BF3·OEt2-promoted intramolecular nucleophilic substitution; Synthesis of dibenzopyranones and coumarins from biaryltriazenes

Article abstract of DOI:10.1002/ejoc.201300660

A simple and highly efficient reaction promoted by Lewis acid has been demonstrated for the synthesis of dibenzopyranones. The metal-free annulation can tolerate a series of functional groups and also allows the synthesis of coumarins and phenanthridinones in good to excellent yields. The synthesis of coumarins through BF₃·OEt₂-promoted intramolecular nucleophilic substitution has been demonstrated. The efficient synthetic methodology provides good to excellent yields of dibenzopyranones and phenanthridinones. Copyright

Full text of DOI:10.1002/ejoc.201300660

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FULL PAPER
Intramolecular Nucleophilic Substitution
X. Shang, L. Xu, W. Yang, J. Zhou,
M. Miao, H. Ren* .......................... 1–11
BF3·OEt2-Promoted
Intramolecular
Nucleophilic Substitution; Synthesis of Di-
benzopyranones and Coumarins from Bi-
aryltriazenes
The synthesis of coumarins through
BF3·OEt2-promoted intramolecular
nucleophilic substitution has been demon-
strated. The efficient synthetic method-
ology provides good to excellent yields of
dibenzopyranones and phenanthridinones.
Keywords: Synthetic methods / Nucleo-
philic substitution / Fused-ring systems /
Lactones / Lewis acids
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X. Shang, L. Xu, W. Yang, J. Zhou, M. Miao, H. Ren
FULL PAPER
DOI: 10.1002/ejoc.201300660
BF3·OEt2-Promoted Intramolecular Nucleophilic Substitution; Synthesis of
Dibenzopyranones and Coumarins from Biaryltriazenes
Xiaobo Shang,[a] Lijun Xu,[b] Weijun Yang,[a] Jun Zhou,[a] Maozhong Miao,[b] and
Hongjun Ren*[b]
Keywords: Synthetic methods / Nucleophilic substitution / Fused-ring systems / Lactones / Lewis acids
A simple and highly efficient reaction promoted by Lewis
acid has been demonstrated for the synthesis of dibenzo-
pyranones. The metal-free annulation can tolerate a series of
functional groups and also allows the synthesis of coumarins
and phenanthridinones in good to excellent yields.
glucocorticoid receptor agonists, endothelial proliferation
inhibitors, and antidyslipidemic agents.[5]
Introduction
Dibenzopyranone serves as the structural core in many
natural products[1] including gilvocarcin V (1a; Scheme 1),
lamellarin D (1b), and other biologically active compounds
(1c–g).[2] Dibenzopyranones also exist naturally in many
food sources including citrus fruits, herbs, and vegetables.[3]
In addition, they have been used as intermediates in the
synthesis of cannabinoids[4] and several pharmaceutically
interesting compounds such as androgen, progesterone,
Several synthetic methodologies are available for the syn-
thesis of dibenzopyranone derivatives. The most popular
method is BBr3-mediated lactonization from the corre-
sponding methoxy-biphenylcarboxylates and methoxy-bi-
phenylcarboxamides (Scheme 2, Path a).[6] The Pd-cata-
lyzed intramolecular direct arylation from the halo-substi-
tuted phenyl benzoates provides an alternative pathway for
the construction of phenyl benzoate derivatives (Path b).[7]
Copper-mediated/microwave-assisted Caryl–Ocarboxylic cou-
pling is another good method with which to synthesize di-
benzopyranone cores (Path c).[8] Alternatively, a highly se-
lective palladium bis(acetoacetonate)/copper(I) chloride
[Pd(acac)2/CuCl] catalytic system also provides an efficient
method with which to synthesize dibenzopyranones
through a decarboxylative cross-coupling and lactonization
sequence (Path d).[9] More recently, ruthenium-catalyzed
cyclotrimerization of aryl diynes,[10] domino reactions of
1,3-bis-silyl enol ethers with benzopyrylium triflates,[11]
Scheme 1. Examples of natural products containing the dibenzo-
pyranone core.
[a] Department of Chemistry, Zhejiang University,
Hangzhou 310027, P. R. China
[b] Department of Chemistry, Zhejiang Sci-Tech University,
Hangzhou 310018, P. R. China
E-mail: renhj@zstu.edu.cn
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201300660.
Scheme 2. Approaches used for the synthesis of the dibenzopy-
ranone core.
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Synthesis of Dibenzopyranones and Coumarins from Biaryltriazenes
Diels–Alder or inverse electron-demand Diels–Alder reac-
tion,[12] and o-phenylbenzoic acid with DIH under irradia-
tion with a tungsten lamp,[13] have been reported.
Results and Discussion
Initially, our research started with the model reaction of
2a, which was treated with BF3·OEt2 (2.8 equiv.) in CH2Cl2
at 40°C; under these conditions, product 3a was obtained
in 70% yield. To improve the yield of the reaction, a range
of solvents were screened (Scheme 3). The yield decreased
greatly when the reaction was carried out in tetra-
Theoretically, phenyl cations can be used directly as elec-
trophiles to construct aromatic compounds, but their appli-
cation is limited owing to their instability.[14] Triazenes are
useful and versatile compounds. They have been studied for
their anticancer potential[15] and used as protecting groups
in combinatorial chemistry[16] and natural product synthe-
sis,[17] and have been incorporated into polymer[18] and
oligomer[19] syntheses. Triazenes can also be transferred to
various functional groups under appropriate conditions.[20k]
Moreover, triazenes have been applied in organic synthe-
sis,[20] organometallic chemistry,[21] as chemodosimeters,[22]
and in pharmacology.[23] Triazene functionality (ArN=N–
NR2) can be viewed as a synthetic equivalent of the diaz-
onium salt. This allows the reactive diazonium salt to be
replaced by the more stable triazine moiety, thus making
reactions easier to handle. In previous work, we reported
the Lewis acid promoted synthesis of carbazoles, dibeno-
furans, dihydrobenzofurans, dibenzothiophenes, and poly-
cyclic aromatic hydrocarbons from biaryl triazenes.[24] Here,
we describe the annulation reaction of triazene bearing an
methyl ester group, leading to dibenzopyranone derivatives
through Lewis acid promoted intramolecular nucleophilic
substitution (Scheme 2, Path e).
Scheme 3. Optimization of the reaction conditions. Reagents and
conditions: triazene ester (0.5 mmol), BF3·OEt2 (2.8 equiv.), solvent
(20 mL), 40°C, 4 h, yields refer to isolated product after flash col-
umn chromatography.
Scheme 4. Lactonization of triazene esters promoted by BF3·OEt2. Reagents and conditions: triazene ester (0.5 mmol), BF3·OEt2
(2.8 equiv.), CH3CN (20 mL), 40°C, 4 h, yields refer to isolated products after flash column chromatography.
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X. Shang, L. Xu, W. Yang, J. Zhou, M. Miao, H. Ren
FULL PAPER
hydrofuran (THF) or N,N-dimethylformamide (DMF), night, the reaction went to completion. However, if only
whereas the use of MeOH enhanced the yield of the prod- one methyl ester group was substituted on the alkene skel-
uct to 75%. When the reaction was carried out in CH3CN eton of 5a, the coumarin was not formed because of the
at 40°C, the yield improved to 95%.
trans conformation of the alkene. Biphenyl (6b and 6d) and
To examine the general applicability of this methodology alkenyl (6c) conjugated coumarins could also be formed un-
in the synthesis of dibenzopyranones, lactonization of vari- der the new conditions (Scheme 5). This method was also
ous diaryltriazene esters with BF3·OEt2 were conducted; expanded to the synthesis of phenanthridinones. When sub-
the results are summarized in Scheme 4. The annulation of strates 7a and 7b were treated with 2.8 equivalents of
triazene esters with a range of functional groups gave the BF3·OEt2, 75 and 55% yield of the corresponding phen-
corresponding dibenzopyranones in good to excellent yields anthridinones 8a and 8b were obtained, respectively
(3a–l; Scheme 4). Functional groups such as ester, cyano, (Scheme 6).
alkenyl and alkynyl all tolerated the reaction conditions (3a,
3b, and 3h–k), even the iodo group was not affected in the
BF3·OEt2 promoted process (3l). Furthermore, steric bulk
near the reaction center had no influence on the yield of
the product (3d).
We then extended the reaction to synthesize coumarins
from a range of triazene dimethyl malonates. Under the op-
timized conditions, 5a was partially transformed into cou-
marin 6a. When the amount of BF3·OEt2 was increased to
5.0 equivalents and the reaction time was extended to over-
Scheme 6. Application of the annulation for the synthesis of phen-
anthridinones. Reagents and conditions: triazene amide (0.5 mmol),
BF3·OEt2 (2.8 equiv.), CH3CN (20 mL), 40°C, overnight, yields re-
fer to isolated products after flash column chromatography.
With respect to the mechanism, the terminal nitrogen
atom and Lewis acid probably form a complex that is essen-
tial to enhance the cleavage of the sp2 C–N bond and subse-
quent reactions through either aryl cations or aryl radicals
(Scheme 7).[25] The methyl ester group serves as an nucleo-
phile to attack the aryl group on the unsaturated nitrogen
atom and forms the target product dibenzopyranone. To
investigate the mechanism of the reaction, radical scaven-
gers such as BHT (butylated hydroxytoluene) and TEMPO
(2,2,6,6-tetramethylpiperidin-1-oxyl)
(Scheme 8)
were
Scheme 5. Application of the annulation for the synthesis of cou-
marins. Reagents and conditions: triazene dimethyl ester
(0.5 mmol), BF3·OEt2 (5.0 equiv.), CH3CN (20 mL), 40°C, over-
night, yields refer to isolated products after flash column
chromatography.
added to the standard reaction systems, but the yield of the
reaction was not affected. We therefore conclude that the
formation of an aryl cation intermediate is favored in this
reaction.
Scheme 7. Proposed mechanism for the annulation reaction.
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Synthesis of Dibenzopyranones and Coumarins from Biaryltriazenes
126.9, 126.5, 115.8, 60.7, 51.7, 51.1, 46.5, 23.9, 23.4, 14.4 ppm. IR
(thin film): ν = 3077, 2976, 2877, 1703, 1289, 1239, 1113 cm–1. MS
˜
(EI): m/z (%) = 381 (15) [M]+, 336 (7), 311 (12), 283 (100), 255
(80), 240 (26). HRMS (EI-TOF): m/z calcd. for C21H23N3O4 [M]+
381.1690; found 381.1690.
Methyl (E)-5Ј-Cyano-2Ј-(pyrrolidin-1-yldiazenyl)-[1,1Ј-biphenyl]-2-
carboxylate (2b): Yield 952 mg (95%); yellow solid; m.p. 88–90 °C.
1H NMR (400 MHz, CDCl3): δ = 7.87 (d, J = 6.0 Hz, 1 H, ArH),
7.59 (d, J = 1.6 Hz,1 H, ArH), 7.52–7.58 (m, 2 H, ArH), 7.49 (d,
J = 6.4 Hz, 1 H, ArH), 7.37–7.44 (m, 1 H, ArH), 7.29 (d, J =
6.4 Hz, 1 H, ArH), 3.82–3.92 (m, 2 H, CH2N), 3.47 (s, 3 H, CH3O),
3.20–3.44 (m, 2 H, CH2N), 1.83–2.02 (m, 4 H, 2CH2CH2N) ppm.
13C NMR (100 MHz, CDCl3): δ = 168.3, 151.5, 138.6, 136.9, 133.3,
132.2, 131.9, 131.6, 131.0, 129.2, 127.4, 119.6, 116.6, 107.5, 51.8,
Scheme 8. The presence of radical scavengers has no effect on the
reaction.
51.2, 46.7, 23.8, 23.3 ppm. IR (thin film): ν = 3068, 2948, 2875,
˜
Conclusions
2220, 1718, 1596, 1382, 1265, 1120 cm–1. MS (EI): m/z (%) = 334
(11) [M]+, 277 (4), 264 (17), 236 (100), 221 (64), 193 (32). HRMS
(EI-TOF): m/z calcd. for C19H18N4O2 [M]+ 334.1430; found
334.1432.
We have developed an efficient method for the lactoniz-
ation of triazene esters promoted by BF3·OEt2. This ap-
proach works well to form various dibenzopyranones with
moderate to excellent yield under mild and transition-
metal-free conditions. Moreover, the approach has been
successfully applied to form coumarins and phenanthrid-
inones. Further extensions of this methodology are being
investigated in our laboratory.
Methyl (E)-5Ј-Methyl-2Ј-(pyrrolidin-1-yldiazenyl)-[1,1Ј-biphenyl]-2-
carboxylate (2c): Yield 368 mg (38%); brown oil. 1H NMR
(400 MHz, CDCl3): δ = 7.85 (dd, J = 8.0, 1.2 Hz, 1 H, ArH), 7.50–
7.55 (m, 1 H, ArH), 7.36–7.41 (m, 2 H, ArH), 7.31 (d, J = 8.4 Hz,
1 H, ArH), 7.17 (s, 1 H, ArH), 7.11–7.15 (m, 1 H, ArH), 3.54 (s, 3
H, CH3O), 3.00–4.00 (m, 4 H, 2 ϫ CH2N), 2.41 (s, 3 H, CH3),
1.83–1.97 (m, 4 H, 2 ϫ CH2CH2N) ppm. 13C NMR (100 MHz,
CDCl3): δ = 168.8, 145.8, 140.6, 135.7, 134.5, 132.5, 131.3, 131.1,
130.0, 128.8, 128.7, 126.4, 116.0, 51.7, 31.5, 23.7, 22.6, 21.0,
Experimental Section
General: THF was dried by sodium and freshly distilled. CH2Cl2
was dried with CaH2 and freshly distilled. DMF was dried with
CaH2 and distilled under reduced pressure. The other materials and
solvents were purchased from commercial suppliers and used with-
out additional purification. NMR spectra were recorded with
Bruker Avance spectrometers operating at 400 or 500 MHz for 1H,
and at 100 or 125 MHz for 13C using TMS as internal standard.
14.1 ppm. IR (thin film): ν = 3057, 2947, 2870, 1715, 1419, 1318,
˜
1289, 1212, 1123, 1085 cm–1. MS (EI): m/z (%) = 323 (15) [M]+,
253 (11), 225 (100), 210 (96), 181 (30), 152 (14). HRMS (EI-TOF):
m/z calcd. for C19H21N3O2 [M]+ 323.1634; found 323.1637.
Methyl
(E)-3Ј,5Ј-Dimethyl-2Ј-(pyrrolidin-1-yldiazenyl)-[1,1Ј-bi-
phenyl]-2-carboxylate (2d): Yield 597 mg (59%); brown oil. 1H
NMR (400 MHz, CDCl3): δ = 7.76 (dd, J = 6.4, 1.2 Hz, 1 H, ArH),
7.42–7.45 (m, 1 H, ArH), 7.27–7.31 (m, 2 H, ArH), 6.99 (s, 1 H,
ArH), 6.93 (s, 1 H, ArH), 3.59 (s, 3 H, CH3O), 3.30–3.50 (m, 4 H,
2 ϫ CH2N), 2.34 (s, 3 H, CH3), 2.25 (s, 3 H, CH3), 1.80–1.97 (m, 4
H, 2 ϫ CH2CH2N) ppm. 13C NMR (100 MHz, CDCl3): δ = 168.5,
145.3, 142.2, 134.6, 133.6, 131.8, 131.6, 131.0, 130.9, 129.6, 128.9,
128.0, 126.0, 51.7, 31.6, 23.7, 22.6, 20.9, 18.8, 14.1 ppm. IR (thin
1
Chemical shifts are given relative to CDCl3 (δ = 7.26 ppm for H
NMR, 77.0 ppm for 13C NMR). Mass spectroscopy data of the
products were collected with an HRMS-TOF instrument or a low-
resolution MS instrument using EI ionization. IR spectra were re-
corded with a Bruker ATR-FTIR spectrometer. Melting points
were measured with an WRS-1A digital point apparatus.
General Procedure for the Synthesis of Aryltriazenes 2a–k: Synthe-
sized from the corresponding substituted phenyl halide (3 mmol)
and substituted boronic acid (1.2 equiv.) in the presence of
[Pd(PPh3)4] (0.05 equiv.) and Cs2CO3 (2.0 equiv.) in 1,4-dioxane
(6 mL) and water (1.5 mL). The mixture was stirred at 100 °C over-
night under a nitrogen atmosphere in a screw-cap vial. Upon com-
pletion of the reaction (determined by TLC analysis), the reaction
was diluted with ethyl acetate and washed with water. The organic
fractions were dried with anhydrous Na2SO4 and concentrated un-
der vacuo. Purification was carried out by flash chromatography
to afford the desired product.
film): ν = 3062, 2948, 2869, 1714, 1424, 1322, 1290, 1251,
˜
1121 cm–1. MS (EI): m/z (%) = 337 (14) [M]+, 267 (6), 239 (100),
224 (93), 209 (28), 181 (18). HRMS (EI-TOF): m/z calcd. for
C20H23N3O2 [M]+ 337.1790; found 337.1790.
3,4ЈЈ-Diethyl 2Ј-Methyl (E)-6-(Pyrrolidin-1-yldiazenyl)-[1,1Ј:4Ј,1ЈЈ-
terphenyl]-2Ј,3,4ЈЈ-tricarboxylate (2e): Yield 1.45 g (91%); yellow
solid; m.p. 106–108 °C. 1H NMR (400 MHz, CDCl3): δ = 8.11–
8.16 (m, 3 H, ArH), 8.07 (s, 1 H, ArH), 8.01 (d, J = 8.4 Hz, 1 H,
ArH), 7.82 (dd, J = 8.4, 1.6 Hz, 1 H, ArH), 7.75 (d, J = 8.4 Hz,
2 H, ArH), 7.49 (t, J = 8.4 Hz, 2 H, ArH), 4.32–4.45 (m, 4 H,
3Ј-Ethyl 2-Methyl (E)-6Ј-(Pyrrolidin-1-yldiazenyl)-[1,1Ј-biphenyl]- 2 ϫ CH3CH2O), 3.82–3.95 (m, 2 H, CH2N), 3.51 (s, 3 H, CH3O),
2,3Ј-dicarboxylate (2a): Yield 1.05 g (92%); yellow solid; m.p. 105–
107 °C. H NMR (400 MHz, CDCl3): δ = 8.03 (s, 1 H, ArH), 8.00
(d, J = 6.8 Hz, 1 H, ArH), 7.86 (d, J = 6.4 Hz, 1 H, ArH), 7.54 (t,
J = 6.0 Hz, 1 H, ArH), 7.45 (d, J = 6.8 Hz, 1 H, ArH), 7.39 (d, J
3.20–3.50 (m, 2 H, CH2N), 1.85–2.02 (m, 4 H, 2 ϫ CH2CH2N),
1.34–1.46 (m, 6 H, 2 ϫ CH3CH2O) ppm. 13C NMR (100 MHz,
CDCl3): δ = 168.5, 166.6, 166.3, 151.8, 144.0, 139.6, 138.5, 135.3,
133.1, 132.0, 131.0, 130.1, 129.8, 129.8, 129.5, 127.7, 126.8, 126.6,
1
= 4.8 Hz, 2 H, ArH), 4.37 (q, J = 5.6 Hz, 2 H, CH3CH2O), 3.79– 115.9, 61.0, 60.7, 51.8, 51.1, 46.6, 23.8, 23.4, 14.3, 14.3 ppm. IR
3.91 (m, 2 H, CH2N), 3.48 (s, 3 H, CH3O), 3.18–3.48 (m, 2 H, (thin film): ν = 3062, 2978, 2874, 1709, 1603, 1232, 1103 cm–1. MS
˜
CH2N), 1.85–2.02 (m, 4 H, 2 ϫ CH2CH2N), 1.39 (t, J = 6.0 Hz, 3
H, CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ = 168.7,
166.7, 151.7, 139.8, 135.9, 132.4, 131.4, 131.3, 131.0, 129.6, 129.0,
(EI): m/z (%) = 529 (16) [M]+, 484 (13), 431 (100), 403 (36), 385
(26), 343 (29). HRMS (EI-TOF): m/z calcd. for C30H31N3O6 [M]+
529.2213; found 529.2219.
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3-Ethyl 2Ј-Methyl (E)-6-(Pyrrolidin-1-yldiazenyl)-[1,1Ј:4Ј,1ЈЈ-ter-
phenyl]-2Ј,3-dicarboxylate (2f): Yield 1.262 g (92%); yellow solid;
m.p. 70–72 °C. 1H NMR (400 MHz, CDCl3): δ = 8.13 (d, J =
1.6 Hz, 1 H, ArH), 8.09 (d, J = 2.4 Hz, 1 H, ArH), 8.01 (dd, J =
8.4, 2.0 Hz, 1 H, ArH), 7.80 (dd, J = 8.0, 2.0 Hz, 1 H, ArH), 7.69
472 mg (31%); brown liquid. 1H NMR (400 MHz, CDCl3): δ =
8.02 (s, 2 H, ArH), 7.99 (dd, J = 8.4, 2.0 Hz, 1 H, ArH), 7.66–7.76
(m, 2 H, ArH), 7.46 (d, J = 8.4 Hz, 1 H, ArH), 7.42 (d, J = 7.6 Hz,
1 H, ArH), 6.54 (d, J = 16.0 Hz, 1 H, C=CH), 4.37 (q, J = 7.2 Hz,
2 H, CH3CH2O), 4.22 (t, J = 6.8 Hz, 2 H, CH2CH2O), 3.80–3.95
(d, J = 7.2 Hz, 2 H, ArH), 7.43–7.51 (m, 4 H, ArH), 7.36–7.41 (m, (m, 2 H, CH2N), 3.49 (s, 3 H, CH3O), 3.13–3.50 (m, 2 H, CH2N),
1 H, ArH), 4.39 (q, J = 7.2 Hz, 2 H, CH3CH2O), 3.80–3.95 (m, 2 1.85–2.02 (m, H, 2 ϫ CH2CH2N), 1.65–1.72 (m, H,
4
2
H, CH2N), 3.52 (s, 3 H, CH3O), 3.20–3.50 (m, 2 H, CH2N), 1.86– CH2CH2CH2O), 1.38–1.50 (m, 5 H, CH3CH2CH2CH2O), 0.96 (t,
2.02 (m, 4 H, 2 ϫ CH2CH2N), 1.41 (t, J = 7.2 Hz, 3 H, J = 7.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3):
CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ = 168.6, 166.6,
151.8, 139.8, 139.7, 138.7, 135.6, 132.9, 131.9, 131.0, 129.7, 129.6,
128.8, 127.7, 127.6, 127.0, 126.6, 115.9, 60.7, 51.7, 51.1, 46.6, 23.8,
δ = 168.1, 166.8, 166.5, 151.7, 143.2, 141.6, 135.1, 133.1, 133.1,
131.9, 130.8, 130.5, 129.9, 128.6, 126.5, 119.0, 115.8, 64.4, 60.7,
51.8, 51.1, 46.6, 30.7, 23.8, 23.4, 19.1, 14.3, 13.7 ppm. IR (thin
23.4, 14.3 ppm. IR (thin film): ν = 3057, 2977, 2879, 1708, 1306,
film): ν = 3068, 2960, 2874, 1710, 1638, 1394, 1309, 1234, 1171,
˜
˜
1231, 1104 cm–1. MS (EI): m/z (%) = 457 (11) [M]+, 359 (100), 331 1105 cm–1. MS (EI): m/z (%) = 507 (8) [M]+, 409 (100), 262 (50),
(28), 316 (26), 299 (19), 215 (16). HRMS (EI-TOF): m/z calcd. for 183 (35). HRMS (EI-TOF): m/z calcd. for C28H33N3O2 [M]+
C27H27N3O4 [M]+ 457.2002; found 457.2001.
507.2369; found 507.2372.
Methyl
4-[(E)-3-butoxy-3-oxoprop-1-en-1-yl]-5Ј-cyano-2Ј-[(E)-
Methyl
(E)-5-Cyano-2-(pyrrolidin-1-yldiazenyl)-[1,1Ј:4Ј,1ЈЈ-ter-
pyrrolidin-1-yldiazenyl]-1,1Ј-biphenyl-2-carboxylate (2k): Yield
1.091 g (79%); yellow solid; m.p. 123–124 °C. 1H NMR (400 MHz,
CDCl3): δ = 8.03 (d, J = 1.6 Hz, 1 H, ArH), 7.65–7.75 (m, 2 H,
ArH), 7.53–7.61 (m, 2 H, ArH), 7.49 (d, J = 8.4 Hz, 1 H, ArH),
7.33 (d, J = 8.0 Hz, 1 H, ArH), 6.54 (d, J = 16.0 Hz, 1 H, CH=C),
4.22 (t, J = 6.8 Hz, 2 H, CH3CH2O), 3.81–3.92 (m, 2 H, CH2N),
3.52 (s, 3 H, CH3O), 3.18–3.48 (m, 2 H, CH2N), 1.86–2.02 (m, 4
H, 2 ϫ CH2CH2N), 1.63–1.71 (m, 2 H, CH2CH2CH2O), 1.38–1.49
phenyl]-2Ј-carboxylate (2g): Yield 1.182 g (96%); yellow solid; m.p
85–86 °C. H NMR (400 MHz, CDCl3): δ = 8.14 (d, J = 2.0 Hz, 1
1
H, ArH), 7.79 (dd, J = 8.0, 2.0 Hz, 1 H, ArH), 7.69 (d, J = 7.6 Hz,
2 H, ArH), 7.64 (d, J = 2.0 Hz, 1 H, ArH), 7.58 (dd, J = 8.4,
1.6 Hz, 1 H, ArH), 7.45–7.53 (m, 3 H, ArH), 7.35–7.43 (m, 2 H,
ArH), 3.82–3.94 (m, 2 H, CH2N), 3.54 (s, 3 H, CH3O), 3.22–3.53
(m, 2 H, CH2N), 1.85–2.04 (m, 4 H, 2 ϫ CH2CH2N) ppm. 13C
NMR (100 MHz, CDCl3): δ = 168.3, 151.7, 140.2, 139.5, 137.4,
136.6, 133.3, 132.8, 131.9, 131.5, 129.8, 128.8, 127.8, 127.8, 127.0,
119.6, 116.7, 107.5, 51.8, 51.3, 46.8, 23.8, 23.3 ppm. IR (thin film):
(m,
2 H, CH2CH2CH2O), 0.96 (t, J = 7.2 Hz, 3 H,
CH3CH2CH2CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ =
167.7, 166.7, 151.5, 142.9, 140.3, 136.1, 133.7, 133.1, 133.0, 132.2,
131.6, 130.7, 128.7, 119.5, 119.4, 116.6, 107.6, 64.5, 51.9, 51.3, 46.8,
ν = 3067, 2948, 2875, 2221, 1719, 1410, 1309, 1238, 1088 cm–1. MS
˜
(EI): m/z (%) = 410 (14) [M]+, 340 (18), 312 (100), 297 (66), 269
(19), 240 (18). HRMS (EI-TOF): m/z calcd. for C25H22N4O2 [M]+
410.1743; found 410.1740.
30.7, 23.8, 23.3, 19.1, 13.7 ppm. IR (thin film): ν = 3087, 2950,
˜
2221, 1729, 1702, 1411, 1309, 1259, 1193, 1085 cm–1. MS (EI): m/z
(%) = 460 (26) [M]+, 390 (14), 362 (100), 306 (76), 291 (15), 274
(26). HRMS (EI-TOF): m/z calcd. for C26H28N4O4 [M]+ 460.2111;
found 460.2108.
3Ј-Ethyl (E)-2-Methyl-4-(phenylethynyl)-6Ј-(pyrrolidin-1-yldiazen-
yl)-[1,1Ј-biphenyl]-2,3Ј-dicarboxylate (2h): Yield 1.083 g (75%); yel-
low solid; m.p. 126–128 °C. 1H NMR (400 MHz, CDCl3): δ = 8.03–
8.05 (m, 2 H, ArH), 8.00 (dd, J = 8.4, 2.4 Hz, 1 H, ArH), 7.70 (dd,
J = 7.6, 2.0 Hz, 1 H, ArH), 7.52–7.58 (m, 2 H, ArH), 7.47 (d, J =
8.4 Hz, 1 H, ArH), 7.33–7.41 (m, 4 H, ArH), 4.38 (q, J = 6.8 Hz,
2 H, CH3CH2O), 3.82–3.93 (m, 2 H, CH2N), 3.51 (s, 3 H, CH3O),
3.21–3.49 (m, 2 H, CH2N), 1.85–2.04 (m, 4 H, 2 ϫ CH2CH2N),
1.40 (t, J = 7.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR (100 MHz,
CDCl3): δ = 167.9, 166.6, 151.7, 139.7, 135.2, 134.0, 132.7, 132.2,
131.6, 131.4, 130.9, 129.9, 128.4, 128.3, 126.5, 122.9, 122.0, 115.8,
90.3, 88.5, 60.7, 51.8, 51.1, 46.6, 23.8, 23.4, 14.3 ppm. IR (thin
3Ј-Ethyl 2-Methyl (E)-4-Iodo-6Ј-(pyrrolidin-1-yldiazenyl)-[1,1Ј-bi-
phenyl]-2,3Ј-dicarboxylate (2l): The substituted aniline (10 mmol,
1.0 equiv.) was dissolved in CH3CN (10 mL) at room temperature,
then concentrated hydrochloric acid (4 mL, 50 mmol, 5.0 equiv.)
was added to the mixture. The solution was stirred and cooled to
–10 °C. After 15 min,
a solution of NaNO2 (10.5 mmol,
1.05 equiv.) in cold water (10 mL) was added dropwise. The re-
sulting solution of the diazonium salt was stirred for 2 h and then
potassium iodide solution (1.2 equiv.) in water (12.4 mL) was
slowly added to the mixture, which was then warmed to room tem-
perature and stirred for 2 h. After completion (reaction monitored
by TLC), the reaction mixture was extracted with ethyl acetate.
The organic layer was dried with anhydrous Na2SO4, concentrated
under reduced pressure, and purified by silica gel chromatography
to give pure product 2l (1.014 g, 20%) as a brown oil. 1H NMR
(400 MHz, CDCl3): δ = 8.17 (d, J = 1.6 Hz, 1 H, ArH), 7.95–8.01
(m, 2 H, ArH), 7.86 (dd, J = 8.4, 1.6 Hz, 1 H, ArH), 7.44 (d, J =
8.4 Hz, 1 H, ArH), 7.11 (d, J = 8.0 Hz, 1 H, ArH), 4.37 (q, J =
6.8 Hz, 2 H, CH3CH2O), 3.81–3.93 (m, 2 H, CH2N), 3.48 (s, 3 H,
film): ν = 3072, 2969, 2259, 1709, 1392, 1230, 1103 cm–1. MS (EI):
˜
m/z (%) = 481 (16) [M]+, 383 (100), 355 (28), 340 (41). HRMS (EI-
TOF): m/z calcd. for C29H27N3O4 [M]+ 481.2002; found 481.2009.
Methyl (E)-5Ј-Cyano-4-(phenylethynyl)-2Ј-(pyrrolidin-1-yldiazenyl)-
[1,1Ј-biphenyl]-2-carboxylate (2i): Yield 1.082 g (83%); yellow solid;
m.p. 161–164 °C. 1H NMR (400 MHz, CDCl3): δ = 8.05 (d, J =
1.2 Hz, 1 H, ArH), 7.69 (dd, J = 8.0, 1.6 Hz, 1 H, ArH), 7.48–7.61
(m, 5 H, ArH), 7.33–7.39 (m, 3 H, ArH), 7.29 (d, J = 7.2 Hz, 1 H,
ArH), 3.82–3.94 (m, 2 H, CH2N), 3.54 (s, 3 H, CH3O), 3.20–3.50
(m, 2 H, CH2N), 1.86–2.04 (m, 4 H, 2 ϫ CH2CH2N) ppm. 13C
NMR (100 MHz, CDCl3): δ = 167.6, 151.5, 138.4, 136.3, 134.2,
133.1, 132.5, 132.3, 132.1, 131.6, 131.1, 131.0, 128.5, 128.4, 122.8,
122.6, 119.5, 116.6, 107.5, 90.7, 88.2, 51.9, 51.3, 46.8, 23.8,
CH3O), 3.18–3.45 (m,
2 H, CH2N), 1.85–2.02 (m, 4 H,
2 ϫ CH2CH2N), 1.39 (t, J = 6.8 Hz, 3 H, CH3CH2O) ppm. 13C
NMR (100 MHz, CDCl3): δ = 167.1, 166.5, 151.6, 140.2, 139.4,
137.6, 134.8, 134.1, 133.0, 130.8, 129.9, 126.5, 115.9, 91.8, 60.7,
23.3 ppm. IR (thin film): ν = 3043, 2947, 2884, 2218, 1710, 1596,
˜
51.9, 51.1, 46.6, 23.8, 23.4, 14.3 ppm. IR (thin film):ν = 3057, 2918,
˜
1383, 1306, 1266 cm–1. MS (EI): m/z (%) = 434 (21) [M]+, 336 (100),
321 (98), 293 (28), 264 (29). HRMS (EI-TOF): m/z calcd. for
C27H22N4O2 [M]+ 434.1743; found 434.1743.
2850, 1704, 1435, 1259, 1230, 1101, 1031 cm–1. MS (EI): m/z (%)
= 507 (8) [M]+, 409 (100), 381 (54), 366 (26), 349 (23). HRMS (EI-
TOF): m/z calcd. for C21H22IN3O4 [M]+ 507.0655; found 507.0655.
3Ј-Ethyl 2-Methyl 4-[(E)-3-Butoxy-3-oxoprop-1-en-1-yl]-6Ј-[(E)-pyr-
rolidin-1-yldiazenyl]-1,1Ј-biphenyl-2,3Ј-dicarboxylate (2j): Yield
General Procedure for the Synthesis of Dibenzopyranones 3a–l:
Boron trifluoride–diethyl ether (2.8 equiv.) was added dropwise to
6
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Job/Unit: O30660
/KAP1
Date: 10-07-13 17:02:53
Pages: 11
Synthesis of Dibenzopyranones and Coumarins from Biaryltriazenes
a stirred solution of 2 (0.5 mmol) in the anhydrous CH3CN
(20 mL) at 40 °C. The mixture was stirred for 4 h. Upon comple-
tion of the reaction (determined by TLC analysis), the mixture was
washed with NaHCO3 and extracted with ethyl acetate. The com-
bined organic extracts were dried with anhydrous Na2SO4 and the
solvent was removed under reduced pressure. The product was
purified by column chromatography.
1735, 1708, 1610, 1271, 1238, 1114, 1032 cm–1. MS (EI): m/z (%)
= 416 (100) [M]+, 371 (68), 343 (23), 315 (10), 287 (8), 259 (8), 213
(18). HRMS (EI-TOF): m/z calcd. for C25H20O6 [M]+ 416.1260;
found 416.1259.
Ethyl 6-Oxo-8-phenyl-6H-benzo[c]chromene-2-carboxylate (3f):
Yield 143 mg (83%); white solid; m.p. 212–214 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.73 (d, J = 2.0 Hz, 1 H, ArH), 8.57 (d, J
= 2.0 Hz, 1 H, ArH), 8.23 (d, J = 8.4 Hz, 1 H, ArH), 8.11 (dd, J
= 8.8, 2.0 Hz, 1 H, ArH), 8.07 (dd, J = 8.4, 1.6 Hz, 1 H, ArH),
Ethyl 6-Oxo-6H-benzo[c]chromene-2-carboxylate (3a): Yield 128 mg
(95%); white solid; m.p. 134–136 °C. 1H NMR (400 MHz, CDCl3):
δ = 8.76 (d, J = 1.2 Hz, 1 H, ArH), 8.40 (d, J = 6.4 Hz, 1 H, ArH), 7.67 (d, J = 7.2 Hz, 2 H, ArH), 7.49 (t, J = 7.6 Hz, 2 H, ArH),
8.21 (d, J = 6.4 Hz, 1 H, ArH), 8.13 (dd, J = 6.8, 1.2 Hz, 1 H,
ArH), 7.87 (t, J = 7.0 Hz, 1 H, ArH), 7.63 (t, J = 7.0 Hz, 1 H,
ArH), 7.39 (d, J = 6.8 Hz, 1 H, ArH), 4.44 (q, J = 5.6 Hz, 2 H,
7.42 (d, J = 7.2 Hz, 1 H, ArH), 7.38 (d, J = 8.8 Hz, 1 H, ArH),
4.44 (q, J = 7.2 Hz, 2 H, CH3CH2O), 1.45 (t, J = 7.2 Hz, 3 H,
CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ = 165.4, 160.5,
CH3CH2O), 1.44 (t, J = 5.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR 153.9, 142.2, 138.5, 133.6, 132.6, 131.2, 129.0, 128.4, 128.4, 126.9,
(100 MHz, CDCl3): δ = 165.5, 160.5, 154.1, 135.1, 134.1, 131.4, 126.8, 124.8, 122.6, 121.4, 117.7, 61.4, 14.3 ppm. IR (thin film): ν
˜
130.6, 129.4, 126.8, 124.9, 122.0, 121.1, 117.9, 117.9, 61.4, = 3062, 2985, 2928, 1716, 1610, 1256, 1199, 1107, 1035 cm–1. MS
14.4 ppm. IR (thin film): ν = 3062, 2973, 2876, 1719, 1410, 1309,
(EI): m/z (%) = 344 (100) [M]+, 316 (28), 299 (63), 271 (6), 243
˜
1239 cm–1. MS (EI): m/z (%) = 268 (83) [M]+, 253 (10), 240 (47), (23), 215 (29). HRMS (EI-TOF): m/z calcd. for C22H16O4 [M]+
223 (100), 195 (10), 167 (34), 139 (60). HRMS (EI-TOF): m/z calcd.
344.1049; found 344.1046.
for C16H12O4 [M]+ 268.0736; found 268.0738.
6-Oxo-8-phenyl-6H-benzo[c]chromene-2-carbonitrile (3g): Yield
134 mg (90%); white solid; m.p. 268–270 °C. H NMR (400 MHz,
CDCl3): δ = 8.66 (d, J = 1.6 Hz, 1 H, ArH), 8.41 (d, J = 2.0 Hz, 1
1
6-Oxo-6H-benzo[c]chromene-2-carbonitrile (3b): Yield 46 mg
(41%); white solid; m.p. 256–257 °C. 1H NMR (400 MHz, CDCl3):
δ = 8.44 (d, J = 6.0 Hz, 1 H, ArH), 8.40 (s, 1 H, ArH), 8.13 (d, J H, ArH), 8.12–8.22 (m, 2 H, ArH), 7.76 (dd, J = 8.8, 2.0 Hz, 1 H,
= 6.4 Hz, 1 H, ArH), 7.93 (t, J = 7.0 Hz, 1 H, ArH), 7.76 (d, J =
6.8 Hz, 1 H, ArH), 7.71 (t, J = 6.4 Hz, 1 H), 7.48 (d, J = 6.8 Hz,
1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 159.8, 153.7, 135.5,
133.4, 132.8, 130.9, 130.3, 127.7, 121.9, 121.3, 119.2, 119.2, 118.0,
ArH), 7.71 (d, J = 7.6 Hz, 2 H, ArH), 7.42–7.55 (m, 4 H,
ArH) ppm. 13C NMR (100 MHz, CDCl3): δ = 159.9, 153.6, 143.3,
138. 4, 134.0, 133.3, 131.4, 129.2, 128.8, 128.7, 127.6, 127.1, 122.6,
121.7, 119.2, 119.1, 118.0, 108.8 ppm. IR (thin film): ν = 3072,
˜
108.7 ppm. IR (thin film): ν = 3087, 2923, 2859, 2225, 1731, 1606,
2921, 2854, 2229, 1748, 1483, 1278, 1249, 1202, 1067 cm–1. MS
(EI): m/z (%) = 297 (100) [M]+, 269 (13), 240 (15), 214 (4). HRMS
(EI-TOF): m/z calcd. for C20H11NO2 [M]+ 297.0790; found
297.0789.
˜
1292, 1265, 1242, 1067, 1031 cm–1. MS (EI): m/z (%) = 221 (100)
[M]+, 193 (42), 164 (26), 138 (9). HRMS (EI-TOF): m/z calcd. for
C14H7NO2 [M]+ 221.0477; found 221.0476.
2-Methyl-6H-benzo[c]chromen-6-one (3c): Yield 79 mg (75%); white
solid; m.p. 123–126 °C. 1H NMR (400 MHz, CDCl3): δ = 8.38 (dd,
J = 6.0, 0.8 Hz, 1 H, ArH), 8.09 (d, J = 6.4 Hz, 1 H, ArH), 7.78–
7.85 (m, 2 H, ArH), 7.54–7.60 (m, 1 H, ArH), 7.21–7.28 (m, 2 H,
ArH), 2.45 (s, 3 H, CH3) ppm. 13C NMR (100 MHz, CDCl3): δ =
161.3, 149.3, 134.8, 134.7, 134.1, 131.3, 130.5, 128.7, 122.7, 121.6,
Ethyl 6-Oxo-8-(phenylethynyl)-6H-benzo[c]chromene-2-carboxylate
(3h): Yield 162 mg (88%); white solid; m.p. 171–173 °C. H NMR
1
(400 MHz, CDCl3): δ = 8.70–8.75 (m, 1 H, ArH), 8.45–8.53 (m, 1
H, ArH), 8.08–8.21 (m, 2 H, ArH), 7.90–7.96 (m, 1 H, ArH), 7.54
(d, J = 3.6 Hz, 2 H, ArH), 7.35–7.45 (m, 4 H, ArH), 4.43 (q, J =
6.8 Hz, 2 H, CH3CH2O), 1.45 (t, J = 6.8 Hz, 3 H, CH3CH2O) ppm.
13C NMR (100 MHz, CDCl3): δ = 165.4, 159.7, 154.0, 137.5, 133.5,
133.2, 131.8, 131.6, 128.9, 128.5, 127.0, 125.1, 124.9, 122.4, 122.2,
121.2, 117.6, 117.4, 21.1 ppm. IR (thin film): ν = 3057, 2920, 2869,
˜
1717, 1267, 1211, 1073, 1037 cm–1. MS (EI): m/z (%) = 210 (100)
[M]+, 181 (43), 152 (22). HRMS (EI-TOF): m/z calcd. for C14H10O2
[M]+ 210.0681; found 210.0682.
121.2, 117.9, 117.5, 92.4, 87.6, 61.5, 14.4 ppm. IR (thin film): ν =
˜
3052, 2923, 2859, 1733, 1712, 1612, 1248, 1112, 1030 cm–1. MS
(EI): m/z (%) = 368 (100) [M]+, 340 (23), 323 (35), 267 (16), 239
(24). HRMS (EI-TOF): m/z calcd. for C24H16O4 [M]+ 368.1049;
found 368.1048.
2,4-Dimethyl-6H-benzo[c]chromen-6-one (3d): Yield 108 mg (96%);
white solid; m.p. 173–175 °C. 1H NMR (400 MHz, CDCl3): δ =
8.36 (dd, J = 8.0, 0.8 Hz, 1 H, ArH), 8.05 (d, J = 8.4 Hz, 1 H,
ArH), 7.73–7.79 (m, 1 H, ArH), 7.62 (s, 1 H, ArH), 7.53 (t, J = 6-Oxo-8-(phenylethynyl)-6H-benzo[c]chromene-2-carbonitrile (3i):
7.6 Hz, 1 H, ArH), 7.11 (s, 1 H, ArH), 2.42 (s, 3 H, CH3), 2.40 (s,
3 H, CH3) ppm. 13C NMR (100 Hz, CDCl3): δ = 161.3, 147.6,
135.1, 134.5, 133.3, 132.7, 130.4, 128.4, 126.5, 121.7, 121.0, 120.2,
Yield 143 mg (89%); white solid; m.p. 214–216 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.56 (s, 1 H, ArH), 8.37 (s, 1 H, ArH),
8.10 (d, J = 8.4 Hz, 1 H, ArH), 8.01 (dd, J = 8.8, 1.6 Hz, 1 H,
117.2, 21.0, 15.8 ppm. IR (thin film): ν = 3082, 2920, 2859, 1714, ArH), 7.76 (dd, J = 8.4, 1.6 Hz, 1 H, ArH), 7.56–7.62 (m, 2 H,
˜
1316, 1123, 1072 cm–1. MS (EI): m/z (%) = 224 (100) [M]+, 209
(30), 181 (21), 165 (17). HRMS (EI-TOF): m/z calcd. for C15H12O2
[M]+ 224.0837; found 224.0834.
ArH), 7.48 (d, J = 8.4 Hz, 1 H, ArH), 7.35–7.43 (m, 3 H,
ArH) ppm. 13C NMR (100 MHz, CDCl3): δ = 159.1, 153.7, 137.9,
133.7, 133.6, 131.9, 131.8, 129.1, 128.5, 127.8, 125.9, 122.2, 122.1,
121.5, 119.2, 118.9, 117.9, 108.9, 93.2, 87.3 ppm. IR (thin film): ν
˜
Ethyl
8-(4-Ethoxycarbonylphenyl)-6-oxo-6H-benzo[c]chromene-2-
= 3063, 2923, 2859, 2229, 1739, 1611, 1483, 1245, 1112, 1067 cm–1.
MS (EI): m/z (%) = 321 (100) [M]+, 293 (10), 264 (16), 238 (4).
HRMS (EI-TOF): m/z calcd. for C22H11NO2 [M]+ 321.0790; found
321.0793.
carboxylate (3e): Yield 183.1 mg (88%); white solid; m.p. 171–
174 °C. 1H NMR (400 MHz, CDCl3): δ = 8.70 (d, J = 2.0 Hz, 1
H, ArH), 8.54 (d, J = 1.6 Hz, 1 H, ArH), 8.22 (d, J = 8.4 Hz, 1 H,
ArH), 8.04–8.12 (m, 4 H, ArH), 7.70 (d, J = 8.0 Hz, 2 H, ArH),
7.34 (d, J = 8.4 Hz, 1 H, ArH), 4.37–4.45 (m, 4 H, 2 ϫ CH3CH2O), Ethyl
(E)-8-(3-Butoxy-3-oxoprop-1-en-1-yl)-6-oxo-6H-benzo[c]-
1.40–1.46 (m, 6 H, 2 ϫ CH3CH2O) ppm. 13C NMR (100 Hz,
CDCl3): δ = 166.0, 165.3, 160.2, 153.9, 142.6, 140.9, 133.5, 133.3,
131.4, 130.2, 128.7, 126.9, 126.8, 124.9, 122.7, 121.4, 117.8, 117.5,
chromene-2-carboxylate (3j): Yield 164 mg (83%); white solid; m.p.
144–145 °C. 1H NMR (400 MHz, CDCl3): δ = 8.72 (d, J = 1.2 Hz,
1 H, ArH), 8.48 (s, 1 H, ArH), 8.20 (d, J = 8.4 Hz, 1 H, ArH),
8.14 (dd, J = 8.4, 1.6 Hz, 1 H, ArH), 7.96 (d, J = 8.0 Hz, 1 H,
61.4, 61.1, 14.3, 14.2 ppm. IR (thin film): ν = 3082, 2985, 2903,
˜
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7

Job/Unit: O30660
/KAP1
Date: 10-07-13 17:02:53
Pages: 11
X. Shang, L. Xu, W. Yang, J. Zhou, M. Miao, H. Ren
FULL PAPER
ArH), 7.72 (d, J = 16.0 Hz, 1 H, C=CH), 7.38 (d, J = 8.0 Hz, 1 H,
ArH), 6.59 (d, J = 16.0 Hz, 1 H, CH=C), 4.43 (q, J = 7.2 Hz, 2 H,
Dimethyl
(E)-2-{[4Ј-(Ethoxycarbonyl)-4-(pyrrolidin-1-yldiazenyl)-
(1,1Ј-biphenyl)-3-yl]methylene}malonate (5b): Yield 3.40 g (73%);
CH3CH2O), 4.23 (t, J = 6.8 Hz, 2 H, CH2CH2O), 1.66–1.74 (m, 2 white solid; m.p. 129–131 °C. 1H NMR (400 MHz, CDCl3): δ =
H, CH2CH2O), 1.39–1.48 (m, 5 H, CH3CH2CH2CH2O), 0.97 (t, J 8.57 (s, 1 H, ArH), 8.09 (d, J = 6.8 Hz, 2 H, ArH), 7.66 (s, 1 H,
= 7.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ
= 166.3, 165.3, 160.0, 154.1, 141.8, 135.7, 135.0, 133.8, 131.9, 130.0,
127.1, 125.1, 122.8, 121.5, 120.9, 117.9, 117.5, 64.7, 61.5, 30.7, 19.1,
ArH), 7.61 (d, J = 6.8 Hz, 3 H, ArH), 7.55 (d, J = 6.8 Hz, 1 H,
ArH), 4.40 (q, J = 5.6 Hz, 2 H, CH3CH2O), 3.90–4.01 (m, 2 H,
CH2N), 3.85 (s, 3 H, CH3O), 3.75 (s, 3 H, CH3O), 3.67–3.75 (m, 3
H, CH3O), 2.00–2.10 (m, 4 H, 2CH2CH2N), 1.41 (t, J = 5.6 Hz, 3
H, CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ = 167.3,
166.4, 164.8, 149.9, 144.4, 141.8, 136.0, 130.1, 129.7, 129.0, 127.5,
126.8, 126.3, 124.9, 117.6, 60.9, 52.4, 52.4, 51.2, 46.8, 23.9, 23.5,
14.3, 13.7 ppm. IR (thin film): ν = 3062, 2956, 2864, 1749, 1706,
˜
1612, 1255, 1169, 1028 cm–1. MS (EI): m/z (%) = 394 (57) [M]+,
349 (17), 338 (100), 321 (43), 293 (61), 265 (11). HRMS (EI-TOF):
m/z calcd. for C23H22O6 [M]+ 394.1416; found 394.1413.
14.3 ppm. IR (thin film): ν = 3048, 2955, 2874, 1714, 1603, 1254,
˜
Butyl (E)-3-(2-Cyano-6-oxo-6H-benzo[c]chromen-8-yl)acrylate (3k):
Yield 131 mg (75%); white solid; m.p. 238–240 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.55 (s, 1 H, ArH), 8.39 (s, 1 H, ArH),
8.14 (d, J = 8.0 Hz, 1 H, ArH), 8.03 (d, J = 8.8 Hz, 1 H, ArH),
7.73–7.78 (m, 2 H, ArH), 7.48 (d, J = 8.4 Hz, 1 H, ArH),
6.63 (d, J = 16.0 Hz, 1 H, C=CH), 4.24 (t, J = 6.4 Hz, 2 H,
1166, 1108 cm–1. MS (EI): m/z (%) = 465 (28) [M]+, 396 (24), 367
(100), 339 (36), 325 (13). HRMS (EI-TOF): m/z calcd. for
C25H27N3O6 [M]+ 465.1900; found 465.1900.
Dimethyl 2-{5-[(E)-3-Butoxy-3-oxoprop-1-en-1-yl]-2-[(E)-pyrrolidin-
1-yldiazenyl]benzylidene}malonate (5c): Yield 2.57 g (58%); white
1
CH2CH2O), 1.68–1.75 (m,
2
H, CH2CH2O), 1.42–1.49 (m,
7.2 Hz, H,
solid; m.p. 69–71 °C. H NMR (400 MHz, CDCl3): δ = 8.47 (s, 1
2
H, CH2CH2CH2O), 0.98 (t,
J
=
3
H, ArH), 7.59 (d, J = 16.0 Hz, 1 H, C=CH), 7.43–7.51 (m, 3 H,
ArH), 6.34 (d, J = 16.0 Hz, 1 H, CH=C), 4.19 (t, J = 6.4 Hz, 2 H,
CH3CH2O), 3.90–4.00 (m, 2 H, CH2N), 3.84 (s, 3 H, CH3O), 3.75
(s, 3 H, CH3O), 3.66–3.74 (m, 2 H, CH2N), 1.98–2.10 (m, 4 H,
2 ϫ CH2CH2N), 1.63–1.73 (m, 2 H, CH2CH2O), 1.37–1.47 (m, 2
H, CH2CH2CH2O), 0.96 (t, J = 7.2 Hz, 3 H, CH3CH2O) ppm. 13C
NMR (100 MHz, CDCl3): δ = 167.1, 164.7, 151.4, 143.7, 141.6,
130.8, 130.3, 128.3, 127.6, 125.3, 117.4, 117.2, 64.4, 52.5, 52.5, 51.4,
CH3CH2CH2CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ =
166.3, 159.3, 153.8, 141.5, 136.7, 134.2, 133.9, 133.6, 130.2, 127.9,
122.7, 121.8, 121.6, 119.3, 118.8, 117.8, 109.0, 64.9, 30.7, 19.2,
13.7 ppm. IR (thin film): ν = 3062, 2958, 2879, 2228, 1752, 1713,
˜
1638, 1166, 1060 cm–1. MS (EI): m/z (%) = 347 (24) [M]+, 291 (100),
274 (58), 247 (40). HRMS (EI-TOF): m/z calcd. for C21H17NO4
[M]+ 347.1158; found 347.1155.
47.0, 30.7, 23.9, 23.4, 19.2, 13.7 ppm. IR (thin film): ν = 3033,
˜
Ethyl 8-Iodo-6-oxo-6H-benzo[c]chromene-2-carboxylate (3l): Yield
166 mg (84%); white solid; m.p. 181–191 °C. H NMR (400 MHz,
CDCl3): δ = 8.73 (d, J = 0.9 Hz, 2 H, ArH), 8.16 (t, J = 2.0 Hz, 1
H, ArH), 8.14 (t, J = 2.0 Hz, 1 H, ArH), 7.94 (d, J = 9.2 Hz, 1 H,
ArH), 7.39 (d, J = 8.4 Hz, 1 H, ArH), 4.44 (q, J = 6.8 Hz, 2 H,
2954, 2874, 1726, 1702, 1625, 1396, 1255, 1220, 1159 cm–1. MS
(EI): m/z (%) = 443 (13) [M]+, 373 (7), 345 (100), 289 (57). HRMS
(EI-TOF): m/z calcd. for C23H29N3O6 [M]+ 443.2056; found
443.2057.
1
CH3CH2O), 1.44 (t, J = 7.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR Dimethyl
(E)-2-{[4Ј-Methoxy-4-(pyrrolidin-1-yldiazenyl)-(1,1Ј-bi-
(100 MHz, CDCl3): δ = 165.4, 159.0, 154.0, 143.9, 139.3, 133.4, phenyl)-3-yl]methylene}malonate (5d): Yield 2.29 g (54%); yellow
1
131.8, 127.1, 124.8, 123.6, 122.5, 118.0, 117.4, 94.5, 61.5, 14.4 ppm.
solid; m.p. 111–113 °C. H NMR (400 MHz, CDCl3): δ = 8.59 (s,
1 H, ArH), 7.58 (d, J = 1.6 Hz, 1 H, ArH), 7.46–7.55 (m, 4 H,
IR (thin film): ν = 3072, 2922, 2859, 1712, 1249, 1103 cm–1. MS
˜
(EI): m/z (%) = 394 (40) [M]+, 349 (39), 86 (77), 58 (53), 43 (100). ArH), 6.96 (d, J = 8.4 Hz, 2 H, ArH), 3.88–4.04 (m, 2 H, CH2N),
HRMS (EI-TOF): m/z calcd. for C16H11IO4 [M]+ 393.9702; found
393.9706.
3.85 (s, 3 H, CH3O), 3.84 (s, 3 H, CH3O), 3.76 (s, 3 H, CH3O),
3.66–3.74 (m, 2 H, CH2N), 1.95–2.12 (m, 4 H, 2CH2CH2N) ppm.
13C NMR (100 MHz, CDCl3): δ = 167.5, 165.0, 159.1, 148.8, 142.3,
137.1, 132.7, 129.4, 127.6, 127.4, 126.0, 124.5, 117.4, 114.3, 55.3,
General Procedure for the Synthesis of Aryltriazenes 5a–d: A mix-
ture of substituted 2-(pyrrolidin-1-ylazo)benzaldehyde (10 mmol),
dimethyl malonate (1.2 equiv.), piperidine (0.2 mL) and benzoic
acid (0.14 g) in benzene (10 mL) was heated to reflux overnight in
a 25 mL flask using a Dean–Stark trap. Upon completion of the
reaction (TLC), the residue was extracted with ethyl acetate. The
combined organic extracts were dried with anhydrous Na2SO4 and
concentrated under reduced pressure. The product was purified by
flash column chromatography and recrystallization using hexane
and ethyl acetate.
52.4, 51.1, 46.8, 23.8, 23.6 ppm. IR (thin film): ν = 3033, 2951,
˜
2874, 1726, 1610, 1435, 1245, 1214, 1168, 1070 cm–1. MS (EI): m/z
(%) = 423 (5) [M]+, 231 (100), 203 (12), 121 (69). HRMS (EI-TOF):
m/z calcd. for C23H25N3O5 [M]+ 423.1794; found 423.1792.
General Procedure for the Synthesis of Coumarins 6a–d: Boron tri-
fluoride–diethyl ether (5.0 equiv.) was added dropwise to a stirred
solution of 5 (0.5 mmol) in anhydrous CH3CN (20 mL) at 40 °C.
The mixture was stirred overnight. Upon completion of the reac-
tion (TLC), the mixture was washed with satd. aq NaHCO3 and
extracted with ethyl acetate. The combined organic extracts were
dried with anhydrous MgSO4 and removed under reduced pressure.
The product was purified by column chromatography.
Dimethyl (E)-2-[5-(Ethoxycarbonyl)-2-(pyrrolidin-1-yldiazenyl)benz-
ylidene]malonate (5a): Yield 2.53 g (65%); white solid; m.p. 117–
1
119 °C. H NMR (400 MHz, CDCl3): δ = 8.51 (s, 1 H, ArH), 8.06
(d, J = 1.6 Hz, 1 H, ArH), 7.97 (dd, J = 6.8, 1.6 Hz, 1 H, ArH),
7.50 (d, J = 6.8 Hz, 1 H), 4.34 (q, J = 5.6 Hz, 2 H, CH3CH2O),
3.96 (t, J = 4.8 Hz, 2 H, CH2N), 3.84 (s, 3 H, OCH3), 3.82 (s, 3
6-Ethyl 3-Methyl 2-Oxo-2H-chromene-3,6-dicarboxylate (6a): Yield
83 mg (60%); white solid; m.p. 169–172 °C. 1H NMR (400 MHz,
H, OCH3), 3.71 (t, J = 5.2 Hz, 2 H, CH2N), 2.01–2.08 (m, 4 H, CDCl3): δ = 8.60 (s, 1 H, ArH), 8.33 (d, J = 2.0 Hz, 1 H, ArH),
2 ϫ CH2CH2N), 1.38 (t, J = 5.6 Hz, 3 H, CH3CH2O) ppm. 13C 8.30 (dd, J = 8.4, 2.0 Hz, 1 H, ArH), 7.40 (d, J = 8.8 Hz, 1 H,
NMR (100 Hz, CDCl3): δ = 167.1, 166.0, 164.7, 153.3, 141.0, 132.1,
129.9, 126.6, 126.3, 125.2, 116.7, 60.8, 52.5, 52.4, 51.4, 47.1, 23.9,
ArH), 4.41 (q, J = 7.2 Hz, 2 H, CH3CH2O), 3.96 (s, 3 H, CH3O),
1.41 (t, J = 7.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR (100 MHz,
CDCl3): δ = 164.7, 163.2, 157.7, 155.9, 148.7, 135.1, 131.5, 127.4,
23.4, 14.3 ppm. IR (thin film): ν = 3048, 2954, 2884, 1727, 1699,
˜
1388, 1243, 1210, 1164, 1122 cm–1. MS (EI): m/z (%) = 389 (12)
[M]+, 358 (2), 344 (7), 291 (84), 263 (100). HRMS (EI-TOF): m/z
calcd. for C19H23N3O6 [M]+ 389.1587; found 389.1589.
118.7, 117.5, 117.0, 61.6, 53.0, 14.3 ppm. IR (thin film): ν = 3062,
˜
2999, 2953, 1751, 1719, 1702, 1572, 1302, 1242, 1208, 1022 cm–1.
MS (EI): m/z (%) = 276 (51) [M]+, 261 (6), 245 (33), 231 (100), 217
8
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O30660
/KAP1
Date: 10-07-13 17:02:53
Pages: 11
Synthesis of Dibenzopyranones and Coumarins from Biaryltriazenes
(30). HRMS (EI-TOF): m/z calcd. for C14H12O6 [M]+ 276.0634; 137.0, 135.8, 133.9, 131.8, 131.1, 130.6, 130.6, 130.5, 128.9, 127.7,
found 276.0630. 126.8, 125.4, 118.2, 117.2, 60.9, 60.7, 51.3, 46.9, 23.7, 23.3, 23.1,
14.3 ppm. IR (thin film): ν = 3315, 2976, 2856, 1708, 1596, 1520,
˜
Methyl
6-(4-Ethoxycarbonylphenyl)-2-oxo-2H-chromene-3-carb-
1270, 1235, 1172, 1103 cm–1. MS (EI): m/z (%) = 310 (100) [M]+,
514 (11), 441 (8), 416 (100), 388 (29), 360 (46). HRMS (EI-TOF):
m/z calcd. for C29H30N4O5 [M]+ 514.2216; found 514.2214.
oxylate (6b): Yield 71 mg (40%); yellow solid; m.p. 205–207 °C. 1H
NMR (400 MHz, CDCl3): δ = 8.63 (s, 1 H, ArH), 8.14 (d, J =
11.2 Hz, 2 H, ArH), 7.89 (dd, J = 11.2, 3.2 Hz, 1 H, ArH), 7.83
(d, J = 2.4 Hz, 1 H, ArH), 7.64 (d, J = 11.2 Hz, 2 H, ArH), 7.45
(d, J = 11.6 Hz, 1 H, ArH), 4.40 (q, J = 9.6 Hz, 2 H, CH3CH2O),
3.96 (s, 3 H,CH3O), 1.41 (t, J = 9.6 Hz, 3 H, CH3CH2O) ppm. 13C
NMR (100 MHz, CDCl3): δ = 166.1, 163.5, 156.4, 154.9, 148.9,
143.0, 137.1, 133.3, 130.3, 130.0, 127.8, 126.9, 118.5, 118.1, 117.4,
Ethyl (E)-2Ј-(4-methylphenyl)carbamoyl-6-(pyrrolidin-1-yldiazenyl)-
[1,1Ј-biphenyl]-3-carboxylate (7b): Yield 630 mg (46%); brown oil.
1H NMR (400 MHz, CDCl3): δ = 7.98–8.05 (m, 3 H, ArH), 7.88–
7.92 (m, 1 H, ArH), 7.42–7.51 (m, 3 H, ArH), 7.23–7.28 (m, 1 H,
ArH), 6.98–7.02 (m, 4 H, ArH), 4.35 (q, J = 5.6 Hz, 2 H,
CH3CH2O), 3.75–3.85 (m, 2 H, CH2N), 3.23–3.50 (m, 2 H, CH2N),
2.24 (s, 3 H, CH3), 1.88–1.98 (m, 4 H, 2 ϫ CH2CH2N), 1.37 (t, J
= 5.6 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 166.7,
166.3, 152.3, 137.0, 136.5, 135.6, 134.4, 133.4, 131.9, 131.0, 130.5,
130.1, 129.2, 128.8, 127.6, 126.8, 119.6, 117.2, 60.9, 51.3, 46.9, 23.8,
61.1, 52.9, 14.3 ppm. IR (thin film): ν = 3052, 2956, 2929, 1758,
˜
1705, 1266, 1204, 1214, 1106 cm–1. MS (EI): m/z (%) = 352 (100)
[M]+, 321 (14), 307 (62), 293 (10). HRMS (EI-TOF): m/z calcd. for
C20H16O6 [M]+ 352.0947; found 352.0949.
Methyl (E)-6-(3-Butoxy-3-oxoprop-1-en-1-yl)-2-oxo-2H-chromene-
3-carboxylate (6c): Yield 83 mg (50%); yellow solid; m.p. 140–
142 °C. H NMR (400 MHz, CDCl3): δ = 8.55 (s, 1 H, ArH), 7.81
(dd, J = 8.8, 1.6 Hz, 1 H, ArH), 7.72 (d, J = 1.6 Hz, 1 H, ArH),
7.68 (d, J = 16.0 Hz, 1 H, C=CH), 7.38 (d, J = 8.8 Hz, 1 H, ArH),
6.46 (d, J = 16.0 Hz, 1 H, CH=C), 4.23 (t, J = 6.4 Hz, 2 H,
CH3CH2O), 3.97 (s, 3 H, CH3O), 1.65–1.75 (m, 2 H, CH2CH2O),
1.38–1.48 (m, 2 H, CH2CH2CH2O), 0.97 (t, J = 7.2 Hz, 3 H,
CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ = 166.5, 163.4,
155.9, 148.5, 141.8, 133.1, 131.6, 129.1, 119.9, 118.7, 118.1, 117.6,
23.4, 20.8, 14.3 ppm. IR (thin film): ν = 3306, 3058, 2976, 2875,
˜
1
1708, 1665, 1598, 1306, 1234, 1106 cm–1. MS (EI): m/z (%) = 456
(15) [M]+, 411 (8), 358 (92), 330 (100), 285 (45), 253 (24). HRMS
(EI-TOF): m/z calcd. for C27H28N4O3 [M]+ 456.2161; found
456.2166.
General Procedure for Synthesis of 8a and 8b: Boron trifluoride–
diethyl ether (2.8 equiv.) was added dropwise to a stirred solution
of 7 (0.5 mmol) in anhydrous CH3CN (20 mL) at 40 °C, and the
mixture was stirred for 4 h. Upon completion of the reaction
(TLC), the mixture was washed with NaHCO3 and extracted with
ethyl acetate. The combined organic extracts were dried with anhy-
drous Na2SO4 and removed under reduced pressure. The product
was purified by column chromatography.
64.7, 53.0, 30.7, 19.2, 13.7 ppm. IR (thin film): ν = 3048, 2961,
˜
2879, 1768, 1747, 1700, 1612, 1568, 1248, 1170, 1007 cm–1. MS
(EI): m/z (%) = 330 (25) [M]+, 299 (9), 274 (100), 257 (58), 243
(26), 229 (13). HRMS (EI-TOF): m/z calcd. for C18H18O6 [M]+
330.1103; found 330.1106.
Methyl
6-(4-Methoxyphenyl)-2-oxo-2H-chromene-3-carboxylate
Ethyl 5-[4-(Ethoxycarbonyl)phenyl]-6-oxo-5,6-dihydrophenanthrid-
1
(6d): Yield 39 mg (25%); yellow solid; m.p. 145–149 °C. H NMR
(500 MHz, CDCl3): δ = 8.62 (s, 1 H, ArH), 7.82 (dd, J = 8.5,
2.0 Hz, 1 H, ArH), 7.73 (d, J = 2.0 Hz, 1 H, ArH), 7.51 (d, J =
8.5 Hz, 2 H, ArH), 7.41 (d, J = 8.5 Hz, 1 H, ArH), 7.01 (d, J =
9.0 Hz, 1 H, ArH), 3.97 (s, 3 H,CH3O), 3.87 (s, 3 H, CH3O) ppm.
13C NMR (125 MHz, CDCl3): δ = 163.8, 159.8, 156.8, 154.2, 149.3,
138.1, 133.1, 131.4, 128.1, 126.9, 118.2, 118.1, 117.1, 114.6, 55.4,
ine-2-carboxylate (8a): Yield 156 mg (75%); white solid; m.p. 133–
1
135 °C. H NMR (400 MHz, CDCl3): δ = 8.63 (s, 1 H, ArH), 8.46
(d, J = 7.6 Hz, 1 H, ArH), 8.02–8.10 (m, 3 H, ArH), 7.97 (d, J =
8.8 Hz, 1 H, ArH), 7.69 (t, J = 8.0 Hz, 1 H, ArH), 7.52 (t, J =
8.0 Hz, 1 H, ArH), 7.22 (d, J = 8.0 Hz, 2 H, ArH), 7.03 (d, J =
8.4 Hz, 1 H, ArH), 4.35–4.45 (m, 4 H, 2 ϫ CH3CH2O), 1.38–1.45
(m, 6 H, 2 ϫ CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ =
166.5, 165.5, 153.6, 150.6, 148.1, 132.8, 131.0, 130.7, 130.4, 129.3,
128.6, 126.2, 125.8, 124.6, 123.8, 122.3, 121.6, 118.3, 116.8, 61.2,
53.0 ppm. IR (thin film): ν = 3048, 2963, 2922, 2859, 1748, 1696,
˜
1271, 1009 cm–1. MS (EI): m/z (%) = 310 (100) [M]+, 295 (35), 279
(19), 267 (14). HRMS (EI-TOF): m/z calcd. for C18H14O5 [M]+
310.0841; found 310.0843.
60.6, 14.3, 14.3 ppm. IR (thin film): ν = 3072, 2977, 2850, 1706,
˜
1674, 1596, 1279, 1252, 1106, 1032 cm–1. MS (EI): m/z (%) = 415
(100) [M]+, 387 (7), 370 (30), 342 (12), 314 (8). HRMS (EI-TOF):
m/z calcd. for C25H21NO5 [M]+ 415.1420; found 415.1422.
General Procedure for Synthesis of 7a and 7b: Substituted phenyl
halide (3 mmol), substituted boronic acid (1.2 equiv.), tetrakis(tri-
phenylphosphane) palladium(0) (0.05 equiv.) and Cs2CO3
(2.0 equiv.) were dissolved in a solution of 1,4-dioxane (6 mL) and
water (1.5 mL). The mixture was stirred at 100 °C overnight under
a nitrogen atmosphere in a screw-cap vial. Upon completion of
the reaction (TLC), the mixture was diluted with ethyl acetate and
washed with water. The organic fractions were dried with anhy-
drous Na2SO4, and concentrated under vacuo. Purification was
carried out by flash chromatography to afford the corresponding
product.
Ethyl
6-Oxo-5-(p-tolyl)-5,6-dihydrophenanthridine-2-carboxylate
1
(8b): Yield 99 mg (55%); yellow solid; m.p. 116–119 °C. H NMR
(400 MHz, CDCl3): δ = 8.65 (s, 1 H, ArH), 8.50 (d, J = 8.0 Hz, 1
H, ArH), 8.07 (d, J = 8.0 Hz, 1 H, ArH), 7.99 (dd, J = 8.8, 1.2 Hz,
1 H, ArH), 7.67 (t, J = 8.0 Hz, 1 H, ArH), 7.52 (t, J = 8.0 Hz, 1
H, ArH), 7.20 (s, 4 H, ArH), 7.11 (d, J = 8.0 Hz, 1 H, ArH), 4.42
(q, J = 7.6 Hz, 2 H, CH3CH2O), 2.39 (s, 3 H, CH3), 1.44 (t, J =
7.2 Hz, 3 H, CH3CH2O) ppm. 13C NMR (100 MHz, CDCl3): δ =
165.8, 154.1, 147.1, 143.1, 133.6, 132.4, 130.9, 130.5, 129.3, 128.5,
125.9, 124.7, 122.9, 121.6, 118.6, 116.9, 61.2, 21.0, 14.4 ppm. IR
Ethyl (E)-2Ј-[(4-Ethoxycarbonylphenyl)carbamoyl]-6-(pyrrolidin-1-
yldiazenyl)-[1,1Ј-biphenyl]-3-carboxylate (7a): Yield 386 mg (25%);
brown oil. 1H NMR (400 MHz, CDCl3): δ = 8.26 (br., 1 H,
CONH), 7.98–8.03 (m, 2 H, ArH), 7.85–7.90 (m, 3 H, ArH), 7.42–
7.54 (m, 3 H, ArH), 7.28 (dd, J = 7.2, 0.8 Hz, 1 H, ArH), 7.19 (d,
J = 8.4 Hz, 2 H, ArH), 4.25–4.38 (m, 4 H, 2 ϫ CH3CH2O), 3.72–
3.85 (m, 2 H, CH2N), 3.22–3.48 (m, 2 H, CH2N), 1.85–2.00 (m, 4
H, 2 ϫ CH2CH2N), 1.32–1.40 (m, 6 H, 2 ϫ CH3CH2O) ppm. 13C
NMR (100 MHz, CDCl3): δ = 167.0, 166.1, 166.0, 152.2, 142.3,
(thin film): ν = 3037, 2904, 2864, 1705, 1663, 1606, 1249, 1106,
˜
1028 cm–1. MS (EI): m/z (%) = 357 (100) [M]+, 328 (28), 284 (5),
252 (5). HRMS (EI-TOF): m/z calcd. for C23H19NO3 [M]+
357.1365; found 357.1364.
Supporting Information (see footnote on the first page of this arti-
1
cle): Experimental procedures, characterization data, copies of H
and 13C NMR spectra for all products.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
9

Job/Unit: O30660
/KAP1
Date: 10-07-13 17:02:53
Pages: 11
X. Shang, L. Xu, W. Yang, J. Zhou, M. Miao, H. Ren
FULL PAPER
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Acknowledgments
The authors thank the National Nature Science Foundation of
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Job/Unit: O30660
/KAP1
Date: 10-07-13 17:02:53
Pages: 11
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Received: May 5, 2013
Published Online: ᭿
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