
The reaction is sensitive toward steric
hindrance when substituted phenylbor-
onic acids are emplyed. However,
when we take 2-furyl boronic acid as
the organometallic reagent, most sub-
strates perform very well to give ben-
zofuran derivatives. In addition, 2-thio-
pheneboronic acid is also a very effec-
tive coupling reagent to give bezothio-
phenes in high yields. A mechanism is
proposed that involves the formation
of an allenylpalladium complex from
Pd0 and propargylic carbonate, fol-
lowed by insertion of an intramolecular
triple bond and the Suzuki coupling re-
action, and then electrocyclization.
À
Keywords: allenes · C C coupling ·
electrocyclic reactions · fused-ring
systems · heterogeneous catalysis ·
palladium
Introduction
converted to toluene or naphthalenes, because of their un-
stable properties.[2] As a matter of fact, the electrocycliza-
tion of diene–allenes (A)were used as a key step in organic
synthesis (Scheme 1).[3] This reaction could be extended to
the arylvinylallene (B), which also takes place the 6p elec-
trocyclization to give naphthalene.[4] However, these allenic
compounds cannot be easily synthesized.[3b,5]
Allene-mediated cyclization reactions have attracted much
attention by chemists.[1] One type of cyclization product, iso-
toluene or its benzo analogues (Scheme 1), can be easily
It has been sporadically reported that the allenylpalladi-
um complex could favorably insert into a triple bond to
form an allenylvinylpalladium species that couples with the
organometallic compounds to produce allene derivatives
conveniently.[6,7]
On the basis of these foundations, we have designed a
tandem reaction of yne–propargylic carbonates and aryl bor-
onic acids catalyzed by palladium(0)to give the arylvinylal-
lenes and followed by electrocyclization in situ to form the
naphthalene, benzofuran, and benzothiophene derivatives.
Herein, we report our preliminary results.
Scheme 1. Allene-mediated cyclization reactions.
[a] Dr. F. Wang, Dr. X. Tong, Prof. Dr. Z. Zhang
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
Results and Discussion
Tandem reaction of yne–propargylic carbonates with aryl
boronic acids—synthesis of multisubstituted naphthalenes:
Following the literature procedure,[6b] when we treated a
mixture of 1, Ph2Zn, and [Pd(dba)2]/4TFP (TFP=trifuryl-
354 Fenglin Rd., Shanghai 200032 (China)
Fax : (+86)216-416-6128
E-mail: zhaoguo@mail.sioc.ac.cn
[b] Dr. J. Cheng
phosphine)in refluxing Et O for 12 h, the starting material
2
Department of Chemistry
Nanjing University, 22 Hankou Rd., Nanjing 210093 (China)
was recovered; no reaction occurred at all. However, when
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DOI: 10.1002/chem.200400573
Chem. Eur. J. 2004, 10, 5338 – 5344

5338 – 5344
we employed PhB(OH)2 instead of Ph2Zn as the organome-
tallic reagent for the coupling reaction, 4-methyl-1,3-dihy-
dro-naphtho[2,3-c]furan (2)can be isolated in 19% yield
within 1 h (Table 1, entry 1). By employing the commercially
employed as the solvent, the yield of 2 did not change at all
(Table 1, entry 8).
To improve the yields of products, we employed propargyl
methyl carbonate 3 as reactant, and 48% of isolated yield of
the product could be achieved (Table 2, entry 1). Other aryl
Table 1. Tandem reaction of propargyl ethyl carbonates with phenylbor-
onic acid.[a]
Table 2. Tandem reaction of propargyl methyl carbonates with aryl bor-
onic acids.[a]
[b]
Entry
Catalyst (5 mol%)Solvent
Yield [%]
1
2
3
4
5
6
7
8
[Pd(dba)2]/4TFP
[Pd(PPh3)4]
THF
THF
THF
THF
THF
THF
THF
5THF/H2O
toluene
dioxane
CH3CN
DMF
19
42[c]
7
42
–
Entry
1
R’C6H4B(OH)2
t [h]
Product
Yield
5/6 [%][b]
Pd(OAc)2/3TFP
Pd(OAc)2/3PPh3
Pd(OAc)2/3P(OMe)3
Pd(OAc)2/3P(o-tol)3
Pd(OAc)2/2L
[Pd(PPh3)4]
[Pd(PPh3)4]
[Pd(PPh3)4]
[Pd(PPh3)4]
[Pd(PPh3)4]
5a/6a
48/65
1
–
–
[d]
43
29
42
trace
trace
35[e]
9
10
11
12
13
5b/6b
61/61
2
3
4
5
2
1
1
2
[Pd(PPh3)4]
THF
[a] All reactions were performed under argon atmosphere with
1
5c/6c
60/69
(0.30 mmol), palladium (5 mol%), and phenylboronic acid (0.45 mmol)
in a specified solvent (3 mL)at 70 8C for 1 h. [b] Yield of isolated product
based on 1. [c] At room temperature no reaction occurred. [d] L=
BINAP, DPPE, DPPP or DPPB. The substrate 1 could be recovered; the
reaction time was 12 h. [e] K2CO3 (0.6 mmol)was added as a base.
5d/6d
45/–[c]
available catalyst [Pd(PPh3)4], a better result was achieved
(Table 1, entry 2).
5e/6e
61/34
Recognizing that the phosphine ligands always play an
important role in transition-metal-catalyzed reactions, the
commercially available bidentate ligands (1,1’-binaphtha-
lene-2,2’-diylbis(diphenylphosphine)(BINA,P) 1,2-bis(di-
phenylphosphino)ethane (DPPE), 1,3-bis(diphenylphosphi-
[a] All reactions were performed under argon atmosphere with
3
(0.30 mmol), [P(PPh3)4] (5 mol%), and aryl boronic acid (0.45 mmol) in
refluxing THF (3 mL). [b] Yield of isolated product based on 3. [c] Un-
identified mixture.
no)propane
(DPPP),
1,4-bis(diphenylphosphino)buta-
ne(DPPB)) and monodentate ligands (PPh3, P(OMe)3, P(o-
Tol)3)were tested for the reaction. Pd(OAc) with bidentate
2
phosphine ligands could not catalyze the reaction; no prod-
ucts were detected at all and the starting material 1 was re-
covered (entry 7). In contrast Pd(OAc)2 with monodentate
phosphine ligands could catalyze the reaction, giving 2 in
the yields ranging from 0% to 42% (entries 3–6). Among
the monophosphine ligands screened, PPh3 gave the best
result with 42% isolated yield. Compound 1 was consumed
boronic acids with electron-withdrawing, electron-donating
groups, or an ortho-substituent, can also react with 3 to give
the corresponding naphthalene derivatives 5b–5e (Table 2,
entries 2–5). When the terminal alkyne moiety of 3 is
blocked by a methyl group, the resulting propargyl methyl
carbonate 4 reacts with phenylboronic acid smoothly, and
the isolated yield of naphthalene derivative (6a)is increased
to 65% (Table 2, entry 1). The para-substituted phenylbor-
onic acids also react with 4 to give the desired products in
moderate yields (Table 2, entries 2, 3). It is not clear why a
low yield of 6e is obtained when electron-rich boronic acid
e reacts with 4 (Table 2, entry 5).
However, no naphthalene product is detected when 4
reacts with 2-MeC6H4B(OH)2; this outcome is different
from that found when propargyl methyl carbonate 3 was
employed as the substrate. From the energy-minimized
model of the allenic intermediate (Figure 1), the 6p system
1
completely and no side product was detected in the H spec-
trum of the solvent-free reaction mixture.
Besides THF, the reaction in other solvents, such as tolu-
ene, CH3CN and DMF, were also investigated; under the
catalysis with [Pd(PPh3)4] compound 2 was separated in
poor yields (Table 1, entries 9, 11, 12). The reaction proceed-
ed in 1,4-dioxane similarly as in THF, the same yield was
obtained (42%, Table 1, entry 10). When K2CO3 was added
as a base, the yield decreased to 35% (Table 1, entry 13). It
is noted that when the mixture of water and THF (1:5)was
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Z. Zhang et al.
FULL PAPER
cluding ortho-substituted phenylboronic acid, to give the
corresponding naphthalene derivatives as the products.
When the a-position of the propargyl carbonates is substi-
tuted, for example, for an ethyl-substituted compound (8),
the reaction even proceeds at room temperature. When a
phenyl group is substituted at the a-position, the yield is
much higher (entry 6). However, for the substrates 9 and 11,
mixtures of products are obtained that cannot be separated
or identified. This may also be attributed to the same reason
that a coplanar 6p system cannot be formed (Figure 1). The
carbon-tethered substrate 12 with methyl carboxylate
groups also reacts with phenylboronic acid to give a carbon-
ring product, but with lower yields.
Figure 1. The energy-minimized (Chem3D ultra 6.0, MM2)model of the
allenic intermediate.
cannot co-exist in one plane, due to the steric hindrance of
two methyl groups, and this prevents the electrocyclization
reaction.
The nitrogen-bridged substrate 7 reacts with phenylboron-
ic acid smoothly to give 13 in 55% of yield (Table 3,
entry 1). Like the oxygen-tethered substrate 3, compound 7
could also react with other substituted aryl boronic acids, in-
Tandem reaction of yne–propargylic carbonates with 2-furyl-
boronic acid and 2-thiopheneboronic acids—synthesis of
benzofurans and benzothiophenes: Besides the aryl boronic
acids, we found that other het-
Table 3. Tandem reaction of yne–propargylic carbonates and aryl bronic acids.[a]
eroaryl boronic acids, such as 2-
[b]
Entry
Carbonates
ArB(OH)2
t [h]
Products
Yield
[%][c]
furylboronic acid and 2-thio-
pheneboronic acid, react more
easily with the yne–propargylic
carbonates to give the corre-
sponding benzofurans and ben-
zothiophenes (Tables 4 and 5).
1
a
1
55
Substrates
with 2-furylboronic
3
and 10 react
acid
smoothly in higher yield than
those with aryl boronic acids
(Table 4, entries 1 and 2); even
2
3
7
7
c
1
2
64
59
the
substrate 19 also gives benzo-
furan in moderate yield
a,a-dimethyl-substituted
d
(Table 4, entry 3). Other sub-
strates such as nitrogen- and
carbon-tethered alkynyl propar-
gylic carbonates react with 2-
furylboronic acid to give the
4
a
1
55
corresponding
benzofurans
(Table 4, entries 4–6).
5
6
7
a
a
a
2
1
1
mixture[d]
–
76
–
The best results are obtained
when we take 2-thiophenebor-
onic acid as the coupling re-
agent. The yields are higher
than those of when aryl and 2-
furylboronic acid are employed
and the reaction time is much
shorter. For substrate 9, which
cannot form naphthalene when
it reacts with phenylboronic
acid (Table 3, entry 5), benzo-
thiophene 30 is afforded in
moderate yield in 30 minutes
(Table 5, entry 4). It seems that
the steric hindrance of carbo-
nates does not have any effect
on the reaction when 2-thiophe-
neboronic acid is applied
(Table 5, entries 3–5 and 8).
mixture[d]
8
a
1
27(29)[e]
[a] The reaction conditions were the same as those in Table 1. [b] For structures of ArB(OH)2 see Table 2.
[c] Yield of isolated product. [d] Mixture products could not be separated or identified. [e] The yield in paren-
thesis is obtained with 5 mol% of Pd(OAc)2/3PPh3 as catalyst.
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Palladium-Catalyzed Tandem Reactions
5338 – 5344
Table 4. Tandem reaction of yne–propargylic carbonates with 2-furylbor-
onic acid.[a]
Table 5. Tandem reaction of yne–propargylic carbonates with 2-thiophe-
neboronic acid.[a]
Entry
Carbonates
t [h]
Products
Yield
[%][b]
Entry
Carbonates
t [h]
Products
Yield
[%][b]
1
0.5
67
1
0.1
91
86
2
3
0.5
75
63
2
3
4
0.5
0.5
0.5
71
62
1
4
5
6
1
59
52
5
0.5
82
0.5
6
7
8
0.5
0.5
1
86
58
79
3
37(45)[c]
[a] The reaction conditions were the same as those in Table 1. [b] Yield
of isolated product. [c] The yield in parenthesis is obtained with 5 mol%
of Pd(OAc)2/3PPh3 as catalyst.
Mechanism investigation: In our initial experiment of yne–
propargylic carbonate 1 with phenylboronic acid, we isolat-
ed another product VI, which is unstable. It directly changed
slowly to 2 at room temperature, or very fast on heating or
with catalytic amount of trifluoroacetic acid (Scheme 2).
Therefore, we believe that the compound VI is one of the
intermediates in the reaction.
[a] The reaction conditions were the same as those in Table 1. [b] Yield
of isolated product.
tramolecular triple bond to generate the alkenylpalladium
intermediate II. The transmetalation of intermediate II with
aryl boronic acid affords the intermediate III, which under-
goes reductive elimination to give arylvinylallene IV. This
allenic compound IV electrocylizes to form the highly conju-
gated intermediate V. Intermediate V either aromatizes di-
rectly to give the final product 2 or reacts through the [1,5]
H-shift to afford the intermediate VI, which further isomer-
izes to give the product 2. The isolation of compound VI[8]
indicates that [1,5] H-shift must have taken place during the
course of the product formation. Compound VI will covert
to the naphthalene product in several hours in air at room
temperature or in a few minutes in the presence of TFA.[1f]
Scheme 2. Formation and subsequent reaction of intermediate VI.
On the basis of these results, we propose a possible reac-
tion mechanism (Scheme 3). Palladium(0)attacks at propar-
gylic carbonate through SN2’ substitution to form an allenyl-
palladium compound (I). Instead of direct coupling with
phenylboronic acid,[7] the intermediate I inserts into the in-
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Z. Zhang et al.
FULL PAPER
temperature, and one drop of trifluoroacetic acid was added; the mixture
was then stirred for about 30 minutes. After evaporation of the solvent
under reduced pressure, the mixture was purified by chromatography on
silica gel with hexane and ethyl acetate as eluent to afford the product.
4-Methyl-1,3-dihydronaphtho[2,3-c]furan (5a/2): 48%, white solid; m.p.
50–518C; 1H NMR (300 MHz, CDCl3): d=8.00–7.96 (m, 2H), 7.81–7.78
(m, 1H), 7.51–7.44 (m, 3H), 5.23–5.22 (m, 4H), 2.53 ppm (s, 3H);
13C NMR (75 MHz, CDCl3): d=137.4, 136.6, 133.5, 132.1, 128.5, 126.2,
125.5, 125.3, 123.5, 117.2, 73.5, 72.8, 15.4 ppm; MS (EI, 70 eV): m/z (%):
184 (100)[ M+], 169 (40), 155 (92), 141 (57), 128 (20), 115 (23); IR
(KBr): n˜ =2854 (w), 1048 (s), 908 (m), 747 cmÀ1 (s); elemental analysis
calcd (%)for C 13H12O: C 84.75, H 6.57; found: C 84.73, H 6.77.
6-Chloro-4-methyl-1,3-dihydronaphtho[2,3-c]furan (5b): 61%, white
solid; m.p. 125–1268C; 1H NMR (300 MHz, CDCl3): d=7.95 (d, J=
2.1 Hz, 1H), 7.74 (d, J=8.7 Hz, 1H), 7.50 (s, 1H), 7.40 (dd, J=2.1,
8.7 Hz, 1H), 5.23 (s, 4H), 2.50 ppm (s, 3H); 13C NMR (75 MHz, CDCl3):
d=137.8, 137.8, 132.9, 131.8, 131.4, 129.9, 126.1, 125.6, 122.7, 117.2, 73.4,
72.7, 15.4 ppm; MS (EI, 70 eV): m/z (%): 218 (100) [M+(35Cl)], 189 (90),
175 (38), 153 (54), 139 (14); IR (KBr): n˜ =2858 (w), 1495 (m), 1081 (m),
1044 (s), 900 (s), 865 cmÀ1 (s); elemental analysis calcd (%) for
C13H11ClO: C 71.40, H 5.07; found: C 71.32, H 5.15.
Scheme 3. The possible mechanism of the tandem reaction of yne–prop-
argylic carbonates and aryl boronic acids.
6-Methyl-4-methyl-1,3-dihydronaphtho[2,3-c]furan (5c): 60%, white
solid; m.p. 100–1018C; 1H NMR (300 MHz, CDCl3): d=7.74–7.69 (m,
2H), 7.48 (s, 1H), 7.31–7.25 (m, 1H), 5.22 (s, 4H), 2.54 (s, 3H), 2.52 ppm
(s, 3H); 13C NMR (75 MHz, CDCl3): d=136.6, 136.4, 135.1, 132.3, 131.7,
128.3, 127.5, 125.4, 122.6, 117.0, 73.5, 72.8, 22.0, 15.4 ppm; MS (EI,
70 eV): m/z (%): 198 (60) [M+], 183 (32), 169 (100), 155 (68), 141 (14),
128 (18), 115 (15); IR (KBr): n˜ =2850 (w), 1505 (w), 1340 (m), 1048 (s),
901 (s), 800 (s), 521 cmÀ1 (m); elemental analysis calcd (%) for C 14H14O:
C 84.81, H 7.12; found: C 84.84, H 7.25.
We have no proof to support the direct aromatization of V
to give the product.
Conclusion
In summary, we found a novel method for the synthesis of
poly-substituted naphthalenes, benzofurans, and benzothio-
phenes by means of the palladium-catalyzed tandem reac-
tion of yne–propargylic carbonates with boronic acids fol-
lowed by electrocyclization. This is an efficient way to build
complex fused ring system from linear molecules. It should
be noted that this method can be used especially for the syn-
thesis of multi-substituted naphthalenes, benzofurans, and
benzothiophenes with regioselectivity. The searching for the
catalyst/ligands to achieve a more efficient coupling of the
yne–propargylic carbonate with aryl boronic acids, and the
application of the method in highly fused aromatic ring syn-
thesis are in progress in our laboratory.
4,8-Dimethyl-1,3-dihydronaphtho[2,3-c]furan (5d): 45%, white solid;
m.p. 83–848C; 1H NMR (300 MHz, CDCl3): d=7.86 (d, J=8.4 Hz, 1H),
7.71 (s, 1H), 7.41–7.36 (m, 1H), 7.30 (d, J=6.6 Hz, 1H), 5.28 (s, 2H),
5.24 (s, 2H), 2.68 (s, 3H), 2.54 ppm (s, 3H); 13C NMR (75 MHz, CDCl3):
d=137.2, 136.2, 134.5, 132.6, 132.1, 126.7, 126.2, 125.0, 121.8, 113.4, 73.8,
72.9, 20.0, 15.8 ppm; MS (EI, 70 eV): m/z (%): 198 (98) [M+], 183 (39),
169 (100), 155 (74), 141 (18), 128 (23), 115 (24), 91 (16); IR (KBr): n˜ =
2838 (m), 1448 (m), 1341 (m), 1048 (s), 904 (s), 793 (s), 750 cmÀ1 (s); ele-
mental analysis calcd (%)for C 14H14O: C 84.81, H 7.12; found: C 84.79,
H 7.32.
6-Methoxy-4-methyl-1,3-dihydronaphtho[2,3-c]furan (5e): 61%, white
solid; m.p. 119–1208C; 1H NMR (300 MHz, CDCl3): d=7.70 (d, J=
9.0 Hz, 1H), 7.45 (s, 1H), 7.21 (d, J=2.4 Hz, 1H), 7.13 (dd, J=2.4,
9.0 Hz, 1H), 5.22 (s, 4H), 3.94 (s, 3H), 2.48 ppm (s, 3H); 13C NMR
(75 MHz, CDCl3): d=157.4, 137.1, 135.0, 133.1, 129.9, 128.8, 124.8, 127.5,
117.0, 102.3, 73.5, 72.9, 55.2, 15.5 ppm; MS (EI, 70 eV): m/z (%): 214 (74)
[M+], 199 (15), 185 (100), 171 (41), 152 (24), 141 (86), 128 (41), 115 (87);
IR (KBr): n˜ =2858 (w), 1618 (s), 1506 (s), 1233 (s), 1180 cmÀ1 (s), 1045
Experimental Section
+
(s); HRMS (MALDI): m/z calcd for C14H15O2 [M++H]: 215.1072;
found: 215.1067.
General: All reactions and manipulations were conducted under Ar at-
mosphere by using standard Schlenk techniques. All solvents were puri-
fied according to standard procedures. Column chromatography was per-
formed using silica gel (200–300 mesh). Melting points were not correct-
ed. NMR spectra were recorded at 300 MHz for 1H and 75 MHz for 13C
spectra, with tetramethylsilane as the internal standard for 1H spectra
and the residual solvent signals as the standard for 13C spectra. Chemical
shifts were downfield reported in ppm. MS, HRMS, IR spectra, and mi-
croanalysis were performed by the State-authorized Analytical Center in
Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.
All catalysts and phosphine ligands were purchased from commercial
sources. The substrates were prepared similarly according to the litera-
ture.
4,9-Dimethyl-1,3-dihydronaphtho[2,3-c]furan (6a): 65%, white solid;
m.p. 139–1418C; 1H NMR (300 MHz, CDCl3): d=8.01–7.98 (m, 2H),
7.52–7.49 (m, 2H), 5.26 (s, 4H), 2.51 ppm (s, 3H); 13C NMR (75 MHz,
CDCl3): d=135.8, 132.5, 125.1, 123.9, 123.8, 73.5, 15.3 ppm; MS (EI,
70 eV): m/z (%): 198 (100) [M+], 183 (81), 169 (74), 155 (91), 141 (31),
128 (27), 115 (27), 91 (15); IR (KBr): n˜ =2839 (w), 1457 (m), 1335 (m),
1038 (s), 908 (s), 759 cmÀ1 (s); elemental analysis calcd (%) for C 14H14O:
C 84.81, H 7.12; found: C 84.45, H 7.08.
6-Chloro-4,9-dimethyl-1,3-dihydronaphtho[2,3-c]furan (6b): 61%, white
solid; m.p. 114–1158C; 1H NMR (300 MHz, CDCl3): d=7.91–7.86 (m,
2H), 7.40 (d, J=8.7 Hz, 1H), 5.21(s, 4H), 2.45 (s, 3H), 2.43 ppm (s, 3H);
13C NMR (75 MHz, CDCl3): d=137.0, 136.1, 133.5, 131.1, 130.8, 125.7,
125.5, 124.0, 123.2, 123.0, 73.4, 73.4, 15.3, 15.3 ppm; MS (EI, 70 eV): m/z
(%): 232 (100) [M+(35Cl)], 217 (81), 203 (72), 189 (45), 165 (36), 153
(55), 91 (44); IR (KBr): n˜ =2847 (m), 1604 (m), 1501 (m), 1461 (m), 1382
(m), 1338 (m), 1096 (m), 1041 (s), 910 (s), 871 (s), 805 cmÀ1 (s); elemental
analysis calcd (%)for C 13H11ClO: C 72.26, H 5.63; found: C 72.28, H
5.75.
General procedure for the palladium-catalyzed tandem reaction of yne–
propargylic carbonates with aryl boronic acids (Method A): A Schlenk
tube was charged
a solution of aryl boronic acid (0.45 mmol)and
[P(PPh3)4] (17.3 mg, 0.015 mmol)in THF (2.0 mL)under argon atmos-
phere. With stirring, a solution of yne–propargylic carbonate (0.3 mmol)
in THF (1.0 mL)was introduced into the tube by syringe in one portion.
The reaction mixture was heated at reflux until the carbonate was con-
sumed as monitored by TLC. The reaction mixture was cooled to room
4,6,9-Trimethyl-1,3-dihydronaphtho[2,3-c]furan (6c): 69%, white solid;
m.p. 95–968C; 1H NMR (300 MHz, CDCl3): d=7.90 (d, J=8.7 Hz, 1H),
5342
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Chem. Eur. J. 2004, 10, 5338 – 5344

Palladium-Catalyzed Tandem Reactions
5338 – 5344
7.77 (s, 1H), 7.34 (d, J=8.7 Hz, 1H), 5.26 (s, 4H), 2.55 (s, 3H), 2.50 ppm
(s, 6H); 13C NMR (75 MHz, CDCl3): d=135.7, 134.8, 134.5, 132.7, 130.6,
127.1, 123.7, 123.6, 123.1, 123.0, 73.5, 73.4, 21.8, 15.3, 15.2 ppm; MS (EI,
70 eV): m/z (%): 212 (100) [M+], 197 (77), 183 (71), 169 (56), 153 (34),
141 (15), 128 (16), 115 (14); IR (KBr): n˜ =2837 (w), 1337 (m), 1041 (s),
909 (s), 810 cmÀ1 (s); HRMS (EI): m/z calcd for C15H16O: 212.1201;
found: 212.1191.
13C NMR (75 MHz, CDCl3): d=172.1, 138.2, 137.1, 133.4, 132.1, 128.7,
128.2, 125.1, 125.0, 123.6, 120.5, 60.2, 53.0, 40.5, 39.7, 15.3 ppm; MS (EI,
70 eV): m/z (%): 298 (25) [M+], 238 (57), 179 (100), 165 (37), 84 (74), 47
(18); IR (CHCl3): n˜ =2955 (w), 1736 (brs), 1435 (s), 1256 (brs), 1073 (m),
734 cmÀ1 (m); HRMS (EI): m/z calcd for C18H18O4: 298.1205; found:
298.1204.
General procedure for the palladium-catalyzed tandem reaction of yne-
propargylic carbonates with furylboronic acid and thiopheneboronic acid
(Method B): A Schlenk tube was charged a solution of furyl boronic acid
or thiopheneboronic acid (0.45 mmol)and [P(PPh 3)4] (17.3 mg,
0.015 mmol)in THF (2.0 mL)under argon atmosphere, with stirring; a
solution of yne–propargylic carbonate (0.3 mmol)in THF (1.0 mL)was
added to the tube by syringe in one portion. The reaction mixture was
heated at reflux until carbonate was consumed as detected by TLC. The
reaction mixture was cooled, evaporated under reduced pressure, and pu-
rified by chromatography on silica gel with hexane and ethyl acetate as
eluent to afford the product.
6-Methoxy-4,9-dimethyl-1,3-dihydronaphtho[2,3-c]furan
(6e):
34%,
white solid; m.p. 135–1368C; 1H NMR (300 MHz, CDCl3): d=7.91 (d,
J=9.3 Hz, 1H), 7.24 (d, J=2.7 Hz, 1H), 7.17 (dd, J=2.7, 9.3 Hz, 1H),
5.25 (s, 4H), 3.95 (s, 3H), 2.48 (s, 3H), 2.46 ppm (s, 3H); 13C NMR
(75 MHz, CDCl3): d=157.1, 136.4, 133.7, 133.5, 127.8, 125.5, 123.9, 122.5,
116.9, 102.9, 73.6, 73.5, 55.2, 15.5, 15.4 ppm; MS (EI, 70 eV): m/z (%):
228 (100)[ M+], 213 (64), 199 (58), 185 (36), 153 (16), 141 (20), 115 (14);
IR (KBr): n˜ =1617 (s), 1423 (m), 1224 (s), 1043 (s), 838 (s), 811 cmÀ1
(m); HRMS (EI): m/z calcd for C15H16O2: 228.1150; found: 228.1151.
4-Methyl-2-(toluene-4-sulfonyl)-2,3-dihydro-1H-benzo[f]isoindole
(13):
55%, white solid; m.p. 172–1738C; 1H NMR (300 MHz, CDCl3): d=7.93
(d, J=8.1 Hz, 1H), 7.81 (d, J=8.1 Hz, 2H), 7.75 (d, J=8.1 Hz, 1H),
7.50–7.46 (m, 3H), 7.32 (d, J=8.1 Hz, 2H), 4.74 (s, 2H), 4.72 (s, 2H),
2.50 (s, 3H), 2.39 ppm (s, 3H); 13C NMR (75 MHz, CDCl3): d=143.7,
134.0, 133.4, 133.3, 133.2, 131.9, 129.8, 128.4, 128.0, 127.6, 125.8, 125.7,
123.5, 119.2, 53.6, 53.0, 21.5, 15.2 ppm; MS (EI, 70 eV): m/z (%): 337 (13)
[M+], 181 (100), 167 (12), 155 (12), 91 (15); IR (KBr): n˜ =1348 (s), 1160
(s), 1098 (m), 670 (s), 546 cmÀ1 (s); HRMS (EI): m/z calcd for
C20H19NO2S: 337.1136; found: 337.1145.
4-Methyl-5,7-dihydro-1,6-dioxa-s-indacene (21): 67%, colorless oil;
1H NMR (300 MHz, CDCl3): d=7.60 (d, J=2.4 Hz, 1H), 7.17 (s, 1H),
6.76 (d, J=2.4 Hz, 1H), 5.23 (s, 2H), 5.18 (s, 2H), 2.37 ppm (s, 3H);
13C NMR (75 MHz, CDCl3): d=154.9, 145.0, 135.1, 131.6, 127.1, 123.4,
104.9, 101.4, 73.7, 72.5, 15.7 ppm; MS (EI, 70 eV): m/z (%): 174 (35) [M+
], 159 (41), 145 (100), 131 (23), 115 (28); IR (CHCl3): n˜ =2852 (s), 1382
(s), 1297 (s), 1141 (s), 1038 (s), 908 (s), 770 (s), 725 ppm (s); HRMS (EI):
m/z calcd for C11H10O2: 174.0681; found: 174.0664.
4-Benzyl-5,7-dihydro-1,6-dioxa-s-indacene (22): 75%, colorless oil;
1H NMR (300 MHz, CDCl3): d=7.58 (d, J=2.1 Hz, 1H), 7.29–7.13 (m,
6H), 6.69 (dd, J=1.2, 2.1 Hz, 1H), 5.18 (s, 2H), 5.04 (s, 2H), 4.11 ppm (s,
2H); 13C NMR (75 MHz, CDCl3): d=155.2, 145.1, 139.2, 136.4, 132.9,
128.6, 128.4, 127.1, 126.3, 126.2, 105.1, 102.2, 73.5, 72.3, 36.8 ppm; MS
(EI, 70 eV): m/z (%): 250 (82) [M+], 221 (38), 172 (100), 159 (34), 131
(35), 115 (47), 78 (40), 51 (41); IR (CHCl3): n˜ =2849 (m), 1379 (s), 1297
(s), 1139 (s), 1043 (s), 909 (m), 735 (m), 701 cmÀ1 (m); HRMS (EI): m/z
calcd for C17H14O2: 250.0994; found: 250.0980.
4,6-Dimethyl-2-(toluene-4-sulfonyl)-2,3-dihydro-1H-benzo[f]isoindole
(14): 64%, white solid; m.p.>2508C (decomp); 1H NMR (300 MHz,
CDCl3): d=7.81 (d, J=8.4 Hz, 2H), 7.69 (s, 1H), 7.65 (d, J=8.4 Hz,
1H), 7.43 (s, 1H), 7.31 (dd, J=8.4 Hz, 3H), 4.73 (s, 2H), 4.71 (s, 2H),
2.52 (s, 3H), 2.48 (s, 3H), 2.39 ppm (s, 3H); 13C NMR (75 MHz, CDCl3):
d=143.7, 135.4, 133.4, 133.2, 133.0, 132.1, 131.5, 129.8, 128.1, 127.9, 127.6,
127.2, 122.6, 118.9, 53.6, 53.0, 22.0, 21.5, 15.1 ppm; MS (EI, 70 eV): m/z
(%): 351 (15) [M+], 195 (100); IR (KBr): n˜ =1346 (s), 1160 (s), 1098 (s),
667 (s), 547 cmÀ1 (s); HRMS (EI): m/z calcd for C20H19NO2S: 351.1293;
found: 351.1290.
4-Isopropyl-8-phenyl-5,7-dihydro-1,6-dioxa-s-indacene (23): 63%, color-
less oil; 1H NMR (300 MHz, CDCl3): d=7.60 (d, J=2.1 Hz, 1H), 7.57–
7.54 (m, 2H), 7.50–7.45 (m, 2H), 7.40–7.36 (m, 1H), 6.91 (d, J=2.1 Hz,
1H), 5.26 (s, 2H), 5.20 (s, 2H), 3.15 (h, J=6.9 Hz, 1H), 1.40 ppm (d, J=
6.9 Hz, 6H); 13C NMR (75 MHz, CDCl3): d=152.9, 144.7, 134.8, 134.6,
133.4, 131.6, 129.0, 128.5, 127.7, 125.5, 117.7, 106.0, 72.9, 72.6, 31.8,
22.0 ppm; MS (EI, 70 eV): m/z (%): 278 (100) [M+], 263 (14), 249 (50),
235 (36), 207 (52), 178 (50), 43 (56); IR (CHCl3): n˜ =2963 (s), 1481 (s),
1375 (s), 1146 (s), 1067 (s), 744 (s), 698 cmÀ1 (s); HRMS (EI): m/z calcd
for C19H18O2: 278.1307; found: 278.1328.
4,8-Dimethyl-2-(toluene-4-sulfonyl)-2,3-dihydro-1H-benzo[f]isoindole
(15): 59%, white solid; m.p. 183–1848C; 1H NMR (300 MHz, CDCl3):
d=7.81 (dd, J=8.4 Hz, 3H), 7.64 (s, 1H), 7.39–7.25 (m, 4H), 4.78 (s,
2H), 4.73 (s, 2H), 2.63 (s, 3H), 2.50 (s, 3H), 2.39 ppm (s, 3H); 13C NMR
(75 MHz, CDCl3): d=143.7, 134.5, 133.8, 133.5, 132.9, 132.5, 132.0, 129.8,
128.5, 127.6, 126.5, 125.4, 121.8, 115.4, 53.9, 53.1, 21.5, 19.9, 15.6 ppm; MS
(EI, 70 eV): m/z (%): 351 (16) [M+], 195 (100); IR (KBr): n˜ =1346 (s),
1160 (s), 1098 (s), 667 (s), 547 cmÀ1 (s); HRMS (EI): m/z calcd for
C20H19NO2S: 351.1293; found: 351.1287.
4-Propyl-6-(toluene-4-sulfonyl)-6,7-dihydro-5H-1-oxa-6-aza-s-indacene
(24): 59%, white solid; m.p. 166–1688C; 1H NMR (300 MHz, CDCl3):
d=7.79 (d, J=8.1 Hz, 2H), 7.56 (d, J=2.1 Hz, 1H), 7.31 (d, J=8.1 Hz,
2H), 7.12 (s, 1H), 6.72 (d, J=2.1 Hz, 2H), 4.69 (s, 2H), 4.65 (s, 2H), 2.67
(t, J=7.2 Hz, 2H), 2.39 (s, 3H), 1.67–1.57 (m, 2H), 0.94 ppm (t, J=
7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3): d=154.9, 145.0, 143.6, 133.5,
132.6, 129.9, 129.8, 128.9, 127.6, 126.8, 105.0, 103.3, 53.6, 52.2, 32.8, 23.1,
21.5, 14.1 ppm; MS (EI, 70 eV): m/z (%): 355 (5) [M+], 199 (42), 170
(58), 115 (54), 91 (100), 71 (71), 39 (68); IR (KBr): n˜ =1340 (s), 1163 (s),
1098 (m), 667 (s), 607 (m), 551 cmÀ1 (m); elemental analysis calcd (%)
for C20H21NO3S: C 67.58, H 5.95, N 3.94; found: C 67.47, H 6.17, N 3.57.
4-Propyl-2-(toluene-4-sulfonyl)-2,3-dihydro-1H-benzo[f]isoindole
(16):
55%, white solid; m.p. 135–1368C; 1H NMR (300 MHz, CDCl3): d=7.95
(d, J=7.8 Hz, 1H), 7.81 (d, J=8.1 Hz, 2H), 7.77–7.74 (m, 1H), 7.49–7.42
(m, 3H), 7.31 (d, J=8.1 Hz, 2H), 4.74 (s, 4H), 2.90–2.85 (m, 2H), 2.40 (s,
3H), 1.69–1.61 (m, 2H), 1.02 ppm (t, J=7.2 Hz, 3H); 13C NMR (75 MHz,
CDCl3): d=143.7, 134.1, 133.7, 133.4, 133.0, 131.2, 129.8, 128.5, 127.6,
125.7, 125.5, 123.5, 119.4, 115.2, 53.5, 52.8, 31.9, 23.4, 21.5, 14.4 ppm; MS
(EI, 70 eV): m/z (%): 365 (17) [M+], 209 (71), 180 (100), 167 (19), 152
(20), 91 (41); IR (KBr): n˜ =1345 (s), 1160 (s), 1100 (s), 669 (s), 547 cmÀ1
(s); elemental analysis calcd (%) for C 22H23NO2S: C 72.30, H 6.34, N
3.83; found: C 72.54, H 6.49, N 3.63.
4-Methyl-5,7-dihydro-1-oxa-s-indacene-6,6-dicarboxylic acid dimethyl
ester (25): 52%, yellow oil; 1H NMR (300 MHz, CDCl3): d=7.53 (d, J=
1.8 Hz, 1H), 7.17 (s, 1H), 6.71 (d, J=1.8 Hz, 1H), 3.76 (s, 6H), 3.68 (s,
2H), 3.58 ppm (s, 2H), 2.41 (s, 3H); 13C NMR (75 MHz, CDCl3): d=
172.1, 154.7, 144.3, 136.5, 132.8, 126.6, 125.8, 105.0, 104.6, 60.5, 53.0, 40.5,
38.5, 15.8 ppm; MS (EI, 70 eV): m/z (%): 288 (35) [M+], 228 (100), 197
(22), 169 (94), 141 (17), 115 (20), 84 (17); IR (CHCl3): n˜ =2956 (w), 1740
(s), 1435 (m), 1251 (s), 1201 cmÀ1 (m); HRMS (EI): m/z calcd for
C16H16O5: 288.0998; found: 288.0970.
4-Benzyl-1,3-dihydro-naphtho[2,3-c]furan (17): 76%, white solid; m.p.
63–658C; 1H NMR (300 MHz, CDCl3): d=7.97–7.94 (m, 1H), 7.85–7.82
(m, 1H), 7.52 (s, 1H), 7.61 (s, 1H), 7.46–7.38 (m, 1H), 7.23–7.15 (m, 1H),
7.12–7.07 (m, 1H) 5.27 (s, 2H), 5.19 (s, 2H), 4.33 ppm (s, 2H); 13C NMR
(75 MHz, CDCl3): d=139.4, 137.8, 137.6, 133.9, 131.9, 128.6, 128.6, 128.5,
128.1, 126.2, 125.8, 125.4, 124.0, 118.4, 73.4, 72.7, 35.4 ppm; MS (EI,
70 eV): m/z (%): 260 (100) [M+], 215 (75), 182 (93), 169 (83), 153 (60),
141 (86), 115 (32), 78 (23); IR (KBr): n˜ =2838 (m), 1056 (s), 909 (m), 740
(s), 705 (s), 509 cmÀ1(m); HRMS (EI): m/z calcd for C19H17O+: 261.1279;
found: 261.1274.
Dimethyl ester of 4-methyl-8-phenyl-5,7-dihydro-1-oxa-s-indacene-6,6-di-
carboxylic acid (26): 37%, yellow oil; 1H NMR (300 MHz, CDCl3): d=
7.59–7.54 (m, 3H), 7.51–7.47 (m, 2H), 7.1–7.35 (m, 1H), 6.77 (d, J=
2.1 Hz, 1H), 3.73 (s, 6H), 3.69 (s, 2H), 3.65 (s, 2H), 2.45 ppm (s, 3H);
13C NMR (75 MHz, CDCl3): d=172.1, 144.6, 143.3, 135.2, 134.5, 134.4,
133.5, 129.5, 128.4, 127.4, 125.0, 119.8, 105.2, 60.5, 53.0, 39.8, 38.8,
Dimethyl ester of 4-methyl-1,3-dihydrocyclopenta[b]naphthalene-2,2-di-
carboxylic acid (18): 27%, yellow oil. 1H NMR (300 MHz, CDCl3): d=
7.95 (d, J=8.4 Hz, 1H), 7.75 (d, J=8.4 Hz, 1H), 7.52 (s, 1H), 7.45–7.33
(m, 3H), 3.76 (s, 6H), 3.74 (s, 2H), 3.72 (s, 2H), 2.59 ppm (s, 2H);
Chem. Eur. J. 2004, 10, 5338 – 5344
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ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
5343

Z. Zhang et al.
FULL PAPER
15.8 ppm; MS (EI, 70 eV): m/z (%): 364 (64) [M+], 304 (71), 245 (66),
202 (21), 84 (100); IR (CHCl3): n˜ =2955 (w), 1736 (s), 1256 (s), 757 cmÀ1
(s); HRMS (MALDI): m/z calcd for C22H20O5Na+: 387.1208; found:
387.1203.
2H), 2.59 ppm (s, 3H); 13C NMR (75 MHz, CDCl3): d=172.0, 139.6,
139.1, 139.0, 135.9, 134.7, 129.9, 128.7, 128.6, 127.7, 127.0, 125.9, 122.0,
60.4, 53.0, 39.8, 39.2, 16.3 ppm; MS (EI, 70 eV): m/z (%): 380 (79) [M+],
320 (73), 289 (15), 261 (100), 247 (22), 84 (54); IR (CHCl3): n˜ =2954 (w),
1736 (s), 1436 (s), 1249 (s), 1073 (m), 703 cmÀ1 (m); HRMS (MALDI):
m/z calcd for C22H20O4SNa+: 403.0980; found: 403.0975.
4-Methyl-5,7-dihydro-6-oxa-1-thia-s-indacene (27): 91%, white solid;
m.p. 69–708C; 1H NMR (300 MHz, CDCl3): d=7.53 (s, 1H), 7.41 (d, J=
5.7 Hz, 1H), 7.36 (dd, J=1.8, 5.7 Hz, 1H), 5.21 (s, 2H), 5.17 (s, 2H),
2.47 ppm (s, 3H); 13C NMR (75 MHz, CDCl3): d=139.5, 138.7, 136.2,
134.8, 125.8, 125.3, 121.3, 111.9, 73.5, 72.6, 16.3 ppm; MS (EI, 70 eV): m/z
(%): 190 (35) [M+], 175 (47), 161 (100), 147 (20), 128 (20), 115 (18); IR
(KBr): n˜ =2848 (w), 1046 (s), 904 (s), 764 (s), 697 cmÀ1 (s); HRMS (EI):
m/z calcd for C11H10OS: 190.0452; found: 190.0449.
Acknowledgement
Financial support for this work was provided by the National Natural Sci-
ence Foundation of China, Chinese Academy of Sciences, and the Sci-
ence and Technology Commission of Shanghai Municipality.
4-Benzyl-5,7-dihydro-6-oxa-1-thia-s-indacene (28): 86%, colorless oil;
1H NMR (300 MHz, CDCl3): d=7.59 (s, 1H), 7.39–7.33 (m, 2H), 7.27–
7.16 (m, 3H), 7.12–7.09 (m, 2H), 5.19 (s, 2H), 5.07 (s, 2H), 4.21 ppm (s,
2H); 13C NMR (75 MHz, CDCl3): d=140.0, 139.2, 138.8, 136.6, 135.6,
128.5, 128.2, 128.0, 126.3, 126.2, 121.6, 112.9, 73.3, 72.4, 37.0 ppm; MS
(EI, 70 eV): m/z (%): 266 (100) [M+], 250 (16), 237 (39), 221 (50), 188
(68), 175 (37), 147 (38), 115 (19); IR (CHCl3): n˜ =2857 (w), 1493 (w),
1054 (s), 740 (m), 699 cmÀ1 (s); HRMS (EI): m/z calcd for C17H14OS:
266.0765; found: 266.0763.
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6117; b)P. Turnbull, H. Moore, J. Org. Chem. 1995, 60, 3274–3275;
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4-Methyl-8-phenyl-5,7-dihydro-6-oxa-1-thia-s-indacene (29): 71%, yellow
1
oil; H NMR (300 MHz, CDCl3): d=7.53–7.39 (m, 7H), 5.23 (s, 2H), 5.15
(s, 2H), 2.50 ppm (s, 3H); 13C NMR (75 MHz, CDCl3): d=139.7, 139.5,
138.6, 135.7, 134.2, 128.8, 128.2, 128.0, 127.5, 126.4, 124.3, 121.7, 73.3,
72.9, 16.2 ppm; MS (EI, 70 eV): m/z (%): 266 (100) [M+], 251 (8), 237
(90), 221 (65), 189 (20), 111 (10); IR (CHCl3): n˜ =2856 (w), 1443 (m),
1361 (m), 1054 (s), 763 (m), 734 (s), 703 cmÀ1 (s); elemental analysis
calcd (%)for C 17H14OS: C 76.66, H 5.30; found: C 76.55, H 5.17.
4-Isopropyl-5,7-dihydro-6-oxa-1-thia-s-indacene (30): 62%, yellow oil;
1H NMR (300 MHz, CDCl3): d=7.55 (s, 1H), 7.50 (d, J=5.4 Hz, 1H),
7.39 (d, J=5.4 Hz, 1H), 5.26 (s, 2H), 5.16 (s, 2H), 3.40 (h, J=7.5 Hz,
1H), 1.37 ppm (d, J=7.5 Hz, 6H); 13C NMR (75 MHz, CDCl3): d=140.3,
137.1, 137.0, 136.3, 133.2, 125.3, 122.0, 112.2, 72.7. 72.4, 31.8, 21.8 ppm;
MS (EI, 70 eV): m/z (%): 218 (100) [M+], 203 (12), 189 (57), 175 (34),
235 (84), 161 (18), 147 (57); IR (CHCl3): n˜ =2964 (s), 1463 (m), 1364 (s),
1059 (s), 918 (s), 841 (s), 777 (s), 702 cmÀ1 (s); HRMS (MALDI): m/z
calcd for C13H15OS+: 219.0844; found: 219.0838.
4-Isopropyl-8-phenyl-5,7-dihydro-6-oxa-1-thia-s-indacene (31): 82%,
yellow oil; 1H NMR (300 MHz, CDCl3): d=7.57–7.38 (m, 7H), 5.32 (s,
2H), 5.08 (s, 2H), 3.44 (h, J=7.2 Hz, 1H), 1.42 ppm (d, J=7.2 Hz, 6H);
13C NMR (75 MHz, CDCl3): d=140.7, 138.6, 138.0, 135.3, 135.0, 134.2,
128.8, 128.2, 128.0, 127.7, 126.0, 122.5, 72.8, 72.4, 31.9, 21.9 ppm; MS (EI,
70 eV): m/z (%): 294 (100) [M+], 279 (15), 265 (27), 251 (34), 235 (21),
223 (71), 84 (21); IR (CHCl3): n˜ =2964 (s), 1359 (m), 1062 (s), 720 (m),
732 (s), 701 cmÀ1 (s); HRMS (EI): m/z calcd for C19H18OS: 294.1078;
found: 294.1064.
[4] a)B. Miller, J. Baghdadchi, J. Org. Chem. 1987, 52, 2391–2396;
b)D. J. Pasto, W. Kong, J. Org. Chem. 1989, 54, 4028–4033; c)P.
Turnbull, H. W. Moore, J. Org. Chem. 1995, 60, 3274–3275.
4-Propyl-6-(toluene-4-sulfonyl)-6,7-dihydro-5H-1-thia-6-aza-s-indacene
(32): 86%, white solid; m.p. 166–1688C; 1H NMR (300 MHz, CDCl3):
d=7.80 (d, J=8.4 Hz, 2H), 7.50 (s, 1H), 7.41–7.30 (m, 4H), 4.71 (s, 2H),
4.69 (s, 2H), 2.77 (t, J=7.8 Hz, 2H), 2.39 (s, 3H), 1.69–1.57 (m, 2H),
0.97 ppm (t, J=7.8 Hz, 3H); 13C NMR (75 MHz, CDCl3): d=143.7,
139.9, 138.4, 133.4, 132.9, 131.8, 131.2, 129.8, 127.6, 126.2, 121.4, 113.9,
53.5, 52.4, 33.2, 23.3, 21.5, 14.3 ppm; MS (EI, 70 eV): m/z (%): 371 (5)
[M+], 215 (56), 186 (100), 173 (22), 115 (17), 91 (46), 65 (14); IR (KBr):
n˜ =2951 (w), 1338 (s), 1162 (s), 1095 (m), 666 (s), 602 cmÀ1 (m); elemen-
tal analysis calcd (%)for C 20H22O2S2: C 64.66, H 5.70, N 3.77; found: C
64.16, H 5.58, N 3.77.
[5] a)R. Baudouy, J. Gore, Bull. Soc. Chim. Fr. 1975, 2166–2170; b)G.
Balme, M. Malacria, J. Gore, Tetrahedron Lett. 1979, 20, 7–10; c)H.
Bross, T. Schneider, H. Hopf, Tetrahedron Lett. 1979, 20, 2129–2132;
d)K. H. Holm, L. Skatteboel, Acta. Chem. Scand. Ser. B. 1984, 38,
783–794; e)D. J. Pasto, W. Kong, J. Org. Chem. 1989, 54, 4028–4033;
f)Y. W. Andemichael, K. K. Wang, J. Org. Chem. 1992, 57, 796–798;
g)J. E. Ezcurra, C. Pham, H. W. Moore, J. Org. Chem. 1992, 57,
4787–4789; h)K. K. Wang, Q. Zhang, J. Liao, Tetrahedron Lett. 1996,
37, 4087–4090; i)M. Prupura, N. Krause, Eur. J. Org. Chem. 1999, 1,
267–275.
[6] a)J. Tsuji, T. Mandai, Angew. Chem. 1995, 107, 2830; Angew. Chem.
Int. Ed. Engl. 1995, 34, 2589–2612; b)W. Oppolzer, A. Pimm, B.
Stammen, W. E. Hume, Helv. Chim. Acta 1997, 80, 623–639; c)R.
Grigg, R. Rasul, V. Savic, Tetrahedron Lett. 1997, 38, 1825–1828.
[7] T. Moriya, N. Miyaura, A. Suzuki, Synlett 1994, 149–151.
[8] Data of VI: 1H NMR (300 MHz, CDCl3): d=7.84–7.81 (m, 1H),
7.31–7.27 (m, 3H), 5.67 (s, 1H), 4.94–4.92 (m, 2H), 4.82–4.81 (m,
2H), 4.77 (s, 1H), 3.61–3.60 ppm (m, 2H); After 24 h in CDCl3 or
add one drop of TFA for several minutes, VI will change to 2 com-
pletely without formation of any other side products.
Dimethyl ester of 4-methyl-5,7-dihydro-1-thia-s-indacene-6,6-dicarboxylic
acid (33): 58%, white solid; m.p. 108–1108C; 1H NMR (300 MHz,
CDCl3): d=7.54 (s, 1H), 7.36–7.32 (m, 2H), 3.76 (s, 6H), 3.69 (s, 2H),
3.63 (s, 2H), 2.51 ppm (s, 2H); 13C NMR (75 MHz, CDCl3): d=172.1,
139.1, 138.5, 136.9, 135.2, 127.9, 125.1, 121.6, 115.1, 60.5, 53.0, 40.4, 38.9,
16.3 ppm; MS (EI, 70 eV): m/z (%): 304 (33) [M+], 244 (85), 185 (100),
171 (31); IR (KBr): n˜ =2952 (w), 1740 (s), 1722 (s), 1252 (s), 1156 (s),
1071 (m), 766 (m), 701 cmÀ1 (m); HRMS (MALDI): m/z calcd for
C16H16O4SNa+: 327.0667; found: 327.0662.
Dimethyl ester of 4-methyl-8-phenyl-5,7-dihydro-1-thia-s-indacene-6,6-di-
carboxylic acid (34): 79%, yellow oil; 1H NMR (300 MHz, CDCl3): d=
7.55–7.46 (m, 4H), 7.43–7.34 (m, 3H), 3.73 (s, 6H), 3.71 (s, 2H), 3.60 (s,
Received: June 8, 2004
Published online: September 20, 2004
5344
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Chem. Eur. J. 2004, 10, 5338 – 5344