Gold(III)-catalyzed tandem conjugate addition/annulation of 4-hydroxycoumarins with α,β-unsaturated ketones

Article abstract of DOI:10.1021/jo201342m

An efficient and selective approach for the synthesis of functionalized pyranocoumarins has been developed via a gold(III)-catalyzed tandem conjugate addition/annulation reaction of 4-hydroxycoumarins with α,β- unsaturated ketones.

Full text of DOI:10.1021/jo201342m

Note
pubs.acs.org/joc
Gold(III)-Catalyzed Tandem Conjugate Addition/Annulation of 4-
Hydroxycoumarins with α,β-Unsaturated Ketones
Yunkui Liu,* Jie Zhu, Jianqiang Qian, Bo Jiang, and Zhenyuan Xu
State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Zhejiang University of Technology, Hangzhou
310014, People’s Republic of China
S
* Supporting Information
ABSTRACT: An efficient and selective approach for the
synthesis of functionalized pyranocoumarins has been
developed via a gold(III)-catalyzed tandem conjugate
addition/annulation reaction of 4-hydroxycoumarins with
α,β-unsaturated ketones.
yranocoumarins are an important class of heterocycles of
wide occurrence in natural products as well as synthetic
1,3-diarylallylic compounds.4c However, the reaction required a
stoichiometric amount of DDQ and resulted in poor
regioselectivity. The reaction of 4-hydroxycoumarins with α,β-
unsaturated aldehydes4d or ketones4e could also give function-
alized pyrano[3,2-c]coumarins, but the former suffered from a
regioselectivity issue, while the latter used the toxic reagent
POCl3. Renaud4f and co-workers have reported a highly
regioselective synthesis of pyrano[3,2-c]coumarins from 4-
hydroxycoumarins and α,β-unsaturated aldehydes, but the
requirement of a commercially unavailable acid catalyst was a
drawback. Thiol-mediated cyclization of coumarin-4-yl prop-2-
ynyl ethers provided an alternative approach to the pyrano[3,2-
c]coumarin derivatives,4k but the scope of the substrates was
limited. As such, it is still desirable to develop efficient and
selective protocols with broad substrate scope for the synthesis
of pyranocoumarins.
P
molecules, exhibiting a broad spectrum of biological activities
such as antifungal, insecticidal, anticancer, anti-HIV, anti-
inflammatory, and antibacterial activities.1 The pyranocoumar-
ins have several scaffold patterns according to different
structural arrays between the pyran2 and the coumarin3 rings
(Figure 1), among which the pyrano[3,2-c]coumarins are the
most synthetically feasible.4
On the other hand, tandem reactions5 usually provide
processes more efficient and environmentally benign than
conventional procedures by omitting the steps of separation
and purification of the reaction intermediates, thus enabling the
construction of molecular diversity and structural complexity
from simple substrates in a single synthetic step. Owing to the
extraordinary reactivity and high selectivity of gold catalysts,6
gold-catalyzed tandem reactions have recently received great
attention and have become powerful tools for the construction
of C−C and C−X bonds.6 In this regard, we are particularly
interested in the construction of heterocyclic systems involving
gold-catalyzed tandem reactions with high selectivity.7,8 For
example, in our previous work, we have successfully developed
efficient and selective methods for the construction of
benzofuran,8a benzopyran,8b and 3,4-dihydrocoumarin8c frame-
works via the strategy of gold-catalyzed tandem reactions.
Herein, we describe an efficient and selective approach to
access functionalized pyrano[3,2-c]coumarins involving a
Figure 1. Different scaffold patterns of pyranocoumarins.
The general approaches to pyrano[3,2-c]coumarins involve
cyclization of commercially available 4-hydroxycoumarins with
the proper electrophiles.4a−j For example, pyrano[3,2-c]-
coumarins could be synthesized via a one-pot reaction of 4-
hydroxycoumarins with propargylic alcohols catalyzed by either
an I2/H2SO4 system4a or a ruthenium complex.4b Unsatisfy-
ingly, this protocol suffered from the use of H2SO4 as a
catalyst4a or a regioselectivity problem.4b He et al. reported a
mild synthesis of pyrano[3,2-c]coumarins involving DDQ-
mediated oxidative cross-coupling of 4-hydroxycoumarins with
Received: July 3, 2011
Published: September 27, 2011
© 2011 American Chemical Society
9096
dx.doi.org/10.1021/jo201342m|J. Org. Chem. 2011, 76, 9096−9101

The Journal of Organic Chemistry
Note
gold(III)-catalyzed tandem conjugate addition/annulation
reaction of 4-hydroxycoumarins with α,β-unsaturated ketones.
For the initial study, 4-hydroxycoumarin 1a and chalcone 2a
were selected as the model substrates to optimize the reaction
conditions (Table 1). When 1a and 2a were treated with AuCl/
desired product when the square-planar complex dichloro-
(pyridine-2-carboxylato)gold(III) (4)9 was employed as a
catalyst in the presence or absence of AgOTf (entries 7−9,
Table 1). When AuCl3 or AgOTf was used alone as a catalyst,
the yield of 3aa only reached 37% and 41%, respectively, a
sharp contrast to the high catalytic efficiency of the combined
AuCl3/3AgOTf system (entries 5, 6, and 12, Table 1). The role
of AgOTf in the combined AuCl3/3AgOTf system is believed
to help the generation of the cationic gold(III) species with
OTf as the counteranion, which thus can efficiently catalyze the
reaction.10,11 Further studies revealed that the catalyst systems
AuCl3/AgOTf, AuCl3/2AgOTf, AuCl3/3AgSbF6, AuCl3/
3AgBF4, and AuCl3/3AgNTf2 gave poor results for the reaction
(entries 3, 4, and 13−15, Table 1). Moreover, when
conventional Lewis or Brϕnsted acids such as ZnCl2, BiCl3,
FeCl3, FeBr3/3AgOTf,10 AlCl3, HCl, and HOTf were surveyed
as catalysts for the reaction, the results showed far less
effectiveness even at a catalyst loading of 30 mol % (entries
16−26, Table 1), indicating that cationic gold(III) species
generated from the AuCl3/3AgOTf catalytic system played a
unique role in achieving high reactivity and selectivity for the
tandem reaction.11
With optimized conditions in hand, we then turned our
attention to the scope of the reaction, and the results are shown
in Table 2. First, a variety of α,β-unsaturated ketones 2 reacted
with 4-hydroxycoumarin (1a) under the optimized reaction
conditions. In most cases, 2 reacted with 1a smoothly to give
the corresponding products 3 in moderate to excellent yields
(45−91%, entries 1−10, Table 2). It seemed that substrates
bearing electron-deficient aromatic rings at the 4-position of 2
(entries 4, 7, and 8, Table 2) gave higher yields of 3 than did
those bearing electron-rich aromatic rings (entries 1, 2, 5, and
6, Table 2). It was found that 2 with electron-deficient aromatic
rings in the 2-position gave better yields of 3 than those with
electron-rich ones (entry 6 vs 5 and 7 vs 8, Table 2). The more
sterically hindered ketone 2i also reacted with 1a smoothly to
furnish the target product in 78% yield (entry 9, Table 2).
When the α,β-unsaturated aldehyde 2k was treated with 1a
under the same conditions, the reaction resulted in a complex
mixture which could not be separated by column chromatog-
raphy (entry 11, Table 2).
a
Table 1. Optimization of Reaction Conditions
b
entry
catalyst (3 mol %)
solvent
yield of 3aa (%)
1
2
3
4
5
AuCl/AgOTf
toluene
toluene
toluene
toluene
toluene
DCE
65
23
38
45
78
60
5
PPh3AuCl/AgOTf
AuCl3/AgOTf
AuCl3/2AgOTf
AuCl3/3AgOTf
THF
MeCN
dioxane
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
toluene
57
62
37
0
6
AuCl3
c
7
4
8
4/AgOTf
4/2AgOTf
AuCl
0
9
0
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
0
PPh3AuCl
0
d
AgOTf
41
27
21
45
16
15
0
AuCl3/3AgSbF6
AuCl3/3AgBF4
AuCl3/3AgNTf2
e
ZnCl2
e
BiCl3
e
FeCl3
e
FeCl3 /AgOTf
5
e
FeCl3 /2AgOTf
10
25
0
e
FeCl3 /3AgOTf
e
FeBr3
e
FeBr3 /3AgOTf
10
0
e
Several substituted 4-hydroxycoumarins 1b−e reacted with
α,β-unsaturated ketones 2 (Table 3). It was found that 1
bearing electron-donating substituents at the 6-position
generally reacted with 2 more smoothly and gave higher yields
of 3 than those bearing electron-withdrawing groups (entries
1−6 vs 7, Table 3). 4-Hydroxy-6-methyl-2-pyrone (5), an
analogue of 4-hydroxycoumarin, also exhibited a good
adaptability with a variety of chalcones with different
substituent patterns and furnished the corresponding products
in moderate to excellent yields (65−91%, entries 8−12, Table
3). In all cases, 3 (or 6) arising from the 1,4-conjugate
addition/annulation process was obtained as the sole product,
suggesting that the reaction is highly regioselective.
AlCl3
ef
,
HCl
0
e
HOTf
none
0
g
0
a
Carried out with 1 mmol of 1a and 1 mmol of 2a in the presence of
b
c
catalyst in solvent (3 mL) at reflux for 6 h. Isolated yields. 4:
dichloro(pyridine-2-carboxylato)gold(III). The amount of catalyst is
0.09 mmol. The amount of catalyst is 0.3 mmol. Aqueous HCl (37
wt %) was used. 1a and 2a were recovered quantitatively.
d
e
f
g
AgOTf (3 mol % based on 1a) in toluene at reflux for 6 h, the
desired product 3aa was isolated in 65% yield (entry 1, Table
1). When the PPh3AuCl/AgOTf catalytic system was used, the
yield of 3aa was reduced to 23% (entry 2, Table 1). Satisfyingly,
the yield of 3aa was increased to 78% in the presence of the
AuCl3/3AgOTf catalytic system (entry 5, Table 1). Solvent
screening showed that toluene was much more suitable than
other solvents, such as DCE, CH3CN, dioxane, and THF (entry
5, Table 1). Control experiments showed that no desired
product was detected without a catalyst (entry 27, Table 1) or
in the presence of AuCl (entry 10, Table 1) or Ph3PAuCl
(entry 11, Table 1) alone. The reaction also gave none of the
On the basis of a previous report,8b,12,13 a possible
mechanism concerning the gold(III)-catalyzed tandem reaction
of 1 (or 5) with 2 is proposed (Scheme 1). First, the activation
of the carbonyl group of the enone 2 by gold(III) species was
followed by the conjugate addition of 1 (or 5) to 2 to form the
intermediate 8.8b,12,13 Protodeauration of 8 furnished the
intermediate 9 and regenerated the gold catalyst.8b,b,12 The
intramolecular annulation of 9 with the aid of the gold catalyst
eventually furnished 3 (or 6).14
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The Journal of Organic Chemistry
Note
a
Table 2. Gold(III)-Catalyzed Reaction of 4-Hydroxycoumarin 1a with α,β-Unsaturated Ketones 2
b
entry
R1
R2
R3
2
product (3)
yield (%)
1
Ph
Ph
Ph
Ph
Ph
H
2a
3aa
3ab
3ac
3ad
3ae
3af
78
74
90
88
45
61
91
86
78
86
2
4-MeC6H4
H
H
H
H
H
H
H
Me
H
H
2b
2c
2d
2e
2f
3
3,4-OCH2OC6H3
4
4-NO2C6H4
5
4-MeC6H4
4-BrC6H4
4-ClC6H4
4-MeC6H4
Ph
Ph
c
6
Ph
7
4-ClC6H4
4-ClC6H4
Ph
2g
2h
2i
3ag
3ah
3ai
8
9
10
Me
Ph
2j
3aj
11
H
Ph
2k
3ak
complex mixture
a
b
c
Reaction conditions: 1a (1 mmol), 2 (1 mmol), AuCl3/3AgOTf (0.03 mmol), toluene (3 mL), reflux, 6 h. Isolated yields. The reaction time was
8 h.
Table 3. Gold(III)-Catalyzed Reaction of Substituted 4-Hydroxycoumarins (1) or 4-Hydroxy-6-methyl-2-pyrone (5) with α,β-
a
Unsaturated Ketones (2)
b
yield (%)
entry
1
1 or 5
R1
R2
R3
H
2
(3 or 6)
X = Me
(1b)
Ph
Ph
2a
98 (3ba)
2
3
1b
1b
Ph
Ph
4-MeC6H4
H
H
2b
2l
94 (3bb)
97 (3bl)
4-
MeOC6H4
4
5
1b
Ph
Ph
Me
2i
87 (3bi)
85 (3ca)
X =
MeO
(1c)
2a
6
7
X = t-Bu
(1d)
2a
2a
82 (3da)
58 (3ea)
X = Cl
(1e)
8
5
5
5
5
2a
2b
2l
65 (6aa)
70 (6ab)
91 (6al)
66 (6ah)
9
10
11
4-
MeC6H4
4-ClC6H4
H
2h
12
5
2i
72 (6ai)
a
b
Reaction conditions: 1 (or 5) (1 mmol), 2 (1 mmol), AuCl3/3AgOTf (0.03 mmol), toluene (3 mL), reflux, 6 h. Isolated yields.
atmosphere. All solvents for the reactions were dried and distilled prior
to use according to standard methods. Melting points were determined
on Buchi B-545 melting point apparatus and were uncorrected. The
1H NMR and 13C NMR spectra were recorded at 25 °C in CDCl3 at
500 and 125 MHz, respectively, with TMS as the internal standard.
Chemical shifts (δ) are expressed in ppm, and coupling constants J are
given in Hz. The IR spectra were recorded on an FT-IR spectrometer.
GC-MS experiments were obtained on an instrument with an EI
source. Elemental analyses were performed on an EA-1110 instrument.
General Procedure for the Gold(III)-Catalyzed Tandem
Conjugate Addition/Annulation of 4-Hydroxycoumarins (1)
or 4-Hydroxy-6-methyl-2-pyrone (5) with α,β-Unsaturated
In summary, we have developed an efficient and highly
regioselective tandem conjugate addition/annulation of 4-
hydroxycoumarins with α,β-unsaturated ketones catalyzed by
AuCl3/3AgOTf, which furnished various functionalized pyrano-
[3,2-c]coumarins in moderate to excellent yields with water as
the sole byproduct.
EXPERIMENTAL SECTION
■
General Considerations. Unless otherwise stated, all reagents
were purchased from commercial suppliers and used without
purifications. All experiments were carried out under a nitrogen
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dx.doi.org/10.1021/jo201342m|J. Org. Chem. 2011, 76, 9096−9101

The Journal of Organic Chemistry
Note
123.9 (2C), 122.8, 117.0, 114.2, 102.4, 102.1, 36.7; MS (EI, 70 eV) m/
z (%) 397 (62) [M+], 350 (15), 275 (100); mp 230−231 °C. Anal.
Calcd for C24H15NO5: C, 72.54; H, 3.80. Found: C, 72.76; H, 3.82.
4-Phenyl-2-p-tolylpyrano[3,2-c]chromen-5(4H)-one (3ae): pale
yellow solid; Rf = 0.68 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1719
(CO) cm−1; 1H NMR (500 MHz, CDCl3) δ 8.0 (dd, J1 = 1.5 Hz, J2
= 7.5 Hz, 1H), 7.66 (dd, J1 = 2.0 Hz, J2 = 7.0, Hz, 2H), 7.58−7.54 (m,
1H), 7.42−7.22 (m, 7H), 6.96 (dd, J1 = 2.0 Hz, J2 = 6.5, Hz, 2H), 5.71
(d, J = 5.0 Hz, 1H), 4.69 (d, J = 5.0 Hz, 1H), 3.86 (s, 3H); 13C NMR
(125 MHz, CDCl3) δ 161.5, 160.4, 155.7, 152.7, 146.8, 143.8, 131.9,
128.6 (2C), 128.4 (2C), 127.1, 126.1, 125.3 (2C), 124.1, 122.6, 116.8,
114.6, 114.0 (2C), 103.8, 102.0, 55.4, 36.6; MS (EI, 70 eV) m/z (%)
366 (39) [M+], 351 (100), 289 (93); mp 156−158 °C.. Anal. Calcd for
C25H18O3: C, 81.95; H, 4.95. Found: C, 81.76; H, 4.91
Scheme 1. Proposed Mechanism
2-(4-Bromophenyl)-4-phenylpyrano[3,2-c]chromen-5(4H)-one4e
(3af): white solid; Rf = 0.40 (cyclohexane/EtOAc, 6/1); IR (KBr) ν
1720 (CO) cm−1; 1H NMR (500 MHz, CDCl3) δ 7.98 (dd, J1 = 1.5
Hz, J2 = 8.0 Hz, 1H), 7.60−7.56 (m, 5H), 7.41−7.22 (m, 7H), 5.84 (d,
J = 5.0 Hz, 1H), 4.70 (d, J = 4.5 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ 161.3, 155.6, 152.8, 146.0, 143.2, 132.1, 131.8 (2C), 131.6,
128.7 (2C), 128.4 (2C), 127.3, 126.2 (2C), 124.2, 123.4, 122.5, 116.9,
114.4, 104.4, 103.6, 36.6; MS (EI, 70 eV) m/z (%) 432 (16) [M+],
353 (100); mp 202−203 °C.
2,4-Bis(4-chlorophenyl)pyrano[3,2-c]chromen-5(4H)-one (3ag):
white solid; Rf = 0.38 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1720
(CO) cm−1; 1H NMR (500 MHz; CDCl3) δ 7.98 (dd, J1 = 1.5 Hz,
J2 = 8.0 Hz, 1H), 7.67−7.57 (m, 3H), 7.44−7.26 (m, 8H), 5.78 (d, J =
5.0 Hz, 1H), 4.68 (d, J = 5.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ
161.3, 155.8, 152.8, 146.4, 141.9, 135.4, 133.2, 132.3, 131.0, 129.9
(2C), 129.0 (2C), 128.9 (2C), 126.1 (2C), 124.4, 122.7, 117.0, 114.3,
103.8, 103.3, 36.2; MS (EI, 70 eV) m/z (%) 420 (51) [M+], 385 (21),
309 (100); mp 239−241 °C. Anal. Calcd for C24H14Cl2O3: C, 68.43;
H, 3.35. Found: C, 68.60; H, 3.38.
Ketones (2). In a 10 mL flask, AuCl3 (9.1 mg, 0.03 mmol), AgOTf
(23.1 mg, 0.09 mmol), and toluene (1 mL) were added. The mixture
was stirred at room temperature for 5 min before a toluene solution (2
mL) of 1 (or 5) (1.0 mmol) and 2 (1.0 mmol) was added. Then the
mixture was stirred under reflux for 6 h. Upon completion, the
resulting mixture was diluted with CH2Cl2 (10 mL) and filtered
through Celite. After evaporation of the solvent under vacuum, the
residue was purified by column chromatography on silica gel (100−
200 mesh) using petroleum ether/EtOAc (3/1−10/1, v/v) as eluent
to give pure 3 (or 6).
2,4-Diphenylpyrano[3,2-c]chromen-5(4H)-one4a (3aa): white
solid; Rf = 0.38 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1720 (C
1
O) cm−1; H NMR (500 MHz, CDCl3) δ 8.02 (dd, J1 = 1.5 Hz, J2 =
8.0 Hz, 1H), 7.74−7.72 (m, 2H), 7.58−7.54 (m, 1H), 7.46−7.21 (m,
10H), 5.84 (d, J = 5.0 Hz, 1H), 4.71 (d, J = 4.5 Hz, 1H); 13C NMR
(125 MHz, CDCl3) δ 161.4, 155.8, 152.8, 147.0, 143.6, 132.7, 132.0,
129.3, 128.7 (2C), 128.6 (2C), 128.5 (2C), 127.2, 124.7 (2C), 124.2,
122.7, 116.8, 114.6, 103.8, 103.7, 36.7; MS (EI, 70 eV) m/z (%) 352
(33) [M+], 275 (100); mp 170−171 °C (lit.4a mp 173−175 °C).
2-Phenyl-4-p-tolylpyrano[3,2-c]chromen-5(4H)-one (3ab): white
solid; Rf = 0.20 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1726 (CO)
4-(4-Chlorophenyl)-2-p-tolylpyrano[3,2-c]chromen-5(4H)-one
(3ah): Pale yellow solid; Rf = 0.50 (cyclohexane/EtOAc, 6/1); IR
1
(KBr) ν 1720 (CO) cm−1; H NMR (500 MHz, CDCl3) δ 8.01
(dd, J1 = 1.5 Hz, J2 = 7.5 Hz, 1H), 7.62−7.56 (m, 3H), 7.39−7.25 (m,
8H), 5.74 (d, J = 5.0 Hz, 1H), 4.67 (d, J = 5.0 Hz, 1H), 2.41 (s, 3H);
13C NMR (125 MHz, CDCl3) δ 161.4, 155.8, 152.8, 147.3, 142.2,
139.5, 133.0, 132.1, 129.8 (2C), 129.6, 129.4 (2C), 128.7 (2C), 124.6
(2C), 124.2, 122.7, 116.8, 114.5, 103.3, 102.3, 36.1, 21.3; MS (EI, 70
eV) m/z (%) 400 (48) [M+], 365 (14), 289 (100); mp 225−227 °C.
Anal. Calcd for C25H17ClO3: C, 74.91; H, 4.27. Found: C, 74.73; H,
4.30.
1
cm−1; H NMR (500 MHz, CDCl3) δ 8.01 (dd, J1 = 1.5 Hz, J2 = 8.0
Hz, 1H), 7.73−7.72 (m, 2H), 7.54 (dd, J1 = 2.0 Hz, J2 = 8.0 Hz, 1H),
7.46−7.25 (m, 7H), 7.12 (d, J = 8.0 Hz, 2H), 5.83 (d, J = 5.0 Hz, 1H),
4.67 (d, J = 5.0 Hz, 1H), 2.30 (s, 3H); 13C NMR (125 MHz, CDCl3)
δ 161.5, 155.6, 152.8, 146.8, 140.7, 136.9, 132.7, 131.9, 129.3 (2C),
129.2, 128.7 (2C), 128.4 (2C), 124.7 (2C), 124.1, 122.7, 116.8, 114.6,
103.91, 103.85, 36.2, 21.1; MS (EI, 70 eV) m/z (%) 366 (79) [M+],
351 (16), 275 (100); mp 188−189 °C. Anal. Calcd for C25H18O3: C,
81.95; H, 4.95. Found: C, 81.71; H, 4.91.
4-(Benzo[d][1,3]dioxol-5-yl)-2-phenylpyrano[3,2-c]chromen-
5(4H)-one (3ac): white solid; Rf = 0.45 (cyclohexane/EtOAc, 4/1);
IR (KBr) ν 1718 (CO) cm−1; 1H NMR (500 MHz, CDCl3) δ 8.01
(dd, J1 = 1.5 Hz, J2 = 8.0 Hz, 1H), 7.74−7.71 (m, 2H), 7.59−7.55 (m,
1H), 7.47−7.33 (m, 5H), 6.90−6.89 (m, 2H), 6.75 (d, J = 8.0 Hz,
1H), 5.90 (d, J = 1.5 Hz, 2H), 5.82 (d, J = 5.0 Hz, 1H), 4.63 (d, J = 5.0
Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 161.5, 155.6, 152.7, 147.9,
146.8, 146.7, 137.7, 132.6, 132.0, 129.2, 128.7 (2C), 124.7 (2C), 124.2,
122.7, 121.7, 116.8, 114.5, 108.9, 108.3, 103.8, 103.7, 101.0, 36.2; MS
(EI, 70 eV) m/z (%) 396 (100) [M+], 275 (76), 189 (19); mp 177−
178 °C. Anal. Calcd for C25H16O5: C, 75.75; H, 4.07. Found: C, 75.92;
H, 4.03.
4-Methyl-2,4-diphenylpyrano[3,2-c]chromen-5(4H)-one (3ai):
white solid; Rf = 0.375 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1722
1
(O−CO) cm−1; H NMR (500 MHz, CDCl3) δ 8.05 (dd, J1 = 1.0
Hz, J2 = 9.0 Hz, 1H), 7.72 (dd, J1 = 1.5 Hz, J2 = 7.0 Hz, 2H), 7.56−
7.21 (m, 11H), 5.52 (s, 1H), 2.05 (s, 3H); 13C NMR (125 MHz,
CDCl3) δ 160.3, 155.0, 152.8, 147.2, 143.8, 132.6, 131.9, 129.1, 128.7
(2C), 128.2 (2C), 127.5 (2C), 126.5, 124.6 (2C), 124.0, 123.1, 116.6,
114.5, 110.0, 107.3, 38.2, 26.2; MS (EI, 70 eV) m/z (%) 366 (40)
[M+], 351 (100), 289 (96); mp 183−184 °C. Anal. Calcd for
C25H18O3: C, 81.95; H, 4.95. Found: C, 81.74; H, 4.91.
2-Methyl-4-phenylpyrano[3,2-c]chromen-5(4H)-one4b (3aj): pale
yellow solid; Rf = 0.70 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1724
(CO) cm−1; 1H NMR (500 MHz, CDCl3) δ 7.86 (dd, J1 = 1.5 Hz,
J2 = 8.0 Hz, 1H), 7.54−7.50 (m, 1H), 7.35−7.19 (m, 7H), 5.06 (dd, J1
= 1.0 Hz, J2 = 4.5 Hz, 1H), 4.50 (d, J = 4.5 Hz, 1H), 2.07 (s, 3H); 13
C
NMR (125 MHz, CDCl3) δ 161.5, 155.9, 152.8, 146.0, 144.2, 131.8,
128.5 (2C), 128.2 (2C), 127.0, 124.0, 122.7, 116.7, 114.5, 104.0, 103.5,
36.5, 18.6; MS (EI, 70 eV) m/z (%) 290 (38) [M+], 275 (7), 213
(100); mp 136−137 °C.
4-(4-Nitrophenyl)-2-phenylpyrano[3,2-c]chromen-5(4H)-one
9-Methyl-2,4-diphenylpyrano[3,2-c]chromen-5(4H)-one4c (3ba):
white solid; Rf = 0.5 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1715
(3ad): pale yellow solid; Rf = 0.38 (cyclohexane/EtOAc, 4/1); IR
1
(KBr): ν 1723 (CO) cm−1; H NMR (500 MHz, CDCl3) δ 8.18
1
(CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.77−7.72 (m, 3H),
(dd, J1 = 1.5 Hz, J2 = 7.0 Hz, 2H), 8.04 (dd, J1 = 1.5 Hz, J2 = 8.0 Hz,
1H), 7.74 (dd, J1 = 1.5 Hz, J2 = 8.0 Hz, 2H), 7.63−7.59 (m, 3H),
7.49−7.35 (m, 5H), 5.80 (d, J = 5.0 Hz, 1H), 4.85 (d, J = 5.5 Hz, 1H);
13C NMR (125 MHz, CDCl3) δ 161.3, 156.3, 152.8, 150.6, 147.8,
147.1, 132.5, 132.1, 129.7, 129.4 (2C), 128.8 (2C), 124.8 (2C), 124.4,
7.47−7.21 (m, 10H), 5.83 (d, J = 5.0 Hz, 1H), 4.70 (d, J = 5.0 Hz,
1H), 2.49 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 161.6, 155.7,
150.9, 146.9, 143.6, 133.9, 133.0, 132.8, 129.2, 128.64 (2C), 128.58
(2C), 128.4 (2C), 127.1, 124.7 (2C), 122.3, 116.6, 114.2, 103.8, 103.6,
9099
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The Journal of Organic Chemistry
Note
36.6, 21.0; MS (EI, 70 eV) m/z (%) 366 (52) [M+], 289 (100); mp
216−218 °C.
19.9; MS (EI, 70 eV) m/z (%) 316 (52) [M+], 239 (100); mp 170−
171 °C.
7-Methyl-2-phenyl-4-p-tolylpyrano[4,3-b]pyran-5(4H)-one
(6ab): pale yellow solid; Rf = 0.40 (cyclohexane/EtOAc, 6/1); IR
9-Methyl-2-phenyl-4-p-tolylpyrano[3,2-c]chromen-5(4H)-one
(3bb): white solid; Rf1= 0.50 (cyclohexane/EtOAc, 8/1); IR (KBr) ν
1721 (CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.76−7.72 (m,
3H), 7.47−7.11 (m, 9H), 5.82 (d, J = 5.0 Hz, 1H), 4.66 (d, J = 5.0 Hz,
1H), 2.49 (s, 3H), 2.30 (s, 3H); 13C NMR (125 MHz, CDCl3) δ
161.6, 155.6, 150.9, 146.8, 140.8, 136.8, 133.8, 132.9, 132.8, 129.3
(2C), 129.1, 128.6 (2C), 128.3 (2C), 124.7 (2C), 122.2, 116.6, 114.3,
104.0, 103.7, 36.2, 21.0 (2C); MS (EI, 70 eV) m/z (%) 380(80) [M+],
365 (15), 303 (7), 289 (100); mp 210−211 °C. Anal. Calcd for
C26H20O3: C, 82.08; H, 5.30. Found: C, 82.25; H, 5.26.
1
(KBr) ν 1720 (CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.60
(dd, J1 = 1.5 Hz, J2 = 8.0 Hz, 2H), 7.40−7.38 (m, 3H), 7.37−7.35(m,
2H), 7.12 (d, J = 8.0 Hz, 2H), 6.00 (s, 1H), 5.72 (d, J = 5.0 Hz, 1H),
4.52 (d, J = 5.0 Hz, 1H), 2.30 (s, 3H), 2.22 (s, 3H); 13C NMR (125
MHz, CDCl3) δ 163.3, 161.3, 160.3, 146.7, 140.9, 136.6, 132.6, 129.2
(2C), 129.0, 128.5 (2C), 128.2 (2C), 124.5 (2C), 103.9, 100.9, 99.1,
35.6, 21.0, 19.9; MS (EI, 70 eV) m/z (%) 330 (75) [M+], 315 (12),
253 (11), 239 (100); mp 195−196 °C. Anal. Calcd for C22H18O3: C,
79.98; H, 5.49. Found: C, 80.21; H, 5.53.
4-(4-Methoxyphenyl)-9-methyl-2-phenylpyrano[3,2-c]chromen-
4-(4-Methoxyphenyl)-7-methyl-2-phenylpyrano[4,3-b]pyran-
5(4H)-one (6al): pale yellow solid; Rf = 0.45 (cyclohexane/EtOAc,
3:1); IR (KBr) ν 1721 (CO) cm−1; 1H NMR (500 MHz, CDCl3) δ
7.60 (d, J = 7.0 Hz, 2H), 7.40−7.25 (m, 5H), 6.84 (d, J = 8.5 Hz, 2H),
6.00 (s, 1H), 5.71 (d, J = 4.5 Hz, 1H), 4.50 (d, J = 5.0 Hz, 1H), 3.76
(s, 3H), 2.21 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 163.3, 161.2,
160.1, 158.6, 146.7, 136.1, 132.6, 129.4 (2C), 129.0, 128.5 (2C), 124.5
(2C), 113.9 (2C), 103.8, 101.0, 99.1, 55.2, 35.1, 19.8; MS (EI, 70 eV)
m/z (%) 346(100) [M+], 331 (2), 239 (76); mp 132−134 °C. Anal.
Calcd for C22H18O4: C, 76.29; H, 5.24. Found: C, 76.01; H, 5.28.
4-(4-Chlorophenyl)-7-methyl-2-p-tolylpyrano[4,3-b]pyran-5(4H)-
one (6ah): brown solid; Rf = 0.25 (cyclohexane/EtOAc, 6/1); IR
(KBr) ν 1721 (CO) cm−1; 1H NMR (500 MHz, CDCl3) δ 7.49 (d,
J = 8.0 Hz, 2H), 7.31−7.25 (m, 4H), 7.19 (d, J = 8.0 Hz, 2H), 6.01 (s,
1H), 5.63 (d, J = 5.0 Hz, 1H), 4.52 (d, J = 5.0 Hz, 1H), 2.37 (s, 3H),
2.23 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 163.2, 161.6, 160.5,
147.2, 142.4, 139.3, 132.8, 129.8 (2C), 129.6, 129.2 (2C), 128.6 (2C),
124.5 (2C), 102.3, 100.5, 99.1, 35.5, 21.3, 19.9; MS (EI, 70 eV) m/z
(%) 364 (49) [M+], 253 (100); mp 180−181 °C. Anal. Calcd for
C22H17ClO3: C, 72.43; H, 4.70. Found: C, 72.73; H, 4.75.
5(4H)-one (3bl): brown solid; Rf = 0.20 (cyclohexane/EtOAc, 6/1);
1
IR (KBr) ν 1717 (CO) cm−1; H NMR (500 MHz, CDCl3) δ
7.76−7.72 (m, 3H), 7.48−7.20 (m, 7H), 6.84 (dd, J1 = 2.0 Hz, J2 = 7.0
Hz, 2H), 5.81 (d, J = 5.0 Hz, 1H), 4.64 (d, J = 5.0 Hz, 1H), 3.76 (s,
3H), 2.48 (s, 3H); 13C NMR (125 MHz, CDCl3) δ 161.7, 158.7,
155.5, 150.9, 146.8, 135.9, 133.9, 132.9, 132.8, 129.5 (2C), 129.1,
128.6 (2C), 124.7 (2C), 122.2, 116.5, 114.2, 114.0 (2C), 103.9, 103.8,
55.2, 35.7, 21.0; MS (EI, 70 eV) m/z (%) 396 (100) [M+], 365 (18),
319 (12), 289 (78); mp 218−219 °C. Anal. Calcd for C26H20O4: C,
78.77; H, 5.09. Found: C, 78.99; H, 5.12.
4,9-Dimethyl-2,4-diphenylpyrano[3,2-c]chromen-5(4H)-one
(3bi): pale yellow solid; Rf = 0.50 (cyclohexane/EtOAc, 6/1); IR
(KBr) ν 1720 (CO) cm−1; 1H NMR (500 MHz, CDCl3) δ 7.79 (d,
J = 1.0 Hz, 1H), 7.72 (dd, J1 = 1.5 Hz, J2 = 3.5 Hz, 2H), 7.50−7.18 (m,
10H), 5.50 (s, 1H), 2.49 (s, 3H), 2.04 (s, 3H); 13C NMR (125 MHz,
CDCl3) δ 160.4, 155.0, 151.0, 147.3, 143.8, 133.7, 132.9, 132.7, 129.1,
128.6 (2C), 128.1 (2C), 127.4 (2C), 126.4, 124.6 (2C), 122.6, 116.3,
114.1, 110.1, 107.1, 38.2, 26.2, 21.1; MS (EI, 70 eV) m/z (%) 380
(40) [M+], 365 (100), 303 (95); mp 245−247 °C. Anal. Calcd for
C26H20O3: C, 82.08; H, 5.30. Found: C, 82.27; H, 5.27.
4,7-Dimethyl-2,4-diphenylpyrano[4,3-b]pyran-5(4H)-one (6ai):
brown solid; Rf1= 0.3 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1722
(CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.60−7.58 (m, 2H),
7.46−7.45 (m, 2H), 7.40−7.30 (m, 5H), 7.20 (m, 1H), 6.01 (d, J = 0.5
Hz, 1H), 5.44 (s, 1H), 2.22 (s, 3H), 1.96 (s, 3H); 13C NMR (125
MHz, CDCl3) δ 162.2, 161.4, 159.6, 147.2, 143.8, 132.5, 128.9, 128.4
(2C), 128.0 (2C), 127.4 (2C), 126.3, 124.4 (2C), 110.0, 104.3, 99.0,
37.4, 25.9, 19.8; MS (EI, 70 eV) m/z (%) 330 (36) [M+], 315 (100),
253 (98), 226 (4); mp 137−139 °C. Anal. Calcd for C22H18O3: C,
79.98; H, 5.49. Found: C, 79.65; H, 5.45.
9-Methoxy-2,4-diphenylpyrano[3,2-c]chromen-5(4H)-one (3ca):
white solid; Rf = 0.6 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1714
1
(CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.72 (dd, J1 = 1.5 Hz,
J2 = 8.5 Hz, 2H), 7.46−7.40 (m, 6H), 7.33−7.13 (m, 5H), 5.83 (d, J =
5.0 Hz, 1H), 4.71 (d, J = 5.0 Hz, 1H), 3.92 (s, 3H); 13C NMR (125
MHz, CDCl3) δ 161.6, 156.0, 155.5, 147.2, 147.0, 143.6, 132.7, 129.3,
128.7 (2C), 128.6 (2C), 128.5 (2C), 127.2, 124.7 (2C), 119.3, 117.9,
115.0, 105.5, 104.0, 103.9, 56.0, 36.7; MS (EI, 70 eV) m/z (%) 382
(59) [M+], 305 (100); mp 206−207 °C. Anal. Calcd for C25H18O4: C,
78.52; H, 4.74. Found: C, 78.69; H, 4.70.
9-tert-Butyl-2,4-diphenylpyrano[3,2-c]chromen-5(4H)-one
ASSOCIATED CONTENT
(3da): white solid; Rf = 0.6 (cyclohexane/EtOAc, 6/1); IR (KBr) ν
■
1
1722 (CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.99 (d, J = 2.0
S
* Supporting Information
Hz, 1H), 7.73 (dd, J1 = 1.5 Hz, J2 = 8.5 Hz, 2H), 7.61 (dd, J1 = 2.0 Hz,
J2 = 8.5 Hz, 1H), 7.48−7.45 (m, 5H), 7.43−7.40 (m, 4H), 5.84 (d, J =
5.0 Hz, 1H), 4.71 (d, J = 5.0 Hz, 1H), 1.42 (s, 9H); 13C NMR (125
MHz, CDCl3) δ 161.8, 156.1, 150.9, 147.4, 147.0, 143.8, 132.9, 129.7,
129.3, 128.8 (2C), 128.7 (2C), 128.5 (2C), 127.2, 124.7 (2C), 118.6,
116.5, 113.9, 104.0, 103.5, 36.7, 34.8, 31.5; MS (EI, 70 eV) m/z (%)
408 (3) [M+]; mp 181−182 °C. Anal. Calcd for C28H24O3: C, 82.33;
H, 5.92. Found: C, 82.55; H, 5.88.
1
Figures giving H and 13C NMR spectra of the products. This
material is available free of charge via the Internet at http://
pubs.acs.org.
AUTHOR INFORMATION
Corresponding Author
*E-mail: ykuiliu@zjut.edu.cn.
■
9-Chloro-2,4-diphenylpyrano[3,2-c]chromen-5(4H)-one4c (3ea):
pale yellow solid; Rf = 0.40 (cyclohexane/EtOAc, 10/1); IR (KBr) ν
ACKNOWLEDGMENTS
1
1721 (CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.94 (d, J = 2.5
■
Financial support from the Natural Science Foundation of
China (No. 21172197) and Zhejiang Province (No.
Y4100201), the Foundation of Science and Technology
Department of Zhejiang Province (2011R09002-09), and the
Opening Foundation of Zhejiang Provincial Top Key Discipline
is gratefully acknowledged.
Hz, 1H), 7.71 (dd, J1 = 1.0 Hz, J2 = 8.5 Hz, 2H), 7.52−7.22 (m, 10H),
5.83 (d, J = 5.0 Hz, 1H), 4.70 (d, J = 5.0 Hz, 1H); 13C NMR (125
MHz, CDCl3) δ 160.8, 154.7, 151.1, 147.1, 143.2, 132.4, 132.0, 129.8,
129.4, 128.8 (2C), 128.7 (2C), 128.5 (2C), 127.4, 124.7 (2C), 122.2,
118.3, 115.7, 104.6, 103.8, 36.7; MS (EI, 70 eV) m/z (%) 386 (56)
[M+], 309 (100); mp 231−232 °C.
7-Methyl-2,4-diphenylpyrano[4,3-b]pyran-5(4H)-one4c (6aa):
brown solid; Rf1= 0.25 (cyclohexane/EtOAc, 6/1); IR (KBr) ν 1721
(CO) cm−1; H NMR (500 MHz, CDCl3) δ 7.60 (dd, J1 = 2.0 Hz,
J2 = 8.5 Hz, 2H), 7.39−7.21 (m, 8H), 6.02 (s, 1H), 5.73 (d, J = 5.0 Hz,
1H), 4.56 (d, J = 5.0 Hz, 1H), 2.24 (s, 3H); 13C NMR (125 MHz,
CDCl3) δ 163.3, 161.4, 160.4, 146.8, 143.8, 132.6, 129.1, 128.52 (2C),
128.51 (2C), 128.4 (2C), 127.0, 124.6 (2C), 103.8, 100.8, 99.1, 36.0,
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