Palladium(II)-Catalyzed Oxidative Annulation of 2-Hydroxynaphthalene-1,4-diones and Internal Alkynes via C-H Functionalization

Article abstract of DOI:10.1021/acs.joc.9b03153

An efficient Pd(II)-catalyzed oxidative annulation of 2-hydroxynaphthalene-1,4-diones and internal alkynes has been developed with high step efficiency. A broad range of functional groups are compatible with this reaction, thus providing a new entry to diverse naphtho[2,3-b]furan-4,9-dione derivatives in good to high yields.

Full text of DOI:10.1021/acs.joc.9b03153

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Note
Palladium(II)-catalyzed Oxidative Annulation of 2-Hydroxynaphthalene-1,4-
diones and Internal Alkynes via C-H Functionalization
Peng Sun, Jiaojiao Yang, Jinsong Peng, Baichuan Mo, Xin Chen, Xiang Li, and Chunxia Chen
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.9b03153 • Publication Date (Web): 15 Apr 2020
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Palladium(II)-catalyzed Oxidative Annulation of 2-Hydroxynaphthalene-1,4-diones
and Internal Alkynes via C-H Functionalization
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Peng Sun,a,b Jiaojiao Yang,a Jinsong Peng,*a Baichuan Mo,a,b Xin Chen,a,b Xiang Lia and
Chunxia Chen*a,b
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a
College of Chemistry, Chemical Engineering and Resource Utilization, Northeast
Forestry University, Harbin 150040, P. R. China.
b
Material Science and Engineering College, Northeast Forestry University, Harbin
150040, P. R. China.
Abstract
An efficient Pd(II)-catalyzed oxidative annulation of 2-hydroxynaphthalene-1,4-diones
and internal alkynes has been developed with high step efficiency. A broad range of
functional groups are compatible with this reaction, thus providing a new entry to
diverse naphtho[2,3-b]furan-4,9-dione derivatives in good to high yields.
Naphtho[2,3-b]furan-4,9-dione unit has been widely found in numerous natural
products and synthetic analogues. As an important privileged structural motif, many
of furonaphthoquinones exhibit versatile biological activities such as antitumor,1
trypanocidal,2 anti-leukemic activity,3 inhibitor of HaCaT cell growth,4 cytotoxic
activity toward KB5 and Vero cells,6 and inhibitor of human keratinocyte
hyperproliferation (A‒D, Fig. 1).7 For instance, Lapacho A has been used as a
longtime folk medicine against inflammatory, infectious, stomach, and skin
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diseases.8 Nowadays, Lapacho A has been developed into an anticancer drug in
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clinical treatments and also used against psoriasis.8
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Figure 1. Biologically active furonaphthoquinones.
Substituted furonaphthoquinones are of great interest in pharmaceutical
research and drug discovery, therefore, considerable efforts have been focused on
the synthetic methods of naphtho[2,3-b]furan-4,9-diones. Over the past decades,
several different approaches for furonaphthoquinone preparation have been
reported (Scheme 1). Mainly starting from 2-hydroxy-1,4-naphthoquinones,
multi-component reaction (Scheme 1a),9 various [3+2] annulation strategies
[thermal cyclization with enamines (Scheme 1b),10 CAN-mediated oxidative
cycloaddition with vinyl sulfide11 and enol ether12 (Scheme 1c), photoaddition13
(Scheme
1d)],
one-pot
cascade
procedure
(Scheme
1e),14 and
transition-metal-catalyzed methods (Scheme 1f and 1g)15 have been developed. In
addition,
other
miscellaneous
methods
such
as
Diels-Alder
cycloaddition/aromatization,16 oxidative cyclization/isomerization,17 Friedel-Crafts
acylation/oxidation,18 base-promoted oxidative coupling of 2-hydroxy-1,4-
naphthoquinones with (Z)-2-ylideneimidazo[1,2-a]pyridin-3(2H)-ones,19
and
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bromine-mediated intramolecular cyclization20 have also been developed. Despite
the significant progress made in the synthesis of furonaphthoquinones, novel
synthetic approaches with milder reaction conditions and enhanced reaction
efficiency are still desirable. For example, Liu15a recently demonstrated an atom- and
step-efficient approach through Pd-catalyzed reverse hydrogenolysis coupling of
2-hydroxy-1,4-naphthoquinones and olefins (Scheme 1f).
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Due to improved atom and step economy, recent years have witnessed an
upsurge in heterocycle synthesis based on metal-catalyzed C-H activation
processes.21 Specifically, oxidative annulation reactions between alkynes and
different partners (such as phenols,22a thiols,22b anilines,22c and benzoic acids22d) set
the stage for the development of practical approaches for the atom-efficient
formation of heterocycles in a limited number of steps.22 For instance, Rh- and
Ru-catalyzed oxidative annulation between α-naphthol and alkynes have been
independently developed for the synthesis of naphthopyrans by Miura23 and
Ackermann,24 respectively. Ackermann25 also demonstrated an atom- and
step-economical synthesis of isocoumarins through oxidative annulations of alkynes
by carboxylic acids using a ruthenium catalyst. Sahoo group developed a novel
one-step synthesis of 2,3-disubstituted benzofurans through Pd-catalyzed oxidative
annulations of phenols with unactivated internal alkynes.26 More recently, Gogoi
described a ruthenium(II)-catalyzed annulation of vinylnaphthols and alkynes to give
spiro-pentacyclic naphthalenones through C-H activation, dearomatization, and
alkyne insertion.27 With our continuous efforts on metal-catalyzed (Cu28 and Pd29)
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oxidative
C-H
functionalization,
herein
we
envisioned
that
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2-hydroxy-1,4-naphthoquinones and alkynes should be suitable substrates for the
synthesis of furonaphthoquinones through palladium-catalyzed oxidative [3+2]
annulation reaction (Scheme 1h).
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Scheme 1. Synthetic methods stating from 2-hydroxy-1,4-naphthoquinones.
2-Hydroxynaphthalene-1,4-dione (1a) was selected as the substrate to react with
diphenylacetylene (2a) in the presence of different combinations of palladium
catalysts, nitrogen-based ligands, and oxidants (Table 1). The blank experiment
(without the catalyst and ligand) was examined in 1,4-dioxane at 80 ℃ for 24 h using
NaOAc as the base, and no desired product was obtained. We then tested the
reaction conditions previously used for oxidative annulations of phenols with
unactivated internal alkynes.26 However, a combination of Pd2(dba)3 (2.5 mol%),
1,10-phenanthroline (Phen, L1, 10 mol%), and NaOAc as the base cannot efficiently
promote the reaction in 1,4-dioxane, and 3aa was obtained in a low yield (26%, entry
1
13
1). The H and C NMR spectroscopy data and melt point of the target 3aa were
consistent with the reported literature.15a A survey of palladium catalysts showed
that PdCl2(PPh3)2 provided better results (35% yield) than Pd2(dba)3, Pd(PPh3)4,
Pd(OAc)2, PdCl2, and PdCl2(MeCN)2 (15-32% yields) with Phen as the ligand and
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Table 1. Condition optimization for the synthesis of 3aaa
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9
yield
yield
(%)c
38
trace
N.D.
78 (73)e
N.D.
18
35
43
trace
15
trace
26
entry
catalyst/ligandb
oxidant/base
entry catalyst/ligandb
oxidant/base
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(%)c
26
1d
2
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8
Pd2(dba)3/L1
Pd(PPh3)4/L1
PdCl2(PPh3)2/L1
Pd(OAc)2/L1
PdCl2/L1
PdCl2(MeCN)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
Cu(OAc)2/NaOAc
Cu(OAc)2/NaOAc
Cu(OAc)2/NaOAc
Cu(OAc)2/NaOAc
Cu(OAc)2/NaOAc
Cu(OAc)2/NaOAc
AgOAc/NaOAc
Ag2CO3/NaOAc
K2S2O8/NaOAc
K2Cr2O7/NaOAc
KMnO4/NaOAc
O2/NaOAc
Cu(OTf)2/NaOAc
Cu(OAc)2/HCOONa
Cu(OAc)2/NaHCO3
16
17
18
19
20
21
22
23
24
25f
26g
27h
28i
29j
30
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/‒
PdCl2(PPh3)2/L2
PdCl2(PPh3)2/L3
PdCl2(PPh3)2/L4
PdCl2(PPh3)2/L5
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
PdCl2(PPh3)2/L1
K2Cr2O7/NaOMe
K2Cr2O7/NaOtBu
K2Cr2O7/NEt3
32
35
24
18
15
35
N.D.
N.D.
53
42
N.D.
15
43
45
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
K2Cr2O7/Zn(OAc)2
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a
26
47
79k/76l/78m
Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol), catalyst (0.01 mmol), ligand (0.02 mmol), oxidant (2 equiv), and base (2
equiv) in solvent (2 mL) at 80 ℃for 24 h. b L1 = 1,10-phenanthroline, L2 = 2,2'-bipyridine, L3 = 4,7-diphenyl-1,10-phenanthroline,
c
d
L4 = 3,4,7,8-tetramethyl-1,10-phenanthroline L5 = oxalaldehyde dioxime. Isolated yield after chromatography. 2.5 mol%
Pd2(dba)3 was used. e One millimole scale. f DMF. g DMSO or DCE. h THF. i MeCN. j toluene. k 100 ℃. l 110 ℃. m 24 h.
Cu(OAc)2 as the oxidant (entries 1-6). Among the range of oxidants [AgOAc, Ag2CO3,
K2S2O8, K2Cr2O7, KMnO4, O2 and Cu(OTf)2, entries 7-13] that were surveyed, K2Cr2O7
appeared to be optimal and gave 3aa with an enhanced yield (53%, entry 10). The
effect of other bases such as HCOONa, NaHCO3, NaOMe, NaOtBu, Et3N, and Zn(OAc)2
on the reaction was next examined (entries 14−19), Zn(OAc)2 provided a better result
with 78% isolated yield (entry 19) probably by the chelated 2-hydroxyketone
coordination to increase the rate of deprotonation. Using Zn(OAc)2 as the base,
examination of nitrogen-containing bidented ligands showed that the Phen (L1) was
most efficient (entry 19), while 2,2’-bipyridyl (L2), ligands with 1,10-phenanthroline
scaffold (L3 and L4), and oxalaldehyde dioxime (L5) produced lower amounts of 3aa
(from trace to 43% yield, entries 21-24). The rigid N,N-pincer phenanthroline-type
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ligands provided better results than the acyclic ligand 2,2’-bipyridyl (78% and 18%, L1
vs L2, entries 19 and 21). A survey of reaction media showed that the use of
1,4-dioxane provided better results than those obtained in DMF, DMSO, DCE, THF,
acetonitrile, and toluene (entries 19 and 25−29). It is worth noting that the N-bearing
bidented ligand is essential to this transformation and 3aa was not produced in the
absence of ligand (entry 20).26 Finally, with increased reaction temperature and time,
yields have not obviously been improved (entry 30). In addition, the reaction can be
carried out on a 1.0 mmol scale without compromising the yield (78% vs 73%).
With the optimized reaction conditions in hand, the scope of this annulation
reaction was then examined. A variety of diversely substituted furonaphthoquinone
3 was obtained in moderate to good yields (Tables 2 and 3). For symmetrically
substituted alkyne substrates 2, the effect of electron-rich and electron-deficient
aryl-substituted alkynes was first investigated (Table 2, 2b−2o, 2r, and 2s). A variety
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of substituents (Me, OMe, F, Cl, and Br) on the internal arylalkynes were applicable,
Table 2. Variation of internal alkynesa,b
a
Reaction conditions: 1a (0.2 mmol), 2a (0.4 mmol), PdCl2(PPh3)2 (0.01 mmol), Phen (0.02 mmol), K2Cr2O7 (0.4
mmol), and Zn(OAc)2 (0.4 mmol) in 1,4-dioxane (2 mL) at 80 ℃ for 24 h. b Isolated yields. c 100 ℃. d The ratio of
the regioisomers was determined by NMR analysis.
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affording the corresponding products in 56−78% yields. Both electron-donating
(2b−c, 2g−h, 2j−k, and 2m) and electron-withdrawing (2d−f, 2i, 2l) substituents can
be incorporated at the para-, meta-, and ortho-position (Table 2, 3ab−3al). The
electronic nature of the aromatic motifs affected the outcome to some extent, the
introduction of electron-withdrawing substituents can afford higher yields. In
addition, dimethyl-substituted (2m), hetero (2n), and fused aryl (α-naphthyl , 2o)
alkynes were also transformed into the corresponding products in 63%, 33%, and 68%
yield, respectively. Because of the lack of conjugation, the symmetrically substituted
alkyl alkyne is less reactive.30 The desired 2,3-dialkyl-substituted
furonaphthoquinone 3ap was obtained from 4-octyne (2p) in only 35% yield. A
similar result was also observed for asymmetrical 1,2-dialkylalkyne, for instance, 31%
yield was obtained for non-4-yne. When asymmetrically substituted internal
arylalkynes were used, potential regioselectivity issue exists in the oxidative
annulation process. For asymmetrical 1,2-diarylalkynes (2r, and 2s), a 1:1 mixture of
two regioisomers was obtained in the two cases (Table 2, 3ar/3ar', and 3as/3as'),
indicating that the difference of electric nature between two aryl groups of
unsymmetrical 1,2-diarylalkynes seem not to affect the regioselectivity. However,
when alkyl, aryl-substituted alkyne, for example, phenyl- and n-butyl-substituted
alkyne 2q was used, the 3-butyl-2-phenylnaphtho[2,3-b]furan-4,9-dione 3aq was
exclusively formed in 67% yield, consistent with the observations of the groups of
Larock,31 Fagnou,30b Sahoo,26 and Patel.32 Finally, terminal alkynes were incompatible
with the protocol due to the formation of alkyne homo-coupling products.30b
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The generality of 2-hydroxynaphthalene-1,4-diones 1 was then examined. As
shown in Table 3, a great variety of 2-hydroxynaphthalene-1,4-diones 1a−1h can be
smoothly converted into the corresponding products 3ba−3ha in good yields
(68−78%). Several funcꢀonal groups, such as Me, OMe, Ph, F, Cl, and Br were
tolerated in the aryl fragment of 1. Generally, the electronic nature of the aromatic
motifs does not seem to affect the efficiency of this transformation, and
electron-donating (Me, OMe, and Ph) and electron-withdrawing substituents (F, Cl,
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and Br) can be incorporated at different positions of aryl moiety.
Table 3. Variation of 2-hydroxynaphthalene-1,4-dionesa,b
O
O
5 mol% PdCl2(PPh3)2
10 mol% Phen, K2Cr2O7, Zn(OAc)2
OH
O
Ph
+
Ph
R
R
1,4-dioxane, 100 ℃, 24
h
Ph
Ph
O
O
1a-1h
2a
3aa-3ha
a
Reaction conditions: 1 (0.2 mmol), 2a (0.4 mmol),
PdCl2(PPh3)2 (0.01 mmol), Phen (0.02 mmol), K2Cr2O7 (0.4
mmol), and Zn(OAc)2 (0.4 mmol) in 1,4-dioxane (2 mL) at
100 ℃ for 24 h. b Isolated yields.
Scheme 2. Proposed mechanistic cycle.
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Two competitive catalytic cycles for the synthesis of furonaphthoquinones have
been proposed in Scheme 2. In the presence of Zn(OAc)2 as the base, the
deprotonation of 2-hydroxynaphthalene-1,4-dione 1 yielded two tautomeric anions
which existed as either carbanion 5 in the keto-form or as oxygen anion 6 in the
enol-form. At this stage, attack of anion onto the electrophilic Pd(II) species may
occur in two different ways (Scheme 2, path A and B). Path A involved the attack of
carbanion 5 onto catalytic active species 4 to form alkyl-Pd(II) species 7.
Subsequently, the coordination of the internal alkyne 2 to 7 would induce its
carbopalladation to afford an alkenyl palladium(II) complex 8. Base-assisted further
deprotonation of the ketone α-carbon of 8 led to O−Pd bond formation, affording
intermediate 9. Palladacycle 9 underwent C−O reductive elimination to afford the
desired product 3 and a Pd(0) species 10, which was oxidized by K2Cr2O7 to
regenerate the active Pd(II) species 4 for the next catalytic cycle. On the other hand,
mechanistic cycle B was initiated by the attack of enol anion 6 onto the electrophilic
Pd(II) species 4, giving the enol-type palladium(II) 11. The coordination followed by
syn migratory insertion of internal alkyne 2 into O-Pd bond then afforded
alkenyl-Pd(II) species 12.33 The final product 3 can be formed possibly through two
distinct pathways (C‒H activation or Heck pathway). The C‒H activation pathway
involved a concerted metalation deprotonation (CMD) transition state34 of alkene to
form the palladacycle 13, which underwent C−C bond-forming reductive elimination
to afford the desired furonaphthoquinone 3 and regenerate a Pd(0) species 10. The
Heck pathway involved an intramolecular syn migratory insertion into the olefin
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moiety of 12, then was followed by an isomerization process to give the
σ-alkyl-palladium(II) acetate 14 with β-hydrogen in a syn position relative to the
palladium atom. A syn β-hydride elimination afforded 3 and a hydridopalladium(II)
acetate, which underwent a reversible reductive elimination to regenerate a Pd(0)
complex 10. Finally, Pd(0) resulting from an elimination process was oxidized to Pd(II)
by K2Cr2O7.
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In conclusion, we have developed a modular approach for rapid syntheses of
diverse naphtho[2,3-b]furan-4,9-dione derivatives through Pd-catalyzed oxidative
annulations of 2-hydroxynaphthalene-1,4-diones with readily accessible unactivated
internal alkynes. The success of the reaction heavily relies on the careful selection of
proper base and oxidant. The combination of Zn(OAc)2 and K2Cr2O7 was found to be
essential for the efficient formation of furonaphthoquinones. This synthetic method
exhibits a broad substrate scope with good yields and excellent regioselectivity for
aryl, alkyl-substituted alkynes. Considering considerable valance of the products for
medicinal science, this reaction could be of synthetic utility for the discovery of
drugs.
EXPERIMENTAL SECTION
General Information. Chemicals were all purchased from commercial supplies and
used without further purification unless otherwise stated. Solvents were dried and
purified according to the standard procedures before use. Reactions were monitored
by analytical thin-layer chromatography (TLC). All reactions were conducted in dried
glassware. Purification of reaction products was done by flash chromatography with
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230−400 mesh silica gel. Internal alkynes (2a‒2m35 and 2q‒2s36) and
2-hydroxynaphthalene-1,4-diones (1a‒1f,37 1h37 and 1g38) were prepared according
to the literature methods. All these substrates are known compounds, and the
spectroscopic and physical data are matched with those from the literature. Melting
points were determined on a melting point apparatus in open capillaries and are
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uncorrected. H NMR spectra were recorded on a 500 MHz spectrometer, and C
NMR spectra were recorded at 125 MHz. Unless otherwise stated,
deuterochloroform (CDCl3) was used as a solvent. Chemical shifts (δ) are given in
parts per million downfield relative to tetramethylsilane (TMS). Chemical shifts for
carbon resonances are reported in parts per million and are referenced to the
carbon resonance of the solvent CHCl3 (δ = 77.16 ppm). Coupling constants are given
in hertz. High-resolution mass spectra were recorded on a BIO TOF Q mass
spectrometer equipped with an electrospray ion source (ESI), operated in the
positive mode.
General procedures for synthesis of naphtho[2,3-b]furan-4,9-dione derivatives. A
10 mL schlenk tube equipped with a magnetic stirring bar was charged with PdCl2
(PPh3)2 (7.0 mg, 5 mol%), phenanthroline (3.6 mg, 10 mol%), K2Cr2O7 (117.6 mg, 2 eq)
and Zn(OAc)2 (73.4 mg, 2 eq), and then internal alkynes (0.4 mmol, 2 eq),
α-hydroxynaphthoquinone derivative (0.2 mmol, 1 eq) were added. 1, 4-Dioxane (2.0
mL) was then added to the mixture via syringe at room temperature under air. The
tube was sealed and put into a preheated oil bath at 80 or 100 ℃ for 24 h. The
mixture was cooled to room temperature, quenched with water (5 mL), and diluted
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with CH2Cl2 (10 mL). The layers were separated, and the aqueous layer was extracted
with 3 × 5 mL of CH2Cl2. The organic layer is washed with saturated aqueous NaCl (15
mL), dried over MgSO4, filtered, and concentrated in vacuo. The crude product is
purified by silica gel column chromatography, eluꢀng with 10−20% ethyl
acetate/petroleum ether.
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2,3-Diphenylnaphtho[2,3-b]furan-4,9-dione (3aa).15a The reaction was carried out on
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a 1.0 mmol scale. Yellow solid, mp 262-264 ℃; yield, 73% (255.5 mg); H NMR (400
MHz, CDCl3) δ 8.28 – 8.22 (m, 1H), 8.12 – 8.07 (m, 1H), 7.78 – 7.69 (m, 2H), 7.61 –
13
7.56 (m, 2H), 7.47 (br, 5H), 7.36 – 7.28 (m, 3H). C{1H} NMR (126 MHz, CDCl3) δ
179.8, 172.4, 154.4, 150.1, 132.8, 132.7, 132.5, 131.5, 129.2, 129.0, 128.8, 128.7,
127.7, 127.6, 127.5, 126.2, 125.9, 125.6, 120.7. HRMS-ESI: [M + H]+ calcd for
+
C24H15O3 m/z 351.1016, found 351.1018.
2,3-Di-p-tolylnaphtho[2,3-b]furan-4,9-dione (3ab). Yellow solid, mp 235-237 ℃;
yield, 63% (47.6 mg); 1H NMR (500 MHz, CDCl3) δ 8.17 (d, J = 7.3 Hz, 1H), 8.02 (d, J =
7.3 Hz, 1H), 7.69 – 7.62 (m, 2H), 7.43 (d, J = 8.0 Hz, 2H), 7.27 (d, J = 7.8 Hz, 2H), 7.22 –
7.19 (m, 2H), 7.05 (d, J = 8.0 Hz, 2H), 2.38 (s, 3H), 2.27 (s, 3H). 13C{1H} NMR (126 MHz,
CDCl3) δ 179.9, 172.4, 154.7, 149.9, 139.0, 137.3, 132.7, 132.6, 132.5, 131.5, 128.8,
128.4, 128.3, 126.2, 126.1, 125.8, 125.6, 124.8, 120.2, 20.5, 20.4. HRMS-ESI: [M + H]+
+
calcd for C26H19O3 m/z 379.1329, found 379.1332.
2,3-Bis(4-methoxyphenyl)naphtho[2,3-b]furan-4, 9-dione (3ac). Yellow solid, mp
233-235 ℃; yield, 60% (49.2 mg); 1H NMR (500 MHz, CDCl3) δ 8.23 (d, J = 7.2 Hz, 1H),
8.09 (d, J = 7.2 Hz, 1H), 7.76 – 7.79 (m, 2H), 7.55 (d, J = 8.9 Hz, 2H), 7.38 (d, J = 8.6 Hz,
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2H), 7.00 (d, J = 8.6 Hz, 2H), 6.84 (d, J = 8.9 Hz, 2H), 3.89 (s, 3H), 3.82 (s, 3H). 13C{1H}
NMR (126 MHz, CDCl3) δ 181.1, 173.3, 160.7, 159.7, 155.8, 150.7, 133.7, 133.64,
133.61, 132.6, 131.4, 129.9, 128.9, 126.9, 126.6, 122.4, 121.3, 120.1, 114.2, 114.1,
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55.4, 55.3. HRMS-ESI: [M + H]+ calcd for C26H19O5 m/z 411.1227, found 411.1229.
2,3-Bis(4-fluorophenyl)naphtho[2,3-b]furan-4,9-dione
(3ad). Yellow solid, mp
267-269 ℃; yield, 73% (56.4 mg); 1H NMR (500 MHz, CDCl3) δ 8.24 (dd, J = 7.4, 1.4
Hz, 1H), 8.10 (dd, J = 7.4, 1.4 Hz, 1H), 7.79 – 7.71 (m, 2H), 7.58 – 7.54 (m, 2H), 7.46 –
7.41 (m, 2H), 7.20 – 7.16 (m, 2H), 7.05 – 7.01 (m, 2H). 13C{1H} NMR (126 MHz, CDCl3)
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δ 179.8, 172.4, 162.4 (163.4, 161.4, d, JC-F = 252 Hz), 161.9 (162.9, 160.9, d, JC-F
=
2
252 Hz), 153.7, 150.4, 132.9, 132.4, 131.4, 130.9 (130.9, 130.8, d, JC-F = 9 Hz), 128.5,
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128.4 (128.4, 128.3, d, JC-F = 9 Hz), 125.9, 125.7, 124.9 (124.88, 124.86, d, JC-F = 2.5
4
3
Hz), 123.6 (123.61, 123.59, d, JC-F = 2.5 Hz), 119.4, 115.1 (115.08, 115.05, d, JC-F = 4
Hz), 114.9 (114.91, 114.88, d, JC-F = 4 Hz). HRMS-ESI: [M + H]+ calcd for C24H13F2O3
3
+
m/z 387.0827, found 387.0825.
2,3-Bis(4-chlorophenyl)naphtho[2,3-b]furan-4,9-dione (3ae). Yellow solid, mp
261-263 ℃; yield, 70% (58.5 mg); 1H NMR (500 MHz, CDCl3) δ 8.24 (d, J = 7.0 Hz, 1H),
8.09 (d, J = 7.0 Hz, 1H), 7.80 – 7.70 (m, 2H), 7.61 (d, J = 8.3 Hz, 2H), 7.48 (d, J = 8.6 Hz,
2H), 7.43 (d, J = 8.6 Hz, 2H), 7.33 (d, J = 8.3 Hz, 2H). 13C{1H} NMR (126 MHz, CDCl3) δ
180.7, 173.4, 154.4, 151.4, 134.0, 133.4, 132.4, 132.12, 132.11, 131.7, 129.3, 128.9,
128.7, 127.1, 127.0, 126.8, 124.6, 123.2, 120.9. HRMS-ESI: [M + H]+ calcd for
+
C24H13Cl2O3 m/z 419.0236, found 419.0237.
2,3-Bis(4-bromophenyl)naphtho[2,3-b]furan-4,9-dione (3af).9c Yellow solid, mp
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237-238 ℃; yield, 66% (66.7 mg); H NMR (500 MHz, CDCl3) δ 8.26 – 8.21 (m, 1H),
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8.11 – 8.07 (m, 1H), 7.79 – 7.71 (m, 2H), 7.50 (d, J = 8.6 Hz, 2H), 7.46 (d, J = 8.4 Hz,
2H), 7.39 (d, J = 8.4 Hz, 2H), 7.31 (d, J = 8.6 Hz, 2H). 13C{1H} NMR (126 MHz, CDCl3) δ
180.7, 173.4, 154.4, 151.4, 136.2, 135.0, 134.0, 133.4, 132.8, 132.4, 131.4, 129.3,
129.2, 129.1, 128.5, 128.4, 127.0, 126.8, 126.7, 120.8.
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2,3-Di-m-tolylnaphtho[2,3-b]furan-4,9-dione (3ag). Yellow solid, mp 235-237 ℃; yield,
62% (46.8 mg); 1H NMR (500 MHz, CDCl3) δ 8.24 (d, J = 7.2 Hz, 1H), 8.09 (d, J = 7.0 Hz,
1H), 7.77 – 7.67 (m, 2H), 7.52 (s, 1H), 7.36 (t, J = 7.5 Hz, 1H), 7.29 – 7.23 (m, 4H), 7.15
(t, J = 6.3 Hz, 2H), 2.40 (s, 3H), 2.30 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 180.8,
173.5, 155.6, 151.0, 138.4, 138.3, 133.7, 133.6, 132.6, 130.6, 130.5, 130.3, 129.8,
129.4, 128.6, 128.5, 128.4, 127.7, 127.0, 126.9, 126.6, 124.4, 121.8, 21.5, 21.4.
+
HRMS-ESI: [M + H]+ calcd for C26H19O3 m/z 379.1329, found 379.1323.
2,3-Bis(3-methoxyphenyl)naphtho[2,3-b]furan-4,9-dione (3ah). Yellow solid, mp
1
225-227 ℃; yield, 56% (45.9 mg); H NMR (500 MHz, CDCl3) δ 8.27 – 8.20 (m, 1H),
8.11 (dd, J = 7.3, 1.4 Hz, 1H), 7.74 – 7.68 (m, 2H), 7.52 (dd, J = 7.6, 1.5 Hz, 1H), 7.34
(td, J = 8.3, 1.5 Hz, 2H), 7.09 (dd, J = 7.4, 1.5 Hz, 1H), 7.01 – 6.93 (m, 2H), 6.89 (t, J =
7.4 Hz, 1H), 6.82 (d, J = 8.3 Hz, 1H), 3.69 (s, 3H), 3.41 (s, 3H). 13C{1H} NMR (126 MHz,
CDCl3) δ 180.7, 173.4, 159.8, 159.5, 155.3, 151.0, 133.8, 133.5, 132.5, 131.7, 129.8,
129.7, 129.6, 126.9, 126.7, 122.3, 121.7, 119.7, 116.5, 115.5, 114.3, 111.6, 55.3, 55.2.
+
HRMS-ESI: [M + H]+ calcd for C26H19O5 m/z 411.1227, found 411.1225.
2,3-Bis(3-chlorophenyl)naphtho[2,3-b]furan-4,9-dione (3ai). Yellow solid, mp
266-268 ℃; yield, 72% (60.2 mg); 1H NMR (500 MHz, CDCl3) δ 8.25 (dd, J = 7.4, 1.3 Hz,
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1H), 8.11 (dd, J = 7.4, 1.3 Hz, 1H), 7.80 – 7.73 (m, 2H), 7.65 (t, J = 1.7 Hz, 1H), 7.49 –
7.42 (m, 3H), 7.36 – 7.33 (m, 3H), 7.24 (d, J = 7.9 Hz, 1H). 13C{1H} NMR (126 MHz,
CDCl3) δ 180.5, 173.5, 154.0, 151.4, 135.0, 134.7, 134.1, 134.0, 133.4, 132.3, 131.6,
130.2, 130.1, 130.0, 129.8, 129.3, 129.1, 128.2, 127.2, 127.0, 126.8, 125.3, 121.1.
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HRMS-ESI: [M + H]+ calcd for C24H13Cl2O3 m/z 419.0236, found 419.0237.
2,3-Di-o-tolylnaphtho[2,3-b]furan-4,9-dione (3aj). Yellow solid, mp 236-238 ℃; yield,
1
60% (45.4 mg); H NMR (500 MHz, CDCl3) δ 8.18 (d, J = 7.5 Hz, 1H), 8.06 – 8.00 (m,
1H), 7.73 – 7.62 (m, 2H), 7.23 – 7.14 (m, 4H), 7.13 – 7.04 (m, 3H), 7.00 (t, J = 7.4 Hz,
1H), 2.24 (s, 3H), 2.06 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 179.8, 172.6, 156.5,
150.8, 136.7, 136.2, 132.8, 132.7, 132.5, 131.5, 129.9, 129.5, 129.4, 129.2, 129.0,
128.6, 128.4, 127.5, 127.0, 125.9, 125.6, 124.7, 124.6, 121.3, 19.5, 19.0. HRMS-ESI:
+
[M + H]+ calcd for C26H19O3 m/z 379.1329, found 379.1332.
2,3-Bis(2-methoxyphenyl)naphtho[2,3-b]furan-4,9-dione (3ak). Yellow solid, mp
227-229 ℃; yield, 58% (47.5 mg); 1H NMR (500 MHz, CDCl3) δ 8.24 (d, J = 7.2 Hz, 1H),
8.09 (d, J = 7.1 Hz, 1H), 7.78 – 7.68 (m, 2H), 7.40 (t, J = 8.2 Hz, 1H), 7.21 (br, 2H), 7.10
(br, 1H), 7.07 – 6.97 (m, 3H), 6.87 (d, J = 3.4 Hz, 1H), 3.82 (s, 3H), 3.65 (s, 3H). 13C{1H}
NMR (126 MHz, CDCl3) δ 180.5, 173.6, 157.4, 157.0, 155.1, 151.8, 133.8, 133.6, 133.5,
132.6, 131.4, 130.9, 130.5, 130.0, 129.6, 126.8, 126.6, 120.6, 120.5, 120.3, 119.8,
+
118.3, 111.2, 110.7, 55.5, 54.9. HRMS-ESI: [M + H]+ calcd for C26H19O5 m/z 411.1227,
found 411.1231.
2,3-Bis(2-chlorophenyl)naphtho[2,3-b]furan-4,9-dione (3al). Yellow solid, mp
227-229 ℃; yield, 72% (60.2 mg); 1H NMR (500 MHz, CDCl3) δ 8.18 (d, J = 7.1 Hz, 1H),
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8.04 (d, J = 6.6 Hz, 1H), 7.73 – 7.65 (m, 2H), 7.58 (br, 1H), 7.43 – 7.34 (m, 3H), 7.29 –
7.27 (m, 2H), 7.21 – 7.14 (m, 2H). 13C{1H} NMR (126 MHz, CDCl3) δ 179.5, 172.4,
152.9, 150.4, 133.9, 133.6, 133.0, 132.9, 132.4, 131.3, 130.6, 129.1, 129.0, 128.99,
128.97, 128.8, 128.2, 128.1, 127.2, 126.1, 126.0, 125.8, 124.2, 120.0. HRMS-ESI: [M +
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H]+ calcd for C24H13Cl2O3 m/z 419.0236, found 4 19.0239.
2,3-Bis(3,5-dimethoxyphenyl)naphtho[2,3-b]furan-4,9-dione (3am). Yellow solid, mp
265-267 ℃; yield, 63% (51.1 mg); 1H NMR (500 MHz, CDCl3) δ 8.17 (dd, J = 7.4, 1.2 Hz,
1H), 8.03 (dd, J = 7.4, 1.2 Hz, 1H), 7.70 – 7.61 (m, 2H), 7.19 (s, 1H), 7.15 (s, 2H),
7.02(br, 1H), 6.98 (s, 2H), 6.90 (s, 1H), 2.29 (s, 6H), 2.16 (s, 6H). 13C{1H} NMR (126
MHz, CDCl3) δ 179.8, 172.4, 154.8, 149.8, 137.1, 137.0, 132.6, 131.6, 130.4, 129.2,
129.1, 128.9, 127.5, 126.5, 125.9, 125.6, 123.9, 120.9, 20.3, 20.2. HRMS-ESI: [M + H]+
+
calcd for C28H23O3 m/z 407.1642, found 407.1644.
2,3-Di(thiophen-2-yl)naphtho[2,3-b]furan-4,9-dione (3an). Yellow solid, mp
183-185 ℃; yield, 33% (23.8 mg); 1H NMR (500 MHz, CDCl3) δ 8.17 (d, J = 6.8 Hz, 1H),
8.04 (d, J = 6.9 Hz, 1H), 7.74 – 7.63 (m, 2H), 7.52 (d, J = 4.0 Hz, 1H), 7.46 (s, 1H), 7.32
(d, J = 3.8 Hz, 1H), 7.19 – 7.15 (m, 2H), 6.99 (br, 1H). 13C{1H} NMR (126 MHz, CDCl3) δ
179.4, 172.1, 152.2, 149.5, 132.9, 132.8, 132.3, 131.4, 129.1, 128.7, 128.6, 128.2,
128.1, 127.5, 127.1, 126.7, 126.5, 125.9, 125.7, 112.0. HRMS-ESI: [M + H]+ calcd for
+
C20H11O3S2 m/z 363.0144, found 363.0146.
2,3-Di(naphthalen-1-yl)naphtho[2,3-b]furan-4,9-dione (3ao). Yellow solid, mp
276-278 ℃; yield, 68% (61.2 mg); 1H NMR (500 MHz, CDCl3) δ 8.31 (d, J = 7.5 Hz,
1H), 8.12 (d, J = 8.2 Hz, 1H), 8.06 (d, J = 7.5 Hz, 1H), 7.89 (d, J = 8.2 Hz, 1H), 7.87 –
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7.74 (m, 5H), 7.71 (t, J = 7.4 Hz, 1H), 7.52 – 7.43 (m, 3H), 7.40 (t, J = 7.6 Hz, 1H), 7.37
– 7.30 (m, 3H), 7.20 (t, J = 7.7 Hz, 1H). 13C{1H} NMR (126 MHz, CDCl3) δ 180.4, 173.8,
157.9, 152.2, 133.9, 133.8, 133.6, 133.54, 133.5, 132.6, 132.3, 131.4, 130.8, 130.4,
129.4, 129.1, 128.6, 128.5, 128.3, 127.8, 127.2, 127.1, 126.8, 126.5, 126.4, 126.0,
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125.6, 125.4, 125.3, 125.2, 124.8, 122.1. HRMS-ESI: [M + H]+ calcd for C32H19O3 m/z
451.1329, found 451.1325.
2,3-Dipropylnaphtho[2,3-b]furan-4,9-dione (3ap). Yellow solid, mp 133-135 ℃; yield,
35% (19.7 mg); 1H NMR (500 MHz, CDCl3) δ 8.02 (d, J = 7.7 Hz, 1H), 7.68 – 7.57 (m,
2H), 7.38 (t, J = 7.5 Hz, 1H), 2.62 (t, J = 7.4 Hz, 2H), 2.56 (t, J = 7.4 Hz, 2H), 1.77 – 1.68
(m, 2H), 1.64 – 1.56 (m, 3H), 1.00 (t, J = 7.4 Hz, 3H), 0.94 (t, J = 7.4 Hz, 3H). 13C{1H}
NMR (126 MHz, CDCl3) δ 181.1, 175.2, 159.0, 155.2, 135.2, 130.3, 129.4, 129.1, 128.6,
121.9, 121.7, 120.4, 27.7, 25.5, 23.0, 21.7, 13.8, 13.7. HRMS-ESI: [M + H]+ calcd for
+
C18H19O3 m/z 283.1329, found 283.1330.
2-Butyl-3-phenylnaphtho[2,3-b]furan-4,9-dione (3aq). Yellow solid, mp 165-167 ℃;
yield, 67% (44.2 mg); 1H NMR (500 MHz, CDCl3) δ 8.23 (dd, J = 5.8, 3.1 Hz, 1H), 8.18
(dd, J = 5.8, 3.1 Hz, 1H), 7.80 (d, J = 7.3 Hz, 2H), 7.78 – 7.71 (m, 2H), 7.51 (t, J = 7.4 Hz,
2H), 7.45 (t, J = 7.3 Hz, 1H), 3.10 – 2.97 (m, 2H), 1.76 – 1.70 (m, 2H), 1.55 – 1.47 (m,
2H), 0.99 (t, J = 7.4 Hz, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 182.0, 173.3, 155.7,
151.2, 133.7, 133.6, 133.5, 132.7, 130.3, 129.6, 129.3, 128.9, 127.1, 126.8, 126.7,
+
122.8, 32.0, 23.9, 22.9, 13.9. HRMS-ESI: [M + H]+ calcd for C22H19O3 m/z 331.1329,
found 331.1324.
Mixture of 2-(4-bromophenyl)-3-phenylnaphtho [2,3-b]furan-4,9-dione (3ar) and
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3-(4-bromophenyl) -2-phenylnaphtho[2,3-b]furan-4,9-dione (3ar'). Yield, 73% (61.6
6
7
1
1
mg); the ratio (3ar:3ar' =1:1) is determined by H NMR; H NMR (500 MHz, CDCl3) δ
8
9
8.23 (d, J = 7.3 Hz, 2H), 8.09 (d, J = 7.3 Hz, 2H), 7.79 – 7.68 (m, 4H), 7.60 (d, J = 8.2 Hz,
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2H), 7.57 (d, J = 7.0 Hz, 2H), 7.51 – 7.40 (m, 10H), 7.37 – 7.32 (m, 4H). C{1H} NMR
(126 MHz, CDCl3) δ 179.8, 179.6, 172.4, 172.3, 154.5, 153.3, 150.26, 150.21, 132.9,
132.84, 132.8, 132.5, 132.4, 131.39, 131.38, 131.0, 130.9, 130.8, 129.0, 128.9, 128.8,
128.6, 128.3, 128.2, 127.8, 127.7, 127.6, 127.2, 126.4, 126.3, 125.9, 125.8, 125.7,
125.6, 123.2, 121.9, 121.2, 119.4. HRMS-ESI: [M + H]+ calcd for C24H14BrO3 m/z
+
429.0121, found 429.0121, 431.0101.
Mixture of 2-(4-chlorophenyl)-3-phenylnaphtho [2,3-b]furan-4,9-dione (3as) and
3-(4-chlorophenyl)- 2-phenylnaphtho[2,3-b]furan-4,9-dione (3as'). Yield, 72% (55.3
1
1
mg); the ratio (3as:3as' =1:1) is determined by H NMR; H NMR (500 MHz, CDCl3) δ
8.17 (d, J = 7.0 Hz, 2H), 8.05 – 7.98 (m, 2H), 7.74 – 7.64 (m, 8H), 7.61 (d, J = 8.4 Hz,
2H), 7.52 (t, J = 8.3 Hz, 4H), 7.47 – 7.42 (m, 5H), 7.40 – 7.24 (m, 6H). 13C{1H} NMR
(126 MHz, CDCl3) δ 179.7, 179.3, 172.6, 172.3, 154.9, 151.7, 150.8, 150.5, 134.4,
133.1, 133.05, 133.0, 132.9, 132.5, 132.3, 131.6, 131.4, 131.3, 130.1, 129.4, 128.7,
128.5, 128.4, 128.2, 128.0, 127.9, 126.8, 126.4, 126.3, 126.0, 125.9, 125.8, 125.7,
123.2, 118.7, 117.6, 117.2, 111.9, 111.4. HRMS-ESI: [M + H]+ calcd for C24H14ClO3
+
m/z 385.0626, found 385.0628, 387.1230.
7-Methoxy-2,3-diphenylnaphtho[2,3-b]furan-4,9-dione (3ba). Yellow solid, mp
274-276 ℃; yield, 71% (53.9 mg); 1H NMR (500 MHz, CDCl3) δ 8.03 (d, J = 8.6 Hz, 1H),
7.69 (d, J = 2.6 Hz, 1H), 7.58 (d, J = 7.0 Hz, 2H), 7.46 (br, 5H), 7.34 – 7.29 (m, 3H), 7.15
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(dd, J = 8.6, 2.6 Hz, 1H), 3.97 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 180.1, 173.4,
164.1, 155.5, 151.1, 134.7, 130.4, 130.0, 129.9, 129.8, 129.3, 128.8, 128.7, 128.62,
128.59, 127.3, 126.9, 122.0, 119.6, 110.6, 56.0. HRMS-ESI: [M + H]+ calcd for
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+
C25H17O4 m/z 381.1121, found 381.1128.
6-Methoxy-2,3-diphenylnaphtho[2,3-b]furan-4,9-dione (3ca). Yellow solid, mp
275-277 ℃; yield, 73% (55.5 mg); 1H NMR (500 MHz, CDCl3) δ 8.17 (d, J = 8.5 Hz, 1H),
7.60 – 7.52 (m, 3H), 7.47 (br, 5H), 7.34 – 7.30 (m, 3H), 7.18 (dd, J = 8.4, 1.8 Hz, 1H),
3.91 (s, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 180.8, 173.0, 164.2, 154.9, 151.6, 135.9,
130.4, 130.0, 129.7, 129.4, 129.1, 128.68, 128.65, 128.61, 128.58, 127.2, 125.8,
121.6, 119.5, 111.2, 55.9. HRMS-ESI: [M + H]+ calcd for C25H17O4 m/z 381.1121,
+
found 381.1127.
6-Fluoro-2,3-diphenylnaphtho[2,3-b]furan-4,9-dione (3da). Yellow solid, mp
1
282-284 ℃; yield, 72% (53 mg); H NMR (500 MHz, CDCl3) δ 8.13 (dd, J = 8.5, 5.3 Hz,
1H), 7.90 (dd, J = 8.6, 2.5 Hz, 1H), 7.58 (d, J = 7.2 Hz, 2H), 7.48 – 7.45 (m, 5H), 7.40 –
7.29 (m, 4H). 13C{1H} NMR (126 MHz, CDCl3) δ 179.5, 172.1, 166.2 (167.2, 165.2, d,
1JC-F = 257 Hz), 156.0, 151.0, 135.4 (135.38, 135.32, d, JC-F = 7.6 Hz), 130.1, 130.04,
3
130.0, 129.96, 129.9, 128.8, 128.7, 128.6, 128.4, 127.3, 122.0, 120.5 (120.6, 120.4, d,
2JC-F = 23 Hz), 113.7 (113.8, 113.6, d, JC-F = 24 Hz). HRMS-ESI: [M + H]+ calcd for
2
+
C24H14FO3 m/z 369.0922, found 369.0921.
6-Chloro-2,3-diphenylnaphtho[2,3-b]furan-4,9-dione (3ea). Yellow solid, mp
282-284 ℃; yield, 68% (52.2 mg); 1H NMR (500 MHz, CDCl3) δ 8.20 (d, J = 1.9 Hz, 1H),
8.03 (d, J = 8.3 Hz, 1H), 7.66 (dd, J = 8.3, 2.0 Hz, 1H), 7.58 (d, J = 7.2 Hz, 2H), 7.50 –
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7.44 (m, 5H), 7.36 – 7.29 (m, 3H). C{1H} NMR (126 MHz, CDCl3) δ 178.7, 171.1,
6
7
155.0, 149.8, 139.8, 132.8, 132.6, 130.8, 129.0, 128.9, 128.8, 127.7, 127.6, 127.5,
8
9
+
127.4, 126.3, 125.7, 120.9. HRMS-ESI: [M + H]+ calcd for C24H14ClO3 m/z 385.0626,
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found 385.0628, 387.1230.
6-Bromo-2,3-diphenylnaphtho[2,3-b]furan-4,9-dione (3fa). Yellow solid, mp
287-289 ℃; yield, 70% (59.9 mg); 1H NMR (500 MHz, CDCl3) δ 8.36 (s, 1H), 7.95 (d, J =
8.2 Hz, 1H), 7.84 (dd, J = 8.1, 1.3 Hz, 1H), 7.58 (d, J = 7.3 Hz, 2H), 7.49 – 7.42 (m, 5H),
7.36 – 7.29 (m, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 179.9, 172.1, 156.0, 150.7,
136.7, 133.7, 132.2, 130.0, 129.99, 129.9, 129.7, 129.3, 128.8, 128.7, 128.6, 128.4,
127.3, 121.9. HRMS-ESI: [M + H]+ calcd for C24H14BrO3 m/z 429.0121, found
+
429.0121, 431.0101.
2,3,6-Triphenylnaphtho[2,3-b]furan-4,9-dione (3ga). Yellow solid, mp 293-295 ℃;
yield, 74% (63.1 mg); 1H NMR (500 MHz, CDCl3) δ 8.48 (s, 1H), 8.15 (d, J = 7.9 Hz, 1H),
7.93 (d, J = 7.7 Hz, 1H), 7.72 (d, J = 7.2 Hz, 2H), 7.60 (d, J = 7.0 Hz, 2H), 7.54 – 7.43 (m,
8H), 7.35 –7.32 (m, 3H). 13C{1H} NMR (126 MHz, CDCl3) δ 180.6, 173.5, 155.6, 151.3,
146.6, 138.8, 133.0, 132.2, 131.8, 130.3, 130.1, 129.9, 129.8, 129.1, 128.9, 128.7,
128.7, 128.6, 127.7, 127.30, 127.29, 125.1, 121.9. HRMS-ESI: [M + H]+ calcd for
+
C30H19O3 m/z 427.1329, found 427.1328.
5-Methyl-2,3-diphenylnaphtho[2,3-b]furan-4,9-dione (3ha). Yellow solid, mp
274-276 ℃; yield, 75% (54.6 mg); 1H NMR (500 MHz, CDCl3) δ 8.04 (s, 1H), 7.98 (d, J =
7.8 Hz, 1H), 7.59 – 7.56 (m, 2H), 7.51 – 7.46 (m, 6H), 7.34 – 7.29 (m, 3H), 2.51 (s, 3H).
13C{1H} NMR (126 MHz, CDCl3) δ 180.7, 173.8, 155.4, 151.2, 144.9, 134.4, 132.5,
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131.4, 130.4, 130.1, 129.7, 128.8, 128.7, 128.61, 128.59, 127.3, 127.2, 127.1, 121.8,
6
7
+
21.8. HRMS-ESI: [M + H]+ calcd for C25H17O3 m/z 365.1172, found 365.1176.
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Supporting Information
The Supporting Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.joc.
1H and 13C{1H} NMR spectra of the products and High-resolution mass spectra of new
compounds (PDF).
AUTHOR INFORMATION
Corresponding Authors
*E-mail: jspeng1998@163.com & jspeng1998@nefu.edu.cn
*E-mail: ccx1759@163.com
ORCID
Jinsong Peng: 0000-0002-7822-4560
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We are grateful for financial support from the Fundamental Research Funds for the
Central Universities (2572017DB07), and Natural Science Foundation of Heilongjiang
Province (B2017002, LC2018003).
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