Oxidant and Transition-Metal-Free Photoinduced Direct Oxidative Annulation of 1-Aryl-2-(furan/thiophen-2-yl)butane-1,3-diones

Article abstract of DOI:10.1021/acs.joc.7b01839

A photoinduced direct oxidative annulation of 1-aryl-2-(furan/thiophen-2-yl)butane-1,3-diones and ethyl-2-(furan-2-yl)-3-oxo-3-(aryl-2-yl)propanoates in EtOH without the need for any transition metals and oxidants provided access to highly functionalized polyheterocyclic 1-(5-hydroxynaphtho[2,1-b]furan-4-yl)ethanones and 1-(5-hydroxyfuran/thieno/pyrrolo[3,2-e]benzofuran-4-yl)ethanones. The phenomenon of excited-state intramolecular proton transfer (ESIPT) was observed for both 1-(5-hydroxynaphtho[2,1-b]furan-4-yl)ethanone and 1-(5-hydroxy furan/thieno/pyrrolo[3,2-e]benzofuran-4-yl)ethanone analogues.

Full text of DOI:10.1021/acs.joc.7b01839

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Article
Oxidant and Transition-Metal-Free Photoinduced Direct Oxidative
Annulation of 1-Aryl-2-(furan/thiophe-2-yl)butane-1,3-diones
Jin Zhang, Xi Zhang, Tao Wang, Xinbo Yao, Pei Wang, Ping Wang, Sisi Jing, Yong Liang, and Zunting Zhang
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b01839 • Publication Date (Web): 24 Oct 2017
Downloaded from http://pubs.acs.org on October 26, 2017
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Oxidant and TransitionꢀMetalꢀFree Photoinduced Direct Oxidative
Annulation of 1ꢀArylꢀ2ꢀ(furan/thiopheꢀ2ꢀyl)butaneꢀ1,3ꢀdiones
‡
‡
Jin Zhang, Xi Zhang, Tao Wang, Xinbo Yao, Pei Wang, Ping Wang, Sisi Jing, Yong
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†
Liang, Zunting Zhang*
Key Laboratory of the Ministry of Education for Medicinal Resources and Natural Pharmaceutical
Chemistry, National Engineering Laboratory for Resource Development of Endangered Crude
Drugs in Northwest of China, and School of Chemistry and Chemical Engineering, Shaanxi
Normal University, Xi’an 710119, People’s Republic of China.
ABSTRACT: A photoinduced direct oxidative annulation of 1ꢀarylꢀ2ꢀ(furan/thiopheꢀ2ꢀyl)butane
ꢀ1,3ꢀdiones and ethylꢀ2ꢀ(furanꢀ2ꢀyl)ꢀ3ꢀoxoꢀ3ꢀ(arylꢀ2ꢀyl)propanoates in EtOH without the needs of
any transitionꢀmetals and oxidants provided access to highly functionalized polyheterocyclic
1ꢀ(5ꢀhydroxynaphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanones and 1ꢀ(5ꢀhydroxyfuran/thieno/pyrrolo[3,2ꢀe]
benzofuranꢀ4ꢀyl)ethanones. The phenomenon of excitedꢀstate intramolecular proton transfer
(
ESIPT) was observed for both 1ꢀ(5ꢀhydroxynaphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanone and 1ꢀ(5ꢀhydroxy
furan/thieno/pyrrolo[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanone analogues.
TOC graphic
INTRODUCTION:
UV irradiation of stilbenes via an initial equilibration to a photostationary mixture of
transꢀstilbene (1aꢀE) and cisꢀstilbene (1aꢀZ) isomers generates an unstable intermediate
dihydrophenanthrene Ι by ring closure of Zꢀisomer (Scheme 1). In the presence of an oxidant such
1
ꢀ4
as O , I , I /CuCl or TCNE, the intermediate I is converted into phenanthrene 2 by the
2
2
2
2
elimination of two hydrogen atoms. It is the most commonly used method for the synthesis of
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phenanthrene analogues and related heterocyclic compounds.
Scheme 1. Photocyclization of Stilbenes
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At present, literature reports on the intermolecular photocyclization via elimination of hydrogen
is very seldom. In 2014, Reiser et al. reported an Irꢀcatalyzed lightꢀinduced dehydrogenation
reaction for the synthesis of naphtho[2,1ꢀb]furans from vinyl radicals, which were generated from
11
αꢀbromochalcones and heteroarenes (Scheme 2). Most of the photoinduced dehydrogenative
reactions need oxidants or transition metals. Our group previously demonstrated, the photoinduced
intramolecular dehydrogenative annulation of 2,3ꢀdi(hetero)arylchromenꢀ4ꢀone for the synthesis
of 13Hꢀbenzo[c]furo[2,3ꢀa]xanthenꢀ13ꢀones without any requirements for transitionꢀmetals and
12
oxidants.
Scheme 2. Intramolecular Dehydrogenation under Photocatalysis
Following our interest in the synthesis of various heteroaromatics via photochemical
13ꢀ16
reactions,
Herein, we report the photocyclization of 1ꢀarylꢀ2ꢀ(furan/thiopheꢀ2ꢀyl)butaneꢀ1,3ꢀ
diones (3) and ethylꢀ2ꢀ(furanꢀ2ꢀyl)ꢀ3ꢀoxoꢀ3ꢀ(arylꢀ2ꢀyl)propanoates (5) to highly functionalized
heteroaromatics 4 or 6 by elimination of a hydrogen molecule from a cyclic intermediate A,
formed by ketoꢀenol tautomerism of 3 or 5 (Scheme 3). Our mild and bench friendly protocols
which do not require any catalysts and oxidants gave access to fluorescent heteroaromatic of type
4
and 6.
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Scheme 3. Photochemical Syntheses of 4 and 6
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RESULTS and DISCUSSION
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Irradiation of 2ꢀ(furanꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdione (3a, 1 mmol) with a highꢀpressure
mercury lamp (500 W) at ambient temperature in MeCN (100 mL) for 8 h gave 4a in 25% yield
(Table 1, entry 1). The yields of 4a were higher (38%ꢀ56%, entries 2ꢀ5) in polar protic solvents,
e.g. ethanol, methanol or butanol comparing to benzene and hexane (14%ꢀ24%, entries 6ꢀ7).
Interestingly, no significant difference was observed for the yields of 4a (44%ꢀ52%) in either dry
EtOH (calcium hydride) or “wet” EtOH (6.7 mL and 5.0 mL of water) (entries 9ꢀ11). Irradiation of
3a in EtOH in the presence of acid (3 M HCl, pH = 4) or base (3 M NaOH, pH = 8) also gave 4a
in comparable yields (56ꢀ59%, entries 12ꢀ13). Similar yield (55%) was observed with a reduced
ꢀ3
concentration of 3a (5×10 mol/L, entry 8). Finally, the addition of an oxidant (1eq. H
2
2
O ) drops
the yield of 4a to 35 % (entries 14). Since no improved result from latter part of the optimization,
ethanol was finally chosen as the solvent for all further reactions (56%, Table 1, entry 2).
a
Table 1. Optimization of the Intramolecular Oxidative Annulation of 3a
b
Entry
Solvent
Time(h)
Yield
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2
3
4
5
6
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CH CN
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25
56
40
38
52
18
14
3
EtOH
MeOH
nꢀBuOH
tꢀBuOH
PhH
6.5
7.5
6
12.5
11.5
11.5
Hexane
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EtOH:H O = 2:1
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EtOH:H O = 3:1
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EtOH (pH = 4)
EtOH (pH = 8)
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2 2
EtOH+1equiv H O
a
Compound 3a (0.2 mmol) was dissolved in various solvents (20 mL) and irradiated with a highꢀpressure mercury
lamp (500 W) under an argon atmosphere at ambient temperature until 3a was completely consumed as indicated
b
c
ꢀ3
by thinꢀlayer chromatography (TLC). Yields of the isolated product were based on 3a. c (3a) = 5 x10 mol/L,
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0 mL EtOH. EtOH was dried by CaH
2
.
With the optimized condition in hand, a large array of naphtho[2,1ꢀb]furans (4aꢀ4h, 4m) and
naphtho[2,1ꢀb]thiophenes (4iꢀ4l) have been synthesized and listed in Table 2. Generally, starting
substrates 3 bearing an electronꢀdonating substituent (–Me) on furan or thiophene ring gave the
corresponding products 4f or 4l in higher yields compared to those without a substituent (4aꢀ4e,
4
iꢀ4k, and 4m). For example, product 4f was obtained in 72%, while 4a was obtained only in 56%
yield. On the other hand, the presence of electronꢀwithdrawing substituents (–F or –CF ) on the
3
benzene ring of 3 gave corresponding products 4 in lower yields. Introduction of the benzofuran or
thiophene ring to substrates 3 led to the formation of rearrangement products 4 in a longer time
than the substrates with a furan ring (4gꢀ4h and 4iꢀ4l vs 4aꢀ4c).
a
Table 2. Synthesis of Naphtho[2,1ꢀb]furans/thiophenes (4aꢀ4m)
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a
All reactions were carried out on 1 mmol of 3 in 100 mL of EtOH and irradiated with a highꢀpressure mercury
lamp (500 W) under an argon atmosphere at ambient temperature until 3 was completely consumed. Isolated yield
was calculated based on 3.
The synthesis of furan/thieno/pyrrolo[3,2ꢀe]benzofurans were also explored under similar
conditions as depicted in Table 3. Generally, substrates 5 bearing furan (Y = O, 5aꢀ5c, 5gꢀ5h and
5
l) and thiophene (Y = S, 5cꢀ5e, 5i and 5k) gave the corresponding cyclization products 6 in
higher yields (6aꢀ6e, 6gꢀ6l) than the pyrrole derivative (6f, Y = NMe). For example, ring closure
product 6a, which contains two furan moieties, was obtained in 60% yield, while the
pyrroleꢀcontaining product 6f was obtained in only 41% yield. The presence of methyl group on
the heterocyclic ring of 5 led to the formation of ring closure products in higher yields (6b, 6d,
3
6hꢀ6i). In addition, the difference of substituents R also affected the yields of compounds 6aꢀ6l.
3
3
Ring closure product 6b (R = Me, 65 %) was obtained in higher yield than 6h (R = OEt, 49%). It
is worth noting that when the furan/thiophene ring on the 2ꢀposition of 3a/3l was instead by
benzene ring (1,2ꢀdiphenylbutaneꢀ1,3ꢀdione), the corresponding intramolecular dehydrogenative
target product was not obtained.
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Table 3. Synthesis of Furan/Thieno/Pyrrolo[3,2ꢀe]benzofurans (6aꢀ6l)
O
O
OH
O
X
R3
X
R3
EtOH
hv
O
O
5a-5l
6a-6l
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OH
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OH
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S
O
6a (60%, 6 h)
6b (65%, 4.5 h)
6c (54%, 4.5 h)
6d (57%, 6 h)
6e (59%, 6 h)
OH
O
OH
O
OH
O
OH
O
OH
O
O
N
O
O
S
OEt
OEt
OEt
O
O
O
O
O
6f (41%, 18 h)
6g (45%, 4 h)
6h (42%, 4 h)
6i (43%, 2.5 h)
6j (63%, 5 h)
OH
S
O
O
OH
O
O
O
OEt
6k (58%, 3.5 h)
6l (44%, 4.4 h)
a
All reactions were carried out on 1 mmol of 5 in 100 mL of EtOH and irradiated with a highꢀpressure mercury
lamp (500 W) under an argon atmosphere at ambient temperature until 5 was completely. Isolated yield was
calculated based on 5.
The fluorescence spectrum of 4 and 6 were performed in EtOH. The excitation and emission
spectra of selected compounds showed yellowꢀgreen fluorescence (4aꢀ4h, 4m, 6aꢀ6f and 6jꢀ6k,
λ
6
1
Ex max = 365ꢀ411 nm; λEm max = 502ꢀ541 nm, see SIꢀTable 1), and blueꢀpurple fluorescence (6gꢀ6h,
i and 6l, λEx max = 323ꢀ371 nm; λEm max = 396ꢀ429 nm, see SIꢀTable 1). Notably,
ꢀ(5ꢀhydroxynaphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanones (4aꢀ4h, 4m) and 1ꢀ(5ꢀhydroxyfuran/thieno/
pyrrolo[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanones (6aꢀ6f and 6jꢀ6k) showed the phenomenon of
excitedꢀstate intramolecular proton transfer (ESIPT), and the Stokes' shift of them were in the
range of 112ꢀ147 nm.
ESIPT molecules always have a sixꢀmembered ring structure via intramolecular Hꢀbonds
between C=O (or =N–) and OꢀH (or NꢀH) groups on the conjugated system, and the ESIPT
phenomenon possesses two remarkable characteristics: relatively large Stokes shifts ( >100 nm )
18ꢀ20
and ketoneꢀenol tautomerism.
The ESIPT phenomenon of 4 and 6 can be attributed to an
intramolecular hydrogen bond formed between the acetyl and hydroxyl in
1ꢀ(5ꢀhydroxynaphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanone (4a) (Scheme 4). The enol form of A could get to
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an excited state A* upon the UV irradiation, followed by the quick conversation to a more stable
keto form B* by ESIPT. With the release of energy, transition state B* emits fluorescence from
the excited state to the ground state B. In this series of processes, 4a has a good Stokes' shift.
Scheme 4. Intramolecular Dehydrogenation under Photocatalysis
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*
H
O
O
O
*
H
O
O
O
A*
B*
hv Enol absorption
Keto emission
H
O
O
H
O
O
O
O
B
A (4a )
A plausible mechanism for the photocyclization of 4 and 6 has been proposed and presented in
Scheme 5. First of all, compound 3 undergoes an initial equilibration to a photostationary mixture
of ketoꢀ3 and enolꢀ3 isomers,followed by a photochemically allowed ring closure of the enolꢀ3 to
give an unstable intermediate A. Then, a thermal suprafacial [1,5]ꢀH shift gives the intermediate B.
The driving force of this [1,5]ꢀsigmatropic shift can be attributed to the reformation of the
16, 21
aromatic furan ring, which stabilizes the system in terms of thermodynamics.
The
22
ketoꢀenol/enolꢀketo tautomerization of B give a synꢀintermediate C. This relevant transformation
23, 24
has been reported in a number of publications.
Finally, the synꢀintermediate C yields
annulation product 4 by the elimination of a hydrogen molecule. To our delight, the formation of
byꢀproduct hydrogen has been successfully detected by Gas Chromatography and the
corresponding experiments were recorded in supporting information (SIꢀFigure S4). Interestingly,
the dehydrogenative annulation product 4 was still obtained in yield 35% with the presence of an
oxidant (H O ), and the intramolecular photoinduced dehydrogenative cyclization was believed to
2
2
proceed through the S1 state.
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Scheme 5. Proposed Mechanisms for Photocyclization Reaction
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In order to validate the rationality of the proposed mechanism, substrate
7
was
subjected to the optimal photocyclization condition (Scheme 6). However, neither
dehydrogenation product nor byproduct (H ) was detected, which could be explained by
8
2
the lacking of ketoꢀenol tautomerization. It was further indicated that the
ketoꢀenol/enolꢀketo tautomerization of the intermediate is crucial for the formation of
heteroaromatics 4/6 via the intramolecular dehydrogenative cyclization.
Scheme 6. Attempted Photocyclization of 1ꢀPhenylꢀ2ꢀ(thiophenꢀ2ꢀyl)ethanones (7)
CONCLUSION
We have developed an efficient protocol for the synthesis of naphtha[2,1ꢀ
heterozryl[3,2ꢀ ]benzofuran by an intramolecular dehydrogenative photocyclization in
b
]heterozryl and
e
EtOH. This photoꢀinduced direct oxidative annulation of 1ꢀarylꢀ2ꢀ(furan/thiopheꢀ2ꢀyl)
butaneꢀ1,3ꢀdiones and ethylꢀ2ꢀ(furanꢀ2ꢀyl)ꢀ3ꢀoxoꢀ3ꢀ(arylꢀ2ꢀyl)propanoates does not require
the usage of transition metalꢀcatalysts and oxidants. The phenomenon of ESIPT with a
more than 110 nm Stokes’ shift for both 1ꢀ(5ꢀhydroxynaphtho[2,1ꢀ
b]furanꢀ4ꢀyl)ethanones
and 1ꢀ(5ꢀhydroxyfuran/thieno/pyrrolo[3,2ꢀ ]benzofuranꢀ4ꢀyl)ethanones has been observed.
e
EXPERIMENTAL PROCEDURES AND ANALYTICAL DATA
General Information. All solvents and reagents were obtained from commercial sources and used without
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further purification. Thinꢀlayer chromatography was performed on precoated silica gel 60 GF254 plates. Silica gel
1
(
200−300 mesh) was used for column chromatography. H NMR spectra were recorded on 300, 400 or 600 MHz
spectrometers. Spectra were referenced internally to the residual proton resonance in CDCl
3
(δ 7.26 ppm) or
1
3
DMSOꢀd (2.50 ppm). C NMR spectra were recorded on 75, 100 or 150 MHz spectrometers and the spectra were
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54
55
56
57
58
59
60
3 6
referenced to CDCl or DMSOꢀd (δ 77.16 ppm or 39.52 ppm, the middle peak). Coupling constants (J) were
reported in hertz (Hz). Highꢀresolution mass spectrometry (HRMS) was performed using electronꢀspray ionization
quadrupoleꢀtime of flight (ESIꢀQꢀTOF) techniques. Melting points were measured with a Xꢀ5 microꢀmelting point
apparatus and are uncorrected. IR spectra were recorded with a Nicolet 170SX FTꢀIR spectrophotometer on KBr
pellets.
General Procedures for Syntheses of Naphtho[2,1ꢀb]furans/thiophenes (4aꢀ4m) and
Furan/Thieno/Pyrrolo[3,2ꢀe]benzofuran (6aꢀ6l).
2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdiones 3a (1 mmol) were added to an EtOH solution (100 mL), and the
mixture was contained in 100 mL quartz tubes, deaerated by bubbling Ar for 30 min and irradiated with a
o
highꢀpressure mercury lamp (500 W), which was cooled to about 20 C with tap water by means of an internal cold
finger. The progress of the reaction was monitored by TLC at regular intervals until 3a had disappeared
completely. Then, the solvent was removed under reduced pressure, and the residue was purified by column
chromatography on silica gel using petroleum etherꢀethyl acetate (50:1→20:1) or chloroformꢀmethanol
(
100:0.5→50:1) to give the corresponding product 4a. Similarly, compounds 4bꢀ4m and 6aꢀ6l were prepared with
the same method as described above with yields 41~72%.
ꢀ(5ꢀHydroxyꢀnaphtho[2,1ꢀb]furanꢀ4ꢀyl)ꢀethanone (4a). Yield: 56%, 144 mg; Yellow solid; m.p.
1
o
1
1
3
34.5ꢀ136.4 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.61 (s, 1H), 8.47 (d, J = 8.3 Hz, 1H), 7.95 (d, J = 8.1 Hz,
1
3
1H), 7.69 (m, 2H), 7.49 (m, 1H), 7.14 (d, J = 1.3 Hz, 1H), 2.97 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm)
3
ꢀ1
2
3
02.7, 162.7, 149.6, 142.6, 130.9, 130.8, 125.8, 124.8, 123.1, 123.0, 114.8, 105.6, 104.7, 31.5. IR (KBr) ν (cm )
140, 2920, 1610, 1574, 1372, 1302, 1255, 1139, 1104, 1024, 982, 867, 768, 728, 694, 599, 557. HRMS (ESI):
+
m/z [M + H] calculated for C14
H
11
O
3
: 227.0708;found 227.0715.
1
ꢀ(5ꢀHydroxyꢀ8ꢀmethylꢀnaphtho[2,1ꢀb]furanꢀ4ꢀyl)ꢀethanone (4b). Yield: 53%, 128 mg; Yellow solid;
o
1
m.p. 125.4ꢀ126.6 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.62 (s, 1H), 8.33 (d, J = 8.5 Hz, 1H), 7.70 (s, 1H),
3
1
3
7
.65 (d, J = 2.1 Hz, 1H), 7.30 (dd, J = 8.5, 2.1 Hz, 1H), 7.09 (d, J = 2.1 Hz, 1H), 2.90 (s, 3H), 2.56 (s, 3H). C
3
NMR (100 MHz, CDCl ) δ (ppm) 202.4, 162.9, 149.8, 142.4, 141.5, 131.2, 126.7, 125.6, 122.7, 120.9, 114.3,
ꢀ
1
1
8
05.5, 104.2, 31.3, 22.2. IR (KBr) ν (cm ) 3738, 2995, 1608, 1467, 1415, 1364, 1306, 1249, 1129, 1026, 986, 858,
+
13, 731, 694, 615. HRMS (ESI): m/z [M + Na] calculated for C15
H
12
O
3
Na: 263.0684; found 263.0688.
1
ꢀ(8ꢀFluoroꢀ5ꢀhydroxyꢀnaphtho[2,1ꢀb]furanꢀ4ꢀyl)ꢀethanone (4c). Yield: 59%, 146 mg; Yellow solid;
o
1
m.p. 141.2ꢀ143.0 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 14.64 (s, 1H), 8.44 (m, 1H), 7.67 (d, J = 2.1 Hz, 1H),
13
7
1
1
.50 (m, 1H), 7.19 (m, 1H), 7.04 (d, J = 2.1 Hz, 1H), 2.91 (s, 3H). C NMR (100 MHz, CDCl
3
) δ (ppm) 202.5,
1
3
3
2
64.3( J = 253 Hz), 162.6, 150.2, 142.7, 132.6( J = 10 Hz), 128.9( J = 10 Hz), 119.7, 114.3( J = 25 Hz), 114.4,
2
ꢀ1
07.8(d, J = 23 Hz), 105.6, 104.2, 31.4. IR (KBr) ν (cm ) 3161, 3016, 1928, 1757, 1609, 1516, 1428, 1362, 1296,
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2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
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5
5
5
5
5
5
5
5
5
5
6
+
1252, 1185, 1138, 1098, 1018, 953, 811, 696, 606. HRMS (ESI): m/z [M + Na] calculated for C14
45.0614; found 245.0619.
ꢀ(5ꢀHydroxyꢀ8ꢀmethoxynaphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanone (4d). Yield: 63%, 163 mg; Yellow solid;
3
H10FO :
2
1
o
1
3
m.p. 181.8ꢀ184.2 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.73 (s, 1H), 8.41 (d, J = 8.0 Hz, 1H), 7.69 (s, 1H),
1
3
7.27 (s, 1H), 7.11 (m, 2H), 4.00 (s, 3H), 2.93 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 202.1, 163.2, 162.1,
3
ꢀ1
1
2
50.4, 142.4, 133.2, 127.9, 117.4, 115.9, 114.2, 105.6, 103.6, 103.4, 55.7, 31.3. IR (KBr) ν (cm ) 3146, 3111,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
928, 2031, 1907, 1739, 1612, 1435, 1384, 1309, 1214, 1149, 1086, 1018, 851, 748, 702, 603, 534. HRMS (ESI):
+
m/z [M + H] calculated for C15
H
13
O
4
: 257.0814; found 257.0814.
1
ꢀ(5ꢀHydroxyꢀ8ꢀ(trifluoromethyl)naphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanone (4e). Yield: 43%, 131 mg;
o
1
Yellow solid; m.p. 125.9ꢀ128.0 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.53 (s, 1H), 8.61 (d, J = 8.7 Hz, 1H),
3
1
3
8
.24 (s, 1H), 7.76 (d, J = 2.1 Hz, 1H), 7.68 (d, J = 8.7 Hz, 1H), 7.21 (d, J = 2.1 Hz, 1H), 2.98 (s, 3H). C NMR
2
1
(
3
100 MHz, CDCl ) δ (ppm) 203.0, 161.8, 150.2, 143.4, 132.2 (J = 32.3 Hz), 127.0, 124.8, 124.5 (J = 270.9 Hz),
3
3
ꢀ1
120.7 (J = 4.2 Hz), 120.6 (J = 3.4 Hz), 115.3, 105.8, 105.6, 31.7. IR (KBr) ν (cm ) 3146, 2923, 1951, 1704, 1616,
+
1
519, 1480, 1418, 1289, 1154, 1108, 1061, 1025, 989, 938, 885, 833, 746, 704, 593. HRMS (ESI): m/z [M + H]
calculated for C H F O : 295.0582; found 295.0588.
1
5
10
3
3
1ꢀ(5ꢀHydroxyꢀ2ꢀmethylnaphtho[2,1ꢀb]furanꢀ4ꢀyl)ethanone (4f). Yield: 72%, 75 mg; Yellow solid;
o
1
m.p. 112.4ꢀ114.7 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 14.45 (s, 1H), 8.46 (d, J = 8.0 Hz, 1H), 7.88 (d, J = 8.0
13
Hz, 1H), 7.65 (m, 1H), 7.46 (m, 1H), 6.71 (s, 1H), 2.90 (s, 3H), 2.52 (s, 3H). C NMR (100 MHz, CDCl
3
) δ (ppm)
2
02.8, 161.6, 152.9, 148.7, 130.7, 130.5, 125.7, 124.4, 123.1, 122.7, 116.2, 104.7, 101.5, 31.5, 14.2. IR (KBr) ν
ꢀ
1
(cm ) 3103, 2917, 1942, 1825, 1616, 1569, 1433, 1364, 1323, 1244, 1168, 1111, 1025, 986, 934, 810, 795, 684,
+
6
15, 544. HRMS (ESI): m/z [M + Na] calculated for C15
H
12
O
3
Na: 263.0684; found 263.0688.
1
ꢀ(5ꢀHydroxynaphtho[2,1ꢀb]benzofuranꢀ6ꢀyl)ethanone (4g). Yield: 46%, 83 mg; Yellow solid; m.p.
o
1
1
3
65.0ꢀ167.4 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.90 (s, 1H), 8.59 (d, J = 8.2 Hz, 1H), 8.46 (d, J = 8.2 Hz,
1
3
1H), 8.24 (d, J = 7.7 Hz, 1H), 7.82 (m, 1H), 7.67 (d, J = 7.7 Hz, 1H), 7.56 (m, 1H), 7.45 (m, 2H), 3.07 (s, 3H).
C
NMR (100 MHz, CDCl ) δ (ppm) 203.0, 164.4, 155.1, 152.0, 132.0, 131.4, 126.0, 124.6, 124.6, 124.5, 123.7,
3
ꢀ
1
1
1
23.0, 122.8, 120.9, 111.7, 109.2, 104.3, 31.8. IR (KBr) ν (cm ) 3061, 3005, 2920, 2319, 1942, 1614, 1566, 1513,
+
437, 1370, 1317, 1267, 1209, 1064, 1022, 856, 738, 674, 510. HRMS (ESI): m/z [M + H] calculated for
18 13 3
C H O : 277.0865; found 277.0868.
1
ꢀ(5ꢀHydroxyꢀ2ꢀmethylnaphtho[2,1ꢀb]benzofuranꢀ6ꢀyl)ethanone (4h). Yield: 57%, 124 mg; Yellow
o
1
solid; m.p. 171.5ꢀ173.6 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.69 (s, 1H), 8.21ꢀ8.28 (m, 1H), 7.88ꢀ7.86 (m,
3
1
3
1
H), 7.72 (m, 1H), 7.47ꢀ7.45 (m, 1H), 7.32ꢀ7.31 (m, 2H), 7.18 (d, J = 8.0 Hz, 1H), 2.81 (s, 3H), 2.51 (s, 3H). C
NMR (100 MHz, CDCl
3
) δ (ppm) 202.6, 164.2, 154.8, 151.9, 141.9, 131.9, 126.2, 125.5, 124.4, 124.2, 123.3,
ꢀ1
1
1
22.4, 120.7, 120.4, 111.3, 108.4, 103.5, 31.6, 22.5. IR (KBr) ν (cm ) 3067, 3120, 2914, 1928, 1748, 1613, 1516,
+
436, 1377, 1272, 1202, 1151, 1102, 1062, 984, 889, 874, 783, 690, 632, 592. HRMS (ESI): m/z [M + Na]
calculated for C H O Na: 313.0841; found 313.0842.
19 14
3
1ꢀ(5ꢀHydroxynaphtho[2,1ꢀb]thiophenꢀ4ꢀyl)ethanone (4i). Yield: 52%, 48 mg; Yellow solid; m.p.
o
1
1
1
40.2ꢀ142.5 C. H NMR (400 MHz, CDCl
H), 7.92 (d, J = 5.5 Hz, 1H), 7.75 (m, 1H), 7.57 (m, 1H), 7.43 (d, J = 5.5 Hz, 1H), 2.94 (s, 3H). C NMR (100
) δ (ppm) 203.1, 164.5, 135.2, 132.6, 131.3, 129.8, 125.8, 124.2, 123.5, 122.5, 122.2, 110.4, 77.36,
3
) δ (ppm) 15.43 (s, 1H), 8.56 (d, J = 8.2 Hz, 1H), 8.21 (d, J = 8.2 Hz,
13
MHz, CDCl
3
ꢀ1
31.6. IR (KBr) ν (cm ) 3035, 2920, 1828, 1604, 1551, 1491, 1420, 1365, 1245, 1163, 1084, 1023, 979, 876, 774,
+
7
02, 648, 586, 506. HRMS (ESI): m/z [M + Na] calculated for C14
H
10
O
2
SNa: 265.0299; found 265.0301.
1
ꢀ(5ꢀHydroxyꢀ8ꢀmethylnaphtho[2,1ꢀb]thiophenꢀ4ꢀyl)ethanone (4j). Yield: 54%, 58 mg; Yellow solid;
o
1
3
m.p. 143.3ꢀ145.4 C. H NMR (400 MHz, CDCl ) δ (ppm) 15.33 (s, 1H), 8.27 (d, J = 8.4 Hz, 1H), 7.77 (s, 1H),
13
3
7.70 (d, J = 5.1 Hz, 1H), 7.27 (m, 2H), 2.79 (s, 3H), 2.52 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 202.6,
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ꢀ
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164.5, 141.7, 135.1, 132.6, 129.2, 127.5, 125.5, 123.0, 122.0, 121.9, 109.7, 31.4, 22.3. IR (KBr) ν (cm ) 3075,
2
987, 1913, 1742, 1589, 1486, 1417, 1365, 1299, 1238, 1092, 1022, 976, 896, 813, 773, 722, 645, 594, 551.
+
HRMS (ESI): m/z [M + Na] calculated for C15
H
12
O
2
SNa: 279.0456; found 279.0457.
1
ꢀ(8ꢀFluoroꢀ5ꢀhydroxynaphtho[2,1ꢀb]thiophenꢀ4ꢀyl)ethanone (4k). Yield: 46%, 48 mg; Yellow solid;
o
1
m.p. 153.2ꢀ155.7 C. H NMR (400 MHz, CDCl ) δ (ppm) 15.46 (s, 1H), 8.53 (dd, J = 8.5, 5.7 Hz, 1H), 7.78 (d, J
3
13
=
5.7 Hz, 1H), 7.74 (m, 1H), 7.42 (d, J = 5.5 Hz, 1H), 7.29 (d, J = 5.5 Hz, 1H), 2.93 (s, 3H). C NMR (100 MHz,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
3
3
3
CDCl ) δ (ppm) 203.0, 164.6 ( J = 254 Hz), 164.2, 136.4, 134.4 ( J = 10 Hz), 129.0 ( J = 10 Hz), 125.8, 122.7,
2
2
ꢀ1
1
22.2, 121.0, 115.2 ( J = 24 Hz), 110.00, 108.3 ( J = 24 Hz), 31.5. IR (KBr) ν (cm ) 3025, 2993, 1904, 1700,
+
1588, 1446, 1411, 1365, 1219, 1208, 1090, 1021, 971, 888, 811, 703, 641, 574, 533. HRMS (ESI): m/z [M + H]
calculated for C H FO S: 261.0386, found 261.0382.
1
4
10
2
1
ꢀ(5ꢀHydroxyꢀ2ꢀmethylnaphtho[2,1ꢀb]thiophenꢀ4ꢀyl)ethanone (4l). Yield: 62%, 52 mg;Yellow solid;
o
1
m.p. 123.1ꢀ125.0 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 15.23 (s, 1H), 8.51 (d, J = 8.3 Hz, 1H), 8.09 (d, J = 8.3
1
3
Hz, 1H), 7.70 (m, 1H), 7.52 (m, 2H), 2.84 (s, 3H), 2.61 (s, 3H). C NMR (100 MHz, CDCl
3
) δ (ppm) 203.0, 163.4,
ꢀ1
1
2
36.7, 134.0, 132.2, 130.9, 129.9, 125.6, 125.4, 124.0, 123.4, 119.9, 110.3, 31.4, 15.5. IR (KBr) ν (cm ) 3070,
914, 2852, 2378, 2307, 1936, 1672, 1602, 1567, 1527, 1418, 1366, 1285, 1235, 1084, 1020, 978, 935 , 874, 803,
+
788, 692, 629, 580, 542. HRMS (ESI): m/z [M + Na] calculated for C15
H
12
O
2
SNa: 279.0456; found 279.0456.
1
ꢀ(10ꢀHydroxyphenanthro[2,1ꢀb]furanꢀ11ꢀyl)ethanone (4m). Yield: 40%, 110 mg; Yellow solid; m.p.
o
1
2
18.6ꢀ220.4 C. H NMR (400 MHz, CDCl
m, 2H), 7.62 (m, 1H), 7.25 (d, J = 8.7 Hz, 1H), 3.03 (s, 3H). C NMR (100 MHz, CDCl
150.7, 143.0, 133.0, 132.2, 132.1, 132.0, 129.1, 128.2, 128.1, 126.0, 122.1, 117.0, 116.1, 105.9, 105.3, 31.9. IR
3
) δ (ppm) 15.66 (s, 1H), 9.92 (d, J = 8.7 Hz, 1H), 7.98 (m, 3H), 7.74
13
(
3
) δ (ppm) 203.2, 165.4,
ꢀ
1
(
KBr) ν (cm ) 3152, 2917, 2357, 1957, 1825, 1686, 1610, 1424, 1374, 1333, 1264, 1207, 1133, 1096, 1023, 974,
+
8
69, 810, 754, 693, 664. HRMS (ESI): m/z [M + H] calculated for C18
H
13
O
3
: 277.0865;found 277.0868.
1
ꢀ(5ꢀHydroxybenzo[1,2ꢀb:4,3ꢀb']difuranꢀ4ꢀyl)ethanone (6a). Yield: 60%, 113 mg; Yellow solid; m.p.
o
1
138.1ꢀ138.9 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 13.73 (s, 1H), 7.86 (d, J = 2.0 Hz, 1H), 7.70 (d, J = 2.1 Hz,
13
1
1
1
H), 6.95 (d, J = 2.0 Hz, 1H), 6.93 (d, J = 2.1 Hz, 1H), 2.92 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 203.2,
3
ꢀ
1
50.1, 149.2, 149.0, 143.5, 140.8, 127.0, 111.4, 106.5, 105.8, 104.1, 31.6. IR (KBr) ν (cm ) 3018, 1612, 1527,
+
475, 1415, 1363, 1299, 1143, 1012, 972, 875, 827, 756, 611, 480. HRMS (ESI): m/z [M + Na] calculated for
12 8 4
C H O Na: 239.0320; found: 239.0298.
1
ꢀ(5ꢀHydroxyꢀ7ꢀmethylbenzo[1,2ꢀb:4,3ꢀb']difuranꢀ4ꢀyl)ethanone (6b). Yield: 67%, 172 mg; Yellow
o
1
solid; m.p. 153.2ꢀ154.4 C. H NMR (400 MHz, CDCl ) δ (ppm) 13.74 (s, 1H), 7.67 (d, J = 1.8 Hz, 1H), 6.88 (d, J
3
1
3
=
3
1.8 Hz, 1H), 6.57 (s, 1H), 2.91 (s, 3H), 2.56 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 203.0, 160.8, 150.3,
ꢀ
1
148.4, 143.3, 140.0, 129.0, 110.9, 105.8, 103.4, 103.1, 31.5, 14.7. IR (KBr) ν (cm ) 3116, 2925, 1828, 1608, 1508,
+
1
404, 1363, 1307, 1211, 1147, 1024, 892, 808, 740, 690, 630, 595. HRMS (ESI): m/z [M + Na] calculated for
C
13
H
10
O
4
Na: 253.0477; found: 253.0477.
1
ꢀ(5ꢀHydroxythieno[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanone (6c). Yield: 54%, 115 mg; Yellow solid; m.p.
o
1
3
149.4ꢀ150.3 C. H NMR (400 MHz, CDCl ) δ (ppm) 13.94 (s, 1H), 7.78 (d, J = 5.2 Hz, 1H), 7.67 (s, 1H), 7.49 (d,
13
3
J = 5.2 Hz, 1H), 6.99 (s, 1H), 2.91 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 202.8, 158.1, 151.5, 143.1, 138.0,
ꢀ
1
1
33.4, 124.9, 122.3, 114.5, 105.7, 103.4, 31.5. IR (KBr) ν (cm ) 2968, 1604, 1527, 1465, 1398, 1357, 1313, 1238,
+
1
134, 1082, 1024, 973, 846, 736, 655, 594, 466. HRMS (ESI): m/z [M + Na] calculated for C12
H
8
O
3
SNa:
255.0092; found: 255.0092.
1
ꢀ(5ꢀHydroxyꢀ7ꢀmethylthieno[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanone (6d). Yield, 57%, 104 mg; Yellow
o
1
solid; m.p. 166.1ꢀ167.0 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 13.90 (s, 1H), 7.64 (s, 1H), 7.16 (s, 1H), 6.92 (s,
13
1
H), 2.90 (s, 3H), 2.67 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 202.5, 157.7, 151.8, 149.2, 142.9, 138.9,
3
ꢀ
1
123.7, 120.7, 113.9, 105.7, 103.0, 31.4, 16.8. IR (KBr) ν (cm ) 3001, 1602, 1525, 1471, 1402, 1359, 1290, 1251,
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5
5
5
5
5
5
5
6
+
1136, 1018, 973, 852, 729, 659, 594, 484. HRMS (ESI): m/z [M + Na] calculated for C13
H
11
O
3
S: 247.0429;
found: 247.0429.
1
ꢀ(5ꢀHydroxyꢀ8ꢀmethylthieno[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanone (6e). Yield: 59%, 117 mg; Yellow
o
1
3
solid; m.p. 172.7ꢀ173.0 C. H NMR (400 MHz, CDCl ) δ (ppm) 13.86 (s, 1H), 7.64 (s, 1H), 7.34 (s, 1H), 7.07 (s,
13
1H), 2.89 (s, 3H), 2.58 (s, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 202.7, 157.9, 151.6, 142.8, 137.7, 133.3,
3
ꢀ1
1
1
2
28.8, 125.2, 114.2, 105.3, 103.1, 31.5, 16.0. IR (KBr) ν (cm ) 2979, 2925, 1639, 1463, 1371, 1319, 1245, 1149,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
+
010, 894, 844, 759, 578, 530, 474. HRMS (ESI): m/z [M + Na] calculated for C13
H
10
O
3
SNa: 269.0248; found:
69.0244.
1
ꢀ(5ꢀHydroxyꢀ6ꢀmethylꢀ6Hꢀfuro[3,2ꢀe]indolꢀ4ꢀyl)ethanone (6f). Yield: 41%, 68 mg; Yellow solid;
o
1
m.p. 127.7ꢀ128.8 C. H NMR (400 MHz, CDCl ) δ (ppm) 14.64 (s, 1H), 7.62 (d, J = 1.4 Hz, 1H), 7.15 (d, J = 2.4
3
13
3
Hz, 1H), 6.92 (d, J = 1.4 Hz, 1H), 6.54 (d, J = 2.5 Hz, 1H), 4.17 (s, 3H), 2.90 (s, 3H). C NMR (100 MHz, CDCl )
ꢀ1
δ (ppm) 202.5, 154.0, 148.4, 142.1, 134.1, 127.7, 121.9, 111.1, 105.8, 102.2, 100.5, 37.0, 31.2. IR (KBr) ν (cm )
3109, 2923, 2856, 1728, 1612, 1471, 1369, 1271, 1107, 1022, 808, 738, 680, 607, 468. HRMS (ESI): m/z [M +
+
Na] calculated for C13
H11NO
3
Na: 252.0637; found: 252.0635.
Ethylꢀ5ꢀhydroxybenzo[1,2ꢀb:4,3ꢀb']difuranꢀ4ꢀcarboxylate (6g). Yield: 45%, 137 mg; White solid; m.p.
o
1
88.7ꢀ89.7 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 11.86 (s, 1H), 7.86 (d, J = 1.6 Hz, 1H), 7.72 (d, J = 1.7 Hz, 1H),
13
6
.97 (d, J = 1.5 Hz, 1H), 6.92 (d, J = 1.7 Hz, 1H), 4.58 (m, 2H), 1.25 (m, 3H). C NMR (150 MHz, CDCl
3
) δ
ꢀ1
(
ppm) 170.6, 149.4, 148.5, 147.7, 144.2, 140.9, 126.1, 112.2, 106.5, 105.4, 96.0, 62.0, 14.5. IR (KBr) ν (cm )
+
3
425, 2927, 2852, 2372, 1735, 1633, 1465, 1394, 1288, 1151, 1074, 1024, 740. HRMS (ESI): m/z [M + Na]
calculated for C H O Na: 269.0426; found: 269.0420.
1
3
10
5
Ethylꢀ5ꢀhydroxyꢀ7ꢀmethylbenzo[1,2ꢀb:4,3ꢀb']difuranꢀ4ꢀcarboxylate (6h). Yield: 49%, 138.5 mg;
o
1
Yellow solid; m.p. 94.5ꢀ96.7 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 11.83 (s, 1H), 7.68 (d, J = 2.1 Hz, 1H), 6.86
13
(
d, J = 2.1 Hz, 1H), 6.58 (s, 1H), 4.57 (m, 2H), 2.56 (s, 3H), 1.52 (m, 3H). C NMR (100 MHz, CDCl ) δ (ppm)
3
ꢀ
1
170.7, 159.9, 149.5, 147.0, 143.9, 140.1, 127.9, 111.7, 105.4, 102.9, 95.0, 61.8, 14.6, 14.5. IR (KBr) ν (cm ) 3118,
2
925, 2856, 2380, 1730, 1662, 1461, 1407, 1363, 1315, 1263, 1091, 1022, 935, 869, 804, 636, 524. HRMS (ESI):
+
m/z [M + H] calculated for C14
H
13
O
5
: 261.0763; found: 261.0761.
Ethylꢀ5ꢀhydroxyꢀ7ꢀmethylthieno[3,2ꢀe]benzofuranꢀ4ꢀcarboxylate (6i). Yield: 43%, 132 mg; White
o
1
solid; m.p. 108.6ꢀ109.3 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 12.00 (s, 1H), 7.67 (d, J = 2.0 Hz, 1H), 7.20 (s,
13
1
1
2
H), 6.93 (d, J = 2.0 Hz, 1H), 4.57 (m, 2H), 2.68 (s, 3H), 1.52 (m, 3H). C NMR (100 MHz, CDCl
3
) δ (ppm)
ꢀ
1
70.5, 156.2, 151.1, 147.9, 143.5, 138.1, 123.4, 120.6, 114.7, 105.3, 94.9, 61.9, 16.7, 14.6. IR (KBr) ν (cm ) 3693,
923, 2858, 2341, 1722, 1654, 1610, 1452, 1319, 1257, 1107, 1024, 887, 804, 757, 582, 487. HRMS (ESI): m/z [M
+
+ Na] calculated for C14
H
12
O
4
SNa: 299.0354; found: 299.0356.
1
ꢀ(5ꢀHydroxybenzo[4,5]furan[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanone (6j). Yield: 63%, 203 mg; Yellow
o
1
3
solid; m.p. 158.5ꢀ159.9 C. H NMR (400 MHz, CDCl ) δ (ppm) 13.53 (s, 1H), 8.01 (d, J = 7.7 Hz, 1H), 7.78 (d, J
1
3
=
1.9 Hz, 1H), 7.69 (d, J = 7.7 Hz, 1H), 7.56 (m, 1H), 7.42 (m, 1H), 7.16 (d, J = 1.9 Hz, 1H), 2.95 (s, 3H). C
NMR (100 MHz, CDCl
3
) δ (ppm) 203.2, 157.7, 150.3, 148.6, 144.4, 141.4, 128.9, 123.5, 122.8, 122.2, 112.7,
ꢀ1
1
11.9, 105.8, 105.5, 31.8. IR (KBr) ν (cm ) 3487, 2923, 2852, 2312, 1533, 1492, 1361, 1296, 1203, 1145, 1095,
+
1
10 4
018, 985, 929, 842, 732, 661, 613, 536, 430. HRMS (ESI): m/z [M + Na] calculated for C16H O Na: 289.0477;
found: 289.0480.
1ꢀ(5ꢀHydroxybenzo[4,5]thieno[3,2ꢀe]benzofuranꢀ4ꢀyl)ethanone (6k). Yield: 58%, 132 mg; Yellow
o
1
3
solid; m.p. 197.1ꢀ198.2 C. H NMR (400 MHz, CDCl ) δ (ppm) 13.73 (s, 1H), 8.34 (m, 1H), 7.97 (d, J = 8.4 Hz,
13
1
1
H), 7.81 (s, 1H), 7.56 (m, 1H), 7.39 (s, 1H), 2.98 (s, 3H). C NMR (100 MHz, CDCl
3
) δ (ppm) 202.8, 157.3,
ꢀ
1
52.3, 143.8, 142.4, 135.2, 133.5, 127.8, 124.8, 124.3, 124.1, 123.5, 114.5, 105.3, 104.7, 31.7. IR (KBr) ν (cm )
3057, 2324, 1722, 1595, 1475, 1357, 1294, 1244, 1137, 1070, 1022, 979, 873, 817, 727, 599, 501. HRMS (ESI):
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7
8
9
+
10 3
m/z [M + Na] calculated for C16H O SNa: 305.0248; found: 305.0241.
Ethylꢀ5ꢀhydroxybenzo[4,5]furan[3,2ꢀe]benzofuranꢀ4ꢀcarboxylate (6l). Yield: 44%, 151.3 mg;
o
1
Yellow solid; m.p. 159.7ꢀ160.3 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 11.83 (s, 1H), 8.06 (d, J = 7.7 Hz, 1H),
7
.81 (d, J = 2.1 Hz, 1H), 7.71 (d, J = 7.7 Hz, 1H), 7.56 (m, 1H), 7.44 (m, 1H), 7.20 (d, J = 2.1 Hz, 1H), 4.61 (m,
13
2H), 1.55 (m, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 170.3, 157.5, 149.6, 147.5, 145.0, 141.4, 128.6, 123.7,
3
ꢀ1
1
23.4, 122.1, 112.7, 105.1, 98.0, 62.2, 14.5. IR (KBr) ν (cm ) 3057, 2324, 1722, 1595, 1475, 1357, 1294, 1244,
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
+
1
137, 1070, 1022, 979, 873, 817, 727, 599, 501. HRMS (ESI): m/z [M + Na] calculated for C17
H
12
O
5
Na:
3
19.0582; found: 319.0592.
Procedures for Syntheses of 2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdiones (3aꢀ3e, 3m).
2
6
According to a typical procedure, a mixture of 1ꢀphenylbutaneꢀ1,3ꢀdione (1.52 mmol), 2,5ꢀdimethoxyꢀ2,5ꢀ
dihydrofuran (DHDMF, 2.3 mmol) and K10 montmorillonite clay (m4a : mK10 mont. = 1:1) was stirred in anhydrous
nꢀhexane at 80 °C for 3 h. Then the catalyst was filtered off and the product purified by column chromatography
on silica gel (petroleum ether/ethyl acetate, 80:1→40:1) to give 3a in 75% yield. Similarly, 3bꢀ3e and 3m were
prepared with yields 52~80% (The reaction scheme was in supporting information, SIꢀScheme S1).
o
1
2
ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdione (3a). Yield: 75%, 260 mg; Yellow solid; m.p. 51.2ꢀ53.6 C. H
NMR (400 MHz, CDCl ) δ (ppm) 17.40 (s, 1H, enol), 7.46 (s, 1H, enol), 7.31 (m, 5H, enol), 6.34 (s, 1H, enol),
3
2
6
6
.04 (d, J = 2.6 Hz, 1H, enol), 2.11 (s, 3H, enol) ppm. 3a is known.
2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(pꢀtolyl)butaneꢀ1,3ꢀdione (3b). Yield: 63%, 243 mg; Yellow solid; m.p. 50.1ꢀ52.3 C.
o
1
3
H NMR (400 MHz, CDCl ) δ (ppm) 17.49 (s, 1H, enol), 7.47 (s, 1H, enol), 7.21 (d, J = 8.1 Hz, 2H, enol), 7.06 (d,
J = 8.1 Hz, 2H, enol), 6.36 (d, J = 3.1 Hz, 1H, enol), 6.06 (d, J = 3.1 Hz, 1H, enol), 2.32 (s, 3H, enol), 2.10 (s, 3H,
1
3
enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 198.0, 185.5, 149.9, 142.2, 141.9, 133.0, 128.8, 128.5, 111.5, 111.5,
+
104.1, 25.1, 21.6 ppm. HRMS (ESI): m/z [M + Na] calculated for C15
H
14
O
3
Na: 265.0841; found: 265.0843.
1
ꢀ(4ꢀFluorophenyl)ꢀ2ꢀ(furanꢀ2ꢀyl)butaneꢀ1,3ꢀdione (3c). Yield: 75%, 250 mg; Yellow solid; m.p.
o
1
5
1.7ꢀ52.8 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.32 (s, 1H, enol), 7.47 (d, J = 1.9 Hz, 1H, enol), 7.21 (m, 1H,
1
3
enol), 6.04 (m, 3H, enol), 6.36 (dd, J = 3.1, 1.9 Hz, 1H, enol), 6.07 (d, J = 3.1 Hz, 1H, enol), 2.12 (s, 3H, enol).
C
1
3
3
3
NMR (100 MHz, CDCl ) δ (ppm) 198.5, 184.1, 162.2 ( J = 245 Hz), 149.0, 142.4, 137.9 ( J = 7 Hz), 129.6 ( J =
4
2
2
8
Hz), 124.1 ( J = 3 Hz), 118.2 ( J = 21 Hz), 115.4 ( J = 23 Hz), 111.9, 111.56, 104.6, 25.1. HRMS (ESI): m/z [M
+
+
H] calculated for C14H12FO3: 247.0770; found: 247.0792.
2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(4ꢀmethoxyphenyl)butaneꢀ1,3ꢀdione (3d). Yield: 60%, 262 mg; Yellow solid; m.p.
o
1
52.1ꢀ53.8 C. H NMR (400 MHz, CDCl ) δ (ppm) 17.62 (s, 1H, enol), 7.48 (d, J = 1.9 Hz, 1H, enol), 7.27 (m, 2H,
3
enol), 6.74 (m, 2H, enol), 6.38 (dd, J = 3.2, 1.9 Hz, 1H, enol), 6.08 (d, J = 3.2 Hz, 1H, enol), 3.78 (s, 3H, enol),
13
2
.08 (s, 3H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 197.3, 185.1, 162.2, 150.0, 142.2, 130.6, 128.0, 113.4,
+
111.5, 111.4, 103.5, 55.4, 24.9. HRMS (ESI): m/z [M + Na] calculated for C15
H
14
O
4
Na: 281.0790; found
2
81.0791.
2
ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(4ꢀ(trifluoromethyl)phenyl)butaneꢀ1,3ꢀdione (3e). Yield: 80%, 307 mg; Yellow oil.
1
3
H NMR (400 MHz, CDCl ) δ (ppm) 17.25 (s, 1H, enol), 7.51 (d, J = 8.3 Hz, 2H, enol), 7.46 (s, 1H, enol), 7.40 (d,
1
3
J = 8.3 Hz, 2H, enol), 6.35 (d, J = 3.2 Hz, 1H, enol), 6.06 (d, J = 3.2 Hz, 1H, enol), 2.13 (s, 3H, enol). C NMR
2
3
(
(
100 MHz, CDCl
1
3
) δ (ppm) 198.9, 183.8, 148.8, 142.5, 139.2, 132.6 ( J = 33 Hz), 128.7, 125.0 ( J = 3 Hz), 123.8
+
J = 273 Hz), 112.0, 111.6, 105.0, 25.2. HRMS (ESI): m/z [M + Na] calculated for C15
H
11
F
3
O
3
Na: 319.0558;
found 319.0562.
2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(naphthalenꢀ1ꢀyl)butaneꢀ1,3ꢀdione (3m). Yield: 72%, 279 mg; Yellow solid; m.p.
o
1
6
7
5.6ꢀ66.7 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.17 (s, 1H, enol), 7.94 (d, J = 8.4 Hz, 1H, enol), 7.58 (d, J =
.8 Hz, 1H, enol), 7.56 (d, J = 1.9 Hz, 1H, enol), 7.28 (m, 2H, enol), 7.11 (m, 2H, enol), 7.03 (m, 1H, enol), 5.83
1
3
(
3
dd, J = 3.2, 1.9 Hz, 1H, enol), 5.56 (d, J = 3.2 Hz, 1H, enol), 2.01 (s, 3H, enol). C NMR (100 MHz, CDCl ) δ
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7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(ppm) 198.2, 187.8, 148.8, 141.9, 133.7, 133.3, 130.1, 130.0, 128.2, 126.8, 126.1, 125.9, 125.2, 124.4, 111.1,
+
+
1
14 3
10.7, 107.3, 25.3. HRMS (ESI): m/z [M + Na] calculated for C18H O Na [M+Na] : 301.0841;found 301.0848.
Syntheses of 2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdiones, 3fꢀ3l.
4
ꢀPicolineꢀNꢀoxide (1.4 mmol) was added with stirring to a suspension of IPrAuCl (0.035 mmol) and AgNTf2
(
0.035 mmol) in dichloromethane (8 mL) and the mixture was stirred for 5 min at room temperature. After that,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
HNTf (0.84 mmol) was added and the mixture was stirred for an additional 5 min. To the resulting solution was
2
added propargyl alcohol (0.7 mmol) and the combined solution was then stirred at room temperature until the
reaction was complete (monitored by TLC). After evaporation of the solution, the residue was purified by column
chromatography on silica gel (petroleum ether/ethyl acetate, 40:1→15:1) to give 3f in a yield of 62%. Similarly,
3gꢀ3l were prepared with yields 55~75% (The reaction scheme was in supporting information, SIꢀScheme S2).
2
ꢀ(5ꢀMethylfuranꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdione (3f). Yield: 62%, 98.5 mg; Yellow solid; m.p.
o
1
3
52.0ꢀ53.5 C. H NMR (400 MHz, CDCl ) δ (ppm) 17.42 (s, 1H, enol), 7.29 (m, 2H, enol), 7.23 (d, J = 7.3 Hz, 1H,
enol), 7.15 (m, 2H, enol), 5.84 (d, J = 3.0 Hz, 1H, enol), 5.82 (d, J = 3.0 Hz, 1H, enol), 2.20 (s, 3H, enol), 2.05 (s,
27
3
H, enol). 3f is known.
2
ꢀ(Benzofuranꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdione (3g). Yield: 73%, 182 mg; Yellow solid; m.p. 64.4ꢀ66.6
o
1
C. H NMR (400 MHz, CDCl ) δ (ppm) 17.53 (s, 1H, enol), 7.47 (m, 2H, enol), 7.39 (d, J = 7.5 Hz, enol), 7.29
3
1
3
(
m, 2H, enol), 7.19 (m, 3H, enol), 6.42 (s, 1H, enol), 2.16 (s, 3H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm)
1
98.2, 186.0, 154.8, 152.4, 135.6, 131.4, 128.8, 128.3, 128.1, 124.4, 122.9, 121.1, 111.4, 108.6, 104.4, 25.3.
+
HRMS (ESI): m/z [M + Na] calculated for C18
H
14
O
3
Na: 301.0841; found 301.0841.
2ꢀ(Benzofuranꢀ2ꢀyl)ꢀ1ꢀ(pꢀtolyl)butaneꢀ1,3ꢀdione (3h). Yield: 75%, 219 mg; Yellow solid; m.p.
o
1
6
3.2ꢀ65.6 C. H NMR (400 MHz, CDCl ) δ (ppm) 17.52 (s, 1H, enol), 7.32 (d, J = 8.2 Hz, 3H, enol), 7.14 (m, 2H,
3
enol), 7.05 (d, J = 7.5 Hz, 1H, enol), 6.78 (d, J = 8.2 Hz,, 2H, enol), 6.27 (s, 1H, enol), 2.04 (s, 3H, enol), 1.97 (s,
13
3
H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 197.8, 185.8, 154.7, 152.6, 141.9, 132.6, 130.1, 128.8, 128.4,
+
124.3, 122.8, 121.0, 111.3, 108.4, 104.0, 25.1, 21.4. HRMS (ESI): m/z [M + H] calculated for C19
H
17
O
3
:
2
93.1178; found 293.1181.
o
1
ꢀPhenylꢀ2ꢀ(thiophenꢀ2ꢀyl)butaneꢀ1,3ꢀdione (3i). Yield: 60%, 93 mg; Yellow solid; m.p. 80.0ꢀ82.8 C.
1
3
H NMR (400 MHz, CDCl ) δ (ppm) 17.62 (s, 1H, enol), 7.43 (s, 1H, enol), 7.41 (s, 1H, enol), 7.33 (d, J = 7.2 Hz,
1H, enol), 7.29 (d, J = 5.5 Hz, 1H, enol), 7.22 (m, 2H, enol), 6.97 (dd, J = 5.5, 3.2 Hz, 1H, enol), 6.82 (d, J = 3.2
13
Hz, 1H, enol), 2.17 (s, 3H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 197.9, 184.3, 138.3, 136.0, 130.7, 130.0,
+
1
28.7, 127.8, 127.3, 127.2, 106.2, 25.6. HRMS (ESI): m/z [M + Na] calculated for C14
H
12
O
2
SNa: 267.0456;
found 267.0458.
2ꢀ(Thiophenꢀ2ꢀyl)ꢀ1ꢀ(pꢀtolyl)butaneꢀ1,3ꢀdione (3j). Yield: 64%, 109 mg; Yellow solid; m.p. 79.2ꢀ81.4
o
1
C. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.67 (s, 1H, enol), 7.32 (s, 1H, enol), 7.30 (m, 2H, enol), 7.02 (d, J = 8.1
1
3
Hz, 2H, enol), 6.98 (m, 1H, enol), 6.83 (dd, J = 3.4, 1.0 Hz, 1H, enol), 2.30 (s, 3H, enol), 2.15 (s, 3H, enol).
C
NMR (100 MHz, CDCl
3
) δ (ppm) 197.7, 184.3, 141.4, 138.7, 133.2, 129.9, 128.9, 128.6, 127.4, 127.2, 105.9, 25.6,
+
21.6. HRMS (ESI): m/z [M + Na] calculated for C H O SNa: 281.0612; found 281.0614.
1
5
14
2
1
ꢀ(4ꢀFluorophenyl)ꢀ2ꢀ(thiophenꢀ2ꢀyl)butaneꢀ1,3ꢀdione (3k). Yield: 68%, 106 mg; Yellow solid; m.p.
o
1
7
8.3ꢀ80.5 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.60 (s, 1H, enol), 7.41 (m, 2H, enol), 7.31 (dd, J = 5.3, 1.1
Hz, 1H, enol), 6.98 (dd, J = 5.3, 3.5 Hz, 1H, enol), 6.89 (m, 2H, enol), 6.82 (dd, J = 3.4, 1.1 Hz, 1H, enol), 2.15 (s,
13
1
3
3
3H, enol). C NMR (100 MHz, CDCl ) δ (ppm) 197.8, 183.3, 164.1 ( J = 253.5 Hz), 138.3, 132.2, 131.3 ( J = 9.1
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Hz), 130.0, 127.5, 124.3, 115.0 ( J = 21.2 Hz), 106.0, 25.5. HRMS (ESI): m/z [M + Na] calculated for
C
14
H11FO
2
SNa: 285.0361; found 285.0365.
2
ꢀ(5ꢀMethylthiophenꢀ2ꢀyl)ꢀ1ꢀphenylbutaneꢀ1,3ꢀdione (3l). Yield: 55%, 85 mg; Yellow solid; m.p.
o
1
1
7
3 3
6.4ꢀ78.3 C. H NMR (400 MHz, CDCl ) δ (ppm) H NMR (400 MHz, CDCl ) δ 17.57 (s, 1H, enol), 7.43 (s, 1H,
enol), 7.4 (d, J = 1.5 Hz, 1H, enol), 7.23 (d, J = 7.5 Hz, 1H, enol), 7.15 (m, 2H, enol), 6.54 (dd, J = 3.3, 1.5 Hz, 1H,
28
enol), 6.51 (d, J = 3.3 Hz, 1H, enol), 2.35 (m, 3H, enol), 2.11 (s, 3H, enol). 3l is known.
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
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33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Syntheses of 1ꢀ(Furan/Thiophen/Pyrrolꢀ2ꢀyl)ꢀ2ꢀ(furanꢀ2ꢀyl)butaneꢀ1,3ꢀdiones (5aꢀ5l).
24
According to
a
typical procedure,
a mixture of 1ꢀ(furanꢀ2ꢀyl)butaneꢀ1,3ꢀdione (11a, 1.4 mmol),
2,5ꢀdimethoxyꢀ2,5ꢀdihydrofuran (DHDMF, 5.6 mmol) and K10 montmorillonite clay (m4a : mK10 mont. = 1:2) was
stirred in anhydrous nꢀhexane at 80 °C for 3 h. Then the catalyst was filtered off and the product purified by
column chromatography on silica gel (petroleum ether/ethyl acetate, 80:1→40:1) to give 5a in 74% yield.
Similarly, 5bꢀ5l were prepared with yields of 53~90% (The reaction scheme was in supporting information,
SIꢀScheme S3).
o
1
1
,2ꢀDi(furanꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5a). Yield: 74%, 225 mg; Yellow solid; m.p. 67.4ꢀ69.2 C. H NMR
(
400 MHz, CDCl ) δ (ppm) 17.31 (s, 1H, enol), 7.53 (m, 2H, enol), 6.50 (d, J = 1.4 Hz, 1H, enol), 6.34 (d, J = 1.4
3
13
Hz, 1H, enol), 6.31 (d, J = 3.3 Hz, 1H, enol), 5.79 (d, J = 3.3 Hz, 1H, enol), 2.02 (s, 3H, enol). C NMR (100
MHz, CDCl ) δ (ppm) 193.3, 176.6, 158.0, 148.7, 148.6, 146.6, 142.6, 118.54, 112.5, 111.9, 111.6, 102.0, 23.5.
3
+
HRMS (ESI): m/z [M + Na] calculated for C12
H
10
O
4
Na: 241.0477; found: 241.0476.
2
ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(5ꢀmethylfuranꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5b). Yield: 77%, 260 mg; Yellow oil. A
1
1
mixture of keto/enol tautomers as 0.9:1 by H NMR. H NMR (400 MHz, CDCl
7.52 (d, J = 1.4 Hz, 1H, enol), 7.05 (d, J = 3.4 Hz, 2H, keto), 6.48 (m, 1H, enol), 6.28 (d, J = 3.2 Hz, 1H, enol),
.14 (d, J = 3.3 Hz, 2H, keto), 5.98 (s, 1H, enol), 5.97 (d, J = 3.2 Hz, 1H, enol), 5.70 (m, 1H, keto), 3.87 (s, 1H,
3
) δ (ppm) 17.37 (s, 1H, enol),
6
13
keto), 2.37 (s, 3H, enol), 2.30 (s, 3H, keto), 2.10 (s, 3H, enol), 2.00 (s, 3H, keto). C NMR (100 MHz, CDCl
ppm) 191.9 (keto), 188.0 (enol), 177.0 (keto), 176.8 (enol), 157. 9 (keto), 157.3 (enol), 149.2 (enol), 148.9 (keto),
147.4 (keto), 142.4 (enol), 120.6 (keto), 117.5 (enol), 111.7 (enol), 111.5 (keto), 109.7 (keto), 109.4 (enol), 109.3
3
) δ
(
(
[
enol), 101.5 (keto), 95.8 (enol), 54.3 (keto), 24.2 (enol), 23.1 (keto), 14.1 (enol), 14.0 (keto). HRMS (ESI): m/z
+
M + Na] calculated for C H O Na: 255.0633; found: 255.0642.
1
3
12
4
1
2
ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(thiophenꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5c). Yield: 72%, 215 mg; Yellow oil. H NMR
(400 MHz, CDCl ) δ (ppm) 17.51 (s, 1H, enol), 7.57 (d, J = 1.5 Hz, 1H, enol), 7.51 (d, J = 1.5 Hz, 1H, enol), 6.95
m, 1H, enol), 6.87 (d, J = 3.2 Hz, 1H, enol), 6.52 (d, J = 3.2 Hz, 1H, enol), 6.37 (d, J = 3.2 Hz, 1H, enol), 2.04 (s,
3
(
1
3
3
1
H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 194.9, 179.9, 148.8, 142.9, 139.4, 133.5, 132.7, 127.9, 112.9,
+
11.7, 102.2, 24.0. HRMS (ESI): m/z [M + Na] calculated for C H O SNa: 257.0248; found: 257.0256.
12 10
3
2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(5ꢀmethylthiophenꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5d). Yield: 68%, 185 mg; Yellow solid;
o
1
m.p. 52.7ꢀ54.2 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.55 (s, 1H, enol), 7.56 (s, 1H, enol), 6.69 (d, J = 3.7 Hz,
1
H, enol), 6.62 (d, J = 3.3 Hz, 1H, enol), 6.51 (s, 1H, enol), 6.35 (d, J = 3.3 Hz, 1H, enol), 2.43 (s, 3H, enol), 2.01
13
(
s, 3H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 194.1, 178.0, 149.6, 148.9, 142.8, 136.9, 133.5, 126.8, 112.8,
+
111.7, 101.8, 23.8, 15.7. HRMS (ESI): m/z [M + Na] calculated for C H O SNa: 271.0405; found: 271.0406.
1
3
12
3
1
2ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(4ꢀmethylthiophenꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5e). Yield: 70%, 201 mg; Yellow oil. H
3
NMR (400 MHz, CDCl ) δ (ppm) 17.52 (s, 1H, enol), 7.56 (s, 1H, enol), 7.10 (s, 1H, enol), 6.70 (s, 1H, enol), 6.52
1
3
(
s, 1H, enol), 6.36 (d, J = 3.2 Hz, 1H, enol), 2.15 (s, 3H, enol), 2.03 (s, 3H, enol). C NMR (100 MHz, CDCl ) δ
3
(ppm) 194.9, 179.7, 148.7, 142.8, 138.6, 138.5, 134.9, 129.7, 112.9, 111.7, 102.1, 24.0, 15.5. HRMS (ESI): m/z [M
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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4
4
4
4
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4
5
5
5
5
5
5
5
5
5
5
6
+
+ Na] calculated for C13
H
12
O
3
SNa: 271.0405; found: 271.0401.
2
ꢀ(Furanꢀ2ꢀyl)ꢀ1ꢀ(1ꢀmethylꢀ1Hꢀpyrrolꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5f). Yield: 53%, 168 mg; Yellow oil. A
1
1
mixture of keto/enol tautomers as 2:5 by H NMR. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.78 (s, 1H, enol), 7.51
(
s, 1H, enol), 7.41 (s, 0.4H, keto), 7.00 (d, J = 3.2 Hz, 0.4H, keto), 6.87 (s, 0.4H, keto), 6.74 (s, 1H, enol), 6.47 (d,
J = 3.0 Hz, 1H, enol), 6.44 (d, J = 3.3 Hz, 0.4H, keto), 6.39 (d, J = 3.9 Hz, 0.4H, keto), 6.24 (d, J = 2.8 Hz, 1H,
enol), 6.14 (m, 0.4H, keto), 5.93 (m, 1H, enol), 5.53 (d, J = 5.3 Hz, 1H, enol), 5.50 (s, 0.4H, keto), 3.95 (m, 1.2H,
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
keto), 3.94 (m, 3H, enol), 2.26 (s, 1.2H, keto), 1.99 (s, 3H, enol). C NMR (100 MHz, CDCl
keto), 189.1 (enol), 182.5 (enol), 182.4 (keto), 150.3 (enol), 148.1 (keto), 142.7 (keto), 142.0 (enol), 132.8 (keto),
131.1 (enol), 129.9 (keto), 127.9 (enol), 121.3 (keto), 119.2 (enol), 111.5 (enol), 111.4 (enol),111.1 (keto), 109.3
3
) δ (ppm) 201.6
(
(
keto), 108.9 (keto), 108.6 (enol), 102.3 (enol), 62.9 (keto), 38.6 (enol), 38.0 (keto), 28.9 (keto), 22.7 (enol).
+
HRMS (ESI): m/z [M + H] calculated for C13
H
14NO
3
: 232.0974; found: 232.0975.
Ethyl 2,3ꢀdi(furanꢀ2ꢀyl)ꢀ3ꢀoxopropanoate (5g). Yield: 85%, 307 mg; Yellow oil. A mixture of keto/enol
1
1
tautomers as 25:7 by H NMR. H NMR (400 MHz, CDCl
3
) δ (ppm) 13.79 (s, 0.28H, enol), 7.61 (s, 1H, keto),
.51 (s, 0.28H, enol), 7.46 (s, 0.28H, enol), 7.40 (s, 0.28H, keto), 7.28 (d, J = 3.6 Hz, 1H, keto), 6.55 (d, J = 3.6 Hz,
H, keto), 6.46 (d, J = 3.4 Hz, 1H, keto), 6.38 (d, J = 2.4 Hz, 1H, keto), 6.36 (d, J = 3.6 Hz, 0.28H, enol), 6.27 (d,
7
1
J = 3.3 Hz, 0.28H, enol), 5.94 (d, J = 3.6 Hz, 0.28H, enol), 5.52 (s, 1H, keto), 4.27 (m, 0.56H, enol), 4.24 (m, 2H,
1
3
keto), 1.26 (m, 0.84H, enol), 1.24 (m, 3H, keto) C NMR (100 MHz, CDCl
66.7 (keto), 163.9 (enol), 151.3 (keto), 150.4 (enol), 147.3 (keto), 147.0 (enol), 146.1 (keto), 145.3 (enol), 142.9
keto), 142.2 (enol), 119.2 (keto), 116.5 (enol), 112.9 (keto), 112.2 (enol), 111.4 (enol), 111.1 (enol), 111.0 (keto),
3
) δ (ppm) 179.7 (keto), 173.2 (enol),
1
(
110.0 (keto), 92.3 (enol), 62.2 (keto), 61.5 (enol), 54.6 (keto), 14.3 (enol), 14.1 (keto). HRMS (ESI): m/z [M +
+
Na] calculated for C13
H
12
O
5
Na: 271.0582; found: 271.0580.
Ethyl 2ꢀ(furanꢀ2ꢀyl)ꢀ3ꢀ(5ꢀmethylfuranꢀ2ꢀyl)ꢀ3ꢀoxopropanoate (5h). Yield: 80%, 284 mg; Yellow oil.
1
1
A mixture of keto/enol tautomers as 50:9 by H NMR. H NMR (400 MHz, CDCl
3
) δ (ppm) 13.79 (s, 0.18H, enol),
7.44 (s, 0.18H, enol), 7.34 (s, 1H, keto), 7.15 (s, 1H, keto), 6.41 (s, 1H keto and 0.18H enol), 6.32 (s, 1H, keto),
6
4
.20 (s, 0.18H, enol), 6.13 (s, 1H, keto), 5.93 (s, 0.18H, enol), 5.83 (d, J = 3.2 Hz, 0.18H, enol), 5.43 (s, 1H, keto),
.21 (m, 0.36H, enol), 4.18 (m, 2H, keto), 2.33 (s, 3H, keto), 2.21 (s, 0.54H, enol), 1.20 (m, 3H keto and 0.54H
1
3
enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 178.65 (keto), 173.10 (enol), 166.73 (keto), 163.89 (enol), 159.00
(keto), 155.95 (enol), 149.76 (keto), 147.04 (enol), 146.31 (keto), 145.31 (enol), 142.61 (keto), 141.78 (enol),
1
6
21.39 (keto), 118.07 (enol), 111.24 (enol), 110.84 (keto), 109.66 (keto), 108.82 (enol), 90.78 (enol), 61.92 (enol),
+
1.12 (keto), 54.10 (keto), 14.10 (enol), 14.01 (keto), 13.93 (keto), 13.62 (enol). HRMS (ESI): m/z [M + Na]
14 5
calculated for C14H O Na: 285.0739; found: 285.0732.
Ethyl 2ꢀ(furanꢀ2ꢀyl)ꢀ3ꢀ(5ꢀmethylthiophenꢀ2ꢀyl)ꢀ3ꢀoxopropanoate (5i). Yield: 69%, 310 mg; Yellow
o
1
1
solid; m.p. 38.2ꢀ40.0 C. A mixture of keto/enol tautomers as 10:3 by H NMR. H NMR (400 MHz, CDCl
3
) δ
(
ppm) 13.88 (s, 0.3H, enol), 7.57 (d, J = 3.8 Hz, 1H, keto), 7.53 (m, 0.3H, enol), 7.39 (d, J = 1.9 Hz, 1H, keto),
6
.85 (d, J = 3.8 Hz, 0.3H, enol), 6.78 (d, J = 3.2 Hz, 1H, keto), 6.62 (d, J = 3.2 Hz, 0.3H, enol), 6.48 (m, 1H, keto
and enol), 6.37 (dd, J = 3.2, 1.9 Hz, 1H, keto), 6.31 (d, J = 3.2 Hz, 0.3H, enol), 5.49 (s, 1H, keto), 4.24 (m, 2H,
13
keto and enol), 2.52 (s, 3H, keto), 2.42 (s, 0.9H, enol), 1.23 (m, 3H keto and 0.9H enol). C NMR (100 MHz,
CDCl
3
) δ (ppm) 183.2 (keto), 173.3 (enol), 168.3 (enol), 166.9 (keto), 151.7 (keto), 147.4 (enol), 147.1 (enol),
1
46.6 (keto), 142.8 (keto), 142.5 (enol), 140.2 (keto), 134.4 (keto), 133.7 (enol), 132.1 (enol), 127.2 (keto), 126.1
(enol), 112.4 (enol), 111.6 (enol), 111.1 (keto), 109.9 (keto), 91.3 (enol), 62.2 (keto), 61.3 (enol), 55.4 (keto), 16.2
+
(
keto), 15.5 (enol), 14.3 (enol), 14.1 (keto). HRMS (ESI): m/z [M + Na] calculated for C14
H
14
O
4
SNa: 301.0510;
found: 301.0512.
1ꢀ(Benzofuranꢀ2ꢀyl)ꢀ2ꢀ(furanꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5j). Yield: 76%, 325 mg; Yellow solid; m.p.
o
1
3
80.1ꢀ82.4 C. H NMR (400 MHz, CDCl ) δ (ppm) 17.30 (s, 1H, enol), 7.61 (s, 1H, enol), 7.51 (d, J = 7.8 Hz, 1H,
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enol), 7.48 (d, J = 7.8 Hz, 1H, enol), 7.38 (m, 1H, enol), 7.21 (m, 1H, enol), 6.56 (s, 1H, enol), 6.37 (d, J = 3.0 Hz,
13
1
1
H, enol), 6.23 (s, 1H, enol), 2.09 (s, 3H, enol). C NMR (100 MHz, CDCl
3
) δ (ppm) 194.9, 176.5, 155.4, 149.4,
+
48.4, 142.8, 127.8, 127.5, 123.7, 122.9, 114.1, 112.1, 111.7, 103.3, 24.0. HRMS (ESI): m/z [M + Na] calculated
12 4
for C16H O Na: 291.0633; found: 291.0633.
1ꢀ(Benzo[b]thiophenꢀ2ꢀyl)ꢀ2ꢀ(furanꢀ2ꢀyl)butaneꢀ1,3ꢀdione (5k). Yield: 58%, 230 mg; Yellow solid;
o
1
m.p. 83.9ꢀ85.6 C. H NMR (400 MHz, CDCl
3
) δ (ppm) 17.46 (s, 1H, enol), 7.77 (d, J = 8.0 Hz, enol), 7.70 (d, J =
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
7
1
.9 Hz, 1H, enol), 7.63 (d, J = 1.3 Hz, 1H, enol), 7.34 (m, 2H, enol), 7.09 (s, 1H, enol), 6.58 (dd, J = 3.1, 1.3 Hz,
13
3
H, enol), 6.43 (d, J = 3.1 Hz, 1H, enol), 2.09 (s, 3H, enol). C NMR (100 MHz, CDCl ) δ (ppm) 195.8, 179.8,
148.4, 143.0, 142.6, 139.0, 138.9, 129.9, 126.9, 125.7, 124.8, 122.4, 113.1, 111.8, 103.2, 24.3. HRMS (ESI): m/z
+
[
M + Na] calculated for C H O SNa: 307.0405; found: 307.0417.
1
6
12
3
Ethyl 3ꢀ(benzofuranꢀ2ꢀyl)ꢀ2ꢀ(furanꢀ2ꢀyl)ꢀ3ꢀoxopropanoate (5l). Yield: 90%, 348 mg; Yellow solid;
o
1
1
m.p. 89.2ꢀ91.9 C. A mixture of keto/enol tautomers as 10:7 by H NMR. H NMR (400 MHz, CDCl
13.81 (s, 0.7H, enol), 7.70 (d, J = 7.8 Hz, 1H, keto), 7.61 (s, 1H, keto), 7.58 (s, 0.7H, enol), 7.55 (s, 1H, keto), 7.52
d, J = 6.8 Hz, 1H, keto), 7.48 (d, J = 8.1 Hz, 0.7H, enol), 7.43 (s, 1H, keto), 7.41 (s, 0.7H, enol), 7.34 (d, J = 7.4
3
) δ (ppm)
(
Hz, 1H, keto), 7.31 (d, J = 7.4 Hz, 0.7H, enol), 7.21 (m, 0.7H, enol), 6.52 (m, 1H keto and 0.7H enol), 6.39 (s, 1H
keto and 0.7H enol), 6.32 (s, 0.7H, enol), 5.66 (s, 1H, keto), 4.24ꢀ431 (m, 2H keto and 1.4H enol), 1.26 (m, 3H
13
keto and 2.1H enol). C NMR (100 MHz, CDCl
56.0 (keto), 155.2 (enol), 151.2 (keto), 148.6 (enol), 146.6 (enol), 145.8 (keto), 143.1 (keto), 142.3 (enol), 129.0
keto), 127.6 (enol), 127.1 (enol), 126.9 (keto), 124.3 (keto), 123.7 (keto), 123.5 (enol), 122.3 (enol), 115.0 (keto),
3
) δ (ppm) 181.7 (enol), 173.0 (keto), 166.6 (enol), 163.9 (keto),
1
(
112.7 (keto), 112.2 (enol), 112.0 (enol), 111.5 (enol), 111.4 (enol), 111.1 (keto), 110.2 (keto), 94.7 (enol), 62.4
+
(
keto), 61.7 (enol), 55.0 (keto), 14.2 (enol), 14.1 (keto). HRMS (ESI): m/z [M + Na] calculated for C17
H
14
O
5
Na:
3
21.0739; found: 321.0750.
29
Syntheses of 1ꢀPhenylꢀ2ꢀthiophenꢀ2ꢀylꢀbutanꢀ1ꢀone (7).
An ovenꢀdried round bottom flask was charged with 65% dispersion of NaH in mineral oil (7.5 mmol),
anhydrous THF (10 ml), 1ꢀphenylꢀ2ꢀ(thiophenꢀ2ꢀyl)ethanone (1.5 mmol), and iodoethane (2.25 mmol). The
o
reaction mixture was heat at reflux overnight, and the reation was quenched at 0 C by adding 1 M HCl and
saturated NaHCO
3
sequentially, then the mixture extracted with ethyl acetate. The combined organic layers were
dried over Na SO , filtered, and concentrated. Purification by silica gel chromatography provided the desired 7 as
2
4
a yellow oil in 28% yield.
1ꢀPhenylꢀ2ꢀthiophenꢀ2ꢀylꢀbutanꢀ1ꢀone (7). Yield: 28%, 97 mg; Colorless oil. H NMR (400 MHz, CDCl
1
3
)
δ (ppm) 7.72 (m, 2H), 7.50 (m, 1H), 7.36ꢀ7.32 (m, 3H), 7.04ꢀ6.99 (m, 2H), 4.98 (s, 1H), 2.54ꢀ2.38 (m, 2H), 0.86
13
(
m, 3H). C NMR (100 MHz, CDCl ) δ (ppm) 201.1, 147.2, 134.1, 133.3, 129.8, 128.5, 127.3, 126.1, 125.5, 32.6,
3
+
7
.7. HRMS (ESI): m/z [M + Na] calculated for C14
H14OSNa: 253.0663; found 253.0657.
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the ACS Publications website.
H detection for the photochemical dehydrocyclization of 3a by GC.
2
Determination of fluorescence quantum yield for 4aꢀ4m and 6aꢀ6l.
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NMR spectra of compounds 3ꢀ6. Fluorescence spectra of 4 and 6.
AUTHOR INFORMATION
Corresponding Author
* Eꢀmail: zhangzt@snnu.edu.cn
ORCID
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Jin Zhang: 0000ꢀ0003ꢀ0178ꢀ8285
Tao Wang: 0000ꢀ0002ꢀ1494ꢀ5297
Yong Liang: 0000ꢀ0002ꢀ7225ꢀ7062
Zunting Zhang: 0000ꢀ0003ꢀ0806ꢀ2452
Author Contributions
‡
Jin Zhang and Xi Zhang contributed equally.
Present Address
†
Department of Molecular Medicine, Beckman Research Institute of city of Hope, Duarte, CA
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Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We are grateful for financial support from the National Natural Science Foundation of China (Nos.
21672132 and 21502110) and the Fundamental Funds Research for the Central Universities (Nos.
GK201503034 and 2016CBY002).
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