Perchloric acid-catalyzed synthesis of 9-aryl xanthenes-9 H-3,6-diol and 1,3,6,8-tetraol in water

Article abstract of DOI:10.1080/00397911.2011.578326

Efficient syntheses of xanthenes have been described using a catalytic amount of perchloric acid in water. The high temperature and lengthy reaction time normally required for formation of xanthenes derivatives are not necessary when using a catalytic amo

Full text of DOI:10.1080/00397911.2011.578326

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Perchloric Acid-Catalyzed Synthesis of 9-
Aryl Xanthenes-9H-3,6-diol and 1,3,6,8-
Tetraol in Water
Nikhil Vidyasagar a , Rabindra Nanda a , Rajesh Mangal a & Muthu K.
Kathiravan b
a Padmashree Dr. D. Y. Patil Institute of Pharmaceutical Sciences and
Research , Pimpri , Pune , India
b Sinhgad College of Pharmacy , Pune , India
Accepted author version posted online: 10 Jan 2012.Published
online: 17 Aug 2012.
To cite this article: Nikhil Vidyasagar , Rabindra Nanda , Rajesh Mangal & Muthu K. Kathiravan (2012)
Perchloric Acid-Catalyzed Synthesis of 9-Aryl Xanthenes-9H-3,6-diol and 1,3,6,8-Tetraol in Water,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 42:21, 3157-3165, DOI: 10.1080/00397911.2011.578326
To link to this article: http://dx.doi.org/10.1080/00397911.2011.578326
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Synthetic Communications1, 42: 3157–3165, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.578326
PERCHLORIC ACID–CATALYZED SYNTHESIS OF
9-ARYL XANTHENES-9H-3,6-DIOL AND
1,3,6,8-TETRAOL IN WATER
Nikhil Vidyasagar,1 Rabindra Nanda,1 Rajesh Mangal,1 and
Muthu K. Kathiravan2
1Padmashree Dr. D. Y. Patil Institute of Pharmaceutical Sciences and
Research, Pimpri, Pune, India
2Sinhgad College of Pharmacy, Pune, India
GRAPHICAL ABSTRACT
Abstract Efficient syntheses of xanthenes have been described using a catalytic amount of
perchloric acid in water. The high temperature and lengthy reaction time normally required
for formation of xanthenes derivatives are not necessary when using a catalytic amount of
perchloric acid. The method is relatively inexpensive, easily available, nonvolatile, nonex-
plosive, and thermally robust to catalyze the reaction at 80 ꢀC by simple heating with good
to excellent yields. The advantages of the reaction involve simple reaction protocol, simple
workup, and improved synthesis in the presence of perchloric acid as catalyst.
Keywords Perchloric acid; phloroglucinol; resorcinol; water; xanthenes
INTRODUCTION
The reaction between aldehydes and phenols is generally catalyzed by an acid
or base to give cyclic oligomers.[1] Homogeneous acid catalysts such as H2SO4, HCl,
and BF3 are commonly used for organic synthesis. Xanthenes and benzoxanthenes
are oxygen-containing heterocyclic ring systems possessing therapeutic and pharma-
ceutical properties such as antiviral,[2] antibacterial,[3] and anti-inflammatory activi-
ties.[4] They are also used as leuco-dyes in laser technology,[5] as antagonists of the
paralyzing action of zoxazolamine,[6] and in fluorescent materials for visualization
of biomolecules.[7] Photodynamic therapy (PDT) is a method of treating tumors
Received December 3, 2010.
Address correspondence to Muthu K. Kathiravan, Department of Pharmaceutical Chemistry,
AISSMS’s College of Pharmacy, Kennedy Road, Near RTO, Pune 411001, India. E-mail:
drmkkathir@gmail.com
3157

3158
N. VIDYASAGAR ET AL.
by combined use of a photosensitizer and light. These compounds are used as sensi-
tizers in PDT.[8] In this method, photosensitizers are injected directly into malignant
tissue and a specific wavelength of light that excites the photosensitizer drug is used,
thereby killing the tumor cells.[9] The xanthene dyes are utilized as agricultural bac-
tericides and also extracted from the natural sources such as soil and plants such as
Indigofera longeracemosa.[10]
The literature methods for the synthesis of benzoxanthenes include the reaction
of 2-naphthol with formamide,[11] 2-naphthol-1-methanol,[12] and carbon monox-
ide.[13] Certain improvements suggested to overcome the hazards associated with
these reactions include mixing 2-naphthol with aldehydes in the presence of a cata-
lyst, such as amberlyst,[14] sulfamic acid,[15] molecular iodine,[16] and AcOH–
H2SO4.[1] All of these methods suffer from one of the following drawbacks, such
as long reaction time, toxic reagents, solvents, and poor yields.[16–17]
Other methods for the synthesis of xanthenes are (1) inter- or intramolecular
trapping of arynes by phenols or aldehydes,[18] (2) Pd-catalyzed cyclization of poly-
cyclic aryl triflate esters,[19] (3) Yb-catalyzed reaction of 2-naphthol and alde-
hydes,[20] and (4) reaction of 2-tetralone and salicylaldehydes under acidic
conditions.[21] Although these methods are efficient for the synthesis of xanthenes,
the application scope is limited to the synthesis of either 9-aryl- or 9-alkyl-substituted
xanthenes. Therefore, the development of a general method for the synthesis of
both 9-aryl- and 9-alkyl-substituted xanthenes is highly desirable for chemical library
synthesis. Recently iron-catalyzed, microwave-promoted cascade benzylation–
cyclization of phenols is reported in which benzyl acetates, benzyl bromides, and
benzyl carbonates are used as benzylating reagents.[22]
The organic reactions in aqueous media have attracted much attention in syn-
thetic organic chemistry, because water is one of the most abundant, cheapest, and
environmentally friendly solvents and it exhibits unique reactivity and selectivity.[23]
Recently Bigdeli et al. reported synthesis of benzoxanthenes under solvent-free
condition at 125 ꢀC.[24]
In continuation of our work exploring water as a solvent,[25] we herein report
for the first time perchloric acid–catalyzed synthesis of 9-aryl xanthenes-9H-3,6-diol
and 9-aryl xanthenes-9H-1,3,6,8-tetraol (Scheme 1) derivatives in water.
RESULTS AND DISCUSSION
An efficient method using catalytic amount of perchloric acid for the synthesis
of 9-aryl xanthenes-9H-3,6-diol and 9-aryl xanthenes-9H-1,3,6,8-tetraol in water is
reported. Aromatic aldehydes carrying different functional groups including
electron-donating (EDG) and electron-withdrawing groups (EWG) were subjected
to study with resorcinol and phloroglucinol. The investigated reaction was compared
under similar reaction conditions in the presence of three different catalysts, oxalic
acid, alum, and perchloric acid. The results are presented in Table 1. The reaction
employing perchloric acid as catalyst is substantially faster (25–30 min), gives better
yields (75–88%), and is nearly quantitative after 25 min. In this event, the choice
of catalyst was crucial for an efficient reaction. Among the catalysts examined so
far, perchloric acid gave the best result and the possible mechanism is depicted in
Scheme 2. Perchloric acid protonates the aldehyde carbonyl group, which is followed

PERCHLORIC ACID–CATALYZED SYNTHESIS
3159
Scheme 1. Synthesis of 9-aryl xanthenes-9H-3,6-diol and 9-aryl xanthenes-9H-1,3,6,8-tetraol.
Table 1. Comparisons of the methods for the synthesis of the 9-aryl xanthenes-9H-3,6-diol and 9-aryl
xanthenes-9H-1,3,6,8-tetraol
Oxalic acid
Alum
Reaction
time (min)
Perchloric acid
Reaction
Yielda
(%)
Yielda
(%)
Reaction
time (min)
Yielda
Compound
R
time (min)
110
(%)
86
1a
76
74
160
78
80
30
30
1b
100
150
88
1c
2a
105
110
105
78
75
78
140
160
140
80
64
72
25
30
25
85
75
80
2b
aIsolated yields.

3160
N. VIDYASAGAR ET AL.
by the attachment of the phenolic aromatic ring. Attack of another Hþ ion from per-
chloric acid to hydroxyl group forms a carbocation and thus initiates the attachment
of the other phenolic ring. Thus the xanthenes ring is formed finally by the removal
of a molecule of water from its intermediate.
The other reactions gave only 64–80% yield after 2–3 h. This effect might be
due to the effect of the perchloric acid used, which is known for its complexing abil-
ity. Further reactions were carried out using a catalytic amount of perchloric acid.
However, the reaction mixture was heated at 80 ꢀC for the synthesis of xanthenes.
In all cases, the desired products were synthesized in good yields within a short
period of time. Another advantage of the reaction is the workup procedure, which is
simple and includes basic filtration to separate the product. The reaction worked well
with aromatic aldehydes (Table 2), giving products in 82–96% yields.
The presence of EWG (20 min, 84%) on the aromatic aldehydes went to com-
pletion at faster rate than EDG donating groups. Also the presence of o-EWG
(20 min, 80%.) accelerated the reaction rate more than m,p-EWG (25 min, 83%).
The reaction is general, tolerates a variety of functional groups, and is applicable
to aldehydes containing EWG as well as EDG. The increase in bulkiness of the sub-
stituents has no significant effect on rate of reaction.
The condensation was achieved under classical heating with water as solvent in
the presence of oxalic acid, alum, and perchloric acid, the latter being a much more
efficient procedure. No products could be isolated with the same temperature con-
ditions with oxalic acid and alum after 30 min, but lesser yields were obtained after
an extended period (2–3 h) at high temperatures (Table 1). The high temperatures
and lengthy reaction time required for formation of xanthenes derivatives are easily
obtained with in a shorter time using a catalytic amount of perchloric acid. The pro-
cess is amenable to scale-up and can be gainfully employed to synthesize a library of
xanthene analogs.
EXPERIMENTAL
Melting points were determined with a Veego melting-point apparatus (VMP
PM, 32=1104) and are uncorrected. Thin-layer chromatography (TLC) was carried
out using silica gel (G-60 mesh). An Rf value was calculated for each compound
using n-hexane–ethyl acetate (1:1) as solvent, and the spots were located using iodine
vapor. Infrared (IR) spectra in KBr were recorded on a Fourier Transform (FT)–IR
1
spectrophotometer with diffuse reflectance attachment (Shimadzu 8400S). H NMR
spectra were obtained using Bruker Avance II 400 NMR spectrometer with
dimethylsulfoxide (DMSO-d6) as solvent. Chemical shifts were expressed in parts
per million relative to tetramethylsilane (TMS) as internal standard. Mass spectra
ware obtained on a double-focusing magnetic sector mass spectrometer using direct
insertion probe with electron impact ion source operating at 70 eV.
Synthesis of 9-Aryl Xanthenes-9H-3,6-diol and 9-Aryl Xanthenes-9H-
1,3,6,8-tetraol
In a typical procedure, resorcinol=phloroglucinol (10 mmol) and substituted
aldehydes (10 mmol) were dissolved in water (5 ml) and stirred. A catalytic amount

PERCHLORIC ACID–CATALYZED SYNTHESIS
3161
Scheme 2. Reaction mechanism.
of perchloric acid 60% (two drops) was added to the stirred solution. The reaction
mixtures were heated at 80 ꢀC for an appropriate time. Solid precipitate starts separ-
ating after 20 min. The progress of the reaction was monitored by thin-layer chroma-
tography (TLC). The solid precipitate obtained was filtered, washed with water,
dried, and recrystallized from ethanol.
The structures of the synthesized xanthene analogs and their characteristic
properties are given in Table 2.
Data for Compounds 1a–1e
9-Phenyl-9H-xanthene-3,6-diol (1a). Orange powder; IR (KBr): t=cmꢁ1
=
¼ 3475–3224 (OH), 3091–3029 (CH), 1610, 1514, 1429 (ring C C), 1076 (ether
1
C-O) 840, 748, 702 (CH); H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.15 (b.s, 2H,
-OH), 5.76 (s, 1H, CH), 6.21–7.10 (m, 11H, Ar-H), 6.32 (s, 2H), 6.39 (s, 2H), 6.90

3162
N. VIDYASAGAR ET AL.
Table 2. Physical properties of 9-aryl xanthenes-9H-3,6-diol and 9-aryl xanthenes-9H-1,3,6,8-tetraol
synthesized using perchloric acid
Compound
R
Reaction time (min)
Melting point (ꢀC)a
210–211
Yield (%)b
1d
1e
25
25
84
83
214–215
1f
20
35
190–191
222–224
80
90
1 g
1 h
35
200–202
86
1i
1j
35
30
145–146
255–257
88
90
2c
2d
25
25
213–214
270–271
78
82
(Continued )

PERCHLORIC ACID–CATALYZED SYNTHESIS
3163
Table 2. Continued
Compound
R
Reaction time (min)
Melting point (ꢀC)a
180–182
Yield (%)b
2e
35
90
2f
35
232–233
86
2 g
2 h
30
30
244–246
240–242
85
89
aMelting points are uncorrected.
bIsolated yields.
(d, 2H, J ¼ 4.32 Hz), 7.08 (s, 1H), 7.10 (s, 2H). EIMS (70 eV, m=z) 290 (Mþ, base
peak), Anal. calcd. for C19H14O3 C: 78.61; H, 4.86. Found: C, 78.21; H, 4.66.
9-(2-Hydroxyphenyl)-9H-xanthene-3,6-diol (1b). Off-white powder ; IR
(KBr): t=cmꢁ1 ¼ 3463–3205 (OH), 3151–3037 (CH), 1606, 1508, 1454 (ring C C),
=
1
1087 (ether C-O), 837, 756 (CH); H NMR (DMSO-d6, 300 Mz): d ppm ¼ 5.43 (s,
3H, -OH), 5.63 (s, 1H, CH), 6.21–6.87 (m, 10H, Ar-H), 6.27 (s, 2H), 6.49 (d, 2H,
J ¼ 5.20 Hz), 6.86 (d, 2H, J ¼ 11.88 Hz). EIMS (70 eV, m=z) 306 (Mþ, base peak).
Anal. calcd. for C19H14O4: C, 74.50; H, 4.61. Found: C, 74.34; H, 4.51.
9-(4-Hydroxyphenyl)-9h-xanthene-3,6-diol (1c). Off-white powder, IR
(KBr): t=cmꢁ1 ¼ 3292–3178 (OH), 3129–3076 (CH) 1604, 1510, 1431 (ring C C),
=
1
1076 (ether C-O), 844, 577 (CH); H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.48
(s, 1H,-OH), 5.69 (s, 2H, -OH), 5.77 (s, 1H, CH), 6.13–6.82 (m, 8H, Ar-H), 6.37
(s, 2H), 6.53 (d, 2H, J ¼ 2.79 Hz), 6.63 (d, 2H, J ¼ 6.36 Hz), 6.82 (d, 2H, J ¼ 6.36 Hz).
EIMS (70 eV, m=z) 306 (Mþ, base peak). Anal. calcd. for C19H14O4: C, 74.50; H,
4.61. Found: C, 74.34, H, 4.51.
9-(4-Chlorophenyl)-9H-xanthene-3,6-diol (1d). Yellow crystals; IR (KBr):
t=cmꢁ1 ¼ 3510–3328 (OH), 3192–3045 (CH), 1612, 1496, 1431 (ring C C), 1087 (ether
=
C-O), 844, 767 (CH); 725 (C-l); 1H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.28 (s, 2H),
5.45 (s, 1H), 6.21–6.68 (m, 6H, Ar-H), 6.24 (s, 2H), 6.68 (d, 2H, J ¼ 2.31 Hz), 6.90, 6.93
(d, 2H, J ¼ 8.01 Hz), 7.18, 7.21 (d, 2H, J ¼ 10.14 Hz). EIMS (70 eV, m=z) 324 (Mþ,
base peak). Anal. Calcd. for C19H13ClO4: C, 70.27; H, 4.03. Found: C, 70.21; H, 4.01.

3164
N. VIDYASAGAR ET AL.
9-(4-Nitrophenyl)-9H-xanthene-3,6-diol (1e). Yellow crystals; IR (KBr):
t=cmꢁ1 ¼ 3321–3228 (OH), 3116–3078 (CH), 1604, 1512, 1431 (ring C C), 1345
(symmetric NO), 1091 (ether C-O), 844 (symmetric NO), 744, 702, 628 (CH);
1H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.38 (s, 2H), 5.63 (s, 1H), 6.30–6.90 (m,
6H, Ar-H), 6.30 (s, 2H), 6.37 (s,2H), 6.83, 6.88 (d, 2H, J ¼ 16.14 Hz), 7.30, 7.33
(d, 2H, J ¼ 8.37 Hz), 8.18, 8.21 (d,2H, J ¼ 10.14 Hz); EIMS (70 eV, m=z) 335 (Mþ,
base peak), 305, 289, 179, 122, 107, 101, 93, 77, 30. Anal. calcd. for C19H13NO5:
C, 68.06; H, 3.91; N, 4.18. Found: C, 68.02; H, 3.78; N, 4.11.
=
Data for Compound 2a–2e
9-Phenyl-9H-xanthene-1,3,6,8-tetraol (2a). Brown powder; IR (KBr):
t=cmꢁ1 ¼ 3315–3203 (OH), 3098–3024 (CH), 1610, 1492, 1444 (ring C C), 1076
=
1
(ether C-O), 827, 748, 698 (CH); H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.10
(b.s, 4H, -OH), 5.41 (s, 1H, CH), 5.70 (s, 2H, CH), 5.88 (s, 2H, CH), 7.01–7.20
(m, 5H), 7.01 (d, 2H), 7.08 (s, 1H), 7.20 (d, 2H). EIMS (70 eV, m=z) 322 (Mþ, base
peak). Anal. calcd. for C19H14O5: C, 70.80; H, 4.38. Found C, 70.71; H, 4.30.
9-(4-Hydroxyphenyl)-9H-xanthene-1,3,6,8-tetraol (2b). Off-white pow-
der; IR (KBr): t=cmꢁ1 ¼ 3292–3196 (OH), 3103–3076 (CH) 1612, 1510, 1438 (ring
C C), 1071 (ether C-O), 815, 567 (CH); 1H NMR (DMSO-d6, 300 MHz): d
=
ppm ¼ 5.30 (s, 5H, -OH), 5.42 (s, 1H, CH), 5.71 (s, 2H, Ar-H), 5.83 (s, 2H,
Ar-H), 6.61 (d, 2H), 6.88 (d, 2H). EIMS (70 eV, m=z) 338 (Mþ, base peak). Anal.
calcd. for C19H14O6: C, 67.45; H, 4.17. Found: C, 67.35; H, 4.12.
9-(4-Nitrophenyl)-9H-xanthene-1,3,6,8-tetraol (2c). Yellow powder; IR
(KBr): t=cmꢁ1 ¼ 3282–3191 (OH), 3130–3078 (CH) 1608, 1512, 1451 (ring C C),
=
1
1056 (ether C-O), 844, 577 (CH); H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.25
(s, 4H, -OH), 5.48 (s, 1H), 5.85 (s, 2H, CH), 5.92 (s, 2H), 7.50 (d, 2H, Ar-H), 8.10
(d, 2H, Ar-H), EIMS (70 eV, m=z) 367 (Mþ, base peak). Anal. calcd. for
C19H13NO7: C, 62.13; H, 3.57; N, 3.81. Found: C, 62.01; H, 3.48, N, 3.43.
9-(4-Chlorophenyl)-9H-xanthene-1,3,6,8-tetraol (2d). Yellow powder; IR
(KBr): t=cmꢁ1 ¼ 3286–3130 (OH), 3192–3045 (CH) 1610, 1488, 1448 (ring C C),
=
1
1095 (ether C-O), 831, 767 (CH); H NMR (DMSO-d6, 300 MHz): d ppm ¼ 5.28
(s, 4H, -OH), 5.45 (s, 1H), 5.95 (s, 2H), 6.10 (s, 2H), 7.21 (d, 2H), 7.46 (d, 2H). EIMS
(70 eV, m=z) 356 (Mþ, base peak). Anal. calcd. for C19H13ClO5: C, 63.97; H, 3.67.
Found: C, 63.81; H, 3.51.
9-(4-Methoxyphenyl)-9H-xanthene-1,3,6,8-tetraol (2e). Buff powder; IR
(KBr): t=cmꢁ1 ¼ 3321–3106 (OH), 3116–3078 (CH) 2877–2837 (OCH3) 1604, 1508,
1442 (ring C C), 1081 (ether C-O), 744, 702, 628 (CH); 1H NMR (DMSO-d6,
=
300 MHz): d ppm ¼ 3.80 (s, 3H, OCH3), 5.30 (s, 4H, -OH), 6.10 (s, 2H), 6.30 (s,
2H) 6.75 (d, 2H), 6.95 (d, 2H), EIMS (70 eV, m=z) 352 (Mþ, base peak). Anal. calcd.
for C20H16O6: C, 64.07; H, 4.89. Found: C, 64.01, H, 4.81.

PERCHLORIC ACID–CATALYZED SYNTHESIS
3165
CONCLUSION
An efficient synthetic route for synthesis of diverse xanthenes was developed. The
products obtained contain no impurities and are isolated with a simple procedure. The
reaction products were obtained in good yields, in spite of starting materials with various
functional groups. Biological evaluation of xanthene derivatives as antimicrobial,
anti-inflammatory agents is currently in progress. Finally, the results provide further
scope for the generation of chemical libraries and can be utilized as potential therapeutic
agents. Thus, perchloric acid could efficiently catalyze the condensation reaction of phe-
nols and aldehydes and may be helpful for catalyst design of xanthene derivatives.
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