Cs2CO3-promoted carboxylation of N-tosylhydrazones with carbon dioxide toward α-arylacrylic acids

Article abstract of DOI:10.1021/jo502908v

A Cs₂CO₃-promoted carboxylation of N-tosylhydrazones and CO₂ has been developed. The reaction proceeded efficiently at 80 C under atmospheric CO₂, gave the corresponding α-arylacrylic acids in moderate to good yields. This method was featured with (1) the employment of Cs₂CO₃ rather than ⁿBuLi as the base; (2) a reaction temperature of 80 C rather than -78 C.

Full text of DOI:10.1021/jo502908v

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Note
Cs2CO3-Promoted Carboxylation of N-Tosylhydrazones
with Carbon Dioxide towards #-Arylacrylic Acids
Song Sun, Jin-Tao Yu, Yan Jiang, and Jiang Cheng
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/jo502908v • Publication Date (Web): 19 Feb 2015
Downloaded from http://pubs.acs.org on February 22, 2015
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Page 1 of 17
The Journal of Organic Chemistry
Cs2CO3-Promoted Carboxylation of N-
Tosylhydrazones with Carbon Dioxide towards α-
Arylacrylic Acids
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Song Sun,† JinꢀTao Yu,† Yan Jiang,† and Jiang Cheng*, †,‡
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†
School of Petrochemical Engineering, Jiangsu Key Laboratory of Advanced Catalytic Materials and
Technology, Jiangsu Province Key Laboratory of Fine Petrochemical Engineering, Changzhou Univerꢀ
sity, Changzhou 213164, P. R. China.
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‡ State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing, 210093, P. R. China
Email: jiangcheng@cczu.edu.cn
RECEIVED DATE (to be automatically inserted after your manuscript is accepted if required
according to the journal that you are submitting your paper to)
ABSTRACT
A Cs2CO3ꢀpromoted carboxylation of Nꢀtosylhydrazones and CO2 has been developed. The reaction
o
proceeded efficiently at 80 C under atmospheric CO2, gave the corresponding αꢀarylacrylic acids in
moderate to good yields. This method was featured with: 1) the employment of Cs2CO3 rather than nBuꢀ
Li as the base; 2) a reaction temperature of 80 oC rather than ꢀ78 oC.
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αꢀArylacrylic acids and their derivatives are important substructure motifs that widely exist in bioꢀ
logically active natural products and medicines (Figure 1). Moreover, they serve as key intermediates
leading to a series of antiꢀinflammatory agents, such as naprosyn, pirprofen and fenoprofen.1ꢀ2 Therefore,
except for the elegant oneꢀstep Pdꢀcatalyzed carbonylation reaction of alkynes with CO towards α, βꢀ
unsaturated carboxylic acids,3 considerable efforts have been paid on the carboxylation reactions of αꢀ
preꢀfunctionalized aryl olefins (Scheme 1).4 For instance, Nolan described Niꢀcatalyzed carboxylation
of organoboronates to generate αꢀarylacrylic acids in moderate yield.4a Kondo reported LiClꢀpromoted
transitionꢀmetalꢀfree carboxylation of organozinc reagents.4b Yu reported ionic liquidꢀpromoted hyꢀ
droxycarbonylation of vinyl bromides to generate α, βꢀunsaturated carboxylic acids using CO as the
carbonyl source.4d However, the αꢀpreꢀfunctionalization of aryl olefins is rather difficult and timeꢀ
consuming. Thus, the development of more practical and efficient procedures using simple starting maꢀ
terials remains an area of synthetic interest.
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Figure 1. Some Biologically Active Compounds Derived from αꢀArylacrylic Acids.
Cl
OH
O
OH
COOH
O
N
O
MeO
O
naprosyn
fenoprofen
pirprofen
N
O
S
O
OH
N
Ph
O
O
OH
HOOC
HO
Ph
A chemokine
receptor modulator
(_)-anisodine
tiaprofennic acid
On the other hand, the Shapiro reaction provides a powerful strategy for the synthesis of natural
products5 and polysubstituted alkenes,6 many of which are not easily accessed by other means. Generalꢀ
ly, a Shapiro reaction involves the treatment of the sulfonyl hydrazone with a base to provide the vinylꢀ
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lithium intermediate, followed by trapping of the vinyl anion with electrophiles to generate correspondꢀ
ing alkeneꢀbased products.7 For example, the in situ generated vinylꢀlithium intermediate could be
trapped by CO2 to give αꢀarylacrylic acids.7h However, the harsh reaction condition such as the requireꢀ
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ment of using strong bases such as nBuLi and an extremely low reaction temperature (ꢀ78 C) dramatiꢀ
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cally decreases its practicality. Thus, the development of more practical and mild procedures is highly
desirable. Herein, we wish to report our study on the Cs2CO3ꢀpromoted carboxylation of Nꢀ
tosylhydrazones with atmospheric CO2 8ꢀ9 towards αꢀarylacrylic acids. The procedure was featured with:
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n
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1) the employment of Cs2CO3 rather than BuLi as the base; 2) a reaction temperature of 80 C rather
than ꢀ78 oC.
Scheme 1. Some Pathways Leading to αꢀArylacrylic Acids
We initiated our investigation on the model reaction of Nꢀtosylhydrazones (1a) with CO2 to optimize
the critical reaction parameters (Table 1). To our delight, we found that in the presence of a catalytic
amount of Pd(OAc)2 and 3 equiv of KOtBu the reaction of 1a under atmospheric CO2 could afford 2a in
25% yield. Interestingly, the process could proceed even in the absence of a palladium catalyst (Table 1,
entry 1). Encouraged by these initial results, other reaction conditions, such as solvent, base, and reacꢀ
tion temperature were also screened. Firstly, the solvent was found to have a profound effect, specificalꢀ
ly DMSO was superior to CH3CN, DMF or dioxane (Table 1, entries 1ꢀ6). Subsequently, other bases
such as LiOtBu, AcONa, K2CO3 and Cs2CO3 were also tested. Cs2CO3 appeared to be the best, deliverꢀ
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Page 4 of 17
o
ing the carboxylation product in 65% yield (Table 1, entries 7ꢀ11). Additionally, 80 C was found to be
more suitable for this reaction (Table 1, entries 11ꢀ13). Furthermore, controlled experiments revealed
that the carbonyl group indeed came from CO2 and the base was essential for this reaction (Table 1, enꢀ
tries 14ꢀ15). However, increasing the pressure of CO2 did not have any positive effect for this transforꢀ
mation (Table 1, entry 16). After considerable experimentation, we found that the combination of 3
equivalents of Cs2CO3 in DMSO at 80 oC under atmospheric CO2 for 12 h served as the optimal condiꢀ
tions for this transformation (Table 1, entry 12).
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Table 1. Selected Results for Screening the Optimized Reaction Conditions a
entry
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base
solvent
DMF
CH3CN
dioxane
toluene
THF
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
DMSO
tem. (oC)
100
100
100
100
100
100
100
100
100
100
100
80
yield (%)b
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
LiOtBu
K2CO3
AcONa
NaH
27
8
trace
trace
< 10
38
trace
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9
trace
< 10
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13
14h
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16i
Cs2CO3
Cs2CO3
Cs2CO3
Cs2CO3
ꢀ
65 (63)c (61)d (43)e
68 (65)f (53)g
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80
80
80
41
0
0
Cs2CO3
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a Reaction conditions: 1a (0.2 mmol), base (0.6 mmol), solvent (2.5 mL), under 1
b
atm of CO2 for 12 h, in a sealed Schlenk tube, unless otherwise noted. Isolated
g
yield. c Cs2CO3 (1.0 mmol), d Cs2CO3 (0.4 mmol), e Cs2CO3 (0.2 mmol), f 7 h, 3
h, h under N2, i CO2 (1.0 MPa).
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With the optimized reaction conditions in hand, we then explored the scope and limitation of this
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transformation in the presence of a variety of functional groups of the Nꢀtosylhydrazones. As shown in
Figure 2, variety of functional groups on the Nꢀtosylhydrazones proceeded smoothly with CO2 and genꢀ
erated the desired carboxylation products in moderate to good yields. Generally, the hindrance of the
phenyl ring of Nꢀtosylhydrazones had some effect on the efficiency. For example, the ortho substituted
substrates resulted in lower yields (2a vs. 2c and 2d Figure 2). Furthermore, the reaction efficiency was
sensitive to the electronic property of the groups on the phenyl ring of Nꢀtosylhydrazones. Substrates
bearing electronꢀdonating groups gave a slightly higher yield than those analogues with electronꢀ
withdrawing groups (2e, 2f and 2g vs 2h, 2i and 2j, 2k vs 2l, Figure 2). Unfortunately, strong electronꢀ
withdrawing groups such as CF3, CN, NO2 inhibited the reaction. Notably, some reactive functional
groups, such as chloro and bromo, which were suitable for potentially further functionalization, survived
in these reactions. In comparison, strong bases such as nBuLi used in traditional Shapiro reactions were
not tolerated well by bromoꢀ and chloroꢀsubstituted derivatives.7 Notably, Nꢀtosylhydrazones with secꢀ
ondary or tertiary carbon in the βꢀposition also worked well under the standard conditions with moderꢀ
ate to good yields (2m-2r). In particular, the procedure was applicable to cyclic substrates. For instance,
2m and 2n were isolated in 62% and 67% yields, respectively. Interestingly, only Zꢀconfiguration prodꢀ
ucts were formed for products 2o-2q.10 (for details, see Figures S1ꢀS4, Supporting Information)
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Figure 2. Scope of Nꢀtosylhydrazones.a
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1 (0.2 mmol), Cs2CO3 (0.6 mmol), DMSO (2.5 mL), at 80 C under 1 atm
of CO2, for 12 h, in a sealed Schlenk tube.
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The carboxylation of 1a with CO2 was examined (Scheme 2) in order to confirm whether CO2
participated in this reaction. αꢀPhenylacrylic acid 2a-13C with Cꢀcarboxyl group was isolated in 61%
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13
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yield. The incorporation of Cꢀcarboxyl was confirmed by EIꢀMS (m/z [M+]: 149, [M+] – COOH: =
103) and 13C NMR (the strong signal at 172.0 ppm in CDCl3), which was similar with the result reportꢀ
ed by Baba11 (Figures S5ꢀS6, Supporting Information).
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Scheme 2. The 13C-Labelling Study
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To gain further insight into the reaction mechanism, Firstly, we tried to examine the main byproducts
of the reaction. When the reaction of 1a with CO2 was conducted under the standard conditions
(Scheme 3), apart from the main product of 2a was isolated in 68% yield, sulfone12 3 (m/z = 260) was
also detected by GCꢀMS as the major byproduct (Figure S7, Supporting Information). However, when
the reaction was conducted in DMSOꢀd6, the deuterated product 4 (m/z = 261) (Figure S8, Supporting
Information) rather than the nonꢀdeuterated 3 (m/z = 260) was detected. As shown in Scheme 4, the
pathway for the formation of the byproduct sulfone may involve Cs2CO3ꢀpromoted deprotonation of (I)
to generate (II), subsequent desulfonation to generate the diazo intermediate (III). Then, the abstraction
of the hydride of DMSO generated (IV), followed by the extrusion of N2 and the nucleophilic addition
of Tsꢀ to (V) generates the final product (VI).13
Scheme 3. Preliminary Mechanism Study
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Scheme 4. Proposed Mechanism for the Byproduct
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On the other hand, the competitive experiment of 1e and 1i under the standard conditions (Figure S9,
Supporting Information) confirmed that the electronꢀdonating group was beneficial for this transforꢀ
mation (Scheme 5, eq 1). On the other hand, styrene did not furnish the corresponding carboxylation
product at all under the optimized reaction conditions (Scheme 5, eq 2).
Scheme 5
Based on the preliminary experimental results, a plausible mechanism for the formation of the desired
carboxylate product is outlined in Scheme 6. It may involve Cs2CO3ꢀpromoted deprotonation of (A) to
generate (B), which would tautomerize to intermediate (C). Subsequently, (C) would be trapped by CO2
to give (D). Then, CꢀH cleavage assisted by base would proceed along with the desulfonation and the
extrusion of N2 leading to (F) (route a). Alternatively, desulfonation of (D) affords (E), followed by Cꢀ
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H cleavage and the extrusion of N2 to generate (F) (route b). Finally, protonation of (F) by acid provides
the desired carboxylic acid (G).
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Scheme 6. Proposed Mechanism for the Carboxylate product
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In conclusion, we have developed a mild and environmentally benigh Cs2CO3ꢀpromoted carboxylaꢀ
tion of Nꢀtosylhydrazones with CO2 leading to the αꢀarylacrylic acids in moderate to good yields. This
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method was different from the traditional Shapiro reaction, where the strong base BuLi and extreme
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low reaction temperature (ꢀ78 C) were not required. Thus, it represents an exceedingly attractive alterꢀ
native to the traditional methods leading to αꢀarylacrylic acids.
EXPERIMENTAL SECTION
General experimental details: Chemicals were used as received without special purification unless
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stated otherwise. H and C NMR were recorded at ambient temperature on a 300 or 400 MHz NMR
spectrometer (75 or 100 MHz for 13C NMR). NMR experiments are reported in δ units, parts per million
(ppm), and were referenced to CDCl3 (δ 7.26 or 77.0 ppm) or DMSOꢀd6 (δ 2.50 or 39.5 ppm) as the inꢀ
ternal standard. All new compounds were further characterized by HRMS. Column chromatography was
performed on silica gel 300−400 mesh.
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General procedure: Nꢀtosylhydrazone (0.2 mmol), Cs2CO3 (0.6 mmol) and DMSO (2.5 mL) was
added into a 10 mL Schlenk tube equipped with a stir bar. The reaction vessel was evacuated and backꢀ
filled with CO2 (1 atm) (this sequence was repeated three times). Then, the sealed Schlenk tube was
stirred at 80 °C for 12 h. After the reaction mixture was cooled to room temperature, 1 M HCl (1 mL)
was added to terminate the reaction and convert the carboxylate into carboxylic acid. The reaction mixꢀ
ture was diluted with EtOAc and washed with water. The organic layer was dried over anhydrous
MgSO4 and concentrated under reduced pressure. The residue was purified by flash column chromatogꢀ
raphy on silica gel with petroleum etherꢀethyl acetate as eluent to give the desired product.
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2-Phenylacrylic acid (2a):3, 14 Flash column chromatography on a silica gel (ethyl acetateꢀpetroleum
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ether, 1:5) gave the product (20.1 mg, 68%) as a white solid. mp 97ꢀ100 C (lit.3 101ꢀ103 oC). 1H NMR
(CDCl3 400 MHz): δ 11.06 (brs, 1H), 7.44ꢀ7.47 (m, 2H), 7.36ꢀ7.41 (m, 3H), 6.57 (s, 1H), 6.04 (s, 1H).
13C NMR (CDCl3 100 MHz): δ 172.2, 140.6, 136.1, 129.5, 128.4, 128.3, 128.1.
2-p-Tolylacrylic acid (2b): Flash column chromatography on a silica gel (ethyl acetateꢀpetroleum ether,
1:5) gave the product (20.4 mg, 63%) as a white solid. mp 90ꢀ92 oC. 1H NMR (CDCl3 400 MHz): δ 7.34
(d, J = 8.1 Hz, 2H), 7.18 (d, J = 7.9 Hz, 2H), 6.49 (s, 1H), 5.99 (s, 1H), 2.37 (s, 3H). 13C NMR (CDCl3
100 MHz): δ 172.1, 140.5, 138.2, 133.2, 128.8, 128.6, 128.3, 21.2. IR (KBr) ν 3438, 3067, 3028, 2993,
2920, 1682, 1606, 1515, 1434, 1336, 1280, 1089, 964 cmꢀ1. MS (EI): 162 (M+); HRMS (ESIꢀTOF) m/z:
calcd. for C10H10NaO2 [M + Na]+ 185.0573, found 185.0576.
2-o-Tolylacrylic acid (2c): Flash column chromatography on a silica gel (ethyl acetateꢀpetroleum ether,
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1
1:5) gave the product (19.1 mg, 59%) as a white solid. mp 93ꢀ95 C. H NMR (CDCl3 400 MHz): δ
7.23ꢀ7.26 (m, 1H), 7.13ꢀ7.20 (m, 3H), 6.64 (dd, J = 1.4 Hz, 1H), 5.84 (dd, J = 1.4 Hz, 1H), 2.24 (s, 3H).
13C NMR (CDCl3 100 MHz): δ 171.2, 141.1, 136.5, 136.2, 130.8, 129.9, 129.5, 128.4, 125.7, 19.8. IR
(KBr) ν 3435, 3066, 3022, 2957, 1726, 1686, 1614, 1577, 1512, 1485, 1379, 966 cmꢀ1. MS (EI): 162
(M+); HRMS (ESIꢀTOF) m/z: calcd. for C10H10NaO2 [M + Na]+ 185.0573, found 185.0576.
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2-(2, 4-Dimethylphenyl)acrylic acid (2d): Flash column chromatography on a silica gel (ethyl acetateꢀ
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petroleum ether, 1:5) gave the product (20.4 mg, 58%) as a white solid. mp 89ꢀ91 C. 1H NMR (CDCl3
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400 MHz): δ 7.00ꢀ7.06 (m, 3H), 6.62 (d, J = 1.6 Hz, 1H), 5.82 (d, J = 7.7 Hz, 1H), 2.34 (s, 3H), 2.21 (s,
3H). 13C NMR (CDCl3 100 MHz): δ 171.9, 141.0, 138.1, 136.0, 133.6, 130.8, 130.6, 129.5, 126.4, 21.1,
19.8. IR (KBr) ν 3432, 3075, 2952, 2921, 1683, 1616, 1577, 1498, 1429, 1305, 1238, 1218 cmꢀ1. MS
(EI): 176 (M+); HRMS (ESIꢀTOF) m/z: calcd. for C11H12NaO2 [M + Na]+ 199.0730, found 199.0733.
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2-(4-Methoxyphenyl)acrylic acid (2e): Flash column chromatography on a silica gel (ethyl acetateꢀ
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petroleum ether, 1:3) gave the product (27.1 mg, 76%) as a white solid. mp 110ꢀ112 C. H NMR
(CDCl3 400 MHz): δ 7.41 (d, J = 8.8 Hz, 2H), 6.92 (d, J = 8.8 Hz, 2H), 6.47 (s, 1H), 5.97 (s, 1H), 3.84
(s, 3H). 13C NMR (CDCl3 75 MHz): δ 172.3, 159.7, 139.9, 129.7, 128.5, 128.0, 113.5, 55.3. IR (KBr) ν
3446, 3087, 3041, 2954, 1697, 1683, 1608, 1512, 1490, 1436, 1334, 1251, 1029 cmꢀ1 MS (EI): 178
(M+); HRMS (ESIꢀTOF) m/z: calcd. for C10H10NaO3 [M + Na]+ 201.0522, found 201.0528.
2-(3-Methoxyphenyl)acrylic acid (2f): Flash column chromatography on a silica gel (ethyl acetateꢀ
petroleum ether, 1:3) gave the product (24.2 mg, 68%) as a colorless oil. 1H NMR (CDCl3, 400 MHz): δ
13
7.25ꢀ7.30 (m, 1H), 6.98ꢀ7.03 (m, 2H), 6.88ꢀ6.91 (m, 1H), 3.82 (s, 3H). C NMR (CDCl3 75 MHz): δ
172.0, 159.3, 140.5, 137.5, 129.6, 129.2, 121.0, 114.3, 113.9, 55.3. IR (KBr) ν 3430, 3076, 2960, 2837,
1699, 1600, 1577, 1489, 1458, 1286, 1253, 1045 cmꢀ1 MS (EI): 178 (M+); HRMS (ESIꢀTOF) m/z: calcd.
for C10H9O3 [M ꢀ H]+ 177.0552, found 177.0548.
2-(Benzo[d][1,3]dioxol-5-yl)acrylic acid (2g): Flash column chromatography on a silica gel (ethyl aceꢀ
o
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tateꢀpetroleum ether, 1:5) gave the product (27.3 mg, 71%) as a white solid. mp 161ꢀ163 C. H NMR
(CDCl3, 300 MHz): δ 6.91ꢀ6.94 (m, 2H), 6.79ꢀ6.81 (m, 1H), 6.46 (d, J = 1.0 Hz, 1H), 5.98 (s, 2H), 5.96
(d, J = 1.0 Hz, 1H). 13C NMR (DMSOꢀd6 100 MHz): δ 167.9, 147.1, 147.0, 140.9, 130.6, 124.8, 121.9,
108.5, 107.8, 101.1. IR (KBr) ν 3446, 3078, 3035, 2904, 1683, 1608, 1502, 1491, 1436, 1245, 1043 cmꢀ
1. MS (EI): 192 (M+); HRMS (ESIꢀTOF) m/z calcd. for C10H7O4 [M ꢀ H]+ 191.0338, found 191.0344.
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2-(4-Chlorophenyl)acrylic acid (2h): Flash column chromatography on a silica gel (ethyl acetateꢀ
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o
petroleum ether, 1:5) gave the product (22.6 mg, 62%) as a white solid. mp 89ꢀ91 C. 1H NMR (CDCl3
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6
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400 MHz): δ 7.33ꢀ7.40 (m, 4H), 6.57 (s, 1H), 6.04 (s, 1H). 13C NMR (CDCl3 100 MHz): δ 171.8, 139.4,
134.5, 134.4, 130.0, 129.8, 128.3. IR (KBr) ν 3432, 3082, 3034, 2923, 1701, 1678, 1612, 1596, 1560,
1490, 1396, 1317, 1218, 1093, 1014, 970 cmꢀ1. MS (EI): 182 (M+); HRMS (ESIꢀTOF) m/z calcd. for
C9H6ClO2 [M ꢀ H]+ 181.0056, found 181.0054.
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2-(4-Bromophenyl)acrylic acid (2i): Flash column chromatography on a silica gel (ethyl acetateꢀ
o
petroleum ether, 1:5) gave the product (25.0 mg, 55%) as a white solid. mp 97ꢀ99 C. 1H NMR (CDCl3
13
400 MHz): δ 7.50 (d, J = 8.4 Hz, 2H), 7.31 (d, J = 8.4 Hz, 2H), 6.57 (s, 1H), 6.04 (s, 1H). C NMR
(CDCl3 100 MHz): δ 171.5, 139.4, 134.9, 131.3, 130.1, 122.7. IR (KBr) ν 3432, 3082, 3033, 2997,
1679, 1612, 1579, 1487, 1313, 1220, 1087, 1010, 831 cmꢀ1. MS (EI): 226 (M+); HRMS (ESIꢀTOF) m/z:
calcd. for C9H6BrO2 [M ꢀ H]+ 224.9551, found 224.9545.
2-(4-Fluorophenyl)acrylic acid (2j): Flash column chromatography on a silica gel (ethyl acetateꢀ
o
1
petroleum ether, 1:5) gave the product (20.2 mg, 61%) as a white solid. mp 107ꢀ109 C. H NMR
(CDCl3 400 MHz): δ 7.40ꢀ7.44 (m, 2H), 7.03ꢀ7.08 (m, 2H), 6.54 (s, 1H), 6.01 (s, 1H). 13C NMR (CDCl3
100 MHz): δ 171.9, 163.2 (d, J = 246.0 Hz), 139.6, 132.1, 130.2 (d, J = 18.9 Hz), 129.5, 115.1 (d, J =
21.4 Hz). IR (KBr) ν 3432, 3082, 1701, 1612, 1512, 1436, 1313, 1228, 1163, 962 cmꢀ1. MS (EI): 166
(M+); HRMS (ESIꢀTOF) m/z: calcd. for C9H6FO2 [M ꢀ H]+ 165.0352, found 165.0340.
2-(Naphthalen-2-yl)acrylic acid (2k): Flash column chromatography on a silica gel (ethyl acetateꢀ
o
1
petroleum ether, 1:3) gave the product (27.3 mg, 69%) as a white solid. mp 116ꢀ118 C. H NMR
(CDCl3 400 MHz): δ 7.94 (s, 1H), 7.83ꢀ7.87 (m, 3H), 7.56 (m, 1H), 7.50 (m, 2H), 6.64 (s, 1H), 6.15 (s,
1H). 13C NMR (CDCl3 100 MHz): δ 172.0, 140.6, 133.6, 133.1, 133.0, 129.7, 128.3, 127.8, 127.7,
127.6, 126.5, 126.3, 126.2. IR (KBr) ν 3445, 3055, 3018, 1697, 1685, 1606, 1506, 1429, 1326, 1253,
1193 cmꢀ1. MS (EI): 198 (M+); HRMS (ESIꢀTOF) m/z: calcd. for C13H9O2 [M ꢀ H]+ 197.0603, found
197.0599.
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2-(6-Methoxynaphthalen-2-yl)acrylic acid (2l):15 Flash column chromatography on a silica gel (ethyl
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acetateꢀpetroleum ether, 1:3) gave the product (34.2 mg, 75%) as a white solid. mp 169ꢀ172 oC (lit.15
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5
6
1
172ꢀ174 oC) H NMR (DMSOꢀd6, 400 MHz): δ 7.78ꢀ7.91 (m, 3H), 7.52ꢀ7.55 (m, 1H), 7.32 (s, 1H),
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8
13
7.16ꢀ7.18 (m, 1H), 6.26 (s, 1H), 6.06 (s, 1H), 3.88 (s, 3H). C NMR (DMSOꢀd6, 100 MHz): δ 168.5,
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158.1, 142.0, 134.3, 132.3, 130.2, 128.5, 127.3, 127.0, 126.7, 125.9, 119.3, 106.2, 55.7.
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3, 4-Dihydronaphthalene-1-carboxylic acid (2m):16 Flash column chromatography on a silica gel
(ethyl acetateꢀpetroleum ether, 1:3) gave the product (21.6 mg, 62%) as a white solid. mp 120ꢀ122 oC.
1H NMR (CDCl3 400 MHz): δ 7.94 (d, J = 7.5 Hz, 1H), 7.45 (t, J = 4.8 Hz, 1H), 7.19ꢀ7.30 (m, 3H), 2.82
(t, J = 7.8 Hz, 2H), 2.45ꢀ2.50 (m, 2H). 13C NMR (CDCl3 100 MHz): δ 172.0, 143.0, 136.2, 130.4, 129.9,
127.7, 127.5, 126.6, 126.2, 27.4, 23.7.
2H-Chromene-4-carboxylic acid (2n): Flash column chromatography on a silica gel (ethyl acetateꢀ
o
1
petroleum ether, 1:3) gave the product (23.6 mg, 67%) as a white solid. mp 134ꢀ136 C. H NMR
(CDCl3 400 MHz): δ 7.97 (dd, J = 7.9 Hz, 1H), 7.18ꢀ7.22 (m, 1H), 7.05 (s, 1H), 6.98 (t, J = 7.7 Hz, 1H),
6.87 (dd, J = 8.1 Hz, 1H), 4.86 (m, 2H). 13C NMR (CDCl3 100 MHz): δ 169.3, 154.1, 134.4, 130.0,
126.4, 121.8, 119.2, 116.3, 64.6. IR (KBr) ν 3434, 3067, 3031, 2981, 2813, 1691, 1625, 1604, 1569,
1487, 1454, 1375, 1226, 1004 cmꢀ1. MS (EI): 176 (M+); HRMS (ESIꢀTOF) m/z: calcd. for C10H7O3 [M ꢀ
H]+ 175.0395, found 175.0389.
(Z)-2-(p-Tolyl)but-2-enoic acid (2o): Flash column chromatography on a silica gel (ethyl acetateꢀ
o
1
petroleum ether, 1:5) gave the product (22.5 mg, 64%) as a white solid. mp 108ꢀ110 C. H NMR
(CDCl3 400 MHz): δ 7.23 (d, J = 7.9 Hz, 2H), 7.13 (d, J = 8.0 Hz, 2H), 6.41 (dd, J = 7.3 Hz, 1H), 2.34
(s, 3H), 2.14 (d, J = 7.3 Hz, 3H). 13C NMR (CDCl3 100MHz): δ 173.5, 139.9, 137.4, 135.4, 134.2,
128.9, 127.8, 21.1, 16.4. IR (KBr) ν 3436, 3075, 3034, 2958, 2923, 2852, 1733, 1685, 1616, 1577, 1512,
1458, 1288, 1076 cmꢀ1. MS (EI): 176 (M+); HRMS (ESIꢀTOF) m/z: calcd. for C11H12NaO2 [M + Na]+
199.0730, found 199.0727.
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(Z)-2-Phenylhex-2-enoic acid (2p): Flash column chromatography on a silica gel (ethyl acetateꢀ
petroleum ether, 1:5) gave the product (28.5 mg, 75%) as a colorless oil. 1H NMR (CDCl3 400 MHz): δ
7.28ꢀ7.39 (m, 5H), 6.35 (t, J = 7.5 Hz, 1H), 2.59 (q, J = 7.4 Hz, 2H), 1.56 (m, 2H), 1.00 (t, J = 7.3 Hz,
3H). 13C NMR (CDCl3 100 MHz): δ 173.4, 145.9, 138.2, 133.4, 128.1, 128.0, 127.6, 32.2, 22.5, 13.8. IR
(KBr) ν 3461, 3078, 3035, 2960, 2931, 2871, 1689, 1608, 1502, 1490, 1419, 1284, 1245, 1236 cmꢀ1. MS
(EI): 190 (M+); HRMS (ESIꢀTOF) m/z: calcd. for C12H14NaO2 [M + Na]+ 213.0886, found 213.0885.
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(Z)-2, 3-Diphenylacrylic acid (2q): Flash column chromatography on a silica gel (ethyl acetateꢀ
petroleum ether, 1:4) gave the product (31.4 mg, 70%) as a white solid. mp 135ꢀ137 oC. The E configure
counterpart is known.10a 1H NMR (CDCl3 400 MHz): δ 7.49ꢀ7.55 (m, 4H), 7.35ꢀ7.45 (m, 6H), 7.12 (s,
1H). 13C NMR (CDCl3 100 MHz): δ 174.9, 136.8, 135.4, 134.1, 133.8, 128.8, 128.7, 128.6, 128.5,
128.4, 126.9. IR (KBr) ν 3432, 3056, 3024, 2925, 1710, 1676, 1635, 1618, 1604, 1569, 1490, 1436,
1373 cmꢀ1. MS (EI): 224 (M+); HRMS (ESIꢀTOF) m/z: calcd. for C15H12NaO2 [M + Na]+ 247.0730,
found 247.0725.
3-Methyl-2-phenylbut-2-enoic acid (2r):17 Flash column chromatography on a silica gel (ethyl acetateꢀ
petroleum ether, 1:5) gave the product (16.9 mg, 48%) as a white solid. mp 150ꢀ152 oC (lit.17 149ꢀ150
1
oC) H NMR (CDCl3 400 MHz): δ 7.33ꢀ7.37 (m, 2H), 7.29ꢀ7.30 (m, 1H), 7.16ꢀ7.18 (m, 2H), 2.24 (s,
3H), 1.71 (s, 3H). 13C NMR (CDCl3 100 MHz): δ 173.2, 151.2, 138.2, 129.6, 128.9, 128.2, 127.1, 24.6,
22.9.
ASSOCIATED CONTENT
Supporting Information:
1H and 13C NMR spectra of all the products. This material is available free of charge via the Internet at
http://pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
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Eꢀmail: jiangcheng@cczu.edu.cn
Notes
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The authors declare no competing financial interest.
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ACKNOWLEDGMENT
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We thank the National Natural Science Foundation of China (nos. 21272028 and 21202013), State Key
Laboratory of Coordination Chemistry of Nanjing University, Jiangsu Key Laboratory of Advanced
Catalytic Materials &Technology, Jiangsu Province Key Laboratory of Fine Petrochemical Engineering,
and the Priority Academic Program Development of Jiangsu Higher Education Institutions for financial
support.
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