NaHSO4/SiO2catalyzed generation of: o -quinone/ o -thioquinone methides: synthesis of arylxanthenes/ arylthioxanthenes via oxa-6π-electrocyclization

Article abstract of DOI:10.1039/d0ob01868f

ortho-Quinone methides, very reactive transient intermediates, are utilized successfully in synthesizing complex organic molecules of natural and biological significance. Among several synthetic protocols, the acid catalyzed generation of ortho-quinone me

Full text of DOI:10.1039/d0ob01868f

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DOI: 10.1039/D0OB01868F
ARTICLE
NaHSO4/SiO2 catalyzed generation of o-quinone/o-thioquinone
methides: Synthesis of arylxanthenes/arylthioxanthenes via oxa-
6π-electrocyclization
Received 00th January 20xx,
Accepted 00th January 20xx
Muthupandi Karthick,a Edwin Konikkara Abi,a Nagamalla Someshwar,a Savarimuthu Philip Anthony,b
Chinnasamy Ramaraj Ramanathana
DOI: 10.1039/x0xx00000x
ortho-Quinone methides, very reactive transient intermediates, are utilized successfully in synthesizing complex organic
molecules of natural and biological significance. Among several synthetic protocols, the acid catalyzed generation of
ortho-quinone methides from suitably substituted phenols is a promising tool for further exploitation in organic synthesis.
Such an interesting reactive species conveniently employed in the synthesis of conformationally restricted triarylmethane
derivatives such as 12/9- arylxanthenes/arylthioxanthenes starting from symmetrical/unsymmetrical 2-
(hydroxydiarylmethyl)phenol/thiophenol, respectively using SiO2-NaHSO4. Conformationally restricted 12/9-
arylxantheses/arylthioxanthenes were obtained in 52 to 96% yields using this protocol, which believed to involve the
formation of o-quinone methides followed by electrocyclic ring closure and isomerization at elevated temperature.
Photophysical studies of selected examples in acidic medium showed turn-on fluorescence by hydride ion transfer
mediated π-conjugated xanthylium salts formation and suggest the application potential in bio-imaging and fluorescence
sensors.
9-Arylxanthenes are unique class of molecules possess
excellent photophysical properties5 and biological activities. This
class of molecules are usually constructed through six distinct
Introduction
The heterocyclic condensed aromatic system such as
protocols: i. Friedel-Crafts reaction of an arene with
aldehyde/benzyl alcohol derivatives followed by cyclic ether
formation or Grignard reaction with carbonyl compounds
followed by cyclic ether formation;6 ii. Formation of diaryl ether
followed by intramolecular Friedel-Crafts cyclization;7 iii. [2+2]-
Cycloaddition between an aldehyde and aryne followed by hetero
Diels-Alder reaction between o-quinone methide and aryne
species (Fig 2a);8 iv. Reaction of dilithium reagents derived from
diaryl ethers with esters or phthalic anhydride or phthalides or
amides;1a,3k,9 v. Reaction of Grignard reagents/organolithium
reagents with xanthones;10 vi. Cross-coupling reaction of aryl
halides with xanthenes.11
xanthene/thioxanthene and their derivatives are an interesting
structural scaffolds present in natural products,1 biologically
active molecules,2 and analytical/industrial substances3 (Figure 1).
Xanthylium/thioxanthylium salts have been utilized as catalysts in
organic photoredox reactions.4
O
O
OH
O
O
OH
H
O
H
O
O
H
OH
O
MeO
O
O
O
OH
HO
O
O
O
H
O
O
O
Acrotione
OMe
Carbanone
Callistrilone A
NH2
With variety of dienophiles, the o-quinone methide
produced complex xanthene derivatives efficiently (Fig. 2a).
This protocol has been successfully employed to synthesize
several natural products.12 Similarly, the vinylic o-quinone
NH2
N
O
O
Cl-
NEt2
Et2N
O
Et2N
O
NEt2
O
N
Tacrine analogue, Drug
for Alzheimer's disease
Rhodamine dye,
anti-bacterial agent
Phosgene detecting
agent
methide,
under
oxa-6π-electrocyclization,
furnished
chromene/xanthene derivatives and natural products13 (Fig
2b). The methide portion of o-quinone methides utilized in
organic transformations is found to be only mono
substituted.13d-g But, under photochemical condition, 3-
phenylbenzofuran-2-one generated the xanthene derivative
along with other products.13h-i Even mono substituted o-
quinone methide with proper conformation failed to undergo
oxa-6π-electrocyclization, instead, smoothly underwent
Fig. 1 Xanthene core in natural products, bioactive molecules and
analytical agents
aDepartment of Chemistry, Pondicherry University, Puducherry – 605 014, India.
bSchool of Chemical & Biotechnology, SASTRA Deemed University, Thanjavur –
613 401, India. Email: crrnath.che@pondiuni.edu.in, Fax: +91-413-2655987;
Tel: +91-413-2654416.
Electronic Supplementary Information (ESI) available: Characterization data of
all compounds: 1H NMR, 13C NMR, HRMS, absorption and emission data for
selected compounds. See DOI: 10.1039/x0xx00000x
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hetero Diels-Alder reaction with dienophile.14 The former the reaction of some of the sodium salt of ortho-hydroxy salicyl
View Article Online
DOI: 10.1039/D0OB01868F
method (cycloaddition) required the generation of reactive alcohols/(ortho-hydroxyaryl)diarylmethanols with acetic acid also
aryne species whereas the later method (oxa-6π- furnished 9-aryl xanthenes in moderate yields.20 With this
electrocyclization) has been very less explored for xanthene background, herein we report the efficient generation of o-
synthesis. Introduction of two aryl groups on methide portion quinone methides from (ortho-hydroxy- aryl)diarylmethanols and
makes the o-quinone methide structure potential to undergo (ortho-mercaptoaryl)diarylmethanols catalyzed by NaHSO4-SiO2
oxa-6π-electrocyclization under suitable condition to generate and subsequent oxa-6π electrocyclization followed by
9-arylxanthenes (Fig. 2c). o-Quinone methides can be isomerization to synthesize the xanthene and thioxanthene
generated13 in situ through several methods from different derivatives, respectively.
types of substrates, among them the acid promoted
generation of o-quinone methides from ortho-hydroxybenzyl
Results and Discussion
alcohols is a promising one. Due to the very reactive nature of
o-quinone methides under acidic condition as well as an
unfavourable geometrical orientation of aryl group in methide
portion, the o-quinone methides are not well exploited in
xanthene skeleton synthesis.
In continuation of our effort in developing efficient
methodology for the synthesis of symmetrical/unsymmetrical
carbinols and triarylmethanes21 we became interested in
developing
a
suitable method for the synthesis of
conformationally restricted triarylmethanes such as 12/9-
arylxanthenes. Based on our hypothesis, a suitable triaryl
carbinol, having ortho-hydroxy group at one of the aryl group, for
example, 3-(hydroxydiphenylmethyl)-naphthalen-2-ol 2aa was
treated with silica supported NaHSO4 catalyst in 1,2-
dichloroethane at 90 oC, as a model reaction.
a. Intermolecular cycloaddition reaction via o-quinone methides (QMs)
Ar
Ar
O
Ar
OH
OH
O
b. Oxa-6p electrocyclization via o-quinone methides (QMs)
OH
Table 1 Optimization of reaction conditionsa
CHO
-H2O
O
OH
O
R
R
OH
R
R
c. This work,
OH
Ar OH
Ar
X
Ar
X
NaHSO4/SiO2
1. Oxa-6-electro-
cyclization
SiO2-NaHSO4
1,2-DCE
OH
2aa
O
2. Isomerization
XH
3aa
o-Quinone/o-thioquinone
Where X = O, S
methide
S.
No.
Catalysts
Catalyst
load (mg)
Temp. Time Yieldb
Fig. 2 Construction of xanthene derivatives
(oC)
(h)
(%)
Heterogeneous solid surface acid catalysts have been
extensively utilized to effect plethora of organic
transformations.15 These classes of catalysts are inexpensive and
are convenient to handle. Particularly, the silica supported
NaHSO4 catalyst, a readily available and non-toxic reagent
system, is used to effect variety of organic transformations16 such
as C-C bond formation, protection and deprotection of functional
groups, construction of heterocyclic scaffolds including xanthene
skeleton,16l etc. The silica supported NaHSO4 catalyst facilitated
the dehydration from benzylic alcohols even under mild
condition. Such a behavior intrigued us to believe that silica
supported NaHSO4 would be a useful catalyst for the generation
of o-quinone methide (o-QM) intermediates through dehydration
of ortho-hydroxybenzyl alcohols (Fig. 2c). During our effort in
1.
NaHSO4/SiO2
NaHSO4/SiO2
NaHSO4/SiO2
NaHSO4/SiO2
NaHSO4/SiO2
NaHSO4/SiO2
NaHSO4/SiO2
NaHSO4/SiO2
-
500
400
300
200
100
50
90
90
6
6
38
42
47
55
73
82
90
94
16
64
72
-
2.
3.
90
6
4.
90
6
5.
90
4
6.
90
4
7.
50
100
110
110
110
110
110
110
110
110
4
8.
50
4
9.
-
36
4
10
11
12
13
14
15
NaHSO4.H2O
NaHSO4
50
50
4
SiO2
50
4
synthesizing
a new chiral BIFOL molecule for asymmetric
CF3COOH
BF3.OEt2
0.22 mL
0.28 mL
50
4
57
-
catalysis, we witnessed the formation of xanthene derivative
from 3-(hydroxydiphenylmethyl)naphthalen-2-ol upon treatment
4
AlCl3
4
66
with NaHSO4-SiO2 in dichloroethane.18
The cis-trans
a 2aa (1 mmol) was used in each experiments, b Isolated product.
isomerization followed by oxa-6π-electrocyclization of
benzylidene-1-tetralones under ultraviolet radiation generated
xanthene derivatives,17 and the generation of o-quinone methide
by solid state dehydration of (o-hydroxyaryl)diphenylmethanols19
prompted us to undertake detailed study on the reaction of
(ortho-hydroxyaryl)diarylmethanols with NaHSO4-SiO2. Further,
The reaction furnished the expected xanthene product 3aa
only in 38% yield (Table 1, entry 1). Encouraged by this result,
experiments were carried out by varying catalyst load,
temperature and reaction time. The results are summarized in
2 | J. Name., 2012, 00, 1-3
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Table 1. Decreasing the catalyst load from 500 mg to 50 mg for 3- this transformation using silica supported NaHVSieOw4ArtcicaletaOlnylisnte.
DOI: 10.1039/D0OB01868F
(hydroxydiphenylmethyl)-naphthalen-2-ol
2aa
(1
mmol) Towards that objective,
a
series of symmetrical and
o
promisingly showed the increase in xanthene formation at 90 C unsymmetrical triaryl carbinols (2aa-2ch, and 6aa-6bi) were first
(Table 1, entry 1 to 6). Further, the reaction also required shorter synthesized by treating various freshly prepared arylmagnesium
reaction time with low catalyst load (Table 1, entries 5 & 6). bromides with esters and ketones (prepared via Weinreb amide)
Increasing reaction temperature from 90 C to 100 C and 110 C respectively. To begin with, the symmetrical triaryl carbinols
enhanced the yield of xanthene 3aa formation (Table 1, entries 6 (2aa-2ch) were subjected to dehydration followed by oxa-6π-
& 8). The excellent yield of 3aa (94%) was obtained at 110 oC (oil electrocyclic ring closure in the presence of silica supported
o
o
o
o
bath temperature) in the presence of 50 mg of silica supported NaHSO4 at 110 C (Table 2). This methodology was found to be
NaHSO4 in 1,2-dichloroethane (Table 1, entry 8).
general as exemplified by the successful conversion of
symmetrical triaryl carbinols 2aa-2ch to corresponding xanthene
derivatives 3aa-3ch in 65-96% yields (Table 2). For example,
phenyl and naphthyl substituted carbinol 2aa and 2af furnished
the corresponding xanthenes 3aa and 3af in 94% and 96% yields
respectively (Table 2). The position of electron donating
functional group, for example methyl, in phenyl ring at ortho and
para position showed predictable difference in product yield
(Table 2, entry 3ac and 3ae). For example, 2-Me substituted
phenyl and 4-Me substituted phenyl containing carbinols 2ac and
2e delivered the corresponding xanthenes 3ac and 3ae
respectively in 65% and 87% yield. The carbinols 2ag-2ai, with
electron withdrawing group at para position in phenyl ring also
afforded the corresponding xanthenes in 68-77% yield (Table 2,
entry 3ag to 3ai). All these triaryl carbinols possess two identical
aryl groups.
To ascertain the role of catalyst in this reaction, an
experiment was performed in the absence of catalyst at 110 C.
o
Even after 36h, the carbinol 2aa was converted to corresponding
12-aryl xanthene 3aa only in 16% yield (Table1, entry 9). The
unique catalytic activity displayed by SiO2-NaHSO4 system was
further established by carrying out the experiments in the
presence of reagents such as NaHSO4.H2O, NaHSO4, SiO2,
.
CH3COOH, BF3 OEt2 and AlCl3. These reagents either failed to
facilitate this reaction (Table 1, entries 12 & 14) or furnished 3aa
only in moderate yields under optimized condition (Table 1,
entries 10, 11, 13 & 15). Therefore, from these experiments it is
concluded that the silica supported NaHSO4 is indeed essential
and better catalyst for xanthene formation from triaryl carbinols
containing ortho-hydroxy group in one of the aryl ring.
Table 2 Synthesis of 12/9-aryl xanthenes 3aa-3ch from 2aa-2ch
Table 3 Synthesis of 12/9-aryl xanthenes 7aa-7bi from 6aa-6bi
R
EWG
R
EWG
OH
OH
NaHSO4/SiO2
NaHSO4/SiO2
EDG
R
EDG
1,2-DCE
110 oC, 2-10 h
R
1,2-DCE
OH
6aa-6bi
OH
O
110 oC, 0.5-12 h
O
7aa-7bi, 52-90%
2aa-2ch
3aa-3ch, 65-96%
O
O
OH
O
O
O
O
O
N
7aa, 90%, 4hm
7ab, 75%, 5hm
7ac, 86%, 6hm
7ad, 77%, 5hm
O
F
CF3
O
O
O
O
O
3aa, 94%, 4hm
3ab, 82%, 0.5hm
3ac, 87%, 3hm
3ad, 75%, 1hm
F
Cl
O
O
O
O
7ae, 81%, 2hm
7af, 88%, 3hm
7ag, 69%, 7hn
7ah, 89%, 10hn
F
O
O
O
F
O
Cl
F3
C
CF3
3ae, 65%, 6hm
3af, 96%, 2hm
3ag, 68%, 12hn
3ah, 77%, 12hn
CF3
O
O
O
O
O
O
O
O
7ai, 84%, 10hn
7bc, 52%,3hm
7bf, 87%, 2hm
7bg, 73%, 4hn
F3
C
CF3
O
CF3
O
3ba, 93%, 3hm
Cl
O
O
O
3ai, 69%, 12hn
3bb, 95%,0.5 hm
3bc, 89%, 2hm
O
O
7bi, 79%, 4hn
m = 50 mg of catalyst for 1 mmol of substrate was used; n = 100 mg of catalyst for 1 mmol of substrate was used
H3
C
O
Cl
O
3bf, 92%, 2hm
3ch, 77%, 4hn
To explore the preference of cyclization among different
electronically substituted aryl rings, the unsymmetrical triaryl
carbinols 6aa-6ai were subjected to cyclization reaction using
m = 50 mg of catalyst for 1 mmol of substrate was used; n = 100 mg of catalyst for 1 mmol of substrate was used
On the basis of these facts and the above optimized results, silica supported NaHSO4 catalyst. As expected, the cyclization
we then turned our attention to explore the substrate scope in occurs with electron rich aryl ring over unsubstituted phenyl ring
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
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(Table 3, entry 7aa-7ad). For example anisyl and phenyl group
The successful cyclization of variety of ortho-hydroxyaryl
View Article Online
DOI: 10.1039/D0OB01868F
substituted carbinol 6aa and 6ab, the anisyl group cyclized in group containing triaryl carbinols in the presence of SiO2-
preference over phenyl group as well as gave a good yield of NaHSO4 in 1,2-dichloroethane, we presume that this
corresponding xanthenes 8a and 8b in 90% and 75% respectively. cyclization strategy may be utilized to synthesize
Aryl ring with electron withdrawing group and a phenyl thioxanthenes from 2-(hydroxydiarylmethyl)-thiophenols
ring present in a triaryl carbinol, the phenyl ring present in involving o-thioquinone methide intermediate. Accordingly,
the methide portion undergo cyclization with methide the treatment of 2-(hydroxydiarylmethyl)thiophenols 8a-8f
o
oxygen to generate the corresponding xanthene derivatives. with SiO2-NaHSO4 in 1,2-dichloroethane at 110 C produced
For example, the carbinols 6ag-6ai were successfully the corresponding thioxanthenes 9a-9f in good to excellent
converted to xanthenes 7ag-7ai with moderate yields. The yields (Table 4).
fused ring systems such as naphthyl and phenanthryl groups
The successful cyclization of variety of (ortho-
hydroxyaryl)diarylmethanols and 2-(hydroxydiarylmethyl)-
thiophenols made us to believe mechanistically that the
tertiary alcohol undergo protonation with SiO2-NaHSO4 and
subsequent elimination of H2O to generate o-
quinone/thioquinone methide intermediate I. This reactive
were preferentially cyclized, as they are more electron rich
compared to phenyl group, to yield 12-aryl xanthenes 7ae
and 7af in 81% and 88% respectively (Table 3). To further
ascertain
the
synthetic
potential
of
oxa-6π-
electrocyclization, the reactions were carried out with
various substituted symmetrical and unsymmetrical ortho-
hydroxy benzyl alcohol derivatives (2ba-2bf, 2ch, and 6bc-
o-quinone/thioquinone methide intermediate
I under
thermal condition might have undergone oxa-6π-
elecrocyclization to yield intermediate II, which upon
isomerization driven by aromatization yield the
xanthene/thioxanthene derivatives (Scheme 1).
6bi) in the presence of SiO2-NaHSO4.
The reaction
proceeded smoothly and effectively leading to the formation
of 9-aryl xanthenes in moderate to an excellent yields (see
Table 2 and 3, entry 3ba-3bf, 3ch, 7bc-7bi). As anticipated
both symmetrical and unsymmetrical triaryl carbinols
underwent cyclization in the presence of catalyst SiO2-
NaHSO4 in 1,2-dichloroethane at 110 oC. Here too the
electron-donating functional group containing phenyl ring or
fused aromatic ring systems cyclized preferentially over
unsubstituted phenyl ring (Table 3, entries 7bc and 7bf).
However, when electron-withdrawing group containing
phenyl ring present in the triaryl carbinol, the unsubstituted
phenyl ring cyclized to give the corresponding 9-aryl
xanthenes (Table 3, entries 7bg and 7bi).
OH
OH2
-H+
-H2
NaHSO4/SiO2
O
XH
X
H
X
I
Oxa-6-
Electro-
cyclization
H
Isomerization
X
H
X
II
MeO
HO
OMe
Oxa-6-
electro-
cyclization
MeO
MeO
NaHSO4/SiO2
Table 4 Synthesis of 9-aryl thioxanthenes 9a-9f from 8a-8f
-H2
O
OH
O
O
OMe
2ad
OMe
Ia
IIa
R
R
OMe
OH
MeO
MeO
NaHSO4
SiO2
/
H2
O
OH
NaHSO4/SiO2
-H+
-MeOH
O
H
O
R
1,2-DCE
110 oC, 1-5 h
O
O
R
Me
IIIa
IVa
3ad
S
SH
8a-8f
9a-9f, 60-92%
Scheme 1 Plausible reaction mechanism for cyclization reaction
O
The isomerization in this transformation is ascertained
from the conversion of 3-(hydroxybis(2-methoxyphenyl)-
methyl)naphthalen-2-ol 2ad to an alcohol, 12-(2-methoxy-
phenyl)-12H-benzo[b]xanthen-12-ol 3ad, instead of 12-(2-
methoxyphenyl)-12H-benzo[b]xanthene. The formation of
alcohol, 12-(2-methoxyphenyl)-12H-benzo[b]xanthen-12-ol
3ad, can be explained only through the formation of
xanthylium ion IVa followed by generation of alcohol 3ad
upon quenching the reaction mixture with H2O. The carbon
attached with inductively electron withdrawing OMe group,
an electron deficient site, can attract electron from methide
oxygen to establish O-C bond of xanthene skeleton (Scheme
S
S
O
S
9a, 90%, 3hm
9b, 92%, 2hm
9c, 83%, 3hm
F
Cl
S
S
F
S
Cl
9d, 85%, 2hm
9e, 60%, 5hn
9f, 72%, 4hn
m = 50 mg of catalyst for 1 mmol of substrate ; n = 100 mg of catalyst for 1 mmol of substrate
4 | J. Name., 2012, 00, 1-3
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1). o-Quinone methides are known to undergo 1,4-addition acid (TfOH, 10 mM) produced a new red shift weak hump at 443
View Article Online
reaction with nitrogen nucleophiles.22
Therefore, the nm that indicates generation of conjugation in xanthenes by the
DOI: 10.1039/D0OB01868F
carbinol 2aa was treated with benzamide, which may act as removal of hydride ion. The intensity of 245 nm peak reduced
a nitrogen nucleophile, in the presence of SiO2-NaHSO4 significantly. It is noted that the stronger acid, TfOH, required
(100mg) at 70 oC in 1,2-dichloroethane. After 12 h, the comparatively low concentration to induce hydride removal
product 2,4,4-triphenyl-4H-naphtho[2,3-e][1,3]oxazine 10aa compared to other acids (Fig. S1a). Further to optimize the
was obtained in 80% yield (Scheme 2). This observation also concentration and rate of hydride ion transfer, different
proves
that
the
(ortho-hydroxyaryl)diarylmethanols concentration of TfOH was added into xanthene (3aa) and
produces the o-quinone methide as an intermediate and monitored the absorption change (Fig. S1b). The appearance of
goes for oxa-6π-electrocyclization reaction to generate the new red shift weak absorption peak at 443 nm was observed
corresponding xanthene derivatives in the absence of added from the addition of 0.1 mM of TfOH onwards. The weak red
nucleophile or 1,4-addition reaction in the presence of shift absorption becomes strong without changing the peak
external nucleophile.
position after 24 h. This suggests that hydride ion transfer
required few hours to complete the reaction and formation of
xanthylium salt 3aaS (Fig. 4). Other xanthene derivatives, 3ac, ah,
ai, and 3ba, and a thioxanthene derivative 9a are also exhibited
similar new red shift absorption in presence of TfOH (Fig 3a and
S2). Absorption peak positions were varied depending on the
electronic substituents in xanthene derivatives. It is noted that
3ab and 3ac also showed strongly red shift weak absorption
around 600 nm along with n-π* transition between 424 nm.
Ph
Ph
Ph
OH
Ph
Ph
Ph
OH
O
OH
NaHSO4/SiO2
2aa
-H2
O
Ph
NH
H
Ph
NH2
H
Ph
NH2
H+
O
O
O
Ph Ph
NH
Ph
Ph
NH
Ph
Ph
O
OH
OH
OH
H
Ph Ph
NH
Ph Ph
N
Ph Ph
NH
-H+
Ph
-H2
O
O
Ph
O
Ph
O
OH2
10aa
Scheme 2 Reaction of o-quinone methide with benzamide
9-Aryl xanthenes and 9-aryl thioxanthenes are capable of
producing “amphihydric” species such as conjugate cations or
anions through the removal of hydride ion or proton
respectively.23 The removal of hydride from 9-phenyl xanthenes
generate 9-phenyl xanthylium ions, which has been used to
examine the hydride transfer mechanism of NADH.24 These
xanthylium/thioxanthylium ions, due to the prevalence of
extending conjugation and planarity, may exhibit useful
photophysical properties and hence the substances derived from
these skeletons may possibly display potential applications in
medical field.3 In order to verify the hydride ion transfer upon
adding acid and resultant photophysical property change, we
performed absorption and emission studies of selected 12-aryl-
12H-benzo[b]xanthenes (3aa-ac, 3ah, 3ai), 9-phenyl xanthene
(3ba) and 9-phenyl thioxanthene (9a). To identify the suitable
Brønsted acid, which can abstract a hydride from 12-aryl-12H-
benzo[b]xanthenes, to generate corresponding xanthylium ions, a
model substrate 12-phenyl-12H-benzo[b]xanthene 3aa was
treated with Brønsted acids with varying pka values (Fig. S1a).
The non-conjugated 12-phenyl-12H-benzo[b]xanthene (3aa) in
chloroform (0.01 mM) showed strong absorption at 245 nm (π-
π* transition) before adding Brønsted acids (Fig. S1a).
Fig. 3 (a) Absorption and (b) fluorescence spectra of 3aa, 3ba and
9a in CHCl3
Comparison of 3aa, 3ba and 9a revealed that increased
conjugation in 3aa showed slightly higher red shift absorption
than 3ba and 9a (Fig. 3a). The conversion of non-conjugated
structure to π-conjugated structure could rigidify the aromatic
unit that might lead to turn-on fluorescence. As such, the
xanthene molecules did not show fluorescence in chloroform. In
contrast, all the molecules showed strongly enhanced
fluorescence after hydride ion transfer by the addition of TfOH
(Fig. 3b and S3). The compound 3ba exhibited strongly enhanced
fluorescence at 514 nm whereas thioxanthene molecule, 9a,
showed highly red shift fluorescence at 560 nm (Fig S4). Xanthene
derivative 3aa showed blue shift moderate fluorescence.
O
O
S
OTf
, 424 nm
OTf
OTf
9aS
, 383 nm
Addition of acetic acid (100 mM), a weak acid, did not show
any significant change in the absorption. In contrast, addition of
trifluoroacetic acid (TFA, 50 mM) and trifluoromethanesulphonic
3aaS
3baS
, 374 nm
Fig. 4 Xanthylium triflate salts
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Organic & Biomolecular Chemistry
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ARTICLE
Journal Name
Thus the photophysical studies of xanthene and thioxanthene carbinols involving o-quinone methide foVrimewaAtritoicnle Onvliniae
DOI: 10.1039/D0OB01868F
derivatives clearly indicated the hydride ion transfer upon dehydration in the presence of NaHSO4/SiO2 followed by
addition of strong organic acid such as TfOH and generated oxa-6π-electrocyclization and isomerization at elevated
fluorescent xanthylium and thioxanthylium ions (Fig. 4).
temperature.
Triaryl thiocarbinols too furnished the
Further, the formation of xanthylium salts with TfOH has also expected thioxanthenes in excellent yields. Two electron
been investigated using NMR spectroscopy. The reaction was rich aryl groups are participated in the cyclization reaction.
carried out in NMR tube. The xanthene, 12-phenyl-12H- Synthesis of chiral 9/12 aryl xanthenes/benzo[b]xanthenes
benzo[b]xanthene 3aa (1 equiv.) was taken in CDCl3 and 2 and their applications in asymmetric catalysis is under
equivalent of TfOH was added at 0 oC. Then the reaction mixture investigation in this laboratory.
was slowly brought to room temperature. The reaction was
monitored every hour, until the completion of reaction.
EXPERIMENTAL SECTION
General Information
Instrumentation: All reactions were performed in oven-dried
round bottom flasks. Stainless steel syringes were used to
transfer air and moisture sensitive liquids. Melting points
reported in this paper are uncorrected and were determined
using Buchi Melting point apparatus M-560. Infrared spectra
were recorded on Thermo Nicolet iS10 FT-IR Spectrophotometer
and are reported in frequency of absorption (cm-1). 1H and 13C
NMR spectra were recorded on Bruker AVANCE – II 400 MHz
spectrometer. NMR spectra for all the samples were measured in
CDCl3 (some cases mixture of CDCl3 and DMSO-d6) using TMS as
an internal standard. The chemical shifts are expressed in δ ppm
down field from the signal of internal TMS. Data are represented
as follows: chemical shift, multiplicity (s = singlet, d = doublet, t =
triplet, q = quartet, dd = doublet of doublet, ddd = doublet of
doublet of doublet, td = triplet of doublet, m = multiplet),
coupling constants in Hertz (Hz) and integration.
Solvents used for the reactions were dried using standard
procedures. For the synthesis, chemicals such as aldehydes
supplied by Aldrich, USA were used. Remaining reagents from
Avra, and Sd Fine Chemicals, India were used. Column
chromatography was performed on Merck silica gel 100-200
mesh, and TLC analyses were facilitated using phosphomolybdic
acid stain in addition to UV light with Merck 60 GF254 pre-coated
silica plates
Fig. 5. 1H and 13C NMR of 3aa and 3aaS
General procedure for the preparation of 12/9-aryl-12/9H-
benzo[b]xanthene derivatives, 3aa-3ch & 7aa-7bi
The 1H NMR spectra clearly showed the disappearance of
tertiary–CH– proton at 12th positions in 3aa after completion of
the reaction (Fig. 5a and 5b). The conversion of non-conjugated
structure to conjugated structure changed the pattern of
aromatic protons also. In addition, 13C NMR spectra showed
disappearance of peak at 45 ppm (chemical shift) in 3aa after
completion of the reaction (Fig. 5c and 5d). Hence, NMR studies
also confirmed the formation of xanthylium salts via hydride ion
transfer in the presence of organic acids at room temperature.
A mixture of triarylcarbinol 2aa-2ch, or 6aa-6bi (1.0 mmol)
and NaHSO4/SiO2 (50 mg) in dry 1,2-dichloroethane (20 mL) was
heated at 100-110 oC with vigorous stirring under N2 atmosphere.
The reaction mixture was then cooled to room temperature,
filtered and concentrated. After removing the solvent under
reduced pressure, the residue was purified through silica gel
column chromatography using hexane/ethyl acetate (99:1) as
eluent to afford 12-aryl-12H-benzo[b]xanthene derivatives, 3a-3i,
or 8a-8i respectively in pure form.
12-Phenyl-12H-benzo[b]xanthene (3aa)
o
Colourless solid (94%, 289 mg); m.p. 169-171 C; IR (KBr, cm-
Conclusion
1): 3056, 2963, 1589, 1448, 1265, 873, 748; 1H (CDCl3, 400 MHz): δ
7.66 (d, J = 8.4 Hz, 1H), 7.56 (d, J = 8.4 Hz, 1H), 7.45 ( d, J = 5.2 Hz,
2H), 7.32-7.28 (m, 1H), 7.22-7.10 (m, 8H), 7.01 (d, J = 7.6 Hz, 1H),
In conclusion, a simple methodology has been devised to
synthesize
9/12
aryl
substituted
xanthenes/-
benzo[b]xanthenes respectively from corresponding triaryl
6 | J. Name., 2012, 00, 1-3
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Organic & Biomolecular Chemistry
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Journal Name
ARTICLE
6.93-6.89 (m, 1H), 5.31 (s, 1H); 13C (CDCl3, 100 MHz): δ 151.5, 8.90 (d, J = 8.8 Hz, 1H), 7.89-7.77 (m, 5H), 7.76-7.72V(imew,A2rtHic)le, O7.n6lin0e-
DOI: 10.1039/D0OB01868F
149.9, 146.2, 133.4, 130.5, 129.7, 129.0, 128.9, 128.5, 128.1, 7.56 (m, 4H), 7.48 (d, J = 8.8 Hz, 1H), 7.39-7.35 (m, 1H), 7.34-7.30
127.6, 126.9, 126.7, 126.3, 124.9, 124.5, 123.3, 116.8, 112.0, (m, 1H), 7.29-7.22 (m, 3H), 7.19-7.15 (m, 1H), 6.84 (s, 1H); 13C
45.1; HRMS (ESI) for C25H17O (M+H) + calculated 309.1279, found (CDCl3, 100 MHz): δC 150.0, 148.6, 142.3, 134.3, 133.3, 132.0,
309.1285.
130.8, 130.5, 130.4, 129.6, 129.3, 128.7, 128.0, 127.7, 127.5,
127.2, 127.1, 126.9, 126.7, 126.7, 126.2, 125.7, 124.4, 124.2,
3-Methoxy-12-(4-methoxyphenyl)-12H-benzo[b]xanthene (3ab)
Colourless solid (90%, 331 mg); m.p. 141-142 C; IR (KBr, cm- 123.1, 123.0, 118.2, 116.7, 112.3, 36.1; HRMS (ESI) for C31H21O
o
1): 2945, 2836, 1592, 1429, 1251, 1026, 821, 743; H (CDCl3, 400 (M+H)+ calculated 409.1592, found 409.1593.
1
MHz): δH 7.77 (d, J = 8.0 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H), 7.55 (d, J 3-Fluoro-12-(4-fluorophenyl)-12H-benzo[b]xanthene (3ag)
o
= 3.2 Hz, 2H), 7.43-7.39 (m, 1H), 7.34-7.30 (m,1H), 7.16 (d, J =8.4
Colourless solid (68%, 234 mg); m.p. 174-176 C; IR (KBr, cm-
Hz, 2H), 7.00-6.97 (d, J= 8.8 Hz, 1H), 6.83 (d, J = 8.4 Hz, 2H), 6.76 1): 3063, 1606, 1500, 1430, 1237, 1166, 1100, 266, 744; 1H (CDCl3,
(d, J = 2.4 Hz, 1H), 6.61 (dd, J = 2.4, 8.4 Hz, 1H), 5.33 (s, 1H), 3.83 400 MHz): δH 7.77 (d, J = 8.4 Hz, 1H), 7.67 (d, J = 8.4 Hz, 1H), 7.56
(s, 3H), 3.77 (s, 3H); 13C (CDCl3, 100 MHz): 159.5, 158.4, 152.2, (s, 1H), 7.51 (s, 1H), 7.45-7.40 (m, 1H), 7.36-7.31 (m, 1H), 7.21-
149.8, 138.8, 133.3, 130.4, 130.2, 129.5, 128.9, 127.6, 127.2, 7.17 (m, 2H), 7.04-6.96 (m, 3H), 6.92 (dd, J = 2.8, 9.6 Hz, 1H), 6.74
126.9, 126.3, 124.4, 117.3, 114.2, 111.9, 110.2, 101.4, 55.6, 55.3, (td, J = 2.8, 8.8 Hz, 1H), 5.38 (s, 1H); 13C (CDCl3, 100 MHz): δC
43.5; HRMS (ESI) for C25H21O3 (M+H)+ calculated 369.1491, found 163.0, 161.0, 160.6, 152.2, 152.1, 149.2, 141.8, 141.8, 133.4,
369.1490.
130.7, 130.6, 130.5, 130.0, 129.9, 128.9, 127.6, 127.0, 126.6,
126.0, 124.8, 120.5, 120.5, 116.0, 115.8, 112.2, 110.8, 110.6,
3-Methyl-12-(p-tolyl)-12H-benzo[b]xanthene (3ac)
Colourless solid (87%, 292); m.p. 261-263 oC; IR (KBr, cm-1): 104.3, 104.1, 43.7; HRMS (ESI) for C23H15F2O (M+H)+ calculated
3046, 2915, 1588, 1501, 1448, 1263, 873, 744; 1H (CDCl3, 400 345.1091, found 345.1087.
MHz): δH 7.77 (d, J = 8.0 Hz, 1H), 7.67 (d, J = 8.0 Hz, 1H), 7.57 (s, 3-Chloro-12-(4-chlorophenyl)-12H-benzo[b]xanthene (3ah)
o
2H), 7.44-7.39 (m, 1H), 7.34-7.30 (m,1H), 7.16-7.09 (m, 4H), 7.04
Colourless solid (77%, 289 mg); m.p. 196-198 C; IR (KBr, cm-
(s, 1H), 7.01 (d, J = 8.0 Hz, 1H), 6.84 (dd, J = 1.2, 8.0 Hz, 1H), 5.37 1): 3051, 1585, 1478, 1254, 1091, 807, 742; H (CDCl3, 400 MHz);
(s, 1H), 2.37 (s, 3H), 2.31 (s, 3H); 13C (CDCl3, 100 MHz): 151.3, δH 7.68 (d, J = 8.0 Hz, 1H), 7.57 (d, J = 8.0 Hz, 1H), 7.47 (s, 1H),
150.0, 143.6, 138.1, 136.4, 133.4, 130.4, 129.6, 129.3, 128.8, 7.41 (s, 1H), 7.61-7.32 (m, 1H), 7.27-7.23 (m, 1H), 7.18-7.13 (m,
128.3, 127.6, 127.1, 126.9, 126.2, 124.3, 124.2, 122.0, 117.1, 3H), 7.06 (d, J = 8.4 Hz, 2H), 6.90 (s, 2H), 5.26 (s, 1H); 13C (CDCl3,
111.9, 44.3, 21.3, 21.1; HRMS (ESI) for C25H21O (M+H)+ calculated 100 MHz); δC. 151.9, 149.2, 144.2, 133.6, 133.5, 133.0, 130.6,
1
337.1587, found 337.1585.
12-(2-Methoxyphenyl)-12H-benzo[b]xanthen-12-ol (3ad)
Colourless solid (75 %, 265 mg); m.p. 200-202 C; IR (KBr, cm- C23H15Cl2O (M+H)+ calculated 377.0500, found 377.0492.
1): 3522, 3054, 1591, 1450, 1255, 1012, 751; 1H (CDCl3, 400 MHz): 3-(Trifluoromethyl)-12-(4-(trifluoromethyl)phenyl)-12H-benzo-
δH 8.03 (dd, J = 7.6, 1.6 Hz, 1H), 7.83 (s, 1H), 7.78 (d, J = 8.4 Hz, [b]xanthene (3ai)
130.5, 129.8, 129.3, 128.9, 128.8, 127.9, 127.6, 127.0, 126.7,
125.5, 124.9, 123.7, 123.0, 117.2, 112.4, 44.0; HRMS (ESI) for
o
1H), 7.68 (d, J = 8.4 Hz, 1H), 7.57 (s, 1H), 7.44-7.39 (m, 1H), 7.30
Colourless solid (69%, 306mg); m.p. 139-140 oC; IR (KBr, cm-1):
(dd, J = 6.8, 0.8 Hz, 1H) 7.29-7.24 (m, 3H), 7.20 (dd, J = 8.4, 1.2 Hz, 3057, 2925, 1919, 1606, 1424, 1331, 1167, 1125, 743, 470; 1H
1H), 7.10 (td, J = 7.6, 0.8 Hz, 1H), 7.03-6.99 (m, 1H), 6.69 (dd, J = (CDCl3, 400 MHz): δ 7.80 (d, J = 8.0 Hz, 1H), 7.69 (d, J = 8.0 Hz ,
8.0, 0.8 Hz, 1H), 3.26 (s, 3H), 3.25 (s, 1H); 13C (CDCl3, 100 MHz): δC 1H), 7.61 (s, 1H), 7.56 (d, J = 8.0 Hz, 2H), 7.52 (d, J = 10.8 Hz, 2H),
155.8, 150.4, 148.8, 136.3, 133.8, 130.1, 129.6, 129.0, 128.9, 7.48-7.44 (m, 1H), 7.39-7.34 (m, 3H), 7.28 (d, J = 8.0 Hz, 1H), 7.19
128.1, 127.8, 127.0, 126.8, 126.6, 125.6, 124.1, 122.8, 120.5, (d, J = 8.0 Hz, 1H), 5.51 (s, 1H); 13C (CDCl3, 100 MHz): δ 151.5,
115.9, 112.5, 110.9, 69.3, 55.5; HRMS (ESI) for C24H18NaO3 149.0, 133.6, 131.2, 130.9, 130.7, 130.3, 129.8, 129.0, 128.8,
(M+Na)+ calculated 377.1154, found 377.1139.
1-Methyl-12-(o-tolyl)-12H-benzo[b]xanthene (3ae)
Colourless solid (65%, 218 mg); m.p. 193-194 C; IR (KBr, cm- for C25H15F6O (M+H)+ calculated 445.1027, found 445.1025.
1): 3023, 2944, 1584, 1457, 1252, 1023, 743, 467; H (CDCl3, 400 9-Phenyl-9H-xanthene (3ba)
127.7, 127.6, 127.1, 126.9, 126.3, 126.2, 126.2, 125.1, 124.7,
122.8, 122.4, 120.0, 120.0, 114.5, 114.5, 112.6, 44.7; HRMS (ESI)
o
1
o
MHz): δ 7.73 (d, J = 8.4 Hz, 1H), 7.71 (s, 1H), 7.67 (d, J = 8.4 Hz,
Colourless solid (93%, 237 mg); m.p. 144-145 C (Lit. 149-150
1H), 7.53 (s, 1H), 7.40-7.36 (m, 1H), 7.32-7.28 (m, 1H), 7.22-7.18 oC); IR (KBr, cm-1): 3020, 1568, 1442, 1250, 890, 749; H (CDCl3,
(m, 1H), 7.15-7.10 (m, 3H), 7.03-7.00 (m, 2H), 6.90 (d, J = 3.2 Hz, 400 MHz): δH 7.18-7.14 (m, 2H), 7.12-7.07 (m, 5H), 7.03 (dd, J =
1H), 5.73 (s, 1H), 2.71 (s, 3H), 2.18 (s, 3H); 13C (CDCl3, 100 MHz): δ 1.2, 8.4 Hz, 2H), 6.95-6.93 (m, 2H), 6.88-6.84 (m, 2H), 5.14 (s, 1H);
152.3, 149.4, 144.3, 137.6, 133.8, 133.3, 130.9, 130.4, 129.4, 13C (CDCl3, 100 MHz): δC.. 151.1, 146.6, 129.8, 128.9, 128.5, 128.0,
127.8, 127.7, 127.5, 127.4, 127.0, 126.9, 126.4, 126.2, 125.2, 126.8, 124.5, 123.3, 116.7, 44.5; HRMS (ESI) for C19H15O (M+H)+
124.3, 123.8, 114.6, 112.0, 39.1, 20.4, 19.7; HRMS (ESI) for calculated 259.1123 found 259.1110.
1
C25H21O (M+H)+ calculated 337.1592, found 337.1580.
14-(Naphthalen-1-yl)-14H-dibenzo[a,i]xanthene (3af)
3-Methoxy-9-(4-methoxyphenyl)-9H-xanthene (3bb)
o
Colourless solid (95%, 302 mg); m.p. 94-95 C; IR (KBr, cm-1):
o
1
Colourless solid (96%, 392 mg); m.p. 261-263 C; IR (KBr, cm- 3018, 2955, 2836, 1604, 1452, 1251, 1025, 805, 746; H (CDCl3,
1
1): 3051, 1623, 1506, 1447, 1263, 741; H (CDCl3, 400 MHz): δH 400 MHz): δH 7.23-7.18 (m, 1H), 7.13-7.10 (m, 3H), 7.06-7.04 (m,
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Journal Name
1H), 7.00-6.98 (m,1H), 6.94 (dd, J = 0.8, 8.4 Hz, 1H), 6.84-6.80 (m, 139.5, 138.3, 135.0, 134.7, 134.5, 129.4, 128.2, V1ie2w7A.8rti,cle1O2n7l.in7e,
DOI: 10.1039/D0OB01868F
2H), 6.67 (d, J = 2.8, Hz, 1H), 6.58 (dd, J = 2.4, 8.4 Hz, 1H), 5.17 (s, 125.9, 124.9, 124.2, 123.9, 123.8, 113.8, 110.9, 110.0, 55.6, 52.5;
1H), 3.81 (s,3H), 3.77 (s, 3H); 13C (CDCl3, 100 MHz): δC 159.4, HRMS (ESI) for C24H19O2 (M+H)+ calculated 339.1385, found
158.3, 151.7, 151.0, 139.3, 130.4, 129.9, 129.5, 127.8, 125.0, 339.1381.
123.3, 116.9, 116.5, 114.2, 110.3, 101.2, 55.5, 55.3, 43.0; HRMS 3-Methyl-12-phenyl-12H-benzo[b]xanthene (7ac)
o
(ESI) for C21H19O3 (M+H)+ calculated 319.1334, found 319.1311.
Colourless solid (86%, 277 mg); m.p. 190-193 C; IR (KBr, cm-
3-Methyl-9-(p-tolyl)-9H-xanthene (3bc)
1): 3023, 2919, 1588, 1499, 1459, 1263, 1163, 738; 1H (CDCl3, 400
o
Colourless solid (89%, 255 mg); m.p. 118-119 C; IR (KBr, cm- MHz): δH 7.67 (d, J = 8.0 Hz, 1H), 7.57 (d, J = 8.4 Hz, 1H), 7.47-7.46
1
1): 3026, 2917, 1599, 1446, 1261, 1111, 801, 751; H (CDCl3, 400 (m, 2H), 7.33-7.29 (m, 1H), 7.24-7.19 (m, 2H), 7.17-7.16 (m, 2H),
MHz): δH 7.39-7.34 (m, 1H), 7.30-7.26 (m, 5H), 7.24-7.21 (m, 1H), 7.15-7.14 (m, 1H), 7.12-7.01 (m, 1H), 6.94 (s, 1H), 6.89 (d, J = 8.0
7.16-7.09 (m, 3H), 6.98-6.96 (m, 1H), 5.36 (m, 1H), 2.51 (m, 3H), Hz, 1H), 6.74 (dd, J = 7.6, 0.8 Hz, 1H), 5.31 (s, 1H), 2.27 (s, 3H); 13
C
2.47 (s, 3H); 13C (CDCl3, 100 MHz): δC..151.2, 150.9, 144.0, 138.0, (CDCl3, 100 MHz): δC 151.3, 150.0, 146.5, 138.2, 133.4, 130.4,
136.2, 129.8, 129.5, 128.4, 127.8, 124.9, 124.3, 123.2, 121.7, 129.6, 129.4, 128.9, 128.8, 128.5, 128.4, 128.1, 127.6, 126.9,
116.9, 116.6, 43.8, 21.2, 21.1; HRMS (ESI) for C21H19O (M+H)+ 126.8, 126.3, 124.4, 124.3, 123.3, 121.8, 117.1, 116.7, 112.0, 44.7,
calculated 287.1430, found 287.1393.
12-(Naphthalen-1-yl)-12H-benzo[a]xanthene (3bd)
Colourless solid (92%, 329 mg); m.p. 120-121 C; IR (KBr, cm- N,N-Dimethyl-12-phenyl-12H-benzo[b]xanthen-3-amine (7ad)
1): 3056, 1620, 1583, 1458, 1250, 1107, 751; 1H (CDCl3, 400 MHz):
21.3; HRMS (ESI) for C24H19O (M+H)+ calculated 323.1436, found
323.1422.
o
o
Pale red solid (77% ,270 mg); m.p. 172-173 C; IR (KBr, cm-1):
1
δH 8.89 (d, J = 8.8 Hz, 1H), 7.90 (d, J = 8.0 Hz, 1H), 7.83 (s, 1H), 3022, 2889, 2809, 1628, 1442, 1260, 1115, 876, 746; H (CDCl3,
7.81-7.76 (m, 2H), 7.69 (d, J = 8.4 Hz, 1H), 7.62-7.57 (m, 2H), 7.46 400MHz): δH 7.76 (d, J = 8.0 Hz, 1H), 7.65 (d, J = 8.4 Hz, 1H), 7.55
(d, J = 9.2 Hz, 1H), 7.43-7.41 (m, 1H), 7.32-7.27 (m, 1H), 7.25-7.18 (s, 1H), 7.54 (s, 1H), 7.41-7.37 (m, 1H), 7.32-7.25 (m, 5H), 7.20-
(m, 5H), 6.90 (qd, J = 8.0, 6.8, 2.0 Hz, 1H), 6.73 (s, 1H); 13C (CDCl3, 7.16 (m, 1H), 6.93 (d, J = 8.4 Hz, 1H), 6.54 (d, J = 2.4 Hz, 1H), 6.43
100 MHz): δC 149.8, 149.8, 143.6, 134.2, 132.0, 130.9, 130.5, (dd, J = 8.4, 2.8 Hz, 1H), 5.35 (s, 1H), 2.97 (s, 6H); 13C (CDCl3,
129.6, 129.5, 129.2, 128.6, 128.6, 127.8, 127.8, 127.2, 127.1, 100MHz): δC 152.1, 150.8, 150.2, 147.0, 133.3, 130.3, 130.0,
127.0, 126.3, 125.7, 125.1, 124.2, 123.6, 123.2, 123.2, 122.9, 128.9, 128.8, 128.5, 127.6, 127.4, 126.8, 126.6, 126.2, 124.3,
118.1, 116.9, 116.4, 35.6; HRMS (ESI) for C27H19O (M+H)+ 112.7, 111.8, 108.4, 99.9, 44.3, 40.7; HRMS (ESI) for C25H22NO
calculated 359.1436, found 359.1405.
(M+H)+ calculated 352.1701, found 352.1698.
3-Chloro-9-(4-chlorophenyl)-6-methyl-9H-xanthene (3ch)
14-Phenyl-14H-dibenzo[a,i]xanthene (7ae)
o
o
Colourless solid (77%, 262 mg); m.p. 139-140 C; IR (KBr, cm-
Colourless solid (81%, 290 mg); m.p. 208-209 C; IR (KBr, cm-
1): H (CDCl3, 400 MHz): δH 7.28-7.27 (m, 1H), 7.25-7.24 (m, 1H), 1): 3020, 1615, 1504, 1446, 1261, 1157, 814, 740; H (CDCl3, 400
7.15 (d, J = 1.6 Hz, 1H), 7.12 (dd, J = 2.0, 6.4 Hz, 2H), 6.97-6.96 (m, MHz): δH 8.03 (d, J = 8.4 Hz, 1H), 7.88 (s, 1H), 7.83 (d, J = 8.8 Hz,
2H), 6.93 (d, J = 8.0 Hz, 1H), 6.89 (d, J = 8.0 Hz, 1H), 6.85-6.82 (m, 2H), 7.77 (dd, J = 3.6, 8.0 Hz, 2H), 7.62 (s, 1H), 7.50-7.47 (m, 2H),
1H), 5.17 (s, 1H), 2.35 (s, 3H); 13C (CDCl3, 100 MHz): δC.. 151.6, 7.42-7.35 (m, 5H), 7.20 (t, J = 7.6 Hz, 2H), 7.08 (d, J = 7.6 Hz, 1H),
150.4, 144.9, 138.6, 133.3, 132.8, 130.8, 129.8, 129.4, 129.1, 6.02 (s, 1H); 13C (CDCl3, 100 MHz): δC 149.7, 149.1, 146.3, 133.3,
124.8, 123.6, 122.7, 120.5, 117.1, 117.1, 43.2, 21.21; HRMS (ESI) 131.8, 130.9, 130.7, 129.3, 129.0, 128.8, 128.4, 127.6, 127.3,
1
1
for C20H15Cl2O (M+H)+ calculated 341.0494, found 341.0456.
127.0, 126.8, 126.8, 126.7, 126.3, 124.5, 124.3, 123.0, 118.2,
116.3, 112.2, 42.4; HRMS (ESI) for C27H19O (M+H)+ calculated
3-Methoxy-12-phenyl-12H-benzo[b]xanthene (7aa)
o
Colourless solid (90%, 311 mg); m.p. 160-162 C; IR (KBr, cm- 359.1426, found 359.1426.
1): 3021, 2963, 1590, 1447, 1255, 1098, 1026, 803, 739; 1H (CDCl3, 16-Phenyl-16H-tribenzo[a,c,i]xanthene (7af)
400 MHz): δH 7.77 (d, J = 8.0 Hz, 1H), 7.66 (d, J = 8.0 Hz, 1H), 7.56
White solid (88%, 359 mg); m.p. 213-215 oC; IR (KBr, cm-1):
(s, 2H), 7.43-7.39 (m, 1H), 7.34-7.31 (m, 2H), 7.29-7.18 (m, 4H), 3017, 2962, 1633, 1450, 1263, 1017, 807, 752; 1H (CDCl3, 400
7.00 (d, J = 8.4 Hz, 1H), 6.77 (d, J = 2.4 Hz, 1H), 6.61 (dd, J = 2.4, MHz): δH 8.75-8.66 (m, 3H), 8.08-8.06 (m, 1H), 7.92 (s, 1H), 7.82-
8.4 Hz, 1H), 5.38 (s, 1H), 3.83 (s, 3H); 13C (CDCl3, 100 MHz): δC 7.74 (m, 5H), 7.57-7.54 (m, 2H), 7.437.40(m, 3H), 7.38-7.35 (m,
159.6, 152.2, 149.8, 146.6, 133.4, 130.4, 130.3, 129.0, 128.9, 1H), 7.20-7.16 (m, 2H), 7.08-7.04 (m, 1H), 6.03 (s, 1H); 13C (CDCl3,
128.5, 127.6, 126.9, 126.8, 126.8, 126.3, 124.4, 117.0, 111.9, 100 MHz): δC 148.7, 146.1, 145.5, 133.2, 131.0, 130.9, 130.5,
110.2, 101.5, 55.5, 44.4; HRMS (ESI) for C24H19O2 (M+H)+ 129.0, 128.3, 128.1, 127.6, 127.4, 127.3, 127.3, 127.0, 127.0,
calculated 339.1385, found 339.1374.
4-Methoxy-12-phenyl-12H-benzo[b]xanthene (7ab)
Colourless solid (75% 253 mg); m.p. 167-168 oC; IR (KBr, cm-1): calculated 409.1592, found 409.1567.
3032, 2947, 1591, 1452, 1277, 1087, 1014, 724; 1H (CDCl3, 400 12-(4-Fluorophenyl)-12H-benzo[b]xanthene (7ag)
126.8, 126.7, 126.3, 125.0, 124.9, 124.6, 123.7, 123.1, 122.7,
122.6, 112.7, 112.3, 42.5; HRMS (ESI) for C27H21O (M+H)+
o
MHz): δH 8.69-8.67 (m, 1H), 8.28 (d, J = 8.8 Hz, 1H), 7.81-7.79 (m,
Colourless solid (69%, 225 mg); m.p. 147-148 C; IR (KBr, cm-
1H), 7.52-7.48 (m, 2H), 7.31-7.28 (m,4H), 7.19-7.16 (m, 2H), 7.11 1): 3053, 1595, 1498, 1226, 1154, 873; H (CDCl3, 400 MHz): δH
(s, 1H), 7.01 (dd, J = 8.4, 2.4 Hz, 1H), 6.89 (d, J = 2.4 Hz, 1H), 5.08 7.67 (d, J = 8.4 Hz, 1H), 7.57 (d, J = 8.4 Hz, 1H), 7.47 (s, 1H), 7.43
(s, 1H), 3.81 (s, 3H); 13C (CDCl3, 100 MHz): δC. 159.1, 151.3, 150.8, (s, 1H), 7.34-7.30 (m, 1H), 7.25-7.20 (m, 1H), 7.18-7.15 (m, 1H),
1
8 | J. Name., 2012, 00, 1-3
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ARTICLE
7.14-7.08 (m, 3H), 6.99-6.98 (m, 1H), 6.95-6.92 (m, 1H), 6.87 (t, J 6.91 (d, J = 8.4 Hz, 1H), 6.70 (d, J = 2.4Hz,1H), 6.59 (dd, J = 8.4, 2.4
View Article Online
13
= 8.8 Hz, 2H), 5.31 (s, 1H); 13C (CDCl3, 100 MHz): δC.. 163.0, 160.6, Hz, 1H), 5.20 (s, 1H), 3.81 (s, 3H); C (CDCl3, 100 MHz): δC 162.9,
151.5, 149.8, 142.0, 141.9, 133.5, 130.4, 132.0, 129.9, 129.5, 160.5, 159.5, 151.7, 150.9, 142.8, 142.7, 130.4, 130.0, 129.9,
128.8, 128.3, 127.6, 126.9, 126.5, 126.5, 124.7, 124.6, 123.4, 129.8, 128.9, 128.5, 128.1, 124.5, 123.4, 116.7, 116.4, 115.8,
116.8, 115.9, 115.7, 112.4, 44.3; HRMS (ESI) for C23H16FO (M+H)+ 115.6, 110.4, 101.3, 55.5, 43.1; HRMS (ESI) for C20H16FO2 (M+H)+
DOI: 10.1039/D0OB01868F
calculated 327.1185, found 327.1173.
calculated 307.1134, found 307.1118.
12-(4-(Trifluoromethyl)phenyl)-12H-benzo[b]xanthene (7ah)
9-(3,5-Bis(trifluoromethyl)phenyl)-3-methoxy-9H-xanthene (7bi)
o
o
Colourless solid (89%, 335 mg); m.p. 127-128 C; IR (KBr, cm-
Colourless solid (79%, 335 mg); m.p. 158-159 C; IR (KBr, cm-
1): 3055, 1603, 1452, 1328, 1270, 1124, 748; 1H (CDCl3, 400 MHz): 1): 3067, 2928, 2842, 1630, 1502, 1453, 1034, 752, 642; 1H (CDCl3,
δH 7.78 (d, J = 8.0 Hz, 1H), 7.68 (d, J = 8.0 Hz, 1H), 7.60 (s, 1H), 400 MHz): δH δ 7.71 (s, 1H), 7.62 (s, 2H), 7.29-7.24 (m, 1H), 7.16
7.54 (s, 2H), 7.53 (s, 1H), 7.45-7.40 (m, 1H), 7.39-7.35 (m, 2H), (d, J = 1.2, 8.4 Hz , 1H), 7.04-6.98 (m, 2H), 6.88 (d, J = 8.4 Hz , 1H),
7.33-7.31 (m, 1H), 7.28-7.26 (m, 1H), 7.22 (dd, J = 1.2, 8.0 Hz, 1H), 6.72 (d, J = 2.4 Hz , 1H), 6.61 (d, J = 2.4, 8.4 Hz , 1H), 5.37 (s, 1H),
7.10 (dd, J = 1.6, 7.6 Hz, 1H), 7.05-7.03 (m, 1H), 5.50 (s, 1H); 13C 3.83 (s, 3H); 13C (CDCl3, 100 MHz): δC 160.1, 151.9, 160.0, 149.3,
(CDCl3, 100 MHz): δC 151.5, 150.1, 149.6, 133.6, 130.4, 129.5, 132.3, 132.0, 131.6, 130.2, 129.6, 128.8, 128.4, 124.7, 123.8,
1293.3, 129.2, 129.1, 129.0, 128.8, 128.7, 128.6, 128.5, 127.6, 122.8, 120.0, 121.0, 117.1, 114.6, 110.9, 101.7, 55.6, 43.8; HRMS
127.00, 126.6, 126.0, 126.0, 125.7, 125.6, 124.7, 123.9, 123.5, (ESI) for C22H15F6O (M+H)+ calculated 425.0976, found 425.0969.
122.9, 117.0, 112.3, 112.2, 44.9; HRMS (ESI) for C24H16F3O (M+H)+
General procedure for the preparation of 9-aryl-9H-
thioxanthene derivatives (9a-9f)
calculated 377.1148, found 377.1112.
12-(3,5-Bis(trifluoromethyl)phenyl)-12H-benzo[b]xanthene (7ai)
Colourless solid (84%, 373 mg); m.p. 168-169 C; IR (KBr, cm-
o
A mixture of (2-mercaptophenyl)diarylmethanol 8a-8f (1.0
mmol) and NaHSO4/SiO2 (50 mg) in dry 1,2-dichloroethane (20
mL) was heated at 100-110 oC with vigorous stirring under N2
atmosphere. The reaction mixture was then cooled to room
temperature, filtered and concentrated. After removing the
solvent under reduced pressure, the residue was purified through
silicagel column chromatography using hexane/ethylacetate
(99:1) as eluent to afford 9-aryl-9H-thioxanthene, 9a-9f in pure
form.
1): 3174, 1636, 1452, 1278, 1175, 1131, 695; 1H (CDCl3, 400 MHz):
δH 7.80 (d, J = 8.4 Hz, 1H), 7.73 (s, 1H), 7.70 (d, J = 8.8 Hz, 1H),
7.69 (s, 2H), 7.63 (s, 1H), 7.53 (s, 1H), 7.50-7.43 (m, 1H), 7.38-7.34
(m, 1H), 7.32-7.30 (m, 1H), 7.30-7.25 (m, 1H), 7.08-7.06 (m, 2H),
5.60 (s, 1H); 13C (CDCl3, 100 MHz): δC 151.5, 149.5, 148.6, 133.7,
132.4, 132.2, 130.5, 129.4, 129.1, 128.8, 128.4, 127.6, 127.1,
126.9, 124.9, 124.8, 124.7, 123.8, 123.0, 121.9, 121.2, 117.4,
112.8, 45.0; HRMS (ESI) for C25H15F6O (M+H)+ calculated
445.1027, found 445.1018.
9-Phenyl-9H-thioxanthene (9a)
Colourless solid (90%, 247 mg); m.p. 99-100 oC; IR (KBr, cm-1):
3-Methoxy-6-methyl-9-phenyl-9H-xanthene (7bc)
1
Colourless solid (52%, 157 mg); m.p. 113-114 C; IR (KBr, cm-
o
3055, 1591, 1494, 1453, 743, 694; H (CDCl3, 400 MHz): δH 7.51-
1): 3020, 2938, 2826, 1610, 1450, 1225, 1025, 815, 732; 1H (CDCl3,
400 MHz): δH 7.19-7.15 (m, 2H), 7.08 (d, J = 7.2 Hz, 2H), 6.98 (s,
1H), 6.84-6.81 (m, 3H), 6.69 (dd, J = 0.4, 8.0 Hz, 1H), 6.57 (d, J =
2.4 Hz, 1H), 6.46 (dd, J = 2.4, 8.8 Hz, 1H), 5.06 (s, 1H), 3.70 (s, 3H),
2.23 (s, 3H); 13C (CDCl3, 100 MHz): δC 159.4, 151.9, 150.8, 147.2,
138.0, 130.5, 129.7, 129.5, 128.8, 128.5, 128.4, 126.6, 124.3,
121.7, 116.9, 116.8, 110.2, 101.5, 55.5, 43.6, 21.2; HRMS (ESI) for
C21H19O2 (M+H)+ calculated 303.1385, found 303.1361.
7.48 (m, 2H) 7.47-7.45 (m, 2H), 7.34-7.28 (m, 4H), 7.27-7.19 (m,
3H), 7.09-7.06 (m, 2H), 5.38 (s, 1H); 13C (CDCl3, 100 MHz): δC
141.0, 137.4, 133.3, 129.7,128.3, 127.9, 127.3, 127.0, 126.7,
126.6, 53.1; HRMS (ESI) for C19H15S (M+H)+ calculated 275.0894,
found 275.0878
3-Methoxy-9-(4-methoxyphenyl)-9Hthioxanthene (9b)
o
Colourless solid (92%, 307 mg); m.p. 94-96 C; IR (KBr, cm-1)
1
3012, 2945, 2826, 1604, 1451, 1257, 1021, 804, 743; H (CDCl3,
400 MHz): δH 7.48 (d, J = 7.2 Hz, 1H), 7.434 (d, J = 7.2 Hz, 1H),
7.35-7.27 (m, 3H), 7.05 (s, 1H), 7.00 (d, J = 8.8 Hz, 2H), 6.88 (d, J =
8.8 Hz, 1H), 6.79 (d, J = 8.0 Hz, 2H), 5.29 (s, 1H), 3.86 (s, 3H), 3.78
(s, 3H); 13C (CDCl3, 100 MHz): δC ; 158.4, 158.2, 138.2, 124.2,
133.6, 132.9, 130.4, 130.3, 130.0, 129.5, 129.0, 127.2, 126.7,
113.7, 113.1, 112.0, 111.9, 55.6, 55.3, 51.5; Mass analysis
(m/z):HRMS (ESI) for C21H18NaO2S (M+Na)+ calculated 357.0925,
found 357.0908.
11-Methoxy-14-phenyl-14H-dibenzo[a,c]xanthene (7bf)
o
Colourless solid (87%, 337 mg); m.p. 183-184 C; IR (KBr, cm-
1): 3012, 2950, 1624, 1500, 1445, 1167, 1122, 1033, 857, 752; H
1
(CDCl3, 400MHz): δH 8.70-8.63 (m, 3H), 8.00-7.97 (m, 1H), 7.76-
7.27 (m, 2H), 7.52-7.50 (m, 2H), 7.35-7.29 (m, 3H), 7.21-7.17 (m,
2H), 7.10-7.06 (m, 1H), 6.88 (d, J = 2.4 Hz, 1H), 6.75 (dd, J = 2.8,
8.8 Hz, 1H), 5.77 (s, 1H), 3.84 (s, 3H); 13C (CDCl3, 100MHz): δC..
159.3, 150.6, 146.6, 145.2, 130.9, 130.6, 129.9, 128.9, 128.1,
127.4, 127.3, 127.2, 126.9, 126.6, 124.9, 124.9, 124.0, 123.0,
122.6, 122.6, 117.3, 112.6, 110.9, 101.5, 55.6, 41.7; HRMS (ESI)
for C28H21O2 (M+H)+ calculated 389.1542, found 389.1531.
3-Methyl-9-(p-tolyl)-9H-thioxanthene (9c)
o
Colourless solid (83%, 251 mg); m.p. 108-110 C; IR (KBr, cm-
1
1): 3027, 2921, 1601, 1442, 1255, 1121, 805, 749; H (CDCl3, 400
MHz): δH 7.47 (dd, J = 7.2, 1.6 Hz, 1H), 7.43 (dd, J = 7.2, 1.6 Hz,
1H), 7.32 (d, J = 7.6 Hz, 1H), 7.31-7.24 (m, 3H), 7.11 (dd, J = 7.6,
1.2 Hz, 1H), 7.05 (d, J = 8.0 Hz, 1H), 6.97 (d, J = 8.0 Hz, 1H), 5.31 (s,
1H), 2.38 (s, 3H), 2.30 (s, 3H); 13C (CDCl3, 100 MHz): δC. 138.3,
9-(4-Fluorophenyl)-3-methoxy-9H-xanthene (7bg)
Colourless semi-solid (73%, 223 mg); IR (KBr, cm-1): 3018,
2941, 2829, 1605, 1451, 1220, 1015, 820, 729; 1H (CDCl3, 400
MHz): δH 7.29-7.18 (m, 2H), 7.17-7.12 (m, 3H), 7.02-6.94 (m,3H),
This journal is © The Royal Society of Chemistry 20xx
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Journal Name
137.9, 136.7, 136.1, 134.7, 133.3, 132.9, 129.6, 129.4, 129.0, 3-(Bis(4-fluorophenyl)(hydroxy)methyl)naphthalen-2-ol (2ag)
View Article Online
o
-1
DOI: 10.1039/D0OB01868F
127.8, 127.7, 127.6, 127.3, 126.8, 126.6, 52.4, 21.1; HRMS (ESI)
for C21H19S (M+H)+calculated 303.1207, found 303.1170.
Colourless solid (77%, 1.58 g); m.p. 170-171 C; IR (KBr, cm ):
3369, 3195, 1635, 1602, 1452, 1105, 838, 564; 1H (CDCl3, 400
12-(Naphthalen-1-yl)-12H-benzo[a]thioxanthene (9d)
MHz): δH 7.74 (s, 1H), 7.64 (d, J = 8.4 Hz, 1H), 7.55 (d, J = 8.0 Hz,
Colourless solid (85%, 318 mg); m.p. 205-207 C; IR (KBr, cm- 1H), 7.45-7.40 (m, 1H), 7.31-7.27 (m, 1H), 7.21-7.18 (m, 5H), 7.03
1): 3051, 1627, 1587, 1455, 1253, 1201, 748; 1H (CDCl3, 400 MHz): (t, J = 8.4 Hz, 4H), 6.95 (s 1H), 4.35 (s, 1H); 13C (CDCl3, 100 MHz):
δH 9.06 (d, J = 8.8 Hz, 1H), 8.04-8.02 (m, 1H), 7.88-82 (m, 2H), δC 163.7, 161.2, 153.2, 140.7, 140.6, 134.6, 132.8, 129.8, 129.7,
7.81-7.75 (m, 3H), 7.66 (dd, J = 7.6, 0.8 Hz, 1H), 7.62-7.54 (m, 3H), 128.3, 127.7, 127.1, 126.0, 124.1, 115.4, 115.1, 112.3, 83.4; HRMS
7.38-7.33 (m, 3H), 7.20 (d, J = 8.0 Hz, 1H), 7.12-7.09 (m, 3H); 13C (ESI) for C23H16F2NaO2 (M+Na)+ calculated 385.1016, found
(CDCl3, 100 MHz): δC..140.5, 135.7, 134.4, 132.7, 132.3, 131.7, 385.1013.
o
130.5, 130.3, 129.9, 129.7, 129.2, 129.0, 127.8, 127.6, 127.3, 3-(Bis(4-chlorophenyl)(hydroxy)methyl)naphthalen-2-ol (2ah)
126.8, 126.8, 126.7, 126.7, 126.7, 126.2, 126.1, 125.4, 125.3,
Colourless solid (80%, 1.58 g); m.p. 175-176 oC; IR (KBr, cm-1):
1
124.9, 123.2, 41.6; HRMS (ESI) for C27H19S (M+H)+ calculated 3292, 3057, 1636, 1581, 1499, 1459, 1010, 826, 746; H (CDCl3,
375.1207, found 375.1187.
3-Fluoro-9-(4-fluorophenyl)-9H-thioxanthene (9e)
Colourless solid (69%, 232 mg); m.p. 122-124 C: IR (KBr, cm- 1H), 7.22 (s, 1H), 7.17 (d, J = 8.8 Hz, 4H), 6.96 (s 1H), 4.28 (s, 1H);
1): 3059, 1590, 1498, 1472, 1229, 815, 744, 504; H (CDCl3, 400 13C (CDCl3, 100 MHz): δC 153.0, 143.2, 134.6, 134.2, 132.4, 129.7,
400 MHz): δH 7.66 (d, J = 8.4 Hz, 1H), 7.56 (d, J = 8.4 Hz, 1H), 7.45-
7.41 (m, 1H), 7.39 (s, 1H), 7.32 (d, J = 8.8 Hz, 4H), 7.30-7.27 (m,
o
1
MHz): δH 7.33 (dd, J = 7.6, 1.6 Hz, 1H), 7.29 (dd, J = 7.2, 1.6 Hz, 129.3, 128.6, 128.3, 127.8, 127.2, 126.0, 124.2, 112.3, 83.2; HRMS
1H), 7.23 (dd, J = 8.4, 5.6 Hz, 1H), 7.21-7.13 (m, 2H), 7.07 (dd, J = (ESI) for C23H16Cl2NaO2 (M+Na)+ calculated 417.0425, found
8.4, 2.4 Hz, 1H), 6.88 (dd, J = 8.4, 2.8 Hz, 1H), 6.86-6.82 (m, 2H), 417.0424.
6.80-6.75 (m, 2H), 5.18 (s, 1H); 13C (CDCl3, 100 MHz): δC 162.9, 3-(Hydroxybis(4-(trifluoromethyl)phenyl)methyl)naphthalen-2-
162.6, 160.5, 160.2, 137.2, 136.5, 135.2, 135.2, 133.1, 133.0, ol (2ai)
132.5, 130.8, 130.7, 129.6, 129.4, 129.3, 127.4, 127.3, 127.1,
115.3, 115.1, 114.3, 114.1, 113.9, 113.7, 51.7; HRMS (ESI) for 3440, 3267, 1628, 1456, 1008, 834, 744; H (CDCl3, 400 MHz): δH
o
Colourless solid (72%, 1.6 g); m.p. 156-157 C; IR (KBr, cm-1):
1
C19H13F2S (M-H)+ calculated 309.0555, found 311.0544.
7.66 (d, J = 8.0 Hz, 1H), 7.62 (d, J = 8.4 Hz, 4H), 7.58 (d, J = 8.4 Hz,
1H), 7.48-7.43 (m, 1H), 7.39 (d, J = 8.0 Hz, 4H), 7.34-7.30 (m, 1H),
3-Chloro-9-(4-chlorophenyl)-9H-thioxanthene (9f)
Colourless solid (64 %, 247 mg); m.p. 133-135 C; IR (KBr, cm- 7.21 (s, 1H), 6.95 (s 1H), 6.93 (s, 1H), 4.69 (s, 1H); 13C (CDCl3, 100
o
1
1): 3055, 1579, 1474, 1327, 1094, 805, 753, 487; H (CDCl3, 400 MHz): δC..152.3, 148.4, 134.5, 132.2, 130.9, 130.5, 130.2, 129.9,
MHz): δH 7.47-7.44 (m, 2H), 7.41 (dd, J = 7.2, 2.0 Hz, 1H), 7.33- 129.8, 128.4, 128.2, 128.1, 128.0, 127.5, 126.0, 125.4, 125.4,
7.24 (m, 4H), 7. 17 (dd, J = 6.4, 2.0 Hz, 2H), 6.92 (d, J = 8.0 Hz, 2H), 125.3, 124.5, 122.7, 112.3, 83.0; HRMS (ESI) for C25H15F6O (M-
5.28 (s, 1H); 13C (CDCl3, 100 MHz): δC. 139.0, 136.7, 135.5, 135.2, OH)+ calculated 445.1022, found 445.1034.
132.9, 132.7, 132.4, 130.5, 129.6, 129.2, 128.5, 127.4, 127.4, 2-(Hydroxydiphenylmethyl)phenol (2ba)26
127.2, 127.1, 126.9, 51.9; HRMS (ESI) for C19H13Cl2S (M+H)+
calculated 343.0115, found 343.0115.
Colourless solid (88 %, 0.97 g); m.p. 143-144 oC; IR (KBr, cm-1):
3437, 3204, 3051, 1587, 1485, 1037, 752; 1H (CDCl3, 400 MHz): δH
8.08 (s, 1H), 7.24 (s, 6H), 7.13-7.12 (m, 5H), 6.79 (d, J = 8.0 Hz,
1H), 6.65 (t, J = 7.6 Hz, 1H), 6.43 (d, J = 8.4 Hz, 1H), 3.76 (s, 1H);
13C (CDCl3, 100 MHz):δC..156.0, 145.0, 130.2, 130.1, 129.7, 128.3,
128.0, 127.9, 119.3, 117.6, 84.5
General procedure to synthesize symmetrical ortho-
(hydroxyldiarylmethyl)aren-2-ol derivatives (2aa-2ch)18, 20
To a solution of methyl 3-hydroxy-2-naphthoate 1a (2 g, 9.9
mmol) or methyl 2-hydroxybenzoate derivatives 1b-1c (10 mmol)
in dry toluene (50 mL) was added dropwise the freshly prepared
aryl magnesium bromide (49.5 mmol or 30 mmol) in THF (20 mL)
at room temperature. The resulting mixture was refluxed for 12
h under N2 atmosphere. The reaction mixture was cooled to
room temperature and quenched with 1N HCl (50 mL). Organic
layer was separated and the aqueous layer was extracted with
ethyl acetate (3 x 50 mL). The combined organic layer was
washed with brine solution (2 x 50 mL), dried over anhydrous
Na2SO4, filtered and the solvent was removed in vacuo. The
residue was purified through silica gel column chromatography
using hexane/ethyl acetate (85:15) as eluent to afford 2aa-2ch in
pure form. Compound data of 2aa-2af were authenticated by
comparing with reported data18 and the data for the derivatives
2ag-2ch are given here.
2-(Hydroxybis(4-methoxyphenyl)methyl)phenol (2bb)20
o
Yellow colour solid (83 %, 1.11 g); m.p. 107-108 C; IR (KBr,
cm-1): 3456, 3187, 2955, 2837, 1607, 1508, 1028, 827, 755; 1H
(CDCl3, 400 MHz): δH 8.31 (s, 1H), 7.19 (tt, J = 8.4, 1.6 Hz, 1H), 7.11
(d, J = 8.8 Hz, 4H), 6.89-6.86 (m, 1H), 6.84 (d, J = 8.8 Hz, 4H), 6.73
(tt, J = 7.6, 1.2 Hz, 1H), 6.53 (dd, J = 8.0, 1.6 Hz, 1H), 3.80 (s, 6H),
3.70 (s, 1H); 13C (CDCl3, 100 MHz): δC 159.2, 156.2, 137.5, 130.5,
130.0, 129.6, 129.1, 119.1, 117.6, 113.5, 84.1, 55.4.
2-(Hydroxydi-p-tolylmethyl)phenol (2bc)20
o
Yellow colour solid (90 %, 1.09 g); m.p. 143-144 C; IR (KBr,
cm-1): 3551, 3432, 3167 3025, 2869, 1587, 1448, 1417, 1022, 816,
1
752; H (CDCl3, 400 MHz): δH 8.21 (s, 1H), 7.08-7.03 (m, 1H), 7.00
(d, J = 8.0 Hz, 4H), 6.96 (d, J = 8.0 Hz, 4H), 6.72 (d, J = 8.4 Hz, 1H),
6.61 (t, J = 7.6 Hz, 1H), 6.44-6.41 (m, 1H), 3.74 (s, 1H), 2.24 (s, 6H);
13C (CDCl3, 100 MHz): δC 156.0, 142.2, 137.6, 130.5, 130.0, 129.5,
10 | J. Name., 2012, 00, 1-3
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129.2, 129.1, 128.9, 128.6, 128.3, 128.1, 128.0, 127.8, 127.6, organic layer was washed with brine solution (2 xV5ie0w mArtLic)l,e dOrnileinde
DOI: 10.1039/D0OB01868F
119.1, 117.5, 84.3, 21.2, 21.1.
over anhydrous Na2SO4, filtered and the solvent was removed in
vacuo. The residue was purified through silica gel column
2-(Hydroxydi(naphthalen-1-yl)methyl)phenol (bd)20
Colourless solid (71 %, 1.07 g); m.p. 163-164 oC; IR (KBr, cm-1): chromatography using hexane/dichloromethane (85:15) as eluent
3437, 3204, 3051, 1587, 1485, 1037, 752; 1H (CDCl3, 400 MHz): δH to afford (3-hydroxynaphthalen-2-yl)(phenyl)methanone
5 as
o
8.70 (s, 1H), 8.44 (d, J = 8.8 Hz, 1H), 7.96-7.91(m, 2H), 7.89 (d, J = yellow colour solid (98%, 4.96 g); m.p. 156-157 C; IR (KBr, cm-1):
1
8.0 Hz, 1H), 7.85 (d, J = 8.0 Hz, 1H), 7.77 (d, J = 8.8 Hz, 1H), 7.50- 3056, 1637, 1602, 1451, 1222, 749, 692; H (CDCl3, 400 MHz): δH
7.45 (m, 1H), 7.44-7.41 (m, 2H), 7.36 (t, J = 8.0 Hz, 1H), 7.28-7.22 11.18 (s, 1H), 8.17 (s, 1H), 7.77 (dd, J = 8.0, 1.2 Hz, 2H), 7.73-7.70
(m, 2H), 7.18 (t, J = 8.4 Hz, 1H), 7.03 (dd, J = 8.4, 1.2 Hz, 1H), 6.97 (m, 2H), 7.68-7.64 (m, 1H), 7.58-7.51 (m, 3H), 7.39 (s, 1H), 7.34-
(d, J = 7.8 Hz, 2H), 6.66-6.62 (m, 1H), 6.48 (dd, J = 8.0, 1.6 Hz, 1H), 7.29 (m, 1H); 13C (CDCl3, 100 MHz):δC 201.8, 157.3, 138.0, 138.0,
4.71(s, 1H); 13C (CDCl3, 100 MHz):δC 156.2, 140.1, 139.2, 135.4, 136.8, 132.4, 129.9, 129.7, 129.6, 128.6, 126.8, 126.3, 124.2,
135.3, 131.1, 131.0, 130.3, 130.0, 129.9, 129.3, 129.2, 127.7, 121.1, 112.4; HRMS (ESI) for C17H13O2 (M+H)+ calculated
127.7, 127.2, 126.2, 126.1, 125.6, 125.4, 125.3, 124.3, 119.7, 249.0916, found 249.0936.
118.1, 88.4
General procedure to synthesize unsymmetrical ortho-
(hydroxyldiarylmethyl)aryl-2-ol derivatives (6aa-6bi)
2-(Bis(4-chlorophenyl)(hydroxy)methyl)-5-methylphenol (2ch)
Colourless solid (76%, 1.09 g); m.p. 175-177 oC; IR (KBr, cm-1):
3553, 3434, 3161 3020, 2868, 1585, 1444, 1414, 1020, 818, 757;
1H (CDCl3, 400 MHz): δ 7.51 (s, 1H), 7.29 (d, J = 2.0, 6.4 Hz, 4H),
7.15-7.12 (m, 4H), 6.69 (d, J = 1.2 Hz , 1H), 6.57 (dt, J = 0.8, 1.6 Hz,
1H), 6.35 (d, J = 8.0 Hz, 1H), 3.95 (s, 1H), 2.29 (s, 3H).13C (CDCl3,
100 MHz): 154.8, 143.5, 140.1, 133.9, 129.7, 129.5, 129.3, 128.3,
127.3, 120.6, 118.0, 83.1, 21.0. HRMS (ESI) for C20H17Cl2O2 (M+H)+
calculated 359.0606 found 359.0618.
To
a
solution
of
(3-hydroxynaphthalen-2-
yl)(phenyl)methanone 5a (0.99 g, 4 mmol) or (2-hydroxy-4-
methoxyphenyl)(phenyl)methanone 5b (1.14, 5 mmol) in dry THF
(50 mL) was added dropwise the freshly prepared arylmagnesium
bromide (10 mmol or 12.5 mmol) in THF (20 mL) at room
temperature. The resulting mixture was refluxed for 12-24 h
under N2 atmosphere. The reaction mixture was cooled to room
temperature and quenched with 2N HCl (50 mL). Organic layer
was separated and the aqueous layer was extracted with ethyl
acetate (3 x 50 mL). The combined organic layer was washed
Synthesis of 3-hydroxy-N-methoxy-N-methyl-2-naphthamide
(4)25
A solution of 3-hydroxy naphthoic acid (10 g, 53.19 mmol) in with brine solution (2 x 50 mL), dried over anhydrous Na2SO4,
dry tetrahydrofuran (THF) (250 mL) was cooled to 0 °C and filtered and the solvent was removed in vacuo. The residue was
treated with carbonyl diimidazole (12.92 g, 79.78 mmol) in purified through silica gel column chromatography using
portions vice. The mixture was stirred at 0 °C for 4 h. Then N,O- hexane/ethyl acetate (85:15) as eluent to afford 6aa-6bi in pure
dimethylhydroxylamine hydrochloride (10.37 g, 106.38 mmol) form.
was added, followed by triethylamine (11.09 mL, 79.78 mmol). 3-(Hydroxy(4-methoxyphenyl)(phenyl)methyl)naphthalen-2-ol,
After stirring for 6h at room temperature, the reaction mixture 6aa
was concentrated and purified through column chromatography
using dichloromethane/ethylacetate (80:20) as eluent to give 3459, 3195, 2948, 2834, 1602, 1451, 1178, 993, 747; H (CDCl3,
Yellow solid (94%, 1.34 g); m.p. 145-146 oC; IR (KBr, cm-1)
1
pure 3-hydroxy-N-methoxy-N-methyl-2-naphthamide
4
as 400 MHz): δ 8.19 (s, 1H), 7.66 (d, J = 8.4 Hz, 1H), 7.54 (d, J = 8.0
colourless solid (9.58 g, 78%). m.p. 136-137 oC; IR (KBr, cm-1): Hz, 1H), 7.43-7.38 (m, 1H), 7.35-7.34 (m, 3H), 7.28-7.22 (m, 4H),
3162, 1643, 1606, 1449, 1234, 1194, 872, 749; 1H (CDCl3, 400 7.14 (d, J = 8.8 Hz, 2H), 7.02 (s, 1H), 6.86 (d, J = 8.8 Hz, 2H), 4.06
MHz): δH 10.36 (s, 1H), 8.48 (s, 1H), 7.75 (d, J = 8.4 Hz, 1H), 7.65 (s, 1H), 3.81 (s, 3H); 13C (CDCl3, 100 MHz): 159.3, 154.0, 144.9,
(d, J = 8.4 Hz, 1H), 7.46 (t, J = 7.2 Hz, 1H), 7.32-7.28 (m, 2H), 3.62 137.0, 134.7, 133.0, 129.8, 129.3, 128.3, 128.2, 128.1, 127.8,
(s, 3H), 3.45 (s, 3H); 13C (CDCl3, 100 MHz):δC 169.3, 155.7, 136.5, 127.6, 126.7, 126.0, 123.6, 113.6, 112.2, 84.2, 55.4; HRMS (ESI)
131.3, 129.2, 128.6, 127.0, 126.2, 123.8, 117.0, 111.8, 61.4, 34.1; for C24H20NaO3 (M+Na)+ calculated 379.1310 found 379.1287.
HRMS (ESI) for C13H14NO3 (M+H)+ calculated 232.0974, found
232.0965.
3-(Hydroxy(3-methoxyphenyl)(phenyl)methyl)naphthalen-2-ol,
6ab
Pale yellow solid (53%, 1.17 g); m.p 156-157 oC; IR (KBr, cm-1):
Synthesis of (3-hydroxynaphthalen-2-yl)(phenyl)methanone (5)
1
To
a
solution of 3-hydroxy-N-methoxy-N-methyl-2-
3463, 3274, 3057, 1636, 1589, 1453, 1234, 1016, 755; H (CDCl3,
naphthamide 4 (4.62 g, 20 mmol) in dry THF (200 mL) was added
dropwise, the freshly prepared phenylmagnesium bromide (30
mmol) in THF (20 mL) at room temperature. The resulting
mixture was refluxed for 6 h under N2 atmosphere. The reaction
mixture was cooled to room temperature and quenched with 2N
HCl (100 mL). Organic layer was separated and the aqueous layer
was extracted with ethyl acetate (3 x 50 mL). The combined
400 MHz): δ 9.13 (s, 1H), 7.72 (d, J = 8.4 Hz, 1H), 7.51 (d, J = 8.0
Hz, 1H), 7.41-7.36 (m, 6H), 7.30-7.24 (m, 3H), 7.03 (d, J = 8.0 Hz,
1H), 6.90-6.87 (m, 2H), 6.52 (dd, J = 7.6, 1.2 Hz, 1H), 6.33 (s, 1H),
3.73 (s, 3H); 13C (CDCl3, 100 MHz): 157.2, 154.8, 144.0, 134.9,
132.3, 132.0, 130.0, 130.0, 128.8, 128.2, 128.0, 127.5, 126.6,
126.0, 123.3, 121.2, 112.2, 112.1, 84.6, 56.0; HRMS (ESI) for
C24H20NaO3 (M+Na)+ calculated 379.1310 found 379.1312.
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Journal Name
3-(Hydroxy(phenyl)(p-tolyl)methyl)naphthalen-2-ol (6ac)
83.7; HRMS (ESI) for C23H17FNaO3 (M+Na)+ calculated 367.1110
View Article Online
Colourless solid (65%, 0.88 g); m.p. 140-141 oC; IR (KBr, cm-1): found 367.1105.
DOI: 10.1039/D0OB01868F
3457, 3201, 3056, 1633, 1697, 1450, 1360, 1230, 1091, 750, 533; 3-(Hydroxy(phenyl)(4-(trifluoromethyl)phenyl)methyl)naph-
1H (CDCl3, 400 MHz): δ 7.99 (s, 1H), 7.58 (d, J = 8.0 Hz, 1H), 7.45 thalene-2-ol (6ah)
(d, J = 8.0 Hz , 1H), 7.34-7.30 (m, 1H), 7.27-7.26 (m, 3H), 7.19-7.15
o
Colourless solid (70%, 1.103 g); m.p. 178-179 C; IR (KBr, cm-
(m, 4H), 7.07 (d, J = 8.4 Hz, 2H), 7.03 (d, J = 8.4 Hz, 2H), 6.92 (s, 1): 3456, 3213, 1629, 1450, 1328, 1068, 1003, 835, 751; 1H (CDCl3,
1H), 3.78 (s, 1H), 2.29 (s, 3H); 13C (CDCl3, 100 MHz): 154.0, 144.9, 400 MHz): δH 7.65 (d, J = 8.0 Hz, 1H), 7.63 (s, 1H), 7.59 (d, J = 8.4
141.9, 137.9, 134.7, 133.0, 129.8, 129.0, 128.3, 128.0, 127.9, Hz, 2H), 7.56 (dd, J = 0.4, 8.4 Hz, 1H), 7.45-7.40 (m, 3H), 7.39-7.36
127.9, 127.6, 126.7, 126.0, 123.6, 112.2, 84.3, 21.2; HRMS (ESI) (m, 3H), 7.31-7.27 (m, 1H), 7.23-7.20 (m, 3H), 6.98 (s, 1H), 4.39 (s,
for C24H20O2Na (M+Na)+ calculated 363.1356, found 363.1348.
3-((4-(Dimethylamino)phenyl)(hydroxy)(phenyl)methyl)
naphthalen-2-ol (6ad)
1H); 13C (CDCl3, 100 MHz): δC..153.2, 148.8, 144.4, 134.6, 132.6,
129.9, 129.9, 128.6, 128.4, 128.3, 127.9, 127.8, 127.1, 126.0,
126.0, 125.3, 125.2, 124.1, 112.3, 83.7; HRMS (ESI) for
Red solid (56 %, 0.89 g); m.p. 107-108 oC; IR (KBr, cm-1): 3312, C27H17F3NaO2 (M+Na)+ calculated 417.1078, found 417.1058.
3055, 1608, 1513, 1450, 1354, 1299, 750; 1H (CDCl3, 400 MHz): δH 3-((3,5-Bis(trifluoromethyl)phenyl)(hydroxy)(phenyl)methyl)
7.67 (d, J = 8.4 Hz, 1H), 7.55 (d, J = 8.4 Hz, 1H), 7.40-7.37 (m, 1H), naphthalen-2-ol (6ai)
7.35-7.33 (m, 3H), 7.28-7.25 (m, 4H), 7.07-7.04 (m, 3H), 6.67 (d, J
Yellow solid (76%, 1.40 g); m.p. 163-165oC; IR (KBr, cm-1):
1
= 9.2 Hz, 2H), 2.97 (s, 6H); 13C (CDCl3, 100 MHz):δC 154.5, 150.2, 3454, 3198, 1624, 1452, 1322, 1056, 1001, 833, 745; H (CDCl3,
145.0, 134.7, 133.5, 132.6, 129.8, 129.7, 129.0, 128.6, 128.3, 400 MHz): δ 7.87 (s, 1H), 7.81 (s, 2H), 7.68 (d, J = 8.0 Hz, 1H), 7.56
128.2, 127.8, 127.6, 126.6, 126.0, 123.4, 112.1, 111.9, 84.6, 40.5; (d, J = 7.6 Hz , 1H) , 7.48-7.43 (m, 1H), 7.41-7.39 (m, 3H), 7.37-
HRMS (ESI) for C25H24NO2 (M+H)+ calculated 370.1802, found 7.30 (m, 1H), 7.24 (s, 1H), 7.23-7.20 (m, 2H), 6.95 (s, 1H), 6.86 (s,
370.1791.
1H), 4.62 (s, 1H); 13C (CDCl3, 100 MHz): 152.3, 148.1, 143.9, 134.5,
132.2, 131.7, 131.3, 130.0, 128.8, 128.7, 128.5, 128.0, 128.0,
127.7, 127.4, 126.0, 124.8, 124.4, 122.1, 122.0, 112.4, 83.0; HRMS
3-(Hydroxy(naphthalen-1-yl)(phenyl)methyl)naphthalen-2-ol
(6ae)
Colourless solid (86%, 1.30 g); m.p. 166-167 oC; IR (KBr, cm-1): (ESI) for C25H15F6O (M-OH)+ calculated 445.1021, found 445.1018.
3370, 3285, 3048, 1636, 1453, 1302, 1087, 1009, 882, 743; 1H 2-(Hydroxy(phenyl)(p-tolyl)methyl)-5-methoxyphenol (6bc)
o
(CDCl3, 400 MHz): δ 8.28 (s, 1H), 8.14 (d, J = 8.4 Hz, 1H), 7.91 (d,
Colourless solid (89%, 1.14 g) m.p. 131-132 C; IR (KBr, cm-1):
1
J = 8.4 Hz , 1H), 7.88 (d, J = 8.4 Hz , 1H), 7.69(d, J = 8.4 Hz , 1H), 3454, 3168, 2962, 2845, 1613, 1436, 1299, 1031, 802; H (CDCl3,
7.54-7.36 (m, 7H), 7.32-7.28 (m, 4H), 7.22-7.18 (m, 1H), 6.98 (s, 400 MHz): δ 8.32 (s, 1H), 7.33-7.31 (m, 3H), 7.22-7.20 (m, 2H),
1H), 6.85 (d, J = 0.8, 7.6 Hz, 1H), 4.46 (s, 1H); 13C (CDCl3, 100 7.15-7.13 (m, 2H), 7.08-7.06 (m, 2H), 6.47 (d, J = 2.8 Hz, 1H), 6.41
MHz): 153.9, 144.5, 140.0, 135.2, 134.7, 132.2, 131.1, 130.2, (d, J = 8.4 Hz, 1H), 6.29 (dd, J = 2.8, 8.8 Hz, 1H), 3.76 (s, 3H), 3.60
129.7, 129.4, 128.5, 128.4, 128.3, 128.0, 127.9, 127.8, 127.6, (s, 1H), 2.36 (s, 3H); 13C (CDCl3, 100 MHz): 160.7, 157.3, 145.3,
126.8, 126.2, 126.0, 125.7, 124.6, 123.6, 112.5, 85.9; HRMS (ESI) 142.3, 137.7, 130.7, 129.0, 128.2, 127.9, 127.8, 127.8, 122.8,
for C25H21O3 (M+Na)+ calculated 399.1361 found 399.1361.
3-(Hydroxy(phenanthren-9-yl)(phenyl)methyl)naphthalen-2-ol
105.1, 102.7, 84.2, 55.3, 21.2;HRMS (ESI) for C21H20NaO3 (M+Na)+
calculated 343.1310 found 343.1297.
(6af)
2-(Hydroxy(phenanthren-9-yl)(phenyl)methyl)-5-methoxy-
o
Light yellow solid (96%, 1.63 g); m.p. 212-213 C; IR (KBr, cm- phenol (6bf)
o
1): 1H (CDCl3+DMSO-d6, 400 MHz): δH 10.21 (s, 1H), 8.66 (d, J = 8.4
Light red colour solid (69%, 1.12 g); m.p. 158-159 C; IR (KBr,
Hz, 1H), 8.62 (d, J = 8.4 Hz, 1H), 8.46 (d, J = 8.4 Hz, 1H), 7.62-7.56 cm-1): 3412, 3286, 3020, 1618, 1582, 1499, 1256, 1102, 1034,
(m, 2H), 7.50-7.38 (m, 4H), 7.30-7.23 (m, 7H), 7.12-7.08 (m, 2H), 756; 1H (CDCl3, 400MHz): δ 8.76 (d, J = 8.0 Hz, 1H), 8.65 (d, J = 8.4
7.01 (s, 1H), 6.91 (s, 1H); 13C (CDCl3, 100 MHz): δC..153.6, 145.4, Hz, 1H), 8.44 (s, 1H), 8.21 (d, J = 8.4 Hz, 1H), 7.68-7.58 (m, 2H),
139.1, 133.8, 131.2, 130.2, 130.5, 129.0, 128.7, 128.4, 127.8, 7.55-7.51 (m, 1H), 7.45-7.38 (m, 6H), 7.11 (s, 1H), 6.55 (d, J = 2.8
127.7, 127.6, 127.1, 126.5, 126.1, 125.7, 125.3, 125.2, 123.0, Hz, 1H), 6.46 (d, J = 8.4 Hz, 1H), 6.63 (dd, J = 2.4, 8.8 Hz, 1H), 4.20
122.4, 122.0, 110.9, 83.9; HRMS (ESI) for C31H22NaO2 (M+Na)+ (s, 1H), 3.77 (m, 3H); 13C (CDCl3, 100MHz): 160.8, 157.0, 145.0,
calculated 449.1517, found 449.1503.
3-((4-Fluorophenyl)(hydroxy)(phenyl)methyl)naphthalen-2-ol
(6ag)
Colourless solid (76%, 1.04 g); m.p. 152-153 oC; IR (KBr, cm-1): calculated 429.1467 found 429.1449.
3430, 3215, 2968, 2864, 1601, 1455, 1168, 973, 737; H (CDCl3, 2-((4-Fluorophenyl)(hydroxy)(phenyl)methyl)-5-methoxyphenol
138.0, 132.1, 130.8, 130.7, 130.5, 130.0, 129.7, 129.7, 128.4,
128.0, 127.8, 127.7, 127.0, 126.5, 126.3, 123.6, 122.4, 122.1,
105.5, 103.0, 85.7, 55.4; HRMS (ESI) for C28H22NaO3 (M+Na)+
1
400 MHz): δ 8.04 (s, 1H), 7.64 (d, J = 8.4 Hz, 1H), 7.53 (d, J = 8.4 (6bg)
o
Hz, 1H), 7.44-7.40 (m, 1H), 7.37-7.34 (m, 3H), 7.30-7.26 (m, 1H),
Light red colour solid (73%, 9.46 g); m.p. 141-142 C; IR (KBr,
7.24-7.22 (m, 3H), 7.21-7.20 (m, 2H), 7.02 (t, J = 8.8 Hz, 2H), 6.99 cm-1): 3447, 3207, 1610, 1510, 1437, 1234, 1162, 1113, 824, 756;
(s, 1H), 4.42 (s, 1H); 13C (CDCl3, 100 MHz): 163.2, 161.3, 153.5, 1H (CDCl3, 400MHz): δ 8.22 (s, 1H), 7.35-7.33 (m, 3H), 7.20-7.16
144.8, 140.7, 140.6, 134.6, 132.9, 129.9, 129.8, 128.4, 128.3, (m, 4H), 7.01 (t, J = 8.8 Hz, 2H), 6.45 (d, J = 2.4.0 Hz, 1H), 6.38 (d, J
128.2, 127.8, 127.7, 126.9, 126.0, 123.9, 115.2, 115.0, 112.2, = 8.8 Hz, 1H), 6.30 (dd, J = 8.8, 2.4 Hz, 1H), 3.82 (s, 1H), 3.75 (m,
12 | J. Name., 2012, 00, 1-3
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3H); 13C (CDCl3, 100MHz): 163.5, 161.1, 160.8, 157.0, 145.2, (s, 1H), 2.36 (s, 6H); 13C (CDCl3, 100 MHz): δC 145.7, 143.2, 137.1,
View Article Online
DOI: 10.1039/D0OB01868F
141.1, 141.0, 130.7, 129.8, 129.7, 128.3, 128.1, 127.7, 122.8, 136.8, 130.0, 129.6, 128.8, 128.5, 127.9, 126.1, 82.7, 21.2; HRMS
115.1, 114.9, 105.2, 102.9, 83.7, 55.4; HRMS (ESI) for C20H17NaO3 (ESI) for C21H20NaOS (M+Na)+ calculated 343.1133, found
(M+Na)+ calculated 347.1059 found 347.1042.
343.1132.
2-((3,5-Bis(trifluoromethyl)phenyl)(hydroxy)(phenyl)methyl)-5-
methoxyphenol (6bi)
(2-Mercaptophenyl)di(naphthalen-1-yl)methanol (8d)
Yellow colour semi solid (72 %, 0.278 g); IR (KBr, cm-1): 3420,
1
Red colour solid (85%, 1.50 g); m.p. 128-129 oC; IR (KBr, cm-1): 3104, 3021, 1602, 1481, 1028, 726; H (CDCl3, 400 MHz): δH 8.26
3440, 3274, 2940, 2854, 1620, 1448, 1279, 1122, 843, 699; 1H (d, J = 8.4 Hz, 1H), 8.13-8.09 (m, 1H), 7.81-7.73 (m, 3H), 7.70-7.59
(CDCl3, 400MHz): δ 7.85 (s, 1H), 7.75 (s, 2H), 7.57 (s, 1H), 7.39- (m, 2H), 7.36-7.31 (m, 2H), 7.27-7.14 (m, 3H), 7.01 (t, J = 8.0 Hz,
7.37 (m, 3H), 7.14-7.12 (m, 2H), 6.45 (d, J = 2.0 Hz, 1H), 6.36-6.35 1H), 6.92-6.85 (m, 2H), 6.69-6.42 (m, 2H), 4.85 (s, 1H); 13C (CDCl3,
(m, 2H), 4.13 (s, 1H), 3.77 (m, 3H); 13C (CDCl3, 100MHz): 161.1, 100 MHz):δC 146.5, 146.0, 141.5, 141.3, 140.4, 140.3, 136.8,
156.4, 148.2, 144.2, 132.0, 131.6, 131.3, 131.0, 130.6, 128.8, 136.7, 135.5, 135.4, 135.2, 131.9, 131.6, 131.6, 130.7, 129.8,
128.7, 128.0, 127.6, 124.8, 122.1, 122.0, 121.9, 105.7, 103.3, 83.3, 129.4, 129.1, 129.1, 128.8, 128.6, 127.3, 126.9, 125.6, 125.4,
55.4; HRMS (ESI) for C22H16NaO3 (M+Na)+ calculated 465.0901 124.6, 124.3, 87.4; HRMS (ESI) for C27H21OS (M+H)+ calculated
found 465.0886.
393.1313, found 393.1320.
Bis(4-fluorophenyl)(2-mercaptophenyl)methanol (8e)
Colourless semi solid (80 %, 1.31 g); IR (KBr, cm-1): 3456, 3187,
2955, 2837, 1607, 1508, 1028, 827, 755; H (CDCl3, 400 MHz): δH
General procedure to synthesize (2-mercaptophenyl)
diarylmethanol derivatives (8a-8f)26
1
To a solution of methyl 2-hydroxybenzoate derivatives (10
mmol) in dry THF (50 mL) was added dropwise the freshly
prepared arylmagnesium bromide (25 mmol) in THF (20 mL) at
room temperature and was stirred for overnight under N2
atmosphere. The reaction mixture was quenched with saturated
NH4Cl solution (50 mL). Organic layer was separated and the
aqueous layer was extracted with dichloromethane (3 x 50 mL).
The combined organic layer was washed with brine solution (2 x
50 mL), dried over anhydrous Na2SO4, filtered and the solvent
was removed in vacuo. The residue was purified through silica gel
column chromatography using hexane/ethyl acetate (80:20) as
eluent to afford 8a-8f in pure form.
7.21 (dd, J = 7.6, 0.8 Hz, 1H), 7.09-7.05 (m, 4H), 7.00 (td, J = 7.6,
1.6 Hz, 1H), 6.90 (dd, J = 7.6, 1.2 Hz, 1H) 6.86-6.82 (m, 4H), 6.49
(dd, J = 8.0, 1.2 Hz, 1H), 5.06 (s, 1H), 3.31 (s, 1H); 13C (CDCl3, 100
MHz): δC 163.3, 160.9, 145.6, 141.5, 141.5, 134.8, 130.5, 129.8,
129.7, 129.1, 128.5, 126.4, 115.2, 114.9, 82.1; HRMS (ESI) for
C19H13F2S (M-OH)+ calculated 311.0701, found 311.0699.
Bis(4-chlorophenyl)(2-mercaptophenyl)methanol (8f)
Colourless semi solid (92 %, 0.33 g); IR (KBr, cm-1): 3389, 3210,
1
2989, 2873, 1610, 1505, 1008, 818, 747; H (CDCl3, 400MHz): δH
7.43 (dd, J = 8.0, 1.2 Hz, 1H), 7.29 (dd, J = 6.4, 2.0 Hz, 4H), 7.23-
7.19 (m, 1H), 7.12 (d, J = 8.8 Hz, 4H), 7.07 (dd, J = 7.6, 1.2 Hz, 1H),
6.60 (dd, J = 7.6, 1.2 Hz, 1H), 4.18 (s, 1H); 13C (CDCl3, 100MHz): δC
144.9, 144.1, 136.5, 133.8, 130.9, 130.0, 129.3, 129.1, 128.5,
127.0, 82.2; HRMS (ESI) for C19H13Cl2S (M-OH)+ calculated
343.0110, found 343.0089.
(2-Mercaptophenyl)diphenylmethanol (8a)26
Colourless semi solid (85%, 0.248 g); IR (KBr, cm-1): 3437,
1
3204, 3051, 1587, 1485, 1037, 752; H (CDCl3, 400 MHz): δH 7.40
(dd, J = 8.0, 1.6 Hz, 1H), 7.38-7.35 (m, 2H), 7.34-7.31 (m, 4H),
7.30-7.28 (m, 4H), 7.18 (td, J = 7.6, 1.6 Hz, 1H), 7.06 (td, J = 7.6,
1.6 Hz, 1H), 6.65 (dd, J = 8.0, 1.6 Hz, 1H), 5.15 (s, 1H), 3.46 (s, 1H);
13C (CDCl3, 100 MHz): δC.146.3, 145.8, 134.8, 130.8, 129.1, 128.5,
128.3, 128.3, 128.2, 128.0, 127.8, 127.6, 126.4, 82.9; HRMS (ESI)
for C19H16NaOS (M+Na)+ calculated 315.0820, found 315.0808.
2-Mercaptophenyl)bis(4-methoxyphenyl)methanol (8b)26
Reddish semi solid (80 %, 0.281 g); IR (KBr, cm-1): 3446, 3181,
Conflicts of interest
There are no conflicts to declare
Acknowledgements
We thank the DST-SERB (CRG/2019/002960), New Delhi for
financial support. MK thanks the CSIR, New Delhi for SRF. DST-
FIST sponsored HRMS facility at Department of Chemistry is
gratefully acknowledged. We acknowledge CIF, Pondicherry
University for NMR/IR data.
1
2955, 2838, 1606, 1505, 1020, 828, 757; H (CDCl3, 400 MHz): δH
7.44 (dd, J = 7.6, 1.2 Hz, 1H), 7.16-7.13 (m, 1H), 7.12 (d, J = 8.8 Hz,
4H) 7.03-6.99 (m, 1H), 6.84 (d, J = 8.8 Hz, 4H), 6.64 (dd, J = 7.6, 0.8
Hz, 1H) 4.14 (s, 1H), 3.80 (s, 6H); 13C (CDCl3, 100 MHz): δC158.9,
145.8, 138.5, 136.8, 129.9, 129.6, 129.3, 128.5, 126.2, 113.4, 82.4,
55.4; HRMS (ESI) for C21H20NaO3S (M+Na)+ calculated 375.1031,
found 370.1013.
Notes and references
2-Mercaptophenyl)di-p-tolylmethanol (8c)
Light reddish semi solid (78 %, 0.25 g); IR (KBr, cm-1): 3424,
3167 3025, 2869, 1577, 1447, 1417, 1032, 716; 1H (CDCl3, 400
MHz): δH 7.44 (dd, J = 7.6, 1.2 Hz, 1H), 7.15-7.11 (m, 5H), 7.10-
7.08 (m, 4H), 7.03-6.99 (m, 1H), 6.63 (dd, J = 8.0, 1.6 Hz, 1H), 4.10
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