Ruthenium/Yb(OTf)3-cocatalyzed dehydrogenative synthesis of 14-substituted-14-H-dibenzo[a,j]xanthenes from β-naphthol and alcohols

Article abstract of DOI:10.1039/c4ra00039k

By employing [P^O]₂Cl₂Ru/Yb(OTf)₃ as a new and efficient catalyst system [P^O = 2-(diphenylphosphino)-2,4-dimethylpentan- 3-one], readily available, abundant alcohols were firstly employed for dehydrogenative synthesis of 14-substituted-14-H-dibenzo[a,j]xanthenes. Due to the inherent stability of alcohols compared to aldehydes, the presented synthetic protocol is adaptable to a broad substrate scope, there is no need for stringent protection in the whole preparation process, providing the potential to prepare products that are currently inaccessible or challenging to prepare using conventional methods. It is an important complement to the conventional synthetic methodologies. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra00039k

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PAPER
Ruthenium/Yb(OTf)3-cocatalyzed dehydrogenative
synthesis of 14-substituted-14-H-dibenzo[a,j]-
xanthenes from b-naphthol and alcohols†
Cite this: RSC Adv., 2014, 4, 14744
a
a
a
ab
*
Xiaoting Wang, Mengmeng Chen, Feng Xie and Min Zhang
By employing [P^O]2Cl2Ru/Yb(OTf)3 as a new and efficient catalyst system [P^O ¼ 2-(diphenylphosphino)-
2,4-dimethylpentan-3-one], readily available, abundant alcohols were firstly employed for dehydrogenative
synthesis of 14-substituted-14-H-dibenzo[a,j]xanthenes. Due to the inherent stability of alcohols compared
to aldehydes, the presented synthetic protocol is adaptable to a broad substrate scope, there is no need for
stringent protection in the whole preparation process, providing the potential to prepare products that are
currently inaccessible or challenging to prepare using conventional methods. It is an important
complement to the conventional synthetic methodologies.
Received 3rd January 2014
Accepted 12th March 2014
DOI: 10.1039/c4ra00039k
www.rsc.org/advances
reactions of aryloxymagnesium halides with triethylortho-
formate,11 2-hydroxyaryl aldehydes with 2-tetralone,12 b-naph-
thols with (1) 2-naphthol-1-methanol,13a (2) formamide,13b (3)
Introduction
Due to the gradual depletion of the earth's limited resources,
the replacement of conventional reagents with abundant and
sustainable feedstocks to synthesize valuable products emerges
as a signicant important subject in modern synthetic chem-
istry. In recent years, alcohols have been extensively employed
as desirable coupling partners for various synthetic purposes.1
In general, the dehydrogenation of the alcohols leading to in
situ formation of aldehydes (or ketones) is considered as the key
step for substrate activation, and the search for suitable catalyst
system which is compatible to both dehydrogenative process
and the formation of the nal products is the main challenging
point.
Xanthenes derivatives constitute an interesting class of
oxygen-containing heterocycles that exhibit diverse biological
activities including antibacterial,2 anti-inammatory,3 and
antiviral activities.4 In addition, these compounds have also
been widely used as dyes in laser technology,5 functional
materials for visualization of biomolecular assemblies6 and
photodynamic therapy,7 as well as antagonists for paralyzing
the action of zoxazolamine.8 Given these extensive functions,
much attention has been focused on developing different
methods for the construction of xanthene derivatives in the past
decades, involving the cycloacylation of carbamates,9 trapping
of benzynes by phenols,10 the coupling or condensation
carbon monoxide,13c (4) acetals13d and (5) aldehydes.14 However,
many of these methods suffer from the drawbacks such as the
need of pre-functionalization step, the use of less environ-
mentally friendly reagents, the generation of stoichiometric
amount of undesirable wastes. Although the condensation of b-
naphthols with aldehydes has provided a simple and straight-
forward pathway to the related end.14 However, the use of
aldehydes as reaction reagents could frequently meet the
following problems: (1) the active carbonyl site may easily
undergo an oxidation or decarbonylation step, leading to
formation of undesirable by-products unless the synthetic
operation follows stringent protection under inert gas,15 or
avoids harsh reaction conditions such as high temperature.16 (2)
Some aldehydes are of high cost or not readily available, the
method for variation of xanthene derivatives is hence restricted.
Given these factors, the search for readily available, inexpensive
and stable alternatives of aldehydes would provide new access
to the xanthene derivatives.
Considering alcohols could be desirable aldehyde alterna-
tives in some cases, we wish to develop a new method for
direct synthesis of 14-aryl (alkyl)-14-H-dibenzo[a,j]xanthenes
from alcohols and b-naphthols by employing suitable catalyst
system. In such a transformation, the alcohol coupling part-
ners would exhibit some signicant advantages such as cost-
effectiveness, thermodynamic stability, abundance and
sustainability comparing to aldehydes. Most importantly,
using alcohols to condense with b-naphthols would provide
the potential to prepare the products that are currently inac-
cessible or challenging to prepare using the conventional
methods.
aSchool of Chemical & Material Engineering, Jiangnan University, Wuxi 214122,
People's Republic of China. E-mail: minzhang@scut.edu.cn; Fax: +86-020-39925999;
Tel: +86-138-02538592
bSchool of Chemistry & Chemical Engineering, South China University of Technology,
381 Wushan Rd, Guangzhou 510640, People's Republic of China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4ra00039k
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Results and discussion
With the aforedescribed idea in mind, we initiate our work by
choosing the synthesis of 14-phenyl-14-H-dibenzo[a,j]xanthene
3a from phenylmethanol 1a and b-naphthol 2a as a model
reaction to evaluate different reaction parameters, so that we
could obtain an efficient catalyst system and the optimal
reaction conditions. Firstly, the reaction was performed at
ꢀ
110 C by using para-toluenesulfonic acid (p-TSA) as a catalyst
Scheme 1 Catalysts employed for optimization of reaction conditions.
and toluene as the reaction solvent, but it failed to give even
trace amount of product (Table 1, entry 1). Gratifyingly, a 23%
yield of desired product was formed by introducing 1 mol% of
RuCl3 to the same reaction system (Table 1, entry 2). However,
the reaction resulted in no product detected while RuCl3 was
used as a sole catalyst (Table 1, entry 3). Based on these
results, the formation of product is believed by cooperative
actions of ruthenium-catalysed dehydrogenation of alcohols1
and acid-catalysed condensation of benzaldehyde with
b-naphthol 2a.14
precursors (Scheme 1, Cat 2–Cat 7) with p-TSA (Table 1, entries
4–9). The results showed that the bis(P^O) ruthenium(II)
complex (Scheme 1, Cat 5) gave the best activity in the
formation of 3a upon GC analysis (Table 1, entry 7). By using
Cat 5 as the preferred ruthenium catalyst, various other acidic
catalysts were then tested for model reaction (Table 1, entries
10–13), Yb(OTf)3 gave a highest product yield. Next, we
combined Cat 5 with Yb(OTf)3, several other organic solvents
were further evaluated for the synthesis of 3a. However, the
results indicated that these solvents are less effective than that
of toluene (Table 1, entries 14–16). Finally, the decrease of
reaction temperature or the catalyst loading led to decreased
product yields (Table 1, entries 17, 18 and 21). In contrast, the
increase of these reaction parameters could not afford
improved yields (Table 1, entries 19, 20 and 22). Hence, the
optimized reaction conditions are as follows: 1 mol% of Cat 5,
10 mol% of Yb(OTf)3, toluene as the reaction solvent, and at
Subsequently, we tried to improve the reaction efficiency by
screening the combinations of other six ruthenium catalyst
Table 1 Optimization of reaction conditionsa
ꢀ
110 C (Table 1, entry 13).
Aer optimizing the reaction conditions, we examined the
generality of our synthetic protocol. Various aryl methanols
were rstly reacted with b-naphthols to generate the corre-
sponding 14-aryl-14-H-dibenzo[a,j]xanthenes. As shown in
Table 2, all the reactions proceeded smoothly and gave the
desired products in moderate to excellent yields upon GC
analyses (Table 2, see 3a–3n). It was found that the substit-
uents on the aryl ring of the aldehydes slightly affected the
product yields. Comparing to electron-rich benzylic alcohols
(i.e. –Me) (Table 2, entries 7 and 14), the ones containing an
electron-withdrawing group (such as –Cl, –NO2) furnished the
products in relatively higher yields (Table 2, entries 2–6 and
9–13). On the other hand, the reactions using nitro-
substituted aryl methanols (see 1e and 1f) afforded lower
product yields than that of chloro-substituted aryl methanols
(see 1b–1d), which is attributed to the in situ generated nitro-
benzaldehydes arising from ruthenium-catalysed dehydroge-
nation of nitro-substituted aryl methanols are less stable than
chloro-benzaldehyde intermediates (Table 2, comparing
entries 2–4 with entries 5 and 6, entries 9–11 with entries 12
and 13). Notably, the products possessing halogenated groups
have the potential for further elaboration of complex mole-
cules via the classical coupling reactions. To further expand
the substrate scope, we next tested the utilization of simple,
abundant and readily-available primary alkyl alcohols as the
coupling partners for the synthesis of 14-alkyl-14-H-dibenzo
[a,j]xanthenes. Interestingly, all the reactions underwent
Entry
Ru-cat
Acid-cat
Solvent
3a, yieldb%
1
2
3
4
5
6
7
8
—
p-TSA
p-TSA
—
p-TSA
p-TSA
p-TSA
p-TSA
p-TSA
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Dioxane
DMSO
—
23
—
Cat 1
Cat 1
Cat 2
Cat 3
Cat 4
Cat 5
Cat 6
Cat 7
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
Cat 5
26
<5
35
56
50
33
<5
<5
32
83
21
<10
<10
70
76
79
83
72
82
9
p-TSA
NH2SO3H
FeCl3
10
11
12
13
14
15
16
17c
18d
19e
20f
21g
22h
AgOTf
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
Yb(OTf)3
DMF
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
a
Reaction conditions: unless otherwise specied, all reactions were
carried out without inert gas protection by using 1a (1.5 mmol), 2a
(1 mmol), catalyst (1 mol%), solvent (1 mL), temperature (110 ꢀC),
b
acid (10 mol%), reaction time (16 h). GC yield using hexadecane as
c
d
an internal standard. Reaction temperature (100 ꢀC). Loading of
e
f
Cat 5 (0.8 mol%). Reaction temperature (120 ꢀC). Loading of Cat
g
h
5 (1.5 mol%). Acid catalyst loading (5 mol%). Acid catalyst loading
(15 mol%).
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Table 2 Efficient synthesis of 14-substituted-14-H-dibenzo[a,j]xanthenes from b-naphthol and alcoholsa
Entry
1
Alcohol 1
b-Naphthol 2
2a: R2 ¼ H
Product 3
Yieldb (%)
1a: R1 ¼ Ph
3a, 83
2
1b: R1 ¼ 4-Cl–C6H4
2a
3b, 85
3
4
1c: R1 ¼ 3-Cl–C6H4
1d: R1 ¼ 2-Cl–C6H4
2a
2a
3c, 80
3d, 78
5
6
7
8
1e: R1 ¼ 4-NO2–C6H4
1f: R1 ¼ 3-NO2–C6H4
1g: R1 ¼ 4-CH3–C6H4
1a
2a
3e, 71
3f, 74
3g, 66
3h, 77
2a
2a
2b: R2 ¼ 6-Br
9
1b
2b
3i, 78
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Table 2 (Contd.)
Entry
10
Alcohol 1
b-Naphthol 2
Product 3
Yieldb (%)
1c
2b
3j, 72
11
12
13
14
15
16
1d
1e
1f
2b
2b
2b
2b
2a
2a
3k, 70
3l, 65
3m, 68
3n, 60
3o, 58
3p, 62
1g
17
18
2a
2a
3q, 60
3r, 63
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Table 2 (Contd.)
Entry
19
Alcohol 1
b-Naphthol 2
Product 3
Yieldb (%)
2a
3s, 61
20
21
1h
1i
2b
2b
3t, 57
3u, 59
22
1j
2b
3v, 56
a
Reaction conditions: unless otherwise specied, all reactions were performed without inert gas protection by using 1 (1.5 mmol), 2 (1 mmol), Cat 5
(1 mol%), Yb(OTf)3 (10 mol%), toluene (1 mL), temperature (110 ꢀC), reaction time (16 h). b GC yield using hexadecane as an internal standard.
efficiently to furnish the expected products in moderate to group generates a polycyclic intermediate F. Finally, thermo-
good yields upon GC analyses (Table 2, entries 15–22). Given dynamic favourable dehydration of F releases the desired
these ndings, our synthetic protocol is suitable for the product 3.
application of both aryl methanols and alkyl primary
alcohols.
On the basis of the above-described experimental facts as
well as the acid-catalysed condensation of aryl aldehydes with
b-naphthols,14 a plausible reaction is depicted in Scheme 2.
The reaction initiates with the dehydrogenation of alcohols
catalyzed by ruthenium catalyst. The in situ formed aldehyde
A is activated by Lewis acid Yb(OTf)3, then followed by a
nucleophilic attack of the a-carbon in the b-naphthol to form
intermediate B. 1,3-Hydrogen shi of B would afford C.
Enone D is then produced via elimination of one molecule of
water from C, which is activated by Yb(OTf)3 and acts as a
Michael acceptor. Aerwards, the Michael addition of another
molecule of b-naphthols to the carbon–carbon double bond
of D would afford intermediate E. The subsequent nucleo-
philic addition of hydroxyl group to the activated carbonyl Scheme 2 Plausible mechanism for the formation of product 3.
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Analytic data of obtained compounds
Conclusions
14-Phenyl-14-H-dibenzo[a,j]xanthene (3a). White solid, mp:
191–192 ꢀC (lit.14f 185 ꢀC); 1H NMR (400 MHz, CDCl3): d 8.38 (d,
J ¼ 8.5 Hz, 2H), 7.80 (dd, J ¼ 14.3, 8.5 Hz, 4H), 7.62–7.42 (m, 6H),
7.39 (t, J ¼ 7.4 Hz, 2H), 7.13 (t, J ¼ 7.7 Hz, 2H), 6.97 (t, J ¼ 7.4 Hz,
1H), 6.48 (s, 1H); 13C NMR (101 MHz, CDCl3): d 148.76, 145.01,
131.48, 131.08, 128.86, 128.80, 128.48, 128.27, 126.79, 126.39,
124.24, 122.70, 118.02, 117.35, 38.05; IR (KBr): 3075, 1592, 1458,
In summary, we have presented a new and straightforward
[P^O]2Cl2Ru/Yb(OTf)3-cocatalyzed synthesis of 14-aryl- and
14-alkyl-14-H-dibenzo[a,j]xanthenes by using stable, abundant,
readily-available and sustainable alcohols as the reaction part-
ners. All the dehydrogenative cyclization process underwent
efficiently to furnish the desired products in moderate to
excellent isolated yields. The method is adaptable to a broad
substrate scope, and has the potential to prepare the
compounds that are currently inaccessible or challenging to
prepare using the conventional methods. In addition, the whole
work-up procedure is operationally simple and there is no need
for special protection. Hence, we believe this new synthetic
protocol is of high importance that complements the existing
synthetic methodologies. Given the importance of 14-aryl- and
14-alkyl-14-H-dibenzo[a,j]xanthenes in various elds, our pre-
sented method has the potential to be frequently used for many
synthetic purposes.
1243, 964, 827, 803, 745, 701 cmꢁ1
.
14-(4-Chlorophenyl)-14-H-dibenzo[a,j]xanthenes (3b). Light
yellow solid, mp: 296 ꢀC (lit.14f 289 ꢀC); 1H NMR (400 MHz,
CDCl3): d 8.31 (d, J ¼ 8.5 Hz, 2H), 7.81 (dd, J ¼ 14.3, 8.5 Hz, 4H),
7.57 (t, J ¼ 7.7 Hz, 2H), 7.52–7.35 (m, 6H), 7.09 (d, J ¼ 8.4 Hz,
2H), 6.46 (s, 1H); 13C NMR (101 MHz, CDCl3): d 148.72, 143.47,
132.10, 131.27, 131.07, 129.49, 129.09, 128.92, 128.64, 126.91,
124.37, 122.41, 118.01, 116.77, 37.38; IR (KBr): 3069, 1592, 1475,
1240, 1103, 832, 807, 741 cmꢁ1
14-(3-Chlorophenyl)-14-H-dibenzo[a,j]xanthenes (3c). White
.
1
solid, mp: 204–205 C (lit.14n 210–211 C); H NMR (400 MHz,
CDCl3): d 8.30 (d, J ¼ 8.5 Hz, 2H), 7.79 (dd, J ¼ 13.9, 8.5 Hz, 4H),
7.57 (t, J ¼ 7.7 Hz, 2H), 7.51–7.35 (m, 6H), 7.05 (t, J ¼ 8.1 Hz, 1H),
6.94 (d, J ¼ 8.0 Hz, 1H), 6.43 (s, 1H); 13C NMR (101 MHz, CDCl3):
d 148.79, 146.89, 134.42, 131.28, 131.07, 129.60, 129.16, 128.90,
128.34, 126.96, 126.75, 126.40, 124.38, 122.40, 118.07, 116.58,
ꢀ
ꢀ
Experimental
General information
All the obtained products were characterized by melting points
(mp), 1H-NMR, 13C-NMR infrared spectra (IR), the 1H-NMR
spectra of the known compounds were found to be identical
with the ones reported in the literatures. Additionally, the new
products were further determined by high resolution mass
spectra (HR-MS). Melting points were measured on an Electro-
themal SGW-X4 microscopy digital melting point apparatus and
are uncorrected; IR spectra were recorded on a FTLA2000
37.75; IR (KBr): 3067, 1591, 1456, 1246, 1082, 964, 813, 746 cmꢁ1
.
14-(2-Chlorophenyl)-14-H-dibenzo[a,j]xanthenes (3d). White
solid, mp: 201–202 ꢀC (lit.14f 215 ꢀC); 1H NMR (400 MHz, CDCl3):
d 8.72 (d, J ¼ 8.5 Hz, 2H), 7.83–7.73 (m, 4H), 7.59 (t, J ¼ 7.1 Hz,
2H), 7.49–7.34 (m, 5H), 7.25–7.21 (m, 1H), 6.88 (pd, J ¼ 7.2, 1.8
Hz, 2H), 6.78 (s, 1H); 13C NMR (101 MHz, CDCl3): d 148.99,
143.60, 131.80, 131.79, 130.93, 129.61, 129.06, 128.64, 127.93,
127.85, 126.91, 124.42, 123.46, 118.09, 118.03, 34.69; IR (KBr):
1
spectrometer; H-NMR and 13C-NMR spectra were obtained on
3056, 1593, 1472, 1108, 827, 811, 749 cmꢁ1
.
Bruker-400. Chemical shis were reported in parts per million
(ppm, d) downeld from tetramethylsilane. Proton coupling
patterns are described as singlet (s), doublet (d), triplet (t),
multiplet (m); high-resolution mass spectra (HRMS) were
recorded on a JEOL JMS-600 spectrometer. TLC was performed
using commercially prepared 100–400 mesh silica gel plates
(GF254), and visualization was effected at 254 nm; all the
reagents were purchased from commercial sources (J&KChe-
mic, TCI, Fluka, Acros, SCRC), and used without further
purication.
14-(4-Nitrophenyl)-14-H-dibenzo[a,j]xanthenes (3e). Light
yellow solid, mp: 327–329 ꢀC (lit.14f 310 ꢀC); 1H NMR (400 MHz,
CDCl3): d 8.27 (d, J ¼ 8.5 Hz, 2H), 7.99 (d, J ¼ 8.7 Hz, 2H), 7.84 (t,
J ¼ 7.6 Hz, 4H), 7.73–7.55 (m, 4H), 7.54–7.33 (m, 4H), 6.59 (s,
1H); 13C NMR (101 MHz, CDCl3): d 152.00, 148.80, 146.33,
131.09, 129.59, 129.06, 128.96, 127.19, 124.58, 123.86, 122.04,
118.06, 115.78, 37.86; IR (KBr): 3071, 1592, 1515, 1340, 1239,
1107, 827, 808, 750 cmꢁ1
.
14-(3-Nitrophenyl)-14-H-dibenzo[a,j]xanthenes (3f). Light
yellow solid, mp: 223–225 ꢀC (lit.14f 211 ꢀC); 1H NMR (400 MHz,
CDCl3): d 8.32 (t, J ¼ 1.8 Hz, 1H), 8.21 (d, J ¼ 8.5 Hz, 2H), 7.73 (q,
J ¼ 8.1 Hz, 6H), 7.56–7.48 (m, 2H), 7.41 (d, J ¼ 8.9 Hz, 2H), 7.34
(t, J ¼ 7.2 Hz, 2H), 7.17 (d, J ¼ 8.3 Hz, 1H), 6.50 (s, 1H); 13C NMR
(101 MHz, CDCl3): d 148.84, 148.26, 146.93, 134.22, 131.07,
131.04, 129.56, 129.49, 129.06, 127.24, 124.57, 122.71, 122.02,
121.68, 118.12, 115.90, 37.72; IR (KBr): 3080, 1621, 1593, 1458,
Typical procedure for the synthesis of 3a
In a schlenk tube equipped with a magnetic stirrer bar, benzyl
alcohol 1a (1.5 mmol, 162.2 mg), b-naphthol 2a (1 mmol, 144.2
mg), [P^O]2Cl2Ru (Cat 5, 0.005 mmol, 3.8 mg) and Yb(OTf)3
(0.05 mmol, 31.0 mg) and toluene (1 mL) were inꢀtroduced
successively. The resulting mixture was stirred at 110 C for 16
h without insert any gas protection. Aer cooling down to
room temperature, the reaction solvent was removed under
vacuum, the residue was directly puried by ash chroma-
tography on silica gel eluting with petroleum ether : ethyl
acetate (30 : 1) to give 14-phenyl-14-H-dibenzo[a,j]xanthene 3a
as a white solid.
1097, 825, 808, 723 cmꢁ1
.
14-(4-Tolyl)-14-H-dibenzo[a,j]xanthenes (3g). Yellow solid,
mp: 228–229 ꢀC (lit.14f 229 ꢀC); 1H NMR (400 MHz, CDCl3): d 8.38
(d, J ¼ 8.5 Hz, 2H), 7.79 (dd, J ¼ 15.9, 8.5 Hz, 4H), 7.56 (t, J ¼ 7.7
Hz, 2H), 7.53–7.32 (m, 6H), 6.94 (d, J ¼ 7.6 Hz, 2H), 6.45 (s, 1H),
2.12 (s, 3H); 13C NMR (101 MHz, CDCl3): d 148.70, 142.12,
135.89, 131.46, 131.09, 129.17, 128.78, 128.74, 128.09, 126.75,
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124.20, 122.71, 118.00, 117.46, 37.62, 20.88; IR (KBr): 3071,
3,11-Dibromo-14-(p-tolyl)-14-H-dibenzo[a,j]xanthene (3n). White
solid, mp: 249–251 ꢀC; 1H NMR (400 MHz, CDCl3): d 8.17 (t, J ¼ 7.5
Hz, 2H), 7.93 (d, J ¼ 2.0 Hz, 2H), 7.67–7.57 (m, 4H), 7.48–7.40 (m,
2H), 7.30 (d, J ¼ 8.1 Hz, 2H), 6.94 (d, J ¼ 7.9 Hz, 2H), 6.26 (s, 1H),
2.12 (s, 3H); 13C NMR (101 MHz, CDCl3): d 148.57, 141.52, 136.35,
132.29, 130.72, 130.04, 129.90, 129.34, 127.97, 127.92, 124.43,
119.11, 118.21, 117.29, 37.70, 20.87; IR (KBr): 3058, 2919, 1584,
1500, 1337, 1249, 1108, 962, 875, 803 cmꢁ1; HRMS calcd for
C28H18Br2O: 527.97, found: 527.9724.
2917, 1621, 1591. 1458, 1248, 1107, 961, 808, 739 cmꢁ1
.
3,11-Dibromo-14-phenyl-14-H-dibenzo[a,j]xanthene (3h). White
solid, mp: 249–251 ꢀC; 1H NMR (400 MHz, CDCl3): d 8.23 (d, J ¼ 9.0
Hz, 2H), 7.98 (d, J¼ 1.7 Hz, 2H), 7.79–7.57 (m, 4H), 7.48 (dd, J¼ 13.1,
8.2 Hz, 4H), 7.17 (t, J ¼ 7.7 Hz, 2H), 7.04 (t, J ¼ 7.4 Hz, 1H), 6.35 (s,
1H); 13C NMR (101 MHz, CDCl3): d 148.66, 144.39, 132.28, 130.74,
130.09, 129.91, 128.64, 128.06, 126.72, 124.40, 119.12, 118.25,
117.19, 38.11; IR (KBr): 3060, 1583, 1500, 1451, 1247, 1107, 961, 892,
796 cmꢁ1; HRMS calcd for C27H16Br2O: 513.96, found: 513.9568.
3,11-Dibromo-14-(4-chlorophenyl)-14-H-dibenzo[a,j]xanthene
(3i). White solid, mp: 295–297 ꢀC; 1H NMR (400 MHz, CDCl3): d
8.14 (d, J ¼ 9.0 Hz, 2H), 7.98 (d, J ¼ 1.9 Hz, 2H), 7.74–7.59 (m,
4H), 7.47 (d, J ¼ 8.9 Hz, 2H), 7.36 (d, J ¼ 8.5 Hz, 2H), 7.11 (d, J ¼
8.5 Hz, 2H), 6.33 (s, 1H); 13C NMR (101 MHz, CDCl3): d 148.66,
142.80, 132.53, 132.29, 130.89, 130.24, 129.73, 129.28, 128.84,
128.32, 124.11, 119.15, 118.39, 116.67, 37.44; IR (KBr): 3075,
1584, 1455, 1253, 1105, 964, 838, 800 cmꢁ1; HRMS calcd for
C27H15Br2ClO: 547.92, found: 547.9176.
14-Benzyl-14-H-dibenzo[a,j]xanthene (3o). White solid, mp:
171–174 ꢀC (lit.14o 178 ꢀC); 1H NMR (400 MHz, CDCl3): d 8.14 (d,
J ¼ 8.5 Hz, 2H), 7.80 (d, J ¼ 8.1 Hz, 2H), 7.65 (d, J ¼ 8.9 Hz, 2H),
7.52 (t, J ¼ 7.6 Hz, 2H), 7.38 (t, J ¼ 7.5 Hz, 2H), 7.08 (d, J ¼ 8.8 Hz,
2H), 6.93 (t, J ¼ 7.3 Hz, 1H), 6.75 (t, J ¼ 7.5 Hz, 2H), 6.02 (d, J ¼
7.5 Hz, 2H), 5.70 (t, J ¼ 4.5 Hz, 1H), 3.19 (d, J ¼ 4.6 Hz, 2H); 13
C
NMR (101 MHz, CDCl3): d 150.15, 137.58, 131.34, 130.87,
129.77, 128.89, 128.35, 127.21, 126.69, 126.08, 124.04, 122.20,
117.42, 115.33, 41.39, 33.07; IR (KBr): 3064, 2926, 1620, 1591,
1456, 1435, 1244, 1103, 968, 816, 739 cmꢁ1
.
3,11-Dibromo-14-(3-chlorophenyl)-14-H-dibenzo[a,j]xanthene
(3j). White solid, mp: 263–264 ꢀC; 1H NMR (400 MHz, CDCl3): d
8.13 (d, J ¼ 9.0 Hz, 2H), 7.96 (d, J ¼ 2.0 Hz, 2H), 7.74–7.57 (m, 4H),
7.47 (d, J ¼ 8.9 Hz, 2H), 7.35(dd, J ¼ 8.8, 4.8 Hz, 2H), 7.09 (t, J ¼ 7.8
Hz, 1H), 7.03–6.94 (m, 1H), 6.30 (s, 1H); 13C NMR (101 MHz,
CDCl3): d 148.69, 146.27, 134.68, 132.27, 130.87, 130.26, 129.77,
129.71, 128.38, 128.16, 127.10, 126.17, 124.08, 119.19, 118.40,
116.44, 37.77; IR(KBr):3071, 1585, 1454, 1250, 1107, 961, 872, 805
cmꢁ1; HRMS calcd for C27H15Br2ClO: 547.92, found: 547.9178.
3,11-Dibromo-14-(2-chlorophenyl)-14-H-dibenzo[a,j]xanthene
(3k). White solid, mp: 217–219 ꢀC; 1H NMR (400 MHz, CDCl3) d
8.47 (d, J ¼ 9.1 Hz, 2H), 7.90 (d, J ¼ 2.0 Hz, 2H), 7.65–7.59 (m,
4H), 7.41 (d, J ¼ 8.9 Hz, 2H), 7.22 (d, J ¼ 4.3 Hz, 2H), 6.93–6.85
(m, 2H), 6.53 (s, 1H); 13C NMR (101 MHz, CDCl3): d 148.79,
142.94, 132.10, 131.63, 130.57, 130.21, 130.19, 129.89, 129.70,
128.23, 128.18, 128.10, 125.21, 119.15, 118.52, 117.76, 34.56; IR
(KBr): 3060, 1631, 1588, 1458, 1259, 1105, 964, 881, 837, 738
cmꢁ1; HRMS calcd for C27H15Br2ClO: 547.92, found: 547.9176.
3,11-Dibromo-14-(4-nitrophenyl)-14-H-dibenzo[a,j]xanthene
(3l). Yellow solid, mp: 303–305 ꢀC; 1H NMR (400 MHz, DMSO): d
8.66 (d, J ¼ 9.1 Hz, 2H), 8.25 (d, J ¼ 1.8 Hz, 2H), 8.00 (dd, J ¼
19.3, 8.9 Hz, 4H), 7.88 (d, J ¼ 8.8 Hz, 2H), 7.77 (dd, J ¼ 9.0, 1.9
Hz, 2H), 7.65 (d, J ¼ 9.0 Hz, 2H), 6.94 (s, 1H); 13C NMR (101
MHz, DMSO): d 152.07, 148.20, 145.94, 132.02, 130.49, 129.94,
129.36, 128.94, 128.89, 125.56, 123.79, 119.00, 117.97, 116.34,
36.03; IR (KBr): 3075, 1585, 1515, 1397, 1253, 1108, 957, 834, 797
cmꢁ1; HRMS calcd for C27H15Br2NO3: 558.94, found: 558.9418.
3,11-Dibromo-14-(3-nitrophenyl)-14-H-dibenzo[a,j]xanthene
14-(4-Chlorobenzyl)-14-H-dibenzo[a,j]xanthene (3p). White
solid, mp: 185–187 ꢀC; 1H NMR (400 MHz, CDCl3): d 8.16 (d, J ¼
8.5 Hz, 2H), 7.81 (d, J ¼ 8.0 Hz, 2H), 7.67 (d, J ¼ 8.9 Hz, 2H), 7.55
(t, J ¼ 7.2 Hz, 2H), 7.40 (t, J ¼ 7.2 Hz, 2H), 7.07 (d, J ¼ 8.9 Hz,
2H), 6.71 (d, J ¼ 8.3 Hz, 2H), 5.87 (d, J ¼ 8.3 Hz, 2H), 5.72 (t, J ¼
4.4 Hz, 1H), 3.17 (d, J ¼ 4.5 Hz, 2H); 13C NMR (101 MHz, CDCl3):
d 150.09, 135.92, 132.06, 131.17, 131.01, 130.88, 128.99, 128.51,
127.25, 126.83, 124.14, 122.05, 117.45, 114.64, 40.33, 32.82; IR
(KBr): 3062, 2922, 1619, 1591, 1458, 1433, 1242, 1102, 968, 806,
740 cmꢁ1; HRMS calcd for C28H19ClO: 406.11, found: 406.1122.
14-Propyl-14-H-dibenzo[a,j]xanthene (3q). White solid, mp:
155–157 ꢀC (lit.14j 152–154 ꢀC); 1H NMR (400 MHz, CDCl3): d 8.16
(d, J ¼ 8.5 Hz, 2H), 7.78 (d, J ¼ 8.1 Hz, 2H), 7.67 (d, J ¼ 8.9 Hz,
2H), 7.52 (ddd, J ¼ 8.3, 6.9, 1.2 Hz, 2H), 7.43–7.22 (m, 4H), 5.46
(t, J ¼ 4.6 Hz, 1H), 1.92 (dt, J ¼ 12.7, 4.6 Hz, 2H), 1.03–0.83 (m,
2H), 0.51 (t, J ¼ 7.3 Hz, 3H); 13C NMR (101 MHz, CDCl3): d
150.01, 131.49, 131.06, 128.86, 128.16, 126.58, 124.08, 122.48,
117.58, 116.78, 38.27, 31.08, 18.17, 14.10; IR (KBr): 3060, 2953,
1590, 1453, 1398, 1241, 1105, 814, 747 cmꢁ1
.
14-Butyl-14-H-dibenzo[a,j]xanthene (3r). White solid, mp:
1
ꢀ
110–112 C; H NMR (400 MHz, CDCl3): d 8.22 (d, J ¼ 8.5 Hz,
2H), 7.84 (d, J ¼ 8.1 Hz, 2H), 7.73 (d, J ¼ 8.9 Hz, 2H), 7.62–7.54
(m, 2H), 7.45–7.32 (m, 4H), 5.53 (t, J ¼ 4.6 Hz, 1H), 2.02 (dt, J ¼
7.9, 4.7 Hz, 2H), 1.01–0.89 (m, 4H), 0.57 (t, J ¼ 6.8 Hz, 3H); 13
C
NMR (101 MHz, CDCl3): d 150.04, 131.51, 131.07, 128.87, 128.18,
126.60, 124.10, 122.50, 117.62, 116.76, 35.81, 31.03, 26.98, 22.86,
13.91; IR (KBr): 3069, 2929, 1592, 1458, 1397, 1239, 1101, 857,
811 cmꢁ1; HRMS calcd for C25H22O: 338.17, found: 338.1670.
1
ꢀ
(3m). Light yellow solid, mp: 159–161 C; H NMR (400 MHz,
CDCl3): d 8.34 (s, 1H), 8.16 (d, J ¼ 9.0 Hz, 2H), 8.02 (d, J ¼ 1.8 Hz,
2H), 7.92 (d, J ¼ 8.1 Hz, 1H), 7.80–7.75 (m, 3H), 7.70 (dd, J ¼ 9.0,
1.9 Hz, 2H), 7.54 (d, J ¼ 8.9 Hz, 2H), 7.35 (t, J ¼ 8.0 Hz, 1H), 6.51
(s, 1H); 13C NMR (101 MHz, CDCl3): d 148.80, 148.38, 146.32,
133.90, 132.29, 131.06, 130.56, 129.69, 129.51, 128.79, 123.69,
122.54, 122.00, 119.26, 118.60, 115.83, 37.73; IR (KBr): 3065,
1614, 1586, 1396, 1258, 1112, 960, 890, 815 cmꢁ1; HRMS calcd
for C27H15Br2NO3: 558.94, found: 558.9419.
14-Pentyl-14-H-dibenzo[a,j]xanthene (3s). Light yellow solid,
1
mp: 104–106 ꢀC (lit.14p 98–99 C); H NMR (400 MHz, CDCl3): d
ꢀ
8.29 (d, J ¼ 8.5 Hz, 2H), 7.91 (d, J ¼ 8.1 Hz, 2H), 7.80 (d, J ¼ 8.9
Hz, 2H), 7.69–7.60 (m, 2H), 7.55–7.46 (m, 2H), 7.41 (d, J ¼ 8.9 Hz,
2H), 5.59 (t, J ¼ 4.6 Hz, 1H), 2.13–2.00 (m, 2H), 1.02 (dd, J ¼ 15.4,
5.4 Hz, 6H), 0.65 (t, J ¼ 6.7 Hz, 3H); 13C NMR (101 MHz, CDCl3):
d 150.01, 131.49, 131.04, 128.83, 128.14, 126.55, 124.06, 122.46,
117.59, 116.77, 35.96, 31.93, 31.03, 24.52, 22.44, 13.89; IR (KBr):
3067, 2930, 1591, 1458, 1433, 1237, 1105, 857, 809 cmꢁ1
.
14750 | RSC Adv., 2014, 4, 14744–14751
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3,11-Dibromo-14-propyl-14-H-dibenzo[a,j]xanthene(3t). Light
RSC Advances
4 R. W. Lambert, J. A. Martin, J. H. Merrett, K. E. B. Parkerand,
G. J. Thomas, PCT Int. Appl., WO9706178, 1997.
yellow solid, mp: 153–156 ꢀC; 1H NMR (400 MHz, CDCl3): d 8.06
(dd, J ¼ 22.2, 5.4 Hz, 4H), 7.74–7.65 (m, 4H), 7.38 (d, J ¼ 8.9 Hz,
2H), 5.41 (t, J ¼ 4.5 Hz, 1H), 1.95 (dt, J ¼ 12.6, 4.6 Hz, 2H), 0.97
(dt, J ¼ 19.4, 7.4 Hz, 2H), 0.68–0.56 (m, 3H); 13C NMR (101 MHz,
CDCl3): d 149.97, 132.25, 130.82, 129.91, 129.89, 127.39, 124.18,
118.66, 118.04, 116.71, 38.35, 31.09, 18.11, 14.02; IR (KBr): 3066,
2947, 1586, 1453, 1396, 1258, 1113, 960, 890, 816 cmꢁ1; HRMS
calcd for C24H18Br2O: 479.97, found: 479.9720.
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3,11-Dibromo-14-butyl-14-H-dibenzo[a,j]xanthene (3u). Light
yellow solid, mp: 139–141 ꢀC; 1H NMR (400 MHz, CDCl3): d 8.06
(dd, J ¼ 21.5, 5.5 Hz, 4H), 7.73–7.64 (m, 4H), 7.39 (d, J ¼ 8.9 Hz,
2H), 5.45–5.32 (m, 1H), 1.98 (dd, J ¼ 16.3, 4.7 Hz, 2H), 0.98 (ddd,
J ¼ 17.8, 14.3, 7.3 Hz, 4H), 0.62 (t, J ¼ 7.1 Hz, 3H); 13C NMR (101
MHz, CDCl3): d 150.00, 132.25, 130.82, 129.90, 127.39, 124.17
(s), 118.69, 118.03, 116.71, 35.87, 31.03, 26.86, 22.72, 13.82; IR
(KBr): 3066, 2925, 1585, 1453, 1395, 1255, 1106, 963, 884, 812
cmꢁ1; HRMS calcd for C25H20Br2O: 493.99, found: 493.9881.
3,11-Dibromo-14-pentyl-14-H-dibenzo[a,j]xanthene (3v). Light
yellow liquid; 1H NMR (400 MHz, CDCl3): d 7.93 (dd, J ¼ 19.3, 5.4
Hz, 4H), 7.59–7.52 (m, 4H), 7.25 (d, J ¼ 8.9 Hz, 2H), 5.27 (t, J ¼ 4.5
Hz, 1H), 1.84 (dd, J ¼ 11.5, 7.7 Hz, 2H), 0.90–0.80 (m, 6H), 0.52 (t,
J ¼ 6.9 Hz, 3H); 13C NMR (101 MHz, CDCl3): d 149.97, 132.24,
130.81, 129.88, 127.38, 124.17, 118.67, 118.03, 116.68, 36.02,
31.80, 31.04, 24.42, 22.38, 13.86; IR (KBr): 3066, 2929, 1585, 1396,
1253, 1106, 955, 878, 806 cmꢁ1; HRMS calcd for C26H22Br2O:
508.00, found: 508.0036.
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The authors are grateful to the funds of the National Natural
Science Foundation of China (21101080), Natural Science Foun-
dation of Jiangsu Province (BK2011144), and Fundamental
Research Funds for the Central Universities of China (2014ZZ0047).
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