N-bromosuccinimide (NBS): A novel and efficient catalyst for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes under solvent-free conditions

Article abstract of DOI:10.1002/hlca.201000243

A novel procedure for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes through one-pot condensation of naphthalen-2-ol with arenecarbaldehydes in the presence of N-bromosuccinimide (NBS) as catalyst under solvent-free conditions is described.

Full text of DOI:10.1002/hlca.201000243

Helvetica Chimica Acta – Vol. 94 (2011)
429
N-Bromosuccinimide (NBS): A Novel and Efficient Catalyst for the Synthesis
of 14-Aryl-14H-dibenzo[a,j]xanthenes under Solvent-Free Conditions
a
b
b
by Setareh Habibzadeh* ), Hassan Ghasemnejad* ), and Mohammad Faraji )
a) Industrial Noshiravani University, Babol, Iran (e-mail: habibzadeh@nit.ac.ir)
b) Islamic Azad University-Babol Branch, Babol, Iran (e-mail: h_ghasem2000@yahoo.it)
A novel procedure for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthenes through one-pot
condensation of naphthalen-2-ol with arenecarbaldehydes in the presence of N-bromosuccinimide
(
NBS) as catalyst under solvent-free conditions is described.
Introduction. – The synthesis of xanthene derivatives is currently of much interest,
and various methods have been reported for their synthesis (see, e.g., [1 – 3]). However,
these methods suffer from one or more disadvantages such as a long reaction time, low
yield, use of toxic solvents, requirement of excess of reagents/catalysts, laborious
workup procedures, and harsh reaction conditions. Thus, the development of an
environmentally benign methodology for the synthesis of benzoxanthene derivatives is
of great interest.
Results and Discussion. – In continuation of our confirming research on various
transformations by halogenating agents [4 – 10], here we report the use of N-
bromosuccinimide (NBS) as a more robust and efficient catalyst in a one-pot synthesis
of the 14-aryl-14H-dibenzo[a,j]xanthene derivatives 3a – 3o by reaction of naphthalen-
2
-ol (2) with different benzaldehydes 1 in excellent yields (87 – 97%) under solvent-free
conditions (Scheme 1 and Table). As shown in the Table, the reactions occurred within
5 – 75 min. The results indicate that the most effective conversion occurred when a
5
substrate/NBS mol ratio of 1:0.19 was used. Longer reaction times were required when
lower amounts of NBS were employed. It is important to note that no 14-aryl-14H-
dibenzo[a,j]xanthenes derivatives were obtained when the reactions were performed in
the absence of NBS.
Scheme 1
ꢀ
2011 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Helvetica Chimica Acta – Vol. 94 (2011)
Table. NBS-Catalyzed Synthesis of 14-Aryl-14H-dibenzo[a,j]xanthenes from Benzaldehydes 1a)
Entry
R
Productb)
Time [min]
Yield [%]c)
M.p. [8]d)
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
H
4-Cl
2-Cl
4-Br
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
55
65
68
59
62
68
75
65
51
55
52
56
74
53
66
95
94
90
93
91
89
87
90
96
95
97
95
90
95
92
181 (183)
288 (287)
214 (215)
298 (296)
191 (190)
309 (312)
292 (293)
214 (213)
227 (228)
206 (205)
199 (197)
95 (93)
3-Br
4-NO2
2-NO2
3-NO2
4-Me
3-Me
4-MeO
2-MeO
2,4-Cl2
4-OH
4-F
1
1
1
1
1
1
225 (227)
141 (140)
237 (238)
a) See also Scheme 1. b) All products are known, and they were characterized by IR- and NMR-spectral
c
d
analysis, and compared with authentic samples. ) Yields of isolated products. ) Melting points of
compounds are consistent with reported values [1 – 3] (in parentheses).
The reaction likely proceeds via initial formation of intermediate 4. The oxonium
species 5 is then formed on reaction with naphthalen-2-ol, which then undergoes
dehydration to afford the desired product 3 (Scheme 2).
The advantages or the characteristic aspects of the method described in this work in
comparison with other previously reported procedures are i) the yields of products
were higher than those reported previously; ii) the catalyst NBS is inexpensive and not
moisture-sensitive, and iii) no special measures are required for the reaction.
In summary, the present methodology shows that NBS is an efficient catalyst in the
one-pot synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives. The main advan-
tages of the presented protocol are mild, clean, and environmentally benign reaction
conditions, as well as the high yields. Furthermore, this method is also expected to find
application in organic synthesis due to the low cost of the reagent. It is believed that this
method will be a useful addition to modern synthetic methodologies.
Experimental Part
General. The chemicals were obtained from either Merck or Fluka. M.p.: Bꢀchi 530 melting-point
apparatus; uncorrected. IR Spectra: Shimadzu-435-U-04 spectrophotometer (KBr pellets). NMR
Spectra: in CDCl , 90-MHz JEOL FT NMR spectrometer.
3
Typical Procedure for the Synthesis of 14-Aryl-14H-dibenzo[a,j]xanthenes. To a mixture of
benzaldehyde (1 mmol) and naphthalen-2-ol (2 mmol), N-bromosuccinimide (NBS; 0.19 mmol,
0
.43 mg) was added, and the mixture was inserted in an oil-bath and heated at 1108 for the appropriate
time (cf. the Table). Completion of the reaction was indicated by TLC. After the reaction was completed,
EtOH was added, and the mixture was heated until the solid crude product was dissolved. Then, the
heterogeneous catalyst was isolated from the mixture by simple filtration. In continuation of workup, the
filtered EtOH soln. was concentrated. Aq. EtOH (15%) was added to the crude product, and the
precipitate was separated and then recrystallized (2Â) from aq. EtOH (15%). The desired pure

Helvetica Chimica Acta – Vol. 94 (2011)
431
Scheme 2
product(s) was characterized by comparison of the physical data with those of known dibenzoxanthenes
1][11].
[
We wish to thank the Industrial Noshiravani University, Babol, Iran, for financial support this
research.

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REFERENCES
[
1] A. R. Khosropour, M. M. Khodaei, H. Moghannian, Synlett 2005, 6, 955.
[2] A. Khoramabadi-zad, S.-A. Akbari, A. Shiri, H. Veisi, J. Chem. Res. 2005, 5, 277.
[3] B. Rajitha, B. S. Kumar, Y. T. Reddy, P. N. Reddy, N. Sreenivasulu, Tetrahedron Lett. 2005, 46, 8691.
[4] H. Ghasemnejad-Bosra, M. Faraje, S. Habibzadeh, F. Ramzaniyan-Lehmali, J. Serb. Chem. Soc.
2010, 75, 299.
[
[
[
[
[
5] D. Azarifar, H. Ghasemnejad-Bosra, M.-A. Zolfigol, M. Tajbaksh, Heterocycles 2006, 68, 175.
6] D. Azarifar, H. Ghasemnejad-Bosra, Synthesis 2006, 1123.
7] D. Azarifar, H. Ghasemnejad Bosra, M. Tajbaksh, J. Heterocycl. Chem. 2007, 44, 467.
8] H. Ghasemnejad-Bosra, M. Haghdadi, I. Gholampour-Azizi, Heterocycles 2008, 75, 391.
9] H. Ghasemnejad-Bosra, M. Haghdadi, O. Khanmohamadi, M. Gholipour, G. Asghari, J. Chin.
Chem. Soc. 2008, 55, 464.
[
[
10] H. Ghasemnejad-Bosra, M. Faraje, S. Habibzadeh, Helv. Chim. Acta 2009, 92, 575.
11] K. Gong, D. Fang, H.-L. Wang, X.-L. Zhou, Z.-L. Liu, Dyes Pigm. 2009, 80, 30.
Received June 27, 2010