Molecular iodine-catalyzed one-pot synthesis of tetrahydrobenzo[a]xanthene- 11-one and diazabenzo[a]anthracene-9,11-dione derivatives

Article abstract of DOI:10.1080/00397911.2010.541966

An efficient one-pot condensation of β-naphthol, aldehydes, and cyclic 1,3-dicarbonyl compounds has been achieved with molecular iodine as a catalyst, thus a variety of tetrahydrobenzo[a]xanthene-11-one and diazabenzo[a] anthracene-9,11-dione derivatives

Full text of DOI:10.1080/00397911.2010.541966

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Molecular Iodine–Catalyzed
One-Pot Synthesis of
Tetrahydrobenzo[a]xanthene-11-one and
Diazabenzo[a]anthracene-9,11-dione
Derivatives
Xiao-Jun Sun a , Jian-Feng Zhou a & Pu-Su Zhao a
a School of Chemistry and Chemical Engineering, Huaiyin Normal
University, Huaian, China
Accepted author version posted online: 17 Nov 2011.Version of
record first published: 25 Jan 2012.
To cite this article: Xiao-Jun Sun, Jian-Feng Zhou & Pu-Su Zhao (2012): Molecular Iodine–Catalyzed
One-Pot Synthesis of Tetrahydrobenzo[a]xanthene-11-one and Diazabenzo[a]anthracene-9,11-
dione Derivatives, Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 42:10, 1542-1549
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Synthetic Communications1, 42: 1542–1549, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.541966
MOLECULAR IODINE–CATALYZED ONE-POT
SYNTHESIS OF TETRAHYDROBENZO[a]XANTHENE-
11-ONE AND DIAZABENZO[a]ANTHRACENE-
9,11-DIONE DERIVATIVES
Xiao-Jun Sun, Jian-Feng Zhou, and Pu-Su Zhao
School of Chemistry and Chemical Engineering, Huaiyin Normal University,
Huaian, China
GRAPHICAL ABSTRACT
Abstract An efficient one-pot condensation of b-naphthol, aldehydes, and cyclic 1,3-dicar-
bonyl compounds has been achieved with molecular iodine as a catalyst, thus a variety of
tetrahydrobenzo[a]xanthene-11-one and diazabenzo[a]anthracene-9,11-dione derivatives
were prepared in good yields.
Keywords Cyclic 1,3-dicarbonyl compounds; molecular iodine; b-naphthol; one-pot
synthesis
INTRODUCTION
Xanthenes and benzoxanthenes have attracted considerable interest because
they possess various biological activities such as antibacterial,[1] anti-inflammatory,[2]
and antiviral[3] activities. These structural motifs have also found a niche as antago-
nists for paralyzing the action of zoxazolamine[4] and demonstrate efficacy in photo-
dynamic therapy.[5] In addition, these compounds have been employed as dyes[6] and
pH-sensitive fluorescent materials for visualization of biomolecular assemblies[7] and
utilized in laser technologies.[8] Thus, a broad utility range has made xanthenes prime
Received August 21, 2010.
Address correspondence to Xiao-Jun Sun, School of Chemistry and Chemical Engineering,
Huaiyin Normal University, Huaian 223300, China. E-mail: sunxiaojun100@126.com
1542

MOLECULAR IODINE–CATALYZED ONE-POT SYNTHESIS
1543
Scheme 1. I2-catalyzed condensation of aldehydes, b-naphthol, and cyclic 1,3-dicarbonyl compounds.
synthetic candidates, thereby accentuating the need to develop newer synthetic
routes for scaffold manipulation of xanthene derivatives. The synthesis of
tetrahydrobenzo[a]xanthen-11-ones has been reported in the presence of strontium
triflate[9] and NaHSO4-SiO2 under reflux in halogenated solvents for long times,[10]
with a catalyst of para-tolunesulfonic acid (p-TSA) in ionic liquid ([bmim]BF4),
and in solvent-free media.[11] They also had been catalyzed by InCl3 or P2O5 under
solvent-free conditions.[12] These synthetic methods afforded good yields but
have limitations of long reaction time, harsh reaction conditions, and expensive
catalysts.
Recently, molecular iodine[13] has received considerable attention as an inex-
pensive, nontoxic, readily available catalyst for various organic transformations to
afford the corresponding products in excellent yields. In this article, we report an
efficient one-pot method for the three-component condensation of b-naphthol,
benzaldehyde, and cyclic-1,3-dicarbonyl compound to synthesis tetrahydro-
benzo[a]xanthene-11-one and diazabenzo[a]anthracene-9,11-dione derivatives using
molecular iodine as the catalyst in acetic acid at reflux (Scheme 1).
RESULTS AND DISCUSSION
The reaction of benzaldehyde 1a, b-naphthol 2, and 5,5-dimethylcyclohexane-
1,3-dione 3 catalyzed by iodine in acetic acid at reflux has been considered as a stan-
dard model reaction.
We studied the catalyst loading on the model reaction. We varied the amount
of catalyst: 5, 10, 15, 20, and 25 mol%. The results revealed that when the reaction
was carried out in the presence of 5, 10, and 15 mol% of catalyst, it gave lower yield
of product even after prolonged reaction time. At the same time, when the amount of
catalyst was 20 mol%, we got excellent yields of product in a short span. Even after
increasing the catalyst loading to 25 mol%, the yields of the products were constant.
So, the use of 20 mol% of catalyst appears to be optimal. The results obtained are
summarized in Table 1.
To study the generality of this procedure, a series of aldehydes and
5,5-dimethylcyclohexane-1,3-dione were applied. The results are shown in Table 2.
Various aromatic aldehydes containing electron-withdrawing and electron-donating

1544
X.-J. SUN, J.-F. ZHOU, AND P.-S. ZHAO
Table 1. Effect of catalyst concentration on model reactiona
Entry
Catalyst (mol%)
Time (h)
Yieldb (%)
1
2
3
4
5
5
10
15
20
25
2.5
2.5
2.5
2.5
2.5
30
49
66
87
87
aReaction of benzaldehyde, b-naphthol, and 5,5-dimethylcyclohexane-1,3-dione in
the presence of iodine in acetic acid at reflux.
bIsolated yield.
substituent at ortho, meta, or para positions show equal ease in forming the product
in good to excellent yields.
With the successful condensation of aromatic aldehydes, b-naphthol, and
5,5-dimethylcyclohexane-1,3-dione 3, we further studied the reaction of aromatic
aldehydes, b-naphthol, and 1,3-dimethylbarbituric acid under similar conditions. It
was found that the corresponding tetrahydrobenzo[a]xanthen-11-one 5 and
diazabenzo[a]anthracene-9,11-diones 6 could also be obtained in good yields
(Table 2).
To further confirm the structures of the products, we also present the crystal
structure of 5a (Fig. 1). X-ray analysis of 5a: Empirical formula C25H22O2, F.W.
˚
354.43, T ¼ 296(2) K, monoclinic, space group P21=n, a ¼ 6.2308(11) A,
3
b ¼ 18.099(3) A, c ¼ 17.063(3) A, b ¼ 93.566(2)ꢀ, V ¼ 1920.4(6) A , Z ¼ 4,
˚
˚
˚
˚
Dc ¼ 1.226
gcmꢁ3
,
F(000) ¼ 752,
k(Mo=Ka) ¼ 0.71073 A,
m ¼ 0.76 cmꢁ1
,
4 < 2h < 52ꢀ, R ¼ 0.0457, Rw ¼ 0.1052
Table 2. I2-catalyzed condensation of aldehydes, b-naphthol, and cyclic 1,3-dicarbonyl compounds to
give 5 and 6 in acetic acid at reflux
Entry
R1
Time (h)
Yielda (%)
Mp (observed=reported[ref]) (ꢀC)
5a
5b
5c
5d
5e
5f
C6H5
4-MeC6H4
4-OMeC6H4
2-ClC6H4
2.5
2.5
2.5
3
87
88
77
89
87
85
70
76
89
70
74
70
68
66
73
152–154=151–153[12]
173–175=176–178[12]
201–203=204–205[12]
173–174=179–180[12]
177–179=180–182[12]
179–181=178–180[12]
221–223=223–225[12]
230–232=not rep.
4-ClC6H4
2.5
2.5
3
4-NO2C6H4
4-OHC6H4
2-FC6H4
5g
5h
5i
2.5
2.5
3
3,4-(OCH2O)C6H3
C6H5
203–205=not rep.
6a
6b
6c
6d
6e
6f
227–229=226–228[12]
199–201=196–198[12]
271–273=270–272[12]
283–285=288–290[12]
287–289=not rep.
4-MeC6H4
2-ClC6H4
3
3.5
3.5
3
4-NO2C6H4
2-FC6H4
3,4-(OCH2O)C6H3
3
204–206=not rep.
aIsolated yield.

MOLECULAR IODINE–CATALYZED ONE-POT SYNTHESIS
1545
Figure 1. Molecular structure of 5a, with 30% probability displacement ellipsoids.
Scheme 2. Tentative mechanism for the formation of compound 5.
A mechanistic rationale portraying the probable sequence of events is given in
Scheme 2.[12] We supposed that the reaction may proceed via the ortho-quinone
methides (o-QM) intermediate, which was formed by the nucleophilic addition of
b-naphthol to aldehyde catalyzed by I2. Subsequent Michael addition of the
o-QM with cyclic 1,3-dicarbonyl and followed by addition of the phenolic hydroxyl
moiety to the carbonyl of ketone provides cyclic hemiketal, which on dehydration
afforded 5.
CONCLUSIONS
In conclusion, we have developed an efficient and environmentally benign meth-
odology for the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-ones

1546
X.-J. SUN, J.-F. ZHOU, AND P.-S. ZHAO
and 8,10-dimethyl-12-aryl-8,12-dihydro-7-oxa-8,10-diazabenzo[a]anthracene-9,11-
diones by a one-pot, multicomponent reaction. The advantages of this method over
other existing methods are mild reaction condition, better yields, easy purification,
and economic viability of the catalyst. We believe that this economically viable pro-
cedure will find practical utility for the one-pot synthesis of novel xanthenes and
anthracenes.
EXPERIMENTAL
Melting points were determined in a WRS-1B digital melting-point instrument
and are uncorrected. Infrared (IR) spectra were recorded on a Nicolet Avatar 360
Fourier transform (FT)–IR instrument. 1H NMR were measured on a Burke
400-MHz spectrometer in CDCl3 with tetramethylsilane (TMS) as internal standard.
Mass spectra (MS) were recorded on an LCQ Advantage instrument. X-ray diffrac-
tion was measured on a Brucker Smart 1000 X diffractometer. All the reagents are
commercially available.
General Procedure
Iodine (0.2 mmol) in acetic acid (3 ml) was added to a mixture of aromatic alde-
hyde (1 mmol), b-naphthol (1 mmol), and cyclic-1,3-dicarbonyl compound
(1.2 mmol). The mixture was stirred at reflux for the given time (Table 2). The pro-
gress of the reaction was monitored by thin-layer chromatography (TLC). After
completion of the reaction, the mixture was treated with aquecus Na2S2O3 solution
and stirred at room temperature for 10 min. The precipitate formed was collected
by filtration at the pump, washed with water, and dried. The crude product was
recystallized from methanol.
Selected Data
Compound 5a. 1H NMR (400 MHz, CDCl3): d 7.87 (d, J ¼ 8.0 Hz, 1H),
7.79–7.74 (m, 2H), 7.44–7.18 (m, 8H), 5.72 (s, 1H), 2.58 (s, 2H), 2.35 (d, J ¼ 16.4 Hz,
1H), 2.26 (d, J ¼ 16.4 Hz, 1H), 1.13 (s, 3H), 1.01 (s, 3H). IR (KBr, cmꢁ1): 3155, 2957,
2886, 1650, 1374, 1229, 1178, 1066, 811. MS (ESI): m=z ¼ 355 [M þ H]þ. Anal. calcd.
for C25H22O2: C, 84.72; H, 6.26. Found: C, 84.65; H, 6.44.
Compound 5b. 1H NMR (400 MHz, CDCl3): d 8.01–7.87 (m, 3H), 7.46–7.41
(m, 3H), 7.17–7.14 (m, 2H), 6.99 (d, J ¼ 7.6 Hz, 2H), 5.54 (s, 1H), 2.72 (s, 2H), 2.56
(d, J ¼ 16.4 Hz, 1H), 2.41 (d, J ¼ 16.4 Hz, 1H), 2.14 (s, 3H), 1.16 (s, 3H), 1.01 (s, 3H).
IR (KBr, cmꢁ1): 3086, 2949, 2868, 1648, 1372, 1228, 1071, 816. MS (ESI): m=z ¼ 369
[MþH]þ. Anal. calcd. for C26H24O2: C, 84.75; H, 6.57. Found: C, 84.91; H, 6.68.
Compound 5c. 1H NMR (400 MHz, CDCl3): d 7.97 (d, J ¼ 8.0 Hz, 1H),
7.78–7.72 (m, 2H), 7.44–7.20 (m, 5H), 6.70 (d, J ¼ 8.0 Hz, 2H), 5.66 (s, 1H), 3.68
(s, 3H), 2.56 (s, 2H), 2.34 (d, J ¼ 16.4 Hz, 1H), 2.26 (d, J ¼ 16.4 Hz, 1H), 1.12 (s,
3H), 1.01 (s, 3H). IR (KBr, cmꢁ1): 3055, 2949, 1644, 1376, 1227, 1172, 1026, 814.
MS (ESI): m=z ¼ 385 [M þ H]þ. Anal. calcd. for C26H24O3: C, 81.22; H, 6.29. Found:
C, 81.11; H, 6.45.

MOLECULAR IODINE–CATALYZED ONE-POT SYNTHESIS
1547
Compound 5d. 1H NMR (400 MHz, CDCl3): d 8.24 (d, J ¼ 8.0 Hz, 1H),
7.76–7.72 (m, 2H), 7.46–7.22 (m, 5H), 7.05–6.96 (m, 2H), 5.96 (s, 1H), 2.58 (s,
2H), 2.34 (d, J ¼ 16.4 Hz, 1H), 2.24 (d, J ¼ 16.4 Hz, 1H), 1.13 (s, 3H), 1.01 (s, 3H).
IR (KBr, cmꢁ1): 3075, 2934, 1648, 1372, 1229, 1175, 1028, 786. MS (ESI):
m=z ¼ 389 [M þ H]þ. Anal. calcd. for C25H21ClO2: C, 77.21; H, 5.44. Found: C,
77.09; H, 5.61.
Compound 5e. 1H NMR (400 MHz, CDCl3): d 7.94 (d, J ¼ 8.0 Hz, 1H),
7.79–7.71 (m, 2H), 7.46–7.14 (m, 7H), 5.68 (s, 1H), 2.56 (s, 2H), 2.34 (d, J ¼ 16.4 Hz,
1H), 2.24 (d, J ¼ 16.4 Hz, 1H), 1.12 (s, 3H), 1.01 (s, 3H). IR (KBr, cmꢁ1): 3074, 2928,
1645, 1374, 1226, 1175, 1082. MS (ESI): m=z ¼ 389 [M þ H]þ. Anal. calcd. for
C25H21ClO2: C, 77.21; H, 5.44. Found: C, 77.12; H, 5.28.
Compound 5f. 1H NMR (400 MHz, CDCl3): d 8.01 (d, J ¼ 8.0 Hz, 2H),
7.80–7.74 (m, 3H), 7.49–7.34 (m, 5H), 5.78 (s, 1H), 2.59 (s, 2H), 2.36 (d, J ¼ 16.4 Hz,
1H), 2.25 (d, J ¼ 16.4 Hz, 1H), 1.13 (s, 3H), 1.02 (s, 3H). IR (KBr, cmꢁ1): 3076, 2934,
1645, 1597, 1374, 1228, 1175, 1026, 825. MS (ESI): m=z ¼ 400 [MþH]þ. Anal. calcd.
for C25H21NO4: C, 75.17; H, 5.30; N, 3.51. Found C, 75.02; H, 5.55; N, 3.72.
Compound 5g. 1H NMR (400 MHz, CDCl3): d 7.98 (d, J ¼ 8.0 Hz, 1H),
7.76–7.73 (m, 2H), 7.46-7.17 (m, 5H), 6.62 (d, J ¼ 8.2 Hz, 2H), 5.65 (s, 1H), 5.48
(s, 1H), 2.58 (s, 2H), 2.34 (d, J ¼ 16.4 Hz, 1H), 2.26 (d, J ¼ 16.4 Hz, 1H), 1.12 (s,
3H), 1.01 (s, 3H). IR (KBr, cmꢁ1): 3306, 2958, 1640, 1572, 1378, 1226, 1175, 1024,
818. MS (ESI): m=z ¼ 371 [MþH]þ. Anal. calcd. for C25H22O3: C, 81.06; H, 5.99.
Found C, 81.21; H, 5.75.
Compound 5h. 1H NMR (400 MHz, CDCl3): d 7.81–7.77 (m, 2H), 7.69 (d,
J ¼ 8.0 Hz, 1H), 7.44–7.28 (m, 3H), 7.04–7.01 (m, 2H), 6.64–6.61 (m, 2H), 5.79 (s,
1H), 2.63 (s, 2H), 2.44 (d, J ¼ 16.4 Hz, 1H), 2.37 (d, J ¼ 16.4 Hz, 1H), 1.17 (s, 3H),
1.02 (s, 3H). IR (KBr, cmꢁ1): 3196, 2957, 2891, 1628, 1380, 1229, 1180, 1032, 811.
MS (ESI): m=z ¼ 373 [MþH]þ. Anal. calcd. for C25H21FO2: C, 80.62, H, 5.68.
Found: C, 80.55; H, 5.82.
Compound 5i. 1H NMR (400 MHz, CDCl3): d 7.99 (d, J ¼ 8.4 Hz, 1H),
7.81–7.76 (m, 2H), 7.49–7.28 (m, 3H), 6.88–6.80 (m, 2H), 6.63 (d, J ¼ 8.0 Hz, 1H),
5.81 (s, 2H), 5.65 (s, 1H), 2.58 (s, 2H), 2.28 (s, 2H), 1.14 (s, 3H), 1.02 (s, 3H). IR
(KBr, cmꢁ1): 3132, 2959, 2878, 1645, 1399, 1226, 1174, 1034, 823. MS (ESI):
m=z ¼ 399 [MþH]þ. Anal. calcd. for C26H22O4: C, 78.37; H, 5.57. Found: C,
78.53; H, 5.62.
Compound 6a. 1H NMR (400 MHz, CDCl3): d 7.96 (d, J ¼ 7.8 Hz, 1H), 7.86
(m, 2H), 7.45–7.36 (m, 5H), 7.21–7.14 (m, 3H), 6.00 (s, 1H), 3.62 (s, 3H), 3.38 (s,
3H). IR (KBr, cmꢁ1): 2926, 1706, 1650, 1485, 1232, 1179. MS (ESI): m=z ¼ 371
[MþH]þ. Anal. calcd. for C23H18N2O3: C, 74.58, H, 4.90; N, 7.56. Found: C,
74.41; H, 4.75; N, 7.71.
Compound 6b. 1H NMR (400 MHz, CDCl3): d 7.98 (d, J ¼ 7.8 Hz, 1H),
7.86–7.80 (m, 2H), 7.45–7.36 (m, 3H), 7.26–7.08 (m, 4H), 5.98 (s, 1H), 3.60 (s,
3H), 3.32 (s, 3H), 2.21 (s, 3H). IR (KBr, cmꢁ1): 2924, 1702, 1646, 1487, 1232,

1548
X.-J. SUN, J.-F. ZHOU, AND P.-S. ZHAO
1179. MS (ESI): m=z ¼ 385 [MþH]þ. Anal. calcd. for C24H20N2O3: C, 74.98; H, 5.24;
N, 7.29. Found: C, 74.72; H, 5.35; N, 7.41.
Compound 6c. 1H NMR (400 MHz, CDCl3): d 8.18 (d, J ¼ 7.8 Hz, 1H),
7.84–7.80 (m, 2H), 7.51–7.30 (m, 5H), 7.08–7.04 (m, 2H), 6.10 (s, 1H), 3.64 (s,
3H), 3.32 (s, 3H). IR (KBr, cmꢁ1): 3058, 2950, 1704, 1655, 1456, 1275, 1184. MS
(ESI): m=z ¼ 405 [M þ H]þ. Anal. calcd. for C23H17ClN2O3: C, 68.23; H, 4.23; N,
6.92. Found: C, 68.15; H, 4.31; N, 7.11.
Compound 6d. 1H NMR (400 MHz, CDCl3): d 8.08 (d, J ¼ 7.8 Hz, 1H),
7.89–7.76 (m, 3H), 7.55–7.41 (m, 5H), 6.01 (s, 1H), 3.62 (s, 3H), 3.31 (s, 3H). IR
(KBr, cmꢁ1): 3070, 2925, 1706, 1665, 1596, 1227, 1175. MS (ESI): m=z ¼ 416
[MþH]þ. Anal. calcd. for C23H17N3O5: C, 66.50, H, 4.12, N; 10.12. Found: C,
66.38; H, 4.33; N, 10.25.
Compound 6e. 1H NMR (400 MHz, CDCl3): d 7.89–7.81 (m, 2H), 7.69 (d,
J ¼ 7.8 Hz, 1H), 7.45–7.41 (m, 3H), 7.09–7.04 (m, 2H), 6.66–6.58 (m, 2H), 6.02 (s,
1H), 3.64 (s, 3H), 3.41 (s, 3H). IR (KBr, cmꢁ1): 3151, 2956, 1710, 1625, 1488,
1231, 1176. MS (ESI): m=z ¼ 389 [MþH]þ. Anal. calcd. for C23H17FN2O3: C,
71.13; H, 4.41; N, 7.21. Found: C, 71.36; H, 4.65; N, 7.05.
Compound 6f. 1H NMR (400 MHz, CDCl3): d 8.46 (d, J ¼ 8.2 Hz, 1H),
7.86–7.83 (m, 2H), 7.50–7.28 (m, 4H), 6.93–6.65 (m, 2H), 6.10 (s, 2H), 5.86 (s,
1H), 3.42 (s, 3H), 3.40 (s, 3H). IR (KBr, cmꢁ1): 3128, 2960, 1724, 1671, 1454,
1282, 1151. MS (ESI): m=z ¼ 415 [MþH]þ. Anal. calcd. for C24H18N2O5: C, 69.56;
H, 4.38; N, 6.76. Found: C, 69.39; H, 4.62; N, 6.60.
ACKNOWLEDGMENT
We are grateful to the Jiangsu Key Laboratory of Chemistry of
Low-Dinensional Materials.
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