Atom-economical synthesis of the functionalized spirocyclic oxindole-butenolide via three-component [2 + 2 + 1] cycloaddition strategy

Article abstract of DOI:10.1039/c2gc00015f

The intermolecular [2 + 2 + 1] multicomponent cycloadditions from readily available isocyanides, activated alkynes and isatins are disclosed. This reaction proceeds by way of a Michael addition-nucleophilic addition- intramolecular cyclization sequence, thus providing new access to spirocyclic oxindole-butenolide with exclusive stereoselectivity in an efficient and atom-economical manner. A broad range of isatins and isocyanides including sterically demanding ones are also found to be compatible with the present protocol, which offers an opportunity for the construction of a new compound library. This protocol also allows the insertion of carbon monoxide into organic molecules without the aid of transition metal catalyst after hydrolysis process. Moreover, the cycloaddition-hydrolysis process by step can be further developed into a practical and powerful one-pot strategy in good yields together with convenient experimental set-up, which adds to its attractiveness.

Full text of DOI:10.1039/c2gc00015f

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PAPER
Atom-economical synthesis of the functionalized spirocyclic
oxindole-butenolide via three-component [2 + 2 + 1] cycloaddition strategy†
Jian Li,*a Yuejin Liu,a Chunju Li,a Haohua Jiea and Xueshun Jia*a,b
Received 5th January 2012, Accepted 10th February 2012
DOI: 10.1039/c2gc00015f
The intermolecular [2 + 2 + 1] multicomponent cycloadditions from readily available isocyanides,
activated alkynes and isatins are disclosed. This reaction proceeds by way of a Michael addition–
nucleophilic addition–intramolecular cyclization sequence, thus providing new access to spirocyclic
oxindole-butenolide with exclusive stereoselectivity in an efficient and atom-economical manner. A broad
range of isatins and isocyanides including sterically demanding ones are also found to be compatible with
the present protocol, which offers an opportunity for the construction of a new compound library. This
protocol also allows the insertion of carbon monoxide into organic molecules without the aid of transition
metal catalyst after hydrolysis process. Moreover, the cycloaddition–hydrolysis process by step can be
further developed into a practical and powerful one-pot strategy in good yields together with convenient
experimental set-up, which adds to its attractiveness.
Introduction
Oxindoles are frequently found core structures in many natural
products and compounds of pharmaceutical significance.1 For
instance, medicines containing this key structure have been used
as the anti-Parkinson’s drug ropinirole and the growth hormone
secretagogues.2 Among the family of these compounds, spiro-
cyclic oxindoles are particularly important due to their unique
structural characteristics and biological activities. Many natural
products, such as alstonisine and horsfiline, have been interesting
synthetic targets to synthetic chemists (Scheme 1).3 As a result,
Scheme 1 Natural products possessing spiro-oxindole as core
structure.
much efforts have been devoted to their syntheses, thus provid-
ing considerable progress in this area.4 Among these methods,
those started from isatin seems to be the most straightforward
approach to this end.5 Recently, we have focused our attention
view of point, methods starting from isocyanides often have dis-
on the syntheses of carbocycles and potentially bioactive hetero-
tinct advantages, including enhanced convergence, inherent
cycles.6 As a continuation, herein we wish to report an efficient
atom economy, and the great variety of isocyanides readily avail-
able for use. In particular, the reactivity of isocyanide can be
electronically and sterically controlled by simply changing the
and atom-economical synthesis of spirocyclic oxindole–buteno-
lide derivatives by three-component [2 + 2 + 1] cycloaddition.
In the past few decades, isocyanides have proved themselves
substituent on nitrogen. On the other hand, the isocyanide chem-
to be irreplaceable one-carbon building blocks in modern
organic chemistry.7 For example, an isocyanide-based multicom-
ponent reaction has emerged as a powerful tool in the syntheses
of heterocycles and pharmaceutical molecules.8 From an organic
istry can serve as powerful carbonylation method, which enables
insertion of carbon monoxide into organic molecules in an
efficient manner. For instance, using isocyanide in Pauson–
Khand reaction (PKR) in place of CO and other transition-metal-
catalyzed insertions have also been investigated.9,10 Considering
the versatility of isocyanide chemistry, we are intended to
develop new carbonylation strategy based on multicomponent
reaction.
It is well known that conjugated alkynoates are among the
most reactive Michael acceptors, nucleophiles including tertiary
amines11 and phosphines12 have been used to trigger such
species in many multibond-forming processes. Prior to this
work, we have also shown that ethyl propiolate underwent a
aDepartment of Chemistry, Shanghai University, 99 Shangda Road,
Shanghai 200444, P. R. China. E-mail: lijian@shu.edu.cn, xsjia@mail.
shu.edu.cn; Fax: +86-21-66132408
bState Key Laboratory of Applied Organic Chemistry, Lanzhou
University, Lanzhou, 730000, P. R. China
†Electronic supplementary information (ESI) available: Copies of 1H
and 13C NMR spectra for compound 4, 5, 6. CCDC reference numbers
836563 (4o) and 836562 (5a). For ESI and crystallographic data in CIF
or other electronic format see DOI: 10.1039/c2gc00015f
1314 | Green Chem., 2012, 14, 1314–1321
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Table 1 Three-component [2 + 2 + 1] cycloaddition of isocyanide 1,
ethyl propiolate 2 and isatin 3ba
tandem conjugated addition process in the presence of o-phenyl-
enediamine to deliver a novel strategy for the construction of
functional 1,5-benzodiazepines.6a According to our assumption,
isocyanide could also serve as a nucleophile to trigger the
corresponding nucleophilic attack towards ethyl propiolate, thus
offering an opportunity for the development of novel three-
component [2 + 2 + 1] cycloaddition reactions. To our knowl-
edge, multicomponent reaction involving isocyanide and alkyl
propiolate has not been reported yet.
Entry
1
Product 4
Time (h)
18
Yieldb (%)
78
Results and discussion
To probe the feasibility of the proposed transformation, 1,1,3,3-
tetramethylbutyl isocyanide 1a, ethyl propiolate 2a, and isatin
3b were used as starting materials. Upon treatment of 2a with 1a
and 3b at 100 °C for 18 hours, a 78% yield of adduct 4a was
observed (Table 1, entry 1). Following this encouraging result,
we turned our attention to the scope and limitation of this
process. A variety of isocyanides 1 were examined under the
optimal conditions and the results were summarized in Table 1.
As shown in Table 1, the present reactions proceeded smoothly
in all cases and all compounds 4 were fully characterized by IR,
1H NMR, 13C NMR, and HRMS spectra.13 Traditionally,
aromatic isocyanide, especially sterically demanding aromatic
isocyanides are considered to be less reactive. Despite the pro-
longed reaction time and somewhat lower yields, these isocya-
nides were found to be compatible with this cycloaddition
protocol (Table 1, entries 3–7).
Having established the scope and limitations with structurally
diverse isocyanides, we sought to briefly investigate the feasi-
bility of substituted isatins 3. During our screening efforts,
various isatins 3 having electron-neutral (Table 2, entry 1), elec-
tron-deficient (Table 2, entries 2–5), and electron-rich substitu-
ents (Table 2, entries 6 and 7) on the aryl ring were used to test
the substitution pattern. Gratifyingly, all isatins performed well
with isocyanide 1a and ethyl propiolate 2a under the optimal
conditions. Moreover, the structure of compound 4o was un-
ambiguously confirmed by single crystal X-ray analysis
(Fig. 1).14 During our investigation, the influence of different
protecting group at the nitrogen of isatin 3 was also examined
(Table 2, entries 8–10). In such cases, the benzyl group turned
out to be another good choice. Furthermore, the protection of
the nitrogen atom of isatin 3 was quite necessary, otherwise the
reaction would become quite complex. With these encouraging
results, other substituted conjugated alkynoate 2b and 2c were
also tested under the optimal conditions. As shown in Table 2,
the blending of selected starting materials essentially led to the
formation of corresponding products 4 (Table 2, entries 11–13).
The mechanism of this three-component cycloaddition reac-
tion has not been unequivocally established, but one reasonable
possibility is proposed to account for the formation of spirocyc-
lic oxindole-butenolide 4 (Scheme 2). The nucleophilic addition
of isocyanide 1 towards conjugated alkynoate essentially leads to
the formation of zwitterionic species A, which is subsequently
captured by the reactive carbonyl group of isatin 3 to form B.
This intermediate experiences further intramolecular cyclization
to yield stable product 4.
4a
4b
2
3
18
48
89
39
4c
4
5
36
72
72
41
4d
4e
4f
6
7
48
24
44
65
4g
a All reactions were carried out with 0.5 mmol of isocyanide 1,
0.6 mmol ethyl propiolate 2, 0.5 mmol isatin 3b in 5 mL toluene and
heated at 100 °C in air. b Yields of product after silica gel
chromatography.
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Table 2 Three-component [2 + 2 + 1] cycloaddition of isocyanide 1a,
ethyl propiolate 2 and substituted isatin 3a
Entry
R2
R3
PGb
Yieldc (%)
1
2
3
4
H
H
H
H
H
H
H
H
H
H
Me
Me
Ph
H
Me
Me
Me
Me
Me
Me
Me
Bne
Bn
Bn
Ph
Me
Me
4h: 91
4a: 78
4i: 88
4j: 93
4k: 90
4l: 65
4m: 92
4n: 86
4o: 85
4p: 59
4q: 71
4r: 63
4s: 39
5-Fluoro
4,6-Dichloro
6-Bromo
5-Nitro
5-Methoxy
5,7-Dimethyl
H
4-Chloro
7-Bromo
H
5
6
7d
8
9
10
11d
12
13
5-Chloro
H
Scheme 3 One-pot syntheses of products 5.
a Reaction conditions: 0.5 mmol of 1,1,3,3-tetramethylbutyl isocyanide
1a, 0.6 mmol ethyl propiolate 2, 0.5 mmol substituted isatin 3, 5 mL
toluene, 100 °C, 18 hours in air. b PG = protecting groups. c Yields of
product after silica gel chromatography. d In such case, reaction was
completed within 72 hours. e Bn = benzyl.
With this highly efficient cycloaddition protocol in hand, we
attempted to hydrolyze the corresponding cycloaddition adducts
4. Treatment of compounds 4 under standard hydrolysis
conditions essentially gave products 5 in excellent yields. To
our delight, the cycloaddition and hydrolysis reactions could
be further developed into a one-pot strategy. As shown in
Scheme 3, the reaction mixture was allowed to react at 0 °C with
concentrated HCl in mixed solvent (EtOH and water) after the
[2 + 2 + 1] cycloaddition was finished, then the mixture was
elevated to room temperature until completion. By merging
cycloaddition–hydrolysis sequences, this one-pot reaction
achieved straightforward and efficient insertion of CO without
the aid of any metal catalyst. During this process, the structure of
5a also confirmed by X-ray analysis.15 Traditionally, carbonyla-
tion chemistry serves as one of the most straightforward method-
ologies for introducing carbonyl functionalities into organic
molecules.16 The cycloaddition involving isocyanide followed
by hydrolysis process enabled the introduction of carbon monox-
ide and quick access to spirocyclic oxindole–butenolide, which
offers new opportunity for their applications in organic
chemistry.
Fig. 1 Single-crystal X-ray structure of 4o.
To further demonstrate the utility of the present annulation
strategy, 1-phenylprop-2-yn-1-one 2d was also examined
(Scheme 4). Pleasingly, the above mentioned cycloaddition reac-
tion proceeded smoothly with 2d to give product 6 in good
yields. In such runs, all reactions could be finished within
12 hours. In particular, these results also advanced the possibility
of stereoselective synthesis of spirocycles with activated alky-
none 2.
Conclusions
In conclusion, we have described a novel three-component
[2 + 2 + 1] cycloaddition reaction to generate functionalized
spirocyclic oxindole-butenolides17 from simple and readily
Scheme 2 Proposed mechanism for the formation of 4.
1316 | Green Chem., 2012, 14, 1314–1321
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[silica: 200–300; eluant: petroleum ether–ethyl acetate] to afford
the desired product 4.
General procedure for the formation of 5
In a 10 mL round-bottomed flask, isatin 3 (0.5 mmol) was added
to a solution of isocyanide 1 (0.5 mmol) and alkynoate 2
(0.6 mmol) in 5 mL toluene. The stirred mixture was heated to
100 °C for several hours and the progress was monitored using
TLC. After completion the reaction mixture was concentrated
under vacuum. The mixture was then dissolved in a EtOH–H2O
(6 mL : 2 mL) solvent, which was then cooled to 0 °C. Hydro-
chloric acid (37%, 2 mmol) was subsequently added to this
cooled solution. The reaction mixture was stirred at 0 °C for
1 hour and then allowed to react at room temperature until the
complete conversion. The residue was poured into saturated
NaHCO3 (100 mL) and the product was extracted with EtOAc
(3 × 50 mL). The organic phase was dried over anhydrous
Na2SO4, filtered and the filtrate was evaporated in vacuo. The
residue was purified by column chromatography on silica gel to
afford the desired product 5.
Scheme 4 Three-component reaction with 1-phenylprop-2-yn-1-
one 2d.
available starting materials in an efficient and atom-economical
manner.18 This method is quite flexible with respect to the vari-
able two carbon units and the broad range of isocyanides as well
as isatins. This protocol can also serve as a powerful carbonyl-
ation method without the aid of transition metal. As a result,
the present strategy has potential to be applied in medicinal and
synthetic chemistry.
General procedure for the formation of 6
Experimental section
Isatin 3 (0.5 mmol) was added to a solution of isocyanide 1
(0.5 mmol) and 1-phenylprop-2-yn-1-one 2d (0.6 mmol) in
5 mL toluene. The stirred mixture was heated to 100 °C for
several hours and the progress was monitored using TLC detec-
tion. After completion the reaction mixture was concentrated
under vacuum. The residue was purified by column chromato-
graphy on silica gel to afford the desired product 6.
General experimental procedures
The NMR spectra were recorded on Bruker AC – 500 spec-
1
trometer (500 MHz for H NMR and 125 MHz for 13C NMR)
1
with CDCl3 as the solvent and TMS as an internal reference. H
NMR spectral data were reported as follows: chemical shift (δ,
ppm), multiplicity, integration, and coupling constant (Hz). 13C
NMR spectral data were reported in terms of the chemical shift.
When peak multiplicities are given, the following abbreviations
are used: s = singlet; d = doublet; t = triplet; q = quartet; m =
multiplet; dd = doublet of doublets; td = triplet of doublet, ddd =
doublet of doublet of doublets. IR spectra were taken as KBr
discs or liquid film with a Bruker vector 22 spectrometer. Low-
Characterization data for all compounds
(4a): White solid. m.p.: 79–81 °C. 1H NMR (500 MHZ, CDCl3):
δ (ppm) = 7.09 (td, 1H, J = 9.0, 2.5 Hz), 7.05 (s, 1H), 6.84
(dd, 1H, J = 7.0, 2.5 Hz), 6.82 (dd, 1H, J = 8.5, 4.0 Hz), 4.06
(qd, 2H, J = 7.0, 4.0 Hz), 3.25 (s, 3H), 1.68 (q, 2H, J = 2.5 Hz),
1.33 (s, 6H), 1.11 (t, 3H, J = 7.0 Hz), 0.97 (s, 9H). 13C NMR
(125 MHZ, CDCl3): δ (ppm) = 170.7, 160.5, 160.4, 158.4,
155.0, 143.7, 140.7, 136.0, 126.5, 126.4, 117.6, 112.4, 112.2,
109.6, 109.5, 88.2, 61.7, 59.0, 53.9, 32.0, 31.7, 30.5, 30.4, 29.7,
26.9, 13.8. IR (KBr) νmax = 3433, 2953, 1739, 1689, 1497,
805 cm−1. MS (ESI): m/z: 417 [M + H]+. HRMS: Calcd for
C23H30FN2O4 [M + H]+ 417.2184, Found 417.2201.
resolution mass spectra were obtained on
a Shimadzu
LCMS-2010EV spectrometer in ESI mode and reported as m/z.
High-resolution mass spectra (HRMS) were recorded on a
Bruker Daltonics, Inc. APEXIII 7.0 TESLA FTMS instrument.
Melting points were obtained on a X-4 digital melting point
apparatus without correction. Chemical yields referred to pure
isolated product. Purification of products was accomplished by
column chromatography packed with silica gel. Solvents were
reagent grade and purified by standard techniques: benzene,
toluene, and dichloromethane were distilled afresh from CaH2.
Unless otherwise stated, all reagents were commercially pur-
chased and used without further purification.
1
(4b): Light yellow solid. m.p.: 142–143 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 7.09 (td, 1H, J = 8.5, 2.5 Hz), 7.04
(s, 1H), 6.84 (dd, 1H, J = 7.2, 2.5 Hz), 6.82 (dd, 1H, J = 9.0, 4.0
Hz), 4.05 (qd, 2H, J = 7.0, 3.5 Hz), 3.25 (s, 3H), 1.28 (s, 9H),
1.11 (t, 3H, J = 7.0 Hz). 13C NMR (125 MHZ, CDCl3): δ (ppm)
= 170.6, 160.5, 160.4, 158.5, 156.3, 143.8, 140.7, 140.6, 135.9,
126.3, 117.6, 117.4, 112.3, 112.1, 109.6, 109.5, 88.3, 88.2, 61.7,
55.2, 29.6, 26.9, 13.8. IR (KBr) νmax = 3436, 2968, 1745, 1497,
1240, 1099 cm−1. MS (ESI): m/z: 361 [M + H]+. HRMS: Calcd
for C19H22FN2O4 [M + H]+ 361.1558, Found 361.1572.
General procedure for the formation of 4
Isatin 3 (0.5 mmol) was added to a solution of isocyanide 1
(0.5 mmol) and alkynoate 2 (0.6 mmol) in 5 mL toluene. The
stirred mixture was heated to 100 °C for several hours and the
progress was monitored using TLC detection. After completion
the reaction mixture was concentrated under vacuum. The
residue was purified by column chromatography on silica gel
1
(4c): Yellow solid. m.p.: 192–193 °C. H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.35 (s, 1H), 7.06 (td, 1H, J = 9.0, 2.5 Hz),
6.98 (d, 2H, J = 7.5 Hz), 6.89 (t, 1H, J = 7.5 Hz), 6.84 (dd, 1H,
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J = 7.5, 2.5 Hz), 6.75 (dd, 1H, J = 9.0, 3.5 Hz), 4.13 (qd, 2H, J
= 7.0, 4.0 Hz), 3.18 (s, 3H), 2.16 (s, 6H), 1.17 (t, 3H, J = 7.0
Hz). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 170.0, 160.4,
160.1, 158.4, 157.9, 146.4, 144.2, 141.0, 140.9, 133.2, 127.6,
125.5, 123.9, 118.0, 117.8, 112.5, 112.3, 109.7, 109.6, 88.2,
62.1, 31.0, 29.8, 27.0, 18.2, 13.9. IR (KBr) νmax = 3429, 2923,
1741, 1692, 1497, 1014 cm−1. MS (ESI): m/z: 409 [M + H]+,
431 [M + Na]+. HRMS: Calcd for C23H22FN2O4 [M + H]+
409.1558, Found 409.1557.
144.0, 135.8, 131.2, 124.9, 124.0, 123.2, 108.8, 88.3, 61.4,
58.8, 53.7, 31.9, 31.6, 30.4, 30.3, 26.7, 13.7. IR (KBr) νmax
=
3435, 2952, 1738, 1243 cm−1. MS (ESI): m/z: 399 [M + H]+.
HRMS: Calcd for C23H31N2O4 [M + H]+ 399.2278, Found
399.2278.
(4i): Light yellow solid. m.p.: 132–133 °C. IR (film) νmax
=
3432, 2952, 1749, 1607, 1011 cm−1 1H NMR (500 MHZ,
.
CDCl3): δ (ppm) = 7.06 (s, 1H), 6.99 (d, 1H, J = 1.5 Hz), 6.79
(d, 1H, J = 1.5 Hz), 4.09 (qd, 2H, J = 7.0, 3.5 Hz), 3.23 (s, 3H),
1.78 (d, 1H, J = 14.5 Hz), 1.56 (d, 1H, J = 14.5 Hz), 1.35 (s,
3H), 1.31 (s, 3H), 1.16 (t, 3H, J = 7.0 Hz), 0.98 (s, 9H). 13C
NMR (125 MHZ, CDCl3): δ (ppm) = 170.5, 160.6, 154.8,
147.1, 141.9, 137.8, 137.1, 132.7, 123.8, 120.0, 108.2, 87.6,
61.7, 59.1, 54.4, 32.0, 31.7, 30.3, 30.0, 27.1, 13.9. MS (ESI):
m/z: 467 [M + H]+. HRMS: Calcd for C22H29Cl2N2O4 [M + H]+
467.1499, Found 467.1514.
1
(4d): Light yellow solid. m.p.: 183–185 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 7.35 (s, 1H), 7.17 (d, 1H, J = 8.0 Hz),
7.08–7.03 (m, 2H), 6.92–6.87 (m, 2H), 6.73 (dd, 1H, J = 8.5,
4.0 Hz), 4.14 (qd, 2H, J = 7.0, 3.5 Hz), 3.17 (s, 3H), 2.21
(s, 3H), 1.17 (t, 3H, J = 7.0 Hz). 13C NMR (125 MHZ, CDCl3):
δ (ppm) = 169.6, 160.4, 159.9, 159.4, 158.4, 147.1, 142.7,
140.8, 132.9, 130.5, 128.5, 126.9, 125.1, 124.6, 118.1, 117.9,
112.8, 112.6, 109.7, 109.6, 88.6, 62.1, 29.8, 27.0, 18.5, 13.9. IR
(KBr) νmax = 2924, 1741, 1694, 1017 cm−1. MS (ESI): m/z: 429
[M + H]+, 451 [M + Na]+. HRMS: Calcd for C22H19ClFN2O4
[M + H]+ 429.1012, Found 429.1013.
(4j): White solid. m.p.: 154–156 °C. 1H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.19 (dd, 1H, J = 7.5, 1.5 Hz), 7.04 (d, 1H,
J = 1.5 Hz), 7.02 (s, 1H), 6.95 (d, 1H, J = 8.0 Hz), 4.06 (qd, 2H,
J = 7.0, 3.5 Hz), 3.24 (s, 3H), 1.67 (s, 2H), 1.32 (s, 6H), 1.12
(t, 3H, J = 7.5 Hz), 0.96 (s, 9H). 13C NMR (125 MHZ, CDCl3):
δ (ppm) = 171.2, 160.4, 154.1, 150.1, 143.8, 143.1, 136.2,
128.1, 126.0, 119.9, 108.6, 87.0, 61.9, 59.1, 54.0, 31.9, 31.6,
30.4, 30.3, 27.2, 13.8. IR (KBr) νmax = 3433, 1744, 1608,
1002 cm−1. MS (ESI): m/z: 477 [M + H]+. HRMS: Calcd for
C23H30BrN2O4 [M + H]+ 477.1384, Found 477.1390.
1
(4e): Yellow solid. m.p.: 148–150 °C. H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.33 (s, 1H), 7.31 (s, 1H), 7.08 (td, 1H, J =
8.5, 2.5 Hz), 6.91 (dd, 1H, J = 8.5, 2.5 Hz), 6.80 (dd, 1H, J =
8.5, 4.0 Hz), 6.46 (d, 1H, J = 3.0 Hz), 6.36 (dd, 1H, J = 9.0, 2.5
Hz), 4.10 (qd, 2H, J = 7.5, 4.0 Hz), 3.84 (s, 3H), 3.75 (s, 3H),
3.24 (s, 3H), 1.14 (t, 3H, J = 7.0 Hz). 13C NMR (125 MHZ,
CDCl3): δ (ppm) = 170.2, 160.3, 160.2, 158.5, 158.3, 157.8,
153.9, 144.3, 140.7, 140.6, 135.0, 127.3, 125.8, 125.7, 124.4,
117.7, 117.5, 112.7, 112.5, 109.5, 109.4, 103.8, 99.0, 88.5, 61.8,
55.8, 55.4, 26.9, 13.8. IR (KBr) νmax = 3434, 1736, 1498, 1271,
1021 cm−1. MS (ESI): m/z: 441 [M + H]+, 463 [M + Na]+.
HRMS: Calcd for C23H21FN2O6Na [M + Na]+ 463.1276, Found
463.1295.
1
(4k): Light yellow solid. m.p.: 143–145 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 8.38 (dd, 1H, J = 8.5, 2.5 Hz), 8.00
(d, 1H, J = 2.5 Hz), 7.08 (s, 1H), 7.00 (d, 1H, J = 8.5 Hz),4.10
(qd, 2H, J = 7.0, 3.5 Hz), 3.35 (s, 3H), 1.67 (q, 2H, J = 14.5
Hz), 1.35 (s, 3H), 1.34 (s, 3H), 1.17 (t, 3H, J = 7.5 Hz), 0.99
(s, 9H). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 171.2, 160.4,
154.1, 150.1, 143.8, 143.1, 136.2, 128.1, 126.0, 119.9, 108.6,
87.0, 61.9, 59.1, 54.0, 31.9, 31.6, 30.4, 30.3, 27.2, 13.8. IR
(KBr) νmax = 3430, 2924, 1752, 1617 cm−1. MS (ESI): m/z: 444
[M + H]+, 466 [M + Na]+. HRMS: Calcd for C23H30N3O6
[M + H]+ 444.2129, Found 444.2141.
(4f): Brown solid. m.p.: 66–68 °C. 1H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.24–7.19 (m, 5H), 7.12 (td, 1H, J = 9.0, 2.5
Hz), 6.91 (dd, 1H, J = 7.0, 2.5 Hz), 6.83 (dd, 1H, J = 8.5, 3.5
Hz), 4.11 (qd, 2H, J = 7.0, 3.5 Hz), 3.26 (s, 3H), 1.16 (t, 3H, J =
7.0 Hz). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 169.9, 160.4,
160.0, 158.7, 158.5, 145.7, 143.3, 134.6, 130.9, 128.9, 125.4,
118.2, 118.0, 112.8, 112.6, 109.9, 109.8, 89.0, 62.1, 27.1, 13.9.
(4l): Light yellow solid. m.p.: 128–130 °C. 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.02 (s, 1H), 6.88 (dd, 1H, J = 8.5,
2.5 Hz), 6.78 (d, 1H, J = 8.5 Hz), 6.68 (d, 1H, J = 2.5 Hz), 4.04
(qd, 2H, J = 7.0, 3.5 Hz), 3.73 (s, 3H), 3.22 (s, 3H), 1.68 (q, 2H,
J = 12.5 Hz), 1.33 (s, 3H), 1.32 (s, 3H), 1.09 (t, 3H, J = 7.0 Hz),
0.97 (s, 9H). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 170.6,
160.5, 156.3, 155.5, 144.1, 137.9, 135.8, 126.0, 115.5, 111.1,
109.3, 88.6, 61.5, 58.8, 55.8, 53.7, 31.9, 31.7, 30.5, 30.4, 26.8,
13.8. IR (KBr) νmax = 3445, 2952, 1732, 1030 cm−1. MS (ESI):
m/z: 451 [M + Na]+. HRMS: Calcd for C24H32N2O5Na
[M + Na]+ 451.2209, Found 451.2231.
IR (KBr) νmax = 3437, 1736, 1679, 1271, 1097, 1010 cm−1
.
MS (ESI): m/z: 437 [M
+
Na]+. HRMS: Calcd for
C21H16ClFN2O4Na [M + Na]+ 437.0675, Found 437.0692.
1
(4g): Light yellow solid. m.p.: 138–140 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 7.39–7.37 (m, 2H), 7.23 (s, 1H),
7.15–7.09 (m, 3H), 6.91 (dd, 1H, J = 7.5, 2.5 Hz), 6.84 (dd, 1H,
J = 8.5, 4.0 Hz), 4.14 (qd, 2H, J = 7.0, 2.5 Hz), 3.26 (s, 3H),
1.16 (t, 3H, J = 7.0 Hz). 13C NMR (125 MHZ, CDCl3): δ (ppm)
= 169.9, 160.0, 158.8, 145.8, 143.8, 140.7, 134.6, 131.9, 131.8,
125.7, 125.5, 118.8, 118.2, 118.0, 112.8, 112.6, 109.9, 109.8,
89.0, 62.1, 27.1, 13.9. IR (KBr) νmax = 2925, 1736, 1271,
1007 cm−1. MS (ESI): m/z: 481 [M + Na]+. HRMS: Calcd for
C21H16BrFN2O4Na [M + Na]+ 481.0170, Found 481.0192.
(4m): Light yellow solid. m.p.: 91–93 °C. 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.01 (s, 1H), 6.91 (s, 1H), 6.72
(s, 1H), 4.06 (qd, 2H, J = 7.0, 3.5 Hz), 3.5 (s, 3H), 2.54 (s, 3H),
2.23 (s, 3H), 1.69 (q, 2H, J = 10.5 Hz), 1.34 (s, 3H), 1.33
(s, 3H), 1.13 (t, 3H, J = 7.0 Hz), 0.98 (s, 9H). 13C NMR (125
MHZ, CDCl3): δ (ppm) = 171.1, 160.7, 155.7, 144.4, 139.8,
135.6, 135.4, 132.7, 125.5, 122.7, 120.2, 88.3, 61.5, 58.8, 53.7,
1
(4h): Light yellow solid. m.p.: 104–105 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 7.39 (td, 1H, J = 7.5, 1.5 Hz),
7.11–7.04 (m, 3H), 6.89 (d, 1H, J = 7.5 Hz), 4.04 (qd, 2H, J =
7.0, 3.5 Hz), 3.26 (s, 3H), 1.68 (q, 2H, J = 5.0 Hz), 1.34 (s, 3H),
1.33 (s, 3H), 1.08 (t, 3H, J = 7.5 Hz), 0.98 (s, 9H). 13C NMR
(125 MHZ, CDCl3): δ (ppm) = 170.8, 160.5, 155.4, 144.6,
32.0, 31.7, 30.5, 30.4, 30.2, 20.7, 18.9, 13.9. IR (KBr) νmax
=
3436, 2925, 1731, 1095 cm−1. MS (ESI): m/z: 427 [M + H]+,
449 [M + Na]+. HRMS: Calcd for C25H35N2O4 [M + H]+
427.2591, Found 427.2596.
1318 | Green Chem., 2012, 14, 1314–1321
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1
(4n): Light yellow solid. m.p.: 85–87 °C. 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.40 (d, 2H, J = 7.5 Hz), 7.33 (t, 2H,
J = 7.5 Hz), 7.26 (q, 2H, J = 8.5 Hz), 7.11 (d, 1H, J = 6.5 Hz),
7.09 (s, 1H), 7.02 (t, 1H, J = 7.5 Hz), 6.76 (d, 1H, J = 8.0 Hz),
5.06 (d, 1H, J = 15.5 Hz), 4.83 (d, 1H, J = 16.0 Hz), 4.11
(qd, 1H, J = 11.0, 7.0 Hz), 3.95 (qd, 1H, J = 11.0, 7.0 Hz), 1.72
(q, 2H, J = 6.5 Hz), 1.37 (s, 3H), 1.36 (s, 3H), 1.01–0.99 (m,
12H). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 171.2, 160.7,
155.5, 144.1, 143.9, 136.2, 135.3, 131.2, 128.9, 127.9, 127.5,
125.1, 124.2, 123.3, 110.0, 88.5, 61.6, 58.9, 53.7, 44.6, 32.0,
31.7, 30.6, 30.5, 13.8. IR (KBr) νmax = 3437, 2952, 1726,
1614 cm−1. MS (ESI): m/z: 475 [M + H]+, 497 [M + Na]+.
HRMS: Calcd for C29H35N2O4 [M + H]+ 475.2591, Found
475.2609.
(4s): Viscous oil. H NMR (500 MHZ, CDCl3): δ (ppm) =
7.58 (dd, 2H, J = 7.0, 1.5 Hz), 7.41–7.37 (m, 4H), 7.18 (d, 1H,
J = 7. 0 Hz), 7.07 (t, 1H, J = 7.5 Hz), 6.90 (d, 1H, J = 7.5 Hz),
3.94 (qd, 1H, J = 11.0, 7.0 Hz), 3.85 (qd, 1H, J = 11.0, 7.0 Hz),
3.29 (s, 3H), 1.67 (t, 1H, J = 7.5 Hz), 1.60 (t, 1H, J = 7.5 Hz),
1.32 (s, 3H), 1.30 (s, 3H),0.94 (s, 9H), 0.86 (t, 3H, J = 7.0 Hz).
13C NMR (125 MHZ, CDCl3): δ (ppm) = 171.9, 161.4, 154.5,
146.3, 144.9, 136.4, 131.1, 130.7, 130.6, 130.1, 129.9, 129.4,
128.7, 127.2, 125.9, 124.1, 123.2, 108.7, 86.7, 61.0, 58.7, 54.7,
32.0, 31.8, 31.6, 30.1, 30.0, 29.8, 26.8, 13.5. IR (film) νmax
=
3445, 2952, 1737, 1613, 1014 cm−1. HRMS: Calcd for
C29H35N2O4 [M + H]+ 475.2597, Found 475.2580.
(5a): White solid. m.p.: 149–150 °C. 1H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.40 (td, 1H, J = 7.5, 1.5 Hz), 7.08–7.03
(m, 2H), 6.93 (s, 1H), 6.90 (d, 1H, J = 8.0 Hz), 4.07 (qd, 2H,
J = 7.0, 3.5 Hz), 3.24 (s, 3H), 1.08 (t, 3H, J = 7.0 Hz). 13C
NMR (125 MHZ, CDCl3): δ (ppm) = 169.8, 168.9, 159.4,
153.9, 144.9, 132.0, 128.0, 124.3, 123.5, 122.2, 109.3, 85.5,
1
(4o): Light yellow solid. m.p.: 103–104 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 7.38–7.32 (m, 4H), 7.28 (d, 1H, J =
7.5 Hz), 7.18 (t, 1H, J = 8.0 Hz), 7.13 (s, 1H), 6.93 (d, 1H, J =
8.0 Hz), 6.64 (d, 1H, J = 8.0 Hz), 5.03 (d, 1H, J = 16.0 Hz),
4.83 (d, 1H, J = 16.0 Hz), 4.15 (qd, 1H, J = 11.0, 7.0 Hz), 3.99
(qd, 1H, J = 11.0, 7.0 Hz), 1.86 (d, 1H, J = 14.5 Hz), 1.60
(d, 1H, J = 14.5 Hz), 1.40 (s, 3H), 1.36 (s, 3H), 1.05 (t, 3H, J =
7.0 Hz), 1.02 (s, 9H). 13C NMR (125 MHZ, CDCl3): δ (ppm) =
170.7, 160.6, 155.2, 145.5, 142.3, 137.2, 134.8, 132.2, 132.1,
127.9, 127.4, 124.2, 121.7, 108.2, 88.2, 61.5, 59.0, 54.2, 44.6,
31.9, 31.7, 30.5, 30.0, 13.8. IR (KBr) νmax = 2924, 1739, 1606,
1220 cm−1. MS (ESI): m/z: 509 [M + H]+. HRMS: Calcd for
C29H34ClN2O4 [M + H]+ 509.2202, Found 509.2201.
62.4, 27.0, 13.7. IR (KBr) νmax = 3447, 1487, 1734, 1009 cm−1
MS (ESI): m/z: 310 [M
Na]+. HRMS: Calcd for
C15H13NO5Na [M + Na]+ 310.0686, Found 310.0696.
.
+
(5b): Light yellow solid. m.p.: 188–189 °C. 1H NMR
(500 MHZ, CDCl3): δ (ppm) = 7.56 (dd, 1H, J = 8.0, 2.0 Hz),
7.22 (d, 1H, J = 2.0 Hz), 6.96 (s, 1H), 6.82 (d, 1H, J = 8.5 Hz),
4.15 (qd, 2H, J = 11.0, 7.0 Hz), 3.27 (s, 3H), 1.18 (t, 3H, J = 7.5
Hz). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 169.4, 168.5,
159.4, 153.5, 144.0, 134.8, 128.2, 127.6, 124.2, 116.0, 110.8,
84.9, 62.7, 27.2, 13.8. IR (KBr) νmax = 3439, 2923, 1783, 1729,
1218 cm−1. MS (ESI): m/z: 388 [M + Na]+. HRMS: Calcd for
C15H12BrNO5Na [M + Na]+ 387.9797, Found 387.9815.
1
(4p): Light yellow solid. m.p.: 120–121 °C. H NMR (500
MHZ, CDCl3): δ (ppm) = 7.43 (dd, 1H, J = 8.0, 1.0 Hz),
7.35–7.23 (m, 5H), 7.09 (s, 1H), 7.06 (dd, 1H, J = 7.5, 1.0 Hz),
6.91 (t, 1H, J = 8.0 Hz), 5.42 (q, 2H, J = 2.0 Hz), 4.15 (qd, 1H,
J = 11.0, 7.0 Hz), 4.04 (qd, 1H, J = 11.0, 7.0 Hz), 1.75 (d, 1H,
J = 14.5 Hz), 1.68 (d, 1H, J = 14.5 Hz), 1.36 (s, 3H), 1.35
(s, 3H), 1.11 (t, 3H, J = 7.0 Hz), 0.99 (s, 9H). 13C NMR (125
MHZ, CDCl3): δ (ppm) = 172.0, 160.5, 154.9, 143.6, 141.5,
137.0, 136.8, 136.3, 128.6, 128.2, 127.2, 126.5, 124.6, 123.3,
103.2, 87.4, 61.7, 59.0, 53.7, 45.3, 31.9, 31.7, 30.5, 30.4, 13.8.
IR (KBr) νmax = 2952, 1742, 1451, 1020 cm−1. MS (ESI): m/z:
553 [M + H]+. HRMS: Calcd for C29H34BrN2O4 [M + H]+
553.1697, Found 553.1723.
(5c): Light yellow solid. m.p.: 174–175 °C. 1H NMR
(500 MHZ, CDCl3): δ (ppm) = 8.40 (d, 1H, J = 8.5 Hz), 8.00
(d, 1H, J = 2.0 Hz), 7.05 (d, 1H, J = 8.5 Hz), 7.01 (s, 1H), 4.16
(qd, 2H, J = 11.0, 7.0 Hz), 3.36 (s, 3H), 1.21 (t, 3H, J = 7.0 Hz).
13C NMR (125 MHZ, CDCl3): δ (ppm) = 169.2, 169.0, 159.4,
152.9, 150.4, 143.9, 128.8, 128.4, 123.4, 120.4, 109.1, 84.0,
62.9, 27.6, 13.8. IR (KBr) νmax = 3458, 1796, 1740, 1618,
1335 cm−1. MS (ESI): m/z: 355 [M + Na]+. HRMS: Calcd for
C15H12N2O7Na [M + Na]+ 355.0537, Found 355.0553.
(5d): Light yellow solid. m.p.: 78–80 °C. 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.34–7.26 (m, 6H), 7.10 (dd, 1H, J =
7.5, 1.0 Hz), 7.05–0.99 (m, 2H), 6.79 (d, 1H, J = 8.0 Hz), 5.02
(d, 1H, J = 16.0 Hz), 4.87 (d, 1H, J = 16.0 Hz), 4.17 (qd, 1H,
J = 11.0, 7.0 Hz), 4.02 (qd, 1H, J = 11.0, 7.0 Hz), 1.04 (t, 3H,
J = 7.0 Hz). 13C NMR (125 MHZ, CDCl3): δ (ppm) = 169.8,
169.1, 159.4, 153.9, 144.1, 134.7, 131.9, 128.9, 128.2, 128.0,
127.4, 124.4, 123.6, 122.3, 110.4, 85.5, 62.4, 44.7, 13.7. IR
(film) νmax = 2925, 1783, 1733, 1613 cm−1. MS (ESI): m/z: 364
[M + H]+, 386 [M + Na]+. HRMS: Calcd for C21H17NO5Na
[M + Na]+ 386.0999, Found 386.1015.
(4q): Light yellow solid. m.p.: 165–166 °C.6d 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.55–7.42 (m, 5H), 7.28 (t, 1H, J =
7.5 Hz), 7.12–7.05 (m, 2H), 6.88 (d, 1H, J = 8.0 Hz), 4.14 (qd,
1H, J = 11.0, 7.5 Hz), 4.03 (qd, 1H, J = 11.0, 7.5 Hz), 2.32
(s, 3H), 1.66 (q, 2H, J = 4.5 Hz), 1.35 (s, 3H), 1.33 (s, 3H), 1.06
(t, 3H, J = 7.0 Hz), 1.00 (s, 9H). 13C NMR (125 MHZ, CDCl3):
δ (ppm) = 171.4, 162.0, 156.0, 147.2, 144.9, 135.5, 134.3,
130.7, 129.8, 128.3, 126.4, 125.9, 124.3, 123.5, 110.0, 86.8,
61.1, 58.3, 54.9, 32.1, 31.8, 30.2, 30.1, 14.0, 12.4. IR (KBr)
νmax = 3445, 2952, 1745, 1501, 1022 cm−1
.
(4r): Light yellow solid. m.p.: 137–139 °C.6d 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.34 (dd, 1H, J = 8.5, 2.0 Hz), 7.02
(d, 1H, J = 2.0 Hz), 6.80 (d, 1H, J = 8.0 Hz), 4.04 (qd, 2H, J =
11.0, 7.0 Hz), 3.25 (s, 3H), 2.30 (s, 3H), 1.56 (s, 2H), 1.32
(s, 3H), 1.30 (s, 3H), 1.07 (t, 3H, J = 7.0 Hz), 0.99 (s, 9H). 13C
NMR (125 MHZ, CDCl3): δ (ppm) = 171.7, 161.8, 155.4,
147.5, 143.5, 134.8, 130.7, 128.5, 127.8, 124.4, 109.6, 86.3,
61.1, 58.3, 55.1, 32.1, 31.8, 30.1, 30.0, 26.9, 13.9, 12.4. IR
(5e): Light yellow solid. m.p.: 145–146 °C.6d 1H NMR (500
MHZ, CDCl3): δ (ppm) = 7.55 (t, 2H, J = 8.5 Hz), 7.44 (t, 3H,
J = 7.5 Hz), 7.35–7.07 (m, 3H), 6.88 (d, 1H, J = 8.0 Hz),
4.22 (qd, 1H, J = 11.0, 7.0 Hz), 4.11 (qd, 1H, J = 11.0, 7.0 Hz),
2.39 (s, 3H), 1.11 (t, 3H, J = 7.0 Hz). 13C NMR (125 MHZ,
CDCl3): δ (ppm) = 172.1, 169.1, 160.8, 145.3, 144.4, 139.7,
131.6, 129.9, 128.7, 126.4, 124.6, 123.8, 122.8, 110.5, 84.5,
62.0, 14.0, 11.5. IR (KBr) νmax = 3439, 1779, 1738, 1614,
(KBr) νmax = 2956, 1743, 1612, 1487, 1328, 1230, 1054 cm−1
.
1024 cm−1
.
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1
Synth. Catal., 2010, 352, 1381; (c) T. Y. Zhang and H. Zhang, Tetrahe-
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(5f): Viscous oil. H NMR (500 MHZ, CDCl3): δ (ppm) =
6.92 (dd, 1H, J = 8.5, 2.5 Hz), 6.81 (d, 1H, J = 8.5 Hz), 6.65
(d, 1H, J = 2.5 Hz), 4.08 (qd, 2H, J = 11.0, 7.5 Hz), 3.70
(s, 3H), 3.25 (s, 3H), 2.37 (s, 3H), 1.09 (t, 3H, J = 7.0 Hz). 13C
NMR (125 MHZ, CDCl3): δ (ppm) = 172.1, 169.5, 160.7,
156.5, 144.2, 139.8, 138.4, 124.2, 116.2, 111.3, 109.6, 84.7,
61.8, 56.0, 27.1, 13.8, 11.5. IR (film) νmax = 2927, 1716, 1498,
1234, 1021, 804 cm−1. MS (ESI): m/z: 354 [M + Na]+. HRMS:
Calcd for C17H17NO6Na [M + Na]+ 354.0954, Found 354.0971.
2 (a) G. Gallagher, P. G. Lavanchy, J. W. Wilson, J. Hieble and
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1
(6a): Brown solid. m.p.: 108–110 °C. H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.75 (d, 2H, J = 7.5 Hz), 7.57(t, 1H, J = 7.5
Hz), 7.43 (t, 2H, J = 7.5 Hz), 7.37 (t, 1H, J = 7.5 Hz), 7.15
(d, 1H, J = 7.0 Hz), 7.02 (t, 1H, J = 7.5 Hz), 6.91 (d, 1H, J =
7.5 Hz), 6.88 (s, 1H), 3.33 (s, 3H), 1.77 (s, 2 Hz), 1.38 (s, 3H),
1.37 (s, 3H), 1.00 (s, 9H). 13C NMR (125 MHZ, CDCl3): δ
(ppm) = 188.6, 171.2, 156.3, 149.1, 145.0, 136.6, 136.1, 133.7,
131.3, 129.4, 129.0, 128.8, 128.5, 124.7, 123.8, 123.2, 109.1,
89.6, 59.1, 53.9, 32.0, 31.8, 30.5, 30.3, 29.8, 27.0. IR (KBr)
νmax = 3547, 2962, 1727, 1612, 1247, 1000 cm−1. HRMS:
Calcd for C27H31N2O3 [M + H]+ 431.2335, Found 431.2323.
(6b): Light yellow solid. m.p.: 163–165 °C. 1H NMR
(500 MHZ, CDCl3): δ (ppm) = 7.75 (t, 2H, J = 7.5 Hz), 7.59
(t, 1H, J = 7.5 Hz), 7.51–7.44 (m, 3H), 7.34 (d, 1H, J = 1.5 Hz),
6.91 (s, 1H), 6.80 (d, 1H, J = 8.0 Hz), 3.31 (s, 3H), 1.72 (q, 2H,
J = 9.0 Hz), 1.37 (s, 6H), 1.00 (s, 9H). 13C NMR (125 MHZ,
CDCl3): δ (ppm) = 188.5, 170.7, 155.7, 148.7, 144.1, 136.6,
136.5, 134.1, 133.9, 129.0, 128.9, 127.0, 126.8, 115.6, 110.6,
89.0, 59.3, 54.1, 32.0, 31.7, 30.5, 30.3, 29.8, 27.1. IR (KBr)
νmax = 3445, 2951, 1742, 1103 cm−1. HRMS: Calcd for
C27H30BrN2O3 [M + H]+ 509.1440, Found 509.1437.
1
(6c): Yellow solid. m.p.: 143–145 °C. H NMR (500 MHZ,
CDCl3): δ (ppm) = 7.83 (d, 2H, J = 8.0 Hz), 7.60 (t, 1H, J = 7.0
Hz), 7.49–7.31(m, 7H), 6.97 (s, 1H), 6.93 (d, 1H, J = 1.0 Hz),
6.63 (d, 1H, J = 1.0 Hz), 5.89 (d, 1H, J = 16.0 Hz), 4.92 (d, 1H,
J = 16.0 Hz), 1.89 (d, 1H, J = 14.5 Hz), 1.64 (d, 1H, J = 14.5
Hz), 1.45 (s, 3H), 1.41(s, 3H), 1.03 (s, 9 Hz). 13C NMR (125
MHZ, CDCl3): δ (ppm) = 188.8, 170.9, 155.7, 147.7, 146.6,
137.7, 137.4, 136.4, 134.4, 133.8, 132.6, 129.2, 129.1, 128.8,
128.1, 127.4, 127.3, 123.7, 119.9, 109.5, 88.8, 59.3, 54.3, 44.9,
32.0, 31.7, 30.6, 29.9, 29.8. IR (KBr) νmax = 3459, 1749, 1607,
1338, 1217, 711 cm−1. HRMS: Calcd for C33H33Cl2N2O3
[M + H]+ 575.1868, Found 575.1852.
Acknowledgements
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(b) N. Chatani, M. Oshita, M. Tobisu, Y. Ishii and S. Murai, J. Am.
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11 For tertiary amine-triggered conjugated additions, see: (a) D. Tejedor,
F. García-Tellado, J. J. Marrero-Tellado and P. de Armas, Chem.–Eur. J.,
2003, 9, 3122; (b) D. Tejedor, S. López-Toso, J. González-Platas and
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F. García-Tellado, J. J. Marrero-Tellado, D. Tejedor, M. A. Maestro and
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We thank the National Natural Science Foundation of China
(21002061, 21142012, 20902057), the State Key Laboratory of
Applied Organic Chemistry, Lanzhou University and the
Leading Academic Discipline Project of Shanghai Municipal
Education Commission (no. J50101) for financial support. We
also thank Dr Hongmei Deng and Min Shao of Laboratory for
Microstructures, Shanghai University for the NMR and single
crystal X-ray analyses.
12 (a) X. Lu, C. Zhang and Z. Xu, Acc. Chem. Res., 2001, 34, 535;
(b) L. W. Ye, J. Zhou and Y. Tang, Chem. Soc. Rev., 2008, 37, 1140;
(c) V. Nair, R. S. Menon, A. R. Sreekanth, N. Abhilash and A. T. Biji,
Acc. Chem. Res., 2006, 39, 520.
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1320 | Green Chem., 2012, 14, 1314–1321
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