Efficient one-pot condensation of β-naphthol, aldehydes, and cyclic 1,3-dicarbonyl compounds catalyzed by p-TSA under solvent-free and sonication conditions

Article abstract of DOI:10.1080/00397910903029966

A facile and efficient procedure has been developed by one-pot condensation of β-naphthol, aldehydes, and cyclic 1,3-dicarbonyl compounds for the synthesis of 8,9,10,12-tetrahydrobenzo[a]xanthen-11-one or 8,9-dihydrobenzo-[f] cyclopenta[b]chromen-10(11H)-

Full text of DOI:10.1080/00397910903029966

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Efficient One-Pot Condensation of β-
Naphthol, Aldehydes, and Cyclic 1,3-
Dicarbonyl Compounds Catalyzed by p-
TSA Under Solvent-Free and Sonication
Conditions
Jianjun Li a , Jia Li a , Jin Fang a & Weike Su a
a Key Laboratory of Pharmaceutical Engineering of Ministry of
Education, College of Pharmaceutical Sciences, Zhejiang University
of Technology, Hangzhou, China
Available online: 04 Mar 2010
To cite this article: Jianjun Li, Jia Li, Jin Fang & Weike Su (2010): Efficient One-Pot Condensation
of β-Naphthol, Aldehydes, and Cyclic 1,3-Dicarbonyl Compounds Catalyzed by p-TSA Under Solvent-
Free and Sonication Conditions, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 40:7, 1029-1039
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Synthetic Communications1, 40: 1029–1039, 2010
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910903029966
EFFICIENT ONE-POT CONDENSATION OF
b-NAPHTHOL, ALDEHYDES, AND CYCLIC
1,3-DICARBONYL COMPOUNDS CATALYZED
BY p-TSA UNDER SOLVENT-FREE AND
SONICATION CONDITIONS
Jianjun Li, Jia Li, Jin Fang, and Weike Su
Key Laboratory of Pharmaceutical Engineering of Ministry of Education,
College of Pharmaceutical Sciences, Zhejiang University of Technology,
Hangzhou, China
A facile and efficient procedure has been developed by one-pot condensation of b-naphthol,
aldehydes, and cyclic 1,3-dicarbonyl compounds for the synthesis of 8,9,10,12-
tetrahydrobenzo[a]xanthen-11-one or 8,9-dihydrobenzo-[f]cyclopenta[b]chromen-10(11H)-
one derivatives catalyzed by p-toluenesulfonic acid under solvent-free and sonication conditions.
Keywords: One-pot condensation; p-TSA; solvent-free; ultrasound irradiation
Xanthenes and benzoxanthenes are of considerable interest in industry as well as in
academia because of their promising biological and pharmaceutical activities such
as antiviral,[1] antibacterial,[2] and anti-inflammatory actions,[3] and they are being
used as zoxazolamine[4,5] and in photodynamic therapy.[6,7] Furthermore, these active
oxygen-containing heterocyclic compounds can also be employed as dyes,[8,9] in laser
technology,[10,11] as pH-sensitive fluorescent materials for the visualization of biomo-
lecules.[12] Thus, the synthesis of this heterocyclic nucleus is of great significance.
Lately, only a few procedures for the preparation of 8,9,10,12-tetrahydrobenzo[a]-
xanthen-11-one or 8,9-dihydrobenzo-[f]cyclopenta[b]chromen-10(11H)-one deriva-
tives have been reported. Catalysts such as NaHSO4 ꢀ SiO2[13] and Sr(OTf)2 have been
used for these reactions,[14] but these methods require long reaction times.
Recently, the utilization of multicomponent reactions (MCRs) to generate
novel, drug-like scaffolds has received great attention from organic chemists because
products can be prepared directly in a single step and diversity can be achieved
simply by varying the reaction substrates.[15–19] Previously, it occured to us that
dihydropyrimidiones,[20]
1-substituted-1H-1,2,3,4-tetrazoles,[21]
2-hydroxy-7,8-
dihydroquinolin-5(6H)-ones, and 7,8-dihydroquinolin-2,5-(1H,6H)-diones[22] could
Received March 13, 2009.
Address correspondence to Weike Su, Key Laboratory of Pharmaceutical Engineering of Ministry
of Education, College of Pharmaceutical Sciences, Zhejiang University of Technology, Hangzhou 310014,
China. E-mail: pharmlab@zjut.edu.cn
1029

1030
J. LI ET AL.
successfully be prepared by MCRs. More recently, we also reported the reaction of
the b-naphthol, aldehydes, and amides to form amidoalkyl naphthols.[23]
p-Toluenesulfonic acid (p-TSA) is a commercially available and very cheap
chemical with good stability. Recently, it has been shown that p-TSA can be used
as a substitute for conventional acidic catalytic materials. The toxicity and volatile
nature of many organic solvents, particularly chlorinated hydrocarbons, that are
widely used in huge amounts for organic reactions pose a serious threat to the
environment. Thus, design of solventless catalytic reactions has received tremendous
attention recently.
Taking these points into consideration, in continuation of our investigations
on these active oxygen-containing heterocyclic compounds,[24,14] herein we report
a new route to 8,9,10,12-tetrahydrobenzo[a]xanthen-11-one or 8,9-dihydrobenzo-
[f]cyclopenta[b]chromen-10(11H)-one derivatives with p-TSA as catalyst under
solvent-free conditions. In addition, all the reactions were carried out under
ultrasonic irradiation because it could accelerate the progress of various organic
transformations with mild reaction conditions, short reaction times, and good yields.
We initially studied the reaction of benzaldehyde 1a, b-naphthol 2, and
5,5-dimethyl-cyclohexane-1,3-dione 3 along with a catalytic amount of p-TSA
(10 mol%) in several classic solvents chosen as the medium for comparison. The
results are summarized in Table 1. 1,2-Dichloroethane (Table 1, entry 5, 93%) and
solvent-free conditions (Table 1, entry 6, 95%) afforded the product 9,9-dimethyl-12-
phenyl-9,10-dihydro-8H-benzo[a]xanthen-11(12H)-one 4a in excellent yields. Table 1
(entry 7) shows that the reaction time is reduced and yields improve in the absence of
Table 1. Optimization of conditions for the condensation reaction of aldehyde, b-naphthol, and dimedonea
Entry
Solvent
Water
THF
Time (h)
Yields (%)b
1
2
3
4
5
6
7
3
30
45
3
CH3CH2OH
[bpy]BF4
(CH2Cl)2
None
3
<10
60
3
1.5
0.5
1.0
93
95
90c
None
aReaction conditions: benzaldehyde 1a (1 mmol), b-naphthol 2 (1 mmol), 5,5-dimethyl-cyclohexane-
1,3-dione 3 (1.2 mmol), p-TSA (0.1 mmol), solvent (3 mL), 70ꢁC.
bIsolated yield.
cThe reaction was carried out by stirring instead of sonic irradiation.

CONDENSATION CATALYZED BY p-TSA
1031
ultrasound irradiation conditions. Taking the reaction yields and environmental
impact into consideration, we carried out this reaction under ultrasonic irradiation
and solvent-free conditions at 70 ꢁC.
Encouraged by this success, we extended this reaction to a range of aldehydes
in the presence of 10 mol% p-TSA under solvent-free and ultrasonic irradiation con-
ditions (Table 2). Varoius aromatic aldehydes with electron-donating and
electron-withdrawing substituents reacted successfully, and the corresponding pro-
ducts 4a–k were obtained in good to excellent yields in 0.5–3 h. These results were
also obtained in the case of the aliphatic and heterocyclic aldehydes (Table 2, entries
12–14). The desired products were characterized by NMR, infrared (IR), and mass
spectroscopy (MS) and also by comparison with authentic samples.
We have not established an exact mechanism for the formation of this kind of
compound; however, a reasonable pathway is shown in Scheme 1. The products may
be formed either through step 1 ! step 2 or through step 3 ! step 4 by referring to
literature.[13] The role of p-TSA comes in step 1, when it catalyzes the
Knoevenagel-type coupling of aldehyde 1 with active methylene compound 3, and
in step 2, when it catalyzes the Michael-type addition of b-naphthol 2 and hetero-
diene 7 to afford the corresponding products 4.
Table 2. p-TSA-promoted
one-pot
condensation
of
b-naphthol,
aldehydes,
and
5,5-dimethyl-cyclohexane-1,3-dionea
Entry
1
R
Time (h)
Product
Yields (%)b
1
2
1a
1b
1c
1d
1e
1f
C6H5
3-F-C6H4
3-Cl-C6H4
0.5
0.5
0.5
0.5
0.5
0.5
2.5
1.0
0.5
0.5
2.5
3.0
2.5
0.5
0.5
4a
4b
4c
4d
4e
4f
4g
4h
4i
95
96
95
97
94
91
90
92
94
94
87
86
85
95c
96c
3
4
3-OH-C6H4
3-NO2-C6H4
3-OCH3-C6H4
5
6
7
1g
1h
1I
1j
3-OMe-4-OH-C6H3
3-Me-4-Me-C6H3
4-OMe-C6H4
4-Cl-C6H4
8
9
10
11
12
13
14
15
4j
1k
1l
CH3CH2
4k
4l
CH3C(CH3)2
2-thiophene
C6H5
1m
1a
1j
4m
a
4-Cl-C6H4
j
aReaction conditions: aldehyde 1 (1 mmol), b-naphthol 2 (1 mmol), 5,5-dimethyl-cyclohexane-1,3-dione
3 (1.2 mmol), p-TSA (0.1 mmol), 70ꢁC.
bIsolated yield.
cCyclopentane-1,3-dione was substituted for 5,5-dimethyl-cyclohexane-1,3-dione 3.

1032
J. LI ET AL.
Scheme 1. Possible mechanism for the formation of compound 4.
Next, we extended this reaction to phenols and a-naphthol under similar con-
ditions. However, in the case of phenol and a-naphthol, the reaction did not proceed
or gave only traces of the expected products under similar conditions after 24 h. A
by-product was characterized, which was formed from the condensation of 2 equiv.
of 5,5-dimethyl-cyclohexane-1,3-dione 3 and 1 equiv. of aldehydes because of their
weaker nucleophilicity compared to b-naphthol.
Table 3. p-TSA-promoted one-pot condensation of b-naphthol, aldehydes, and cyclopentane-1,3-dionea
Entry
1
R
Time (h)
Product
Yields (%)b
1
2
3
4
5
6
7
8
1a
1d
1f
C6H5
3-OH-C6H4
0.5
0.5
0.5
0.5
0.5
2.5
2.5
1.0
6a
6d
6f
95
96
93
92
94
85
80
90
3-OCH3-C6H4
3-Me-4-Me-C6H3
4-Cl-C6H4
1h
1j
6h
6j
1k
1n
1o
CH3CH2
2-Furan
2-OMe-4-OMe-C6H3
6k
6n
6o
9
1p
1q
0.5
1.0
6p
6q
91
86
10
C6H5CH2
aReaction conditions: aldehyde
(1.2 mmol), p-TSA (0.1 mmol), 70ꢁC.
bIsolated yield.
1 (1 mmol), b-naphthol 2 (1 mmol), cyclopentane-1,3-dione 5

CONDENSATION CATALYZED BY p-TSA
1033
We next tried to observe the effect of substituents in 5,5-dimethyl-1,3-
cyclohexanedione 3 using cyclopentane-1,3-dione 5. Both aromatic and aliphatic
aldehydes 1 reacted well with 2 and 5 in the presence of 10 mol% of p-TSA to afford
6 in good to high yields under similar conditions (Table 3).
In summary, we have developed a facile and efficient method for the
synthesis of 8,9,10,12-tetrahydrobenzo[a]xanthen-11-one or 8,9-dihydrobenzo-
[f]cyclopenta[b]chromen-10(11H)-one derivatives. The easy workup procedure, short
reaction times, solvent-free conditions, and good yields make this method an
important addition to the existing methodologies.
EXPERIMENTAL
All reagents are commercially available and were used without any purification.
Melting points were recorded on a Buchi B-540 capillary melting-point apparatus and
¨
are uncorrected. 1H NMR and 13C NMR spectra were recorded on a Varian Mercury
Plus-400 instrument using CDCl3 as the solvent with tetramethylsilane (TMS) as an
internal standard at room temperature. Chemical shifts are given in d relative to
TMS; the coupling constants J are given in hertz. IR spectra were recorded on an
Avatar 370 Fourier transform (FT)–IR spectrophotometer. MS were measured with
Finnigan Trace DSQ (EI, CI) or Thermo Finnigan LCQ-Advantage (ESI).
General Procedure for the Synthesis of Product 4 or 6
A mixture of aldehyde 1 (1.0 mmol), b-naphthol 2 (1.0 mmol), dimedone 3 or 5
(1.2 mmol), and p-TSA (10 mol%) were irradiated at 70 ꢁC in the presence of ultra-
sonic waves for a certain time as shown in Tables 2 and 3. The progress of the reac-
tion was monitored by thin-layer chromatography (TLC) until the disappearance of
aldehyde. After the completion of the reaction, water (15 mL) was added and the
crude product was extracted with ethyl acetate (3 ꢂ 10 mL). The organic layer was
dried (MgSO4) and evaporated, and the crude product was purified through crystal-
lization from ethanol to afford a pure product.
Data
9,9-Dimethyl-12-phenyl-9,10-dihydro-8H-benzo[a]xanthen-11(12H)-one
(4a). Mp 154–155 ꢁC. nmax (KBr)=cmꢃ1 3125, 2954, 1651, 1595, 1398, 1375, 1228,
1176, 1025, 808, 743, 699, 510. 1H NMR (400 MHz, CDCl3): dH 7.99 (1H, d,
J ¼ 8.4 Hz, Ar-H), 7.79–7.75 (2H, m, Ar-H), 7.45–7.31 (5H, m, Ar-H), 7.19–7.15
(2H, m, Ar-H), 7.07–7.03 (1H, m, Ar-H), 5.71 (1H, s, CH), 2.57 (2H, s, CH2),
2.27 (2H, m, CH2), 1.12 (3H, s, CH3), 0.96 (3H, s, CH3). 13C NMR (100 MHz,
CDCl3): dC 196.9, 163.9, 147.8, 144.7, 131.5, 131.4, 128.8, 128.4, 128.2, 127.0,
126.2, 124.9, 123.7, 117.7, 117.0, 114.3, 50.9, 41.4, 34.7, 32.2, 29.3, 27.1. MS (ESI)
m=z 355 ([M þ 1]þ, 100), 274 (20).
12-(3-Fluorophenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
1
11(12H)-one (4b). Mp 157–158 ꢁC. H NMR (400 MHz, CDCl3): dH 7.93 (1H, d,
J ¼ 8.0 Hz, Ar-H), 7.80–7.77 (2H, m, Ar-H), 7.46–7.32 (3H, m, Ar-H), 7.26–7.11

1034
J. LI ET AL.
(2H, m, Ar-H), 7.00–6.96 (1H, m, Ar-H), 6.77–6.75 (1H, m, Ar-H), 5.72 (1H, s, CH),
2.57 (2H, s, CH2), 2.28 (2H, m, CH2), 1.12 (3H, s, CH3), 0.97 (3H, s, CH3). 13C
NMR (100 MHz, CDCl3): dC 196.8, 164.1, 164.0, 161.6, 147.8, 147.2, 147.1, 131.5,
131.2, 129.6, 129.5, 129.1, 127.1, 125.0, 124.1, 123.4, 117.0, 116.9, 115.4, 115.2,
113.7, 113.3, 113.1. MS (EI) m=z 372.2 (Mþ, 30), 277.1 (100). HRMS (EI): calcd.
for C25H21FO2 [Mþ]: 372.1526; found: 372.1515.
12-(3-Chlorophenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
1
11(12H)-one (4c). Mp 180–181 ꢁC. H NMR (400 MHz, CDCl3): dH 7.91 (1H, d,
J ¼ 8.0 Hz, Ar-H), 7.80–7.77 (2H, m, Ar-H), 7.47–7.25 (5H, m, Ar-H), 7.11 (1H, t,
J ¼ 8.0 Hz, Ar-H), 7.05–7.02 (1H, m, Ar-H), 5.69 (1H, s, CH), 2.57 (2H, s, CH2),
2.28 (2H, m, CH2), 1.12 (3H, s, CH3), 0.97 (3H, s, CH3). 13C NMR (100 MHz,
CDCl3): dC 196.7, 164.1, 147.8, 146.7, 134.1, 131.5, 131.2, 129.4, 129.1, 128.4,
127.1, 126.8, 126.5, 125.0, 123.4, 117.0, 116.8, 113.7, 50.8, 41.4, 36.2, 34.5, 32.2,
29.2, 27.1, 18.4. MS (ESI) m=z 389.1 ([M þ 1]þ, 100). HRMS (EI): calcd. for
C25H21ClO2 [Mþ]: 388.1230; found: 388.1238.
12-(3-Hydroxyphenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
1
11(12H)-one (4d). Mp 240–242 ꢁC. H NMR (400 MHz, CDCl3): dH 9.22 (1H, s,
OH), 8.02 (1H, d, J 8.8 Hz, Ar-H), 7.92 (2H, d, J 9.2 Hz, Ar-H), 7.53–7.42 (3H,
m, Ar-H), 6.93 (1H, m, Ar-H), 6.73 (1H, d, J ¼ 8.4 Hz, Ar-H), 6.65 (1H, s, Ar-H),
6.44 (1H, d, J ¼ 8.4 Hz, Ar-H), 5.49 (1H, s, CH), 2.63 (2H, m, CH2), 2.33 (1H, d,
J ¼ 15.6 Hz, CH2), 2.15 (1H, d, J ¼ 16.8 Hz, CH2), 1.06 (3H, s, CH3), 0.91 (3H, s,
CH3). 13C NMR (100 MHz, CDCl3): dC 195.8, 163.7, 157.1, 147.2, 146.2, 131.0,
130.7, 129.0, 128.5, 127.1, 124.9, 123.2, 118.9, 117.4, 117.1, 115.1, 113.2, 50.1,
33.9, 31.9, 28.8, 26.3. MS (ESI) m=z 369.3 ([M ꢃ 1]þ, 100). HRMS (EI): calcd. for
C25H22O3 [Mþ]: 370.1569; found: 370.1577.
9,9-Dimethyl-12-(3-nitrophenyl)-9,10-dihydro-8H-benzo[a]xanthen-
11(12H)-one (4e). Mp 169–170 ꢁC. nmax (KBr)=cmꢃ1 3125, 2954, 2864, 1649,
1596, 1529, 1375, 1344, 1225, 1025, 812, 748, 683, 510. 1H NMR (500 MHz, CDCl3):
d
H 8.12–7.79 (6H, m, 7.47–7.35 (4H, m, Ar-H), 5.82 (1H, s, CH), 2.61 (2H, s, CH2),
2.29 (2H, m, CH2), 1.13 (3H, s, CH3), 0.95 (3H, s, CH3). 13C NMR (125 MHz,
CDCl3): dC 196.8, 164.6, 148.4, 147.8, 146.8, 134.9, 131.6, 131.0, 129.7, 129.1,
128.7, 127.4, 125.2, 123.3, 123.1, 121.6, 117.3, 116.0, 113.1, 50.8, 41.4, 34.8, 32.3,
29.3, 27.1. MS (EI) m=z 399 (Mþ, 8), 165 (56), 221 (40), 277 (100).
12-(3-Methoxyphenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
1
11(12H)-one (4f). Mp 169–170 ꢁC. H NMR (400 MHz, CDCl3): dH 8.00 (1H, d,
J ¼ 8.4 Hz, Ar-H), 7.76 (2H, m, Ar-H), 7.45–7.30 (7.08 (1H, t, J ¼ 8.0 Hz, Ar-H),
6.94–6.89 (2H, m, Ar-H), 5.69 (1H, s, CH), 3.70 (3H, s, CH3), 2.56 (2H, s, CH2),
2.27 (2H, d, J ¼ 5.6 Hz, CH2), 1.11 (3H, s, CH3), 0.97 (3H, s, CH3). 13C NMR
(100 MHz, CDCl3): dC 196.8, 163.9, 159.4, 147.7, 146.3, 131.4, 129.0, 128.8, 128.3,
126.9, 124.8, 123.6, 121.0, 117.5, 117.0, 114.6, 114.1, 111.2, 55.0, 50.9, 41.4, 34.6,
32.2, 29.2, 27.2. MS (ESI) m=z 385.3 ([M þ 1]þ, 100). HRMS (EI): calcd. for
C26H24O3 [Mþ]: 384.1725; found: 384.1735.
12-(4-Hydroxy-3-methoxyphenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo-
1
[a]xanthen-11(12H)-one (4g). Mp 164–166 ꢁC. H NMR (400 MHz, CDCl3): dH

CONDENSATION CATALYZED BY p-TSA
1035
7.98 (1H, d, J ¼ 8.4 Hz, Ar-H), 7.79–7.74 (2H, m, Ar-H), 7.45–7.35 (2H, m, Ar-H),
7.31 (1H, d, J ¼ 9.2 Hz, Ar-H), 7.00 (1H, m, Ar-H), 6.68–6.63 (2H, m, Ar-H), 5.64
(1H, s, CH), 3.82 (3H, s, CH3), 2.56 (2H, s, CH2), 2.28 (2H, d, J ¼ 5.2 Hz, CH2),
1.11 (3H, s, CH3), 0.98 (3H, s, CH3). 13C NMR (100 MHz, CDCl3): dC 197.2,
163.8, 147.7, 146.1, 143.8, 137.0, 131.5, 131.4, 128.7, 128.4, 126.9, 124.9, 123.7,
121.0, 117.8, 117.0, 114.1, 111.4, 55.9, 50.9, 41.4, 34.1, 32.2, 29.3, 27.1. MS (ESI)
m=z 399.3 ([M ꢃ 1]þ, 100).
12-(3,4-Dimethylphenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
11(12H)-one (4h). Mp 181–182 ꢁC. nmax (KBr)=cmꢃ1 3125, 2958, 1650, 1593, 1398,
1371, 1237, 1226, 1172, 819, 747, 478. 1H NMR (500 MHz, CDCl3): dH 8.04 (1H, d,
J ¼ 8.5 Hz, Ar-H), 7.77–7.72 (2H, m, Ar-H), 7.43–7.25 (3H, m, 7.10–7.03 (2H, m,
Ar-H), 6.91 (1H, d, J ¼ 8.0 Hz, Ar-H), 5.63 (1H, s, CH), 2.56 (2H, m, CH2), 2.27
(2H, m, CH2), 2.13 (3H, s, CH3), 2.09 (3H, s, CH3), 1.11 (3H, s, CH3), 0.99 (3H,
s, CH3). 13C NMR (125 MHz, CDCl3): dC 196.2, 163.8, 147.7, 142.3, 136.2, 134.4,
131.5, 129.7, 129.5, 128.7, 128.4, 127.0, 125.9, 124.9, 123.8, 118.1, 117.1, 114.5,
51.0, 41.4, 34.3, 32.4, 29.2, 27.4, 20.0, 19.4. MS (EI) m=z 382 (Mþ, 40), 277 (100).
12-(4-Methoxyphenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
11(12H)-one (4i). Mp 205–206 ꢁC. nmax (KBr)=cmꢃ1 3121, 2958, 1652, 1607, 1507,
1
1462, 1382, 1218, 1143, 1028, 834, 747, 661, 539. H NMR (400 MHz, CDCl3): dH
7.98 (1H, d, J ¼ 8.4 Hz, Ar-H), 7.78–7.73 (2H, m, Ar-H), 7.45–7.24 (5H, m,
Ar-H), 6.71–6.69 (2H, m, Ar-H), 5.66 (1H, s, CH), 3.68 (3H, s, CH3), 2.56 (2H, s,
CH2), 2.27 (2H, m, CH2), 1.11 (3H, s, CH3), 0.97 (3H, s, CH3). 13C NMR
(100 MHz, CDCl3): dC 197.0, 163.7, 157.8, 147.7, 137.2, 131.5, 131.4, 129.4, 128.7,
128.4, 127.0, 124.9, 123.7, 117.9, 117.1, 114.4, 113.6, 55.1, 50.9, 41.4, 33.9, 32.3,
29.3, 27.2. MS (EI) m=z 384 (Mþ, 40), 277 (100).
12-(4-Chlorophenyl)-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-
11(12H)-one (4j). Mp 181–182 ꢁC. nmax (KBr)=cmꢃ1 3133, 2958, 1648, 1596, 1483,
1
1400, 1375, 1224, 1139, 1009, 841, 747, 535. H NMR (500 MHz, CDCl3): dH 7.90
(1H, d, J ¼ 8.5 Hz, Ar-H), 7.79–7.76 (2H, m, Ar-H), 7.45–7.25 (5H, m, Ar-H),
7.14–7.12 (2H, m, Ar-H), 5.68 (1H, s, CH), 2.56 (2H, s, CH2), 2.28 (2H, m, CH2),
1.12 (3H, s, CH3), 0.96 (3H, s, CH3). 13C NMR (125 MHz, CDCl3): dC 196.9,
164.1, 147.7, 143.3, 131.9, 131.5, 131.2, 129.8, 129.1, 128.5, 128.4, 127.2, 125.0,
123.5, 117.1, 113.9, 50.9, 41.4, 34.2, 32.3, 29.3, 27.1. MS (EI) m=z 388 (Mþ, 15),
221 (20), 277 (100).
12-Ethyl-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-11(12H)-one
(4k). nmax (KBr)=cmꢃ1 3130, 2960, 1651, 1595, 1394, 1225, 1177, 1145, 813, 748,
1
649, 480. H NMR (400 MHz, CDCl3): dH 8.10 (1H, d, J ¼ 8.0 Hz, Ar-H), 7.82
(1H, d, J ¼ 8.0 Hz, Ar-H), 7.70 (1H, d, J ¼ 9.0 Hz, Ar-H), 7.56–7.53 (1H, m,
Ar-H), 7.45–7.42 (1H, m, Ar-H), 7.20 (1H, d, J ¼ 8.5 Hz, Ar-H), 4.74 (1H, t,
J ¼ 4.0 Hz, CH), 2.55 (2H, d, J ¼ 3.5 Hz, Ar-H), 2.37 (2H, d, J ¼ 4.5 Hz, Ar-H),
1.86–1.83 (2H, m, CH2), 1.20 (3H, s, CH3), 1.16 (3H, s, CH3), 0.61 (3H, t, J ¼ 7.5 Hz,
CH3). 13C NMR (100 MHz, CDCl3): dC 197.6, 166.3, 148.7, 131.5, 131.2, 128.6,
128.0, 126.7, 124.8, 123.3, 117.7, 116.8, 112.1, 51.1, 41.4, 32.2, 29.7, 28.7, 27.4,
27.3, 9.0. MS (EI) m=z 305 ([M ꢃ 1]þ, 2), 85 (100), 124 (60), 221 (65), 275 (90).

1036
J. LI ET AL.
12-tert-Butyl-9,9-dimethyl-9,10-dihydro-8H-benzo[a]xanthen-11(12H)-one
(4l). Mp 110–111 ꢁC. nmax (KBr)=cmꢃ1 3125, 2962, 1642, 1592, 1394, 1220, 1176,
1
1005, 812, 750, 616, 490. H NMR (400 MHz, CDCl3): dH 8.21 (1H, d, J ¼ 9.0 Hz,
Ar-H), 7.80 (1H, d, J ¼ 8.0 Hz, Ar-H), 7.72 (1H, d, J ¼ 9.0 Hz, Ar-H), 7.52–7.49
(1H, m, Ar-H), 7.43–7.40 (1H, m, Ar-H), 7.28 (1H, d, J ¼ 9.0 Hz, Ar-H), 4.62
(1H, s, CH), 2.65 (1H, d, J ¼ 18.0 Hz, CH2), 2.52 (1H, d, J ¼ 18.0 Hz, CH2), 2.42
(1H, d, J ¼ 16.5 Hz, CH2), 2.28 (1H, d, J ¼ 16.5 Hz, CH2), 1.27 (3H, s, CH3), 1.14
(3H, s, CH3), 0.78 (9H, s, CH3). 13C NMR (100 MHz, CDCl3): dC 197.2, 167.6,
150.6, 132.7, 131.3, 128.2 (CH), 127.8, 126.0, 124.6, 118.4, 116.8, 113.9, 51.0, 41.6,
40.0, 35.9, 31.7, 30.1, 27.8, 27.4. MS (EI) m=z 277 ([M ꢃ 57]þ, 100), 165 (45), 221 (30).
9,9-Dimethyl-12-(thiophen-2-yl)-9,10-dihydro-8H-benzo[a]xanthen-
11(12H)-one (4m). Mp 180–181 ꢁC. nmax (KBr)=cmꢃ1 3105, 2958, 1651, 1593, 1376,
1224, 1177, 1147, 1009, 813, 746, 700, 661, 507. 1H NMR (500 MHz, CDCl3): dH 8.04
(1H, d, J ¼ 8.5 Hz, Ar-H), 7.82–7.78 (2H, m, Ar-H), 7.51–7.30 (3H, m, Ar-H),
7.01–7.00 (1H, m, CH), 6.77–6.74 (2H, m, CH), 6.04 (1H, s, CH), 2.57 (2H, s,
CH2), 2.35 (2H, s, CH2), 1.14 (3H, s, CH3), 1.05 (3H, s, CH3). 13C NMR
(125 MHz, CDCl3): dC 196.8, 164.6, 148.6, 147.8, 131.4, 129.1, 128.4, 127.2, 126.3,
125.1, 125.0, 124.0, 123.5, 117.2, 117.1, 113.8, 50.9, 41.4, 32.3, 29.4, 29.3, 27.2. MS
(EI) m=z 360 (Mþ, 75), 165 (55), 221 (50), 277 (100), 327 (60).
11-Phenyl-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-one (6a).
Mp 237–238 ꢁC. nmax (KBr)=cmꢃ1 3391, 3125, 1705, 1667, 1596, 1377, 1232, 1101,
1011, 942, 811, 747, 696, 528, 509. 1H NMR (400 MHz, CDCl3): dH 7.84–7.77
(3H, m, Ar-H), 7.40–7.38 (3H, m, Ar-H), 7.28–7.26 (2H, m, Ar-H), 7.21–7.18 (2H,
m, Ar-H), 7.12–7.09 (1H, m, Ar-H), 5.58 (1H, s, CH), 2.84–2.73 (2H, m, CH2),
2.55–2.45 (2H, m, CH2). 13C NMR (125 MHz, CDCl3): dC 202.5, 177.1, 149.2,
143.6, 131.8, 131.7, 129.6, 128.5, 128.4, 128.2, 127.2, 126.6, 125.2, 124.2, 118.9,
117.4, 116.1, 36.0, 33.8, 25.4. MS (EI) m=z 312 (Mþ, 20), 235 (100).
11-(3-Hydroxyphenyl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-
one (6d). Mp > 300 ꢁC. 1H NMR (400 MHz, CDCl3): dH 9.23 (1H, s, OH),
7.99–7.86 (3H, m, Ar-H), 7.54–7.42 (4H, m, Ar-H), 7.00–6.96 (1H, m, Ar-H), 6.69
(1H, d, J ¼ 8.0 Hz, Ar-H), 6.55–6.46 (2H, m, Ar-H), 5.41 (1H, s, CH), 2.90–2.76
(2H, m, CH2), 2.51–2.41 (2H, m, CH2). 13C NMR (100 MHz, CDCl3): dC 201.4,
176.8, 157.2, 148.4, 145.3, 131.3, 131.1, 129.6, 129.1, 128.4, 127.0, 125.1, 123.9,
118.8, 117.9, 117.4, 116.0, 114.9, 113.4, 35.1, 33.5, 24.7. MS (ESI) m=z 329.1
([M þ 1]þ, 100). HRMS (EI): calcd. for C22H16O3 [Mþ]: 328.1099; found: 328.1106.
11-(3-Methoxyphenyl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-
one (6f). Mp 197–198 ꢁC. 1H NMR (400 MHz, CDCl3): dH 7.83–7.78 (3H, m,
Ar-H), 7.41–7.36 (3H, m, Ar-H), 7.13–7.09 (1H, m, Ar-H), 6.85–6.83 (2H, m,
Ar-H), 6.66–6.64 (1H, m, Ar-H), 5.55 (1H, s, CH), 3.71 (3H, s, CH3), 2.80–2.75
(2H, m, CH2), 2.51–2.49 (2H, m, CH2). 13C NMR (100 MHz, CDCl3): dC 202.3,
177.1, 159.6, 149.2, 145.1, 131.8, 131.7, 129.5, 129.3, 128.4, 127.1, 125.1, 124.1,
120.6, 118.7, 117.3, 115.9, 114.3, 111.6, 55.1, 35.9, 33.7, 25.3. MS (ESI) m=z 343.2
([M þ 1]þ, 100). HRMS (EI): calcd. for C23H18O3 [Mþ]: 342.1256; found: 342.1267.

CONDENSATION CATALYZED BY p-TSA
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11-(3,4-Dimethylphenyl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-
10(11H)-one (6h). Mp 223–224 ꢁC. nmax (KBr)=cmꢃ1 3407, 3131, 1709, 1670, 1591,
1
1396, 1237, 943, 825, 746, 498. H NMR (500 MHz, CDCl3): dH 7.83–7.79 (3H, m,
Ar-H), 7.40–7.36 (3H, m, Ar-H), 7.03–6.93 (3H, m, Ar-H), 5.50 (1H, s, CH),
2.79–2.75 (2H, m, CH2), 2.50–2.47 (2H, m, CH2), 2.13 (3H, s, CH3), 2.12 (3H, s,
CH3). 13C NMR (125 MHz, CDCl3): dC 202.5, 177.1, 149.2, 141.2, 136.6, 134.8,
131.9, 131.8, 129.7, 129.4, 129.3, 128.4, 127.1, 125.5, 125.1, 124.2, 119.2, 117.4,
116.5, 35.5, 33.8, 25.3, 19.9, 19.4. MS (EI) m=z 340 (Mþ, 10), 178 (22), 235 (100).
11-(4-Chlorophenyl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-
one (6j). Mp 233–234 ꢁC. nmax (KBr)=cmꢃ1 3426, 3131, 1699, 1658, 1396, 1233,
1
1088, 1013, 9445, 819, 744, 527. H NMR (500 MHz, CDCl3): dH 7.85–7.82 (2H,
m, Ar-H), 7.71–7.69 (1H, m, Ar-H), 7.41–7.38 (3H, m, Ar-H), 7.21–7.15 (4H, m,
Ar-H), 5.55 (1H, s, CH), 2.84–2.75 (2H, m, CH2), 2.56–2.45 (2H, m, CH2). 13C
NMR (125 MHz, CDCl3): dC 202.4, 177.2, 149.2, 142.0, 132.4, 131.8, 131.6, 129.9,
129.5, 128.7, 128.6, 127.3, 125.3, 124.0, 118.3, 117.4, 115.5, 35.5, 33.8, 25.4. MS
(EI) m=z 346 (Mþ, 10), 141 (20), 235 (100).
11-Ethyl-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-one (6k). Mp
1
166–167 ꢁC. H NMR (400 MHz, CDCl3): dH 8.02 (1H, d, J ¼ 8.4 Hz, Ar-H), 7.83
(1H, d, J ¼ 8.0 Hz, Ar-H), 7.73 (1H, d, J ¼ 8.4 Hz, Ar-H), 7.57–7.44 (2H, m,
Ar-H), 7.24 (1H, d, J ¼ 8.0 Hz, Ar-H), 4.61 (1H, s, CH), 2.92–2.55 (4H, m, CH2),
2.00–1.89 (2H, m, CH2), 0.61 (3H, t, J ¼ 7.6 Hz, CH3). 13C NMR (100 MHz, CDCl3):
dC 203.3, 179.8, 149.4, 131.7, 131.4, 128.6, 126.8, 125.0, 123.3, 117.4, 117.1, 116.8,
33.9, 29.8, 26.6, 25.2, 9.0. MS (ESI) m=z 265.2 ([M þ 1]þ, 100). HRMS (EI): calcd.
for C18H16O2 [Mþ]: 264.1150; found: 264.1156.
11-(Furan-2-yl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-one
1
(6n). Mp 220–222 ꢁC. H NMR (400 MHz, CDCl3): dH 7.97 (1H, d, J ¼ 8.4 Hz,
Ar-H), 7.84–7.81 (2H, m, Ar-H), 7.52–7.42 (2H, m, Ar-H), 7.35 (1H, d, J ¼ 8.8 Hz,
Ar-H), 7.18 (1H, m, CH), 6.20–6.19 (1H, m, CH), 6.08 (1H, d, J ¼ 7.2 Hz, CH), 5.68
(1H, s, CH), 2.93–2.76 (2H, m, CH2), 2.64–2.54 (2H, m, CH2). 13C NMR (100 MHz,
CDCl3): dC 202.4, 178.6, 155.2, 149.0, 141.8, 132.1, 131.8, 129.9, 128.7, 127.4, 125.5,
123.8, 117.7, 114.2, 110.5, 106.9, 34.0, 29.7, 25.6. MS (EI) m=z 302.2 (Mþ, 30).
HRMS (EI): calcd. for C20H14O3 [Mþ]: 302. 0943; found: 302.0951.
11-(2,4-Dimethoxyphenyl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-
10(11H)-one (6o). Mp 192–193 ꢁC. 1H NMR (400 MHz, CDCl3): dH 8.00 (1H, d, J
8.4 Hz, Ar-H), 7.77–7.73 (2H, m, Ar-H), 7.42–7.31 (3H, m, Ar-H), 6.93 (1H, d,
J ¼ 8.4 Hz, Ar-H), 6.42–6.29 (2H, m, Ar-H), 5.80 (1H, s, CH), 3.93 (3H, s,
OCH3), 3.69 (3H, s, OCH3), 2.80 (2H, s, CH2), 2.47 (2H, s, CH2). 13C NMR
(100 MHz, CDCl3): dC 202.5, 177.3, 159.4, 157.3, 148.8, 132.0, 131.6, 130.5, 128.8,
128.2, 126.9, 125.4, 124.9, 124.0, 119.3, 117.7, 117.2, 105.3, 99.0, 56.1, 55.1, 33.8,
29.1, 25.3. MS (ESI) m=z 373.1 ([M þ 1]þ, 100). HRMS (EI): calcd. for C24H20O4
[Mþ]: 372.1362; found: 372.1371.
11-(Benzo[d][1,3]dioxol-5-yl)-8,9-dihydrobenzo[f]cyclopenta[b]chromen-
10(11H)-one (6p). Mp 228–230 ꢁC. 1H NMR (400 MHz, CDCl3): dH 7.83–7.80 (3H,
m, Ar-H), 7.41–7.35 (3H, m, Ar-H), 6.81–6.78 (1H, m, Ar-H), 6.69–6.63 (2H, m,

1038
J. LI ET AL.
Ar-H), 5.83 (2H, d, J ¼ 13.6 Hz, Ar-H), 5.49 (1H, s, CH), 2.84–2.72 (2H, m, CH2),
2.52–2.49 (2H, m, CH2). 13C NMR (100 MHz, CDCl3): dC 202.4, 176.9, 149.0,
147.7, 146.1, 137.7, 131.8, 129.5, 128.4, 127.1, 125.1, 124.1, 121.4, 118.8, 117.3,
116.1, 108.7, 108.0, 100.8, 35.6, 33.7, 25.3. MS (ESI) m=z 357.1 ([M þ 1]þ, 100).
HRMS (EI): calcd. for C23H16O4 [Mþ]: 356.1049; found: 356.1054.
11-Benzyl-8,9-dihydrobenzo[f]cyclopenta[b]chromen-10(11H)-one (6q).
1
Mp 181–182 ꢁC. H NMR (400 MHz, CDCl3): dH 8.14 (1H, d, J ¼ 8.4 Hz, Ar-H),
7.87 (1H, d, J ¼ 8.0 Hz, Ar-H), 7.72 (1H, d, J ¼ 8.8 Hz, Ar-H), 7.65–7.61 (1H, m,
Ar-H), 7.53–7.49 (1H, m, Ar-H), 7.09–6.96 (4H, m, Ar-H), 6.32 (2H, d, J ¼ 7.2 Hz,
Hz, Ar-H), 4.89 (1H, t, J ¼ 3.6 Hz, CH), 3.21–3.20 (2H, m, CH2), 2.60–2.44 (4H, m,
CH2). 13C NMR (100 MHz, CDCl3): dC 203.1, 179.8, 149.4, 137.4, 131.6, 131.2,
129.6, 128.8, 128.7, 127.3, 127.1, 126.1, 125.1, 123.1, 116.9, 116.4, 115.9, 38.6,
33.7, 30.6, 25.0. MS (ESI) m=z 327.2 ([M þ 1]þ, 100). HRMS (EI): calcd. for
C23H18O2 [Mþ]: 326.1307; found: 372.1297.
ACKNOWLEDGMENT
We are grateful to the Science and Technology Projects of Zhejiang
(Nos. 2008C11046 and 2007C21111) for financial support.
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