β-Cyclodextrin in water: Highly facile biomimetic one pot deprotection of phenolic THP/MOM/Ac/Ts ethers and concomitant regioselective cyclization of chalcone epoxides and 2′-aminochalcones

Article abstract of DOI:10.1039/c5ra15996b

A mild and efficient one-pot deprotection of THP/MOM/Ac/Ts ethers and the concomitant cyclization of chalcone epoxides to 2-hydroxyindanones or 2′-aminochalcones to aza-flavanones using β-cyclodextrin in water has been developed. β-CD was found to be highly effective at carrying out the deprotection and sequential transformations in an eco-friendly environment affording moderate to excellent yields (59-99%) at 60 °C in 8-22 min. Water, an eco-friendly reaction medium, has been utilized for the first time in this reaction. The merits of the presented protocol include the high yields and catalyst reusability and the protocol precludes the use of metals and organic solvents. The present method is much milder but more advanced than those reported earlier.

Full text of DOI:10.1039/c5ra15996b

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ARTICLE
β-Cyclodextrin in water: Highly facile biomimetic one pot
deprotection of phenolic THP/MOM/Ac/Ts ethers and
concomitant regioselective cyclization of chalcone epoxides and
2’-aminochalcones
Sumit Kumar*, Nishant Verma, Naseem Ahmed*
Received 00th January 20xx,
Accepted 00th January 20xx
A mild and efficient one-pot deprotection of THP/MOM/Ac/Ts ethers and concomitant cyclization of chalcone epoxides to
2-hydroxyindanones and 2’-aminochalcones to aza-flavanones using β-Cyclodextrin in water has been developed. β-CD
was found to be highly effective in carrying out deprotection and sequel transformations under eco-friendly environment
affording moderate to excellent yields (59-99%) at 60 oC in 8-22 min. Water, an eco-friendly reaction medium, has been
utilized for the first time in this reaction. The merits of the presented protocol include high yields, catalyst reusability and
preclude use of metals and organic solvents. The present method is very much milder but more advanced than those
reported earlier.
DOI: 10.1039/x0xx00000x
www.rsc.org/
MeOH,5c enzymes,5d metallo-enzyme,5e metal complexes,5f
antibodies,5g montmorillonite K-10,5h I2,5i NaBO3,5j and TFA.5k Most
Introduction
Protection and deprotection of hydroxyl groups have fundamental
importance and most frequently used strategies in the multi-steps
organic syntheses. In particular, these two phenomena are
extremely important because of their presence in a number of
natural products, biological and synthetic compounds such as
carbohydrates, peptides, macrolides, nucleotides, steroids and
polyethers.1 Among the various methods for protecting hydroxy
group, the formation of tetrahydropyranyl ethers (THPEs) is the
most commonly employed methods due to its easy formation and
inertness to various reaction conditions like strong bases such as
metal hydrides, organolithium compounds, Grignard reagents,
catalytic hydrogenation and alkylating or acylating conditions.2
Likewise, methoxymethyl chloride (MOMCl), acetyl chloride/acetic
anhydride (CH3COCl/Ac2O) and tosyl chloride (TsCl) are also
important reagents for the alcoholic and phenolic group protection.
Various methods have been reported for the deprotection of THPEs
that include protic acids,3a-d BF3–etherate,3e LiBr,3f LiOTf,3g LiBF4,3h
LiClO4,3i In(OTf)3,3j Sc(OTf)3,3k, I2,3l InCl3,3m ZrCl3,3n CuCl2,3o NH4Cl,3p
and other catalysts. Similarly, Many catalysts have been used to
remove MOM group under acidic conditions such as using protic
acids,4a Lewis acids,4b Lewis acid-thiol,4c boron halides,4d YbCl3,4e
CBr4-PPh3,4f ZnBr2,4g silica-supported NaHSO4,4h and TMSOTf
(TESOTf)-2,2’-bipyridyl.4i Several catalysts have been reported for
the deacetylation and detosylation of alcohols and phenols under
acidic and basic conditions including NaOMe,5a micelles,5b Zn-
of these methods, however have one or other drawbacks such as
low yields, long reaction times, reflux at high temperature, excess
amounts of reagents and tedious workup procedures.6 Hence, there
is still scope to develop milder and efficient methods in the
detetrahydropyranylation, demethoxymethylation, deacetylation
and detosylation of hydroxyl groups.
Similarly, various reagents and reaction conditions have been
previously employed for the cyclization of chalcones to aza-
flavanones such as acids,7a bases,7b-d silica gel,7e-g light,7h
electrolysis,7i nanocrystalline MgO,7j zeolites,7k L-Proline,7l
Yb(OTf)3,7m-n silica gel supported TaBr5,7o alumina supported-
CeCl3.7H2O-NaI,7p and microwave.7q-r Most of these procedures
however have drawbacks for example low yields, use of toxic
metals and organic solvents and harsh reaction conditions.
Therefore, in metal free green context, cyclodextrins are emerging
as alternative catalyst for numerous challenging organic reactions
due to their fine tuning of their physico-chemical properties.8-10
Cyclodextrins (CDs), which are cyclic oligosaccharides possessing
hydrophobic cavities, exert microenvironmental effects leading to
selective reactions. They catalyze reactions by supramolecular
catalysis through non-covalent bonding forming reversible host-
guest complexes just like in enzymes. We used β-Cyclodextrin as
the catalyst because it is easily accessible and inexpensive among
the CDs. The concept of green chemistry has attracted the attention
of performing reactions in aqueous medium. However the
fundamental problem in performing the organic reactions in water
is that many organic substrates are hydrophobic and are insoluble
in water. But this can be overcome by the use of cyclodextrins.11
As a continuation of our recent findings of YbCl3-catalyzed ring-
opening of epoxides4e herein, we report a simple and efficient
green protocol for the biomimetic one pot deprotection of
MOM/THP/Ac/Ts ethers and also the concomitant regioselective
cyclization of chalcone epoxides to 2-hydroxyindanones and 2’-
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aminochalcones to aza-flavanones employing
a
mild and smoothly with β-cyclodextrin in water at 20 and 10 mol% catalyst
environmentally friendly catalyst β-CD in water as a novel reagent loading with the same capacity providing the product 15a
under microwave condition. These 2-hydroxyindanones and aza- (deprotection with cyclization) in 95% yield (Tables 1, entries 13,
flavanones are widely used as synthetic intermediates of high 14), but further decreasing the catalyst loading to 5 mol% furnished
significance in organic and medicinal chemistry.
the product 15a in only 65% yield even after prolonging the
reaction time and temperature (Tables 1, entry 15).
Results and discussion
Table 2. Optimization of the solvent and reaction time on yields of
deprotection and concomitant cyclization.
In our initial study toward the development of this methodology, a
model reaction was conducted by treating the substrate 15 in the
presence of various metal salts and then finally β-cyclodextrin.
Initially, the catalytic efficiency of different Lewis acids (CdCl2, CoCl2,
FeCl3, ZnCl2, SrCl2, CuCl2, NH4Cl, CuI2, InCl3, HgCl2, SnCl2.2H2O and
CeCl3) was screened (Table 1).
The metal halides such as CdCl2, CoCl2, FeCl3 and ZnCl2 did not show
any catalytic activity in the formation of product 15a instead
yielded the side product b in excellent yields (Table 1, entries 1-4).
SrCl2 was unable to give any of the products (Table 1, entry 5). CuCl2
yielded only the deprotected product a without cyclization in good
yield (Table 1, entry 6). The Lewis acids like NH4Cl, CuI2 and InCl3
exhibited poor to moderate catalytic activity at 10 mol % catalyst
loading furnishing the product 15a in 5-67% yields with the
formation of side products a and b also (Table 1, entries 7-9). The
HgCl2, SnCl2.2H2O and CeCl3 were found to be the good catalyst at
10 mol% catalyst loading, which gave 55-75% yields of product 3b
without forming any side products within 4-10 min (Table 1, entries
10-12). Then, the catalyst optimization was achieved for the catalyst
β-cyclodextrin in water.
Entry Solvent
Condition Temp
Time
(min)
15
Yielda
(%)
32
(0C)
70
1
2
3
4
5
6
7
8
9
Acetonitrile MWb
DCM
THF
Acetone
DMF
DMSO
H2O
MWb
MWb
MWb
MWb
MWb
MWb
MWb
CHc
40
65
55
80
80
60
60
60
13
10
12
8
10
10
8
5h
51
55
63
71
88
99
89
81
H2O
H2O
Reaction was carried out on a 1 mmol scale; aIsolated yields.
We also screened solvents like acetonitrile, CH2Cl2, THF, acetone,
DMF, DMSO and neat H2O where solvents like CH2Cl2, THF, acetone,
DMF and DMSO gave good results (Table 2, entries 2-6). However,
neat H2O was found to give the best results with quantitative
Table 1. Optimization of reaction conditions for deprotection and
concomitant cyclization of chalcone epoxide.
0
conversion (99%) at 60 C under microwave irradiation. Despite the
excellent results, we further explored other reaction conditions for
the above reaction in order to target the optimum protocol for the
transformation. For example, the reaction was subjected to
conventional heating also, however it resulted in 81% yield of the
product (Table 2, entry 9) in 5h. The advantages of use of
microwave irradiation over conventional heating helped in the
reduction in reaction time from hours to minutes. Hence, the
optimum conversion of substrates 15 to product 15a was attained
when the reaction was carried out by utilising 10 mol % β-
cyclodextrin in water at 60 0C for 10 min under microwave
condition.
Then, under optimal reaction condition, we carried out reactions of
deprotection of various phenolic and alcoholic THP/MOM/Ac/Ts
ethers and concomitant ring opening of chalcone epoxides using β-
cyclodextrin in water (Table 3). The reaction underwent
deprotection and sequel cyclization in excellent yields for
Entry Catalyst
Mol%
Temp
(0C)
Time
(min)
Yieldd (%)
15a
a
b
1
CdCl2
CoCl2
FeCl3
ZnCl2
SrCl2
10
10
10
10
10
10
10
10
10
10
10
5
40
40
40
40
40
40
40
40
40
40
40
40
60
60
80
4
-
-
90
94
93
91
-
2
2
-
-
3
2
-
-
4
2
-
-
5
10
10
10
5
-
-
6
CuCl2
NH4Cl
CuI2
-
84
55
40
10
-
-
7
5
-
8
20
67
55
58
75
95
95
65
-
9
InCl3
5
20
-
10
11
12
13c
14c
15c
HgCl2
SnCl2.2H2O
CeCl3
β-CD
5
detetrahydropyranylation,
demethoxymethylation
and
10
4
-
-
deacetylation (92–99%) but in moderate yields for detosylation
-
-
o
(61–74%) within 8-9 min at 60 C (Table 3, entries 1–9). In case of
20
10
5
10
10
20
-
-
chalcones (5-14), only deprotection was observed without
cyclization. Interestingly, the deprotection of THP/MOM ethers
followed by the Friedel–Crafts alkylation was observed for the
chalcone epoxides (15-21) giving the corresponding 2-
hydroxyindanones (15a-21a) in excellent yields (95–99%) within 10
min. We also subjected alicyclic tetrahydropyranyl tosylates (22-26)
to the same reaction protocol which resulted in moderate yields
(59–63%) of their respective products (22a-26a) in 14-15 min. All
the synthesized products were characterized by mass, FTIR, NMR
and also comparing with the available literature.4e, 5k
β-CD
β-CD
-
-
-
-
Reaction was carried out on
a 1 mmol scale; *Anton Paar
Monowave-300 reactor®; H2O was used as solvent for entry 13-15;
dIsolated yields.
To optimize the catalyst loading, three consecutive reactions were
carried out in 20, 10 and 5 mol% catalyst loadings under microwave
irradiation (Tables 1, entries 13-15). The reaction proceeded
2 | J. Name., 2012, 00, 1-3
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Table 3. β-CD mediated one pot deprotection and sequel cyclization of chalcone epoxides under MW condition.
Entry
Substrate
Product
Time (min)
Yields (%)
a
b
c
d
1
8
99
99
99
73
2
9
99
99
99
70
3
4
8
8
99
98
98
97
-
-
99
61
O
5
8
95
94
97
68
OTHP/MOM/Ac/Ts
5
Cl
6
7
8
8
95
96
94
95
98
94
72
70
8
9
8
8
93
95
95
94
94
97
67
69
10
8
93
92
97
70
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11
8
8
8
95
96
93
93
92
97
95
93
94
72
72
74
12
13
14
15
8
95
99
98
99
97
71
10
-
-
16
17
18
10
10
10
99
98
96
98
99
97
-
-
-
-
-
-
19
10
98
95
-
-
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20
10
10
96
99
95
97
-
-
-
-
21
22
23
14
14
-
-
-
-
-
-
62
60
24
25
14
15
-
-
-
-
-
-
61
59
OTs
Br
O
25
Br
O
26
15
-
-
-
63
Reactions were carried out on a 1 mmol scale at 60 0C under MWI, β-CD (10 mol %); a,b,c,d Isolated yields from OTHP, OMOM, OAc and OTs
respectively.
The scope of β-cyclodextrin as catalyst was also tested for the cyclodextrin catalyzed the isomerization of 2’-aminochalcones to
cyclization of 2’-aminochalcones (27-36) to their corresponding aza- their corresponding aza-flavanones in excellent yields (70-96%)
flavanones (27a-36a). Under optimal reaction conditions, β- within 9-22 min (Table 4).
Table 4. β-CD mediated one pot deprotection and concomitant cyclization of 2’-aminochalcones under MW condition.
Entry
1
Substrate
Product
Time (min)
15
Yield (%)
96
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2
20
18
20
90
3
4
92
93a, 92b, 95c, 70d
5
6
7
20
10
9
88a, 90b, 94c,73d
96
95
8
9
93
9
22
12
81
89
10
Reactions were carried out on 1 mmol scale at 60 °C under MWI, β-CD (10 mol %); a,b,c,d Isolated yields from OTHP, OMOM, OAc and OTs
respectively.
In addition, we also studied the substituents effects of electron- time (Table 2; 35a). In case of cyclization of 2’-hydroxychalcones to
donating to electron-withdrawing groups of Ar2 ring of 2’- their corresponding oxa-flavanones, reaction didn’t proceed and
aminochalcones on the reaction rate and product yields. As this might be due to poor nucleophilicity of the hydroxyl group
anticipated, electron donating groups enhanced the cyclization to under similar reaction conditions.
give the corresponding aza-flavanones in good yields while electron All the isolated products were confirmed by their IR, 1H NMR
withdrawing groups slow down the cyclization leading to moderate spectral analysis and with available literature data.7o-p For example,
yields of aza-flavanones. For example, electron-donating groups the
1H-NMR
spectrum
of
2-(3,4-dimethoxyphenyl)-2,3-
such as –CH3, OCH3 and –SCH3 groups on Ar2 afforded the product dihydroquinolin-4(1H)-one 33a shows a doublet of doublets at 5.43
in excellent yields at a faster rate (Table 2; 32a-34a, 36a). The ppm due to -CH proton at 2- position and 2 doublet of doublets (dd)
substituents such as -F and -Cl on Ar2 furnished the corresponding at 2.88-3.13 ppm due to -CH2 proton at 3-position which is the
products in excellent yields (90-92%) but took longer reaction time characteristic of flavanone and peak of one H at 12.17 ppm due to -
(Table 2; 28a, 29a). Similarly, electron-withdrawing group such as – NH is in agreement with cyclization of 2’-aminochalcone to aza-
NO2 on Ar2 gave product in 81% yields and took longer reaction flavanone.
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A plausible reaction mechanism for the THP ether deprotection and F254, Merck) were used for thin-layer chromatography (TLC) and
the simultaneous intramolecular Friedel–Crafts alkylation is spots were visualized under UV light. Silica gel column
depicted in scheme 1. The role of β-CD appears to be not only to chromatography was performed using silica gel 60–120 mesh size
activate the THP ether and epoxide by hydrogen bonding but also (RANKEM Limited). IR spectra were recorded with KBr on Thermo
to promote highly regioselective ring opening from β-carbon due to Nicolet FT-IR spectrophotometer. 1H NMR and 13C NMR spectra
considerable electron deficient character at the benzylic position were recorded on Jeol ECX 400 MHz and Bruker Spectrospin DPX
not on α-carbon due to a 4-membered cyclobutanone (unstable 500 MHz spectrometer using CDCl3 as a solvent and trimethylsilane
intermediate, Route-2) (Fig. 1). Therefore, route 1 was preferred to (TMS) as an internal standard. Spectra were processed using Bruker
route
2
because of stable carbocation formation and the Topspin® 3.0.b.8. Splitting patterns are designated as follows; s =
nucleophilic attack took place at the β-carbon because of better singlet, d = doublet, dd = doublets of doublet, m = multiplet, br =
resonance stabilized benzal intermediate which resulted in faster broad. Chemical shift (δ) values are given in ppm. Mass spectra
epoxide ring opening from β-carbon resulting in a five membered were collected using a direct inlet system (70 eV) with a VL detector
ring which on subsequent hydrolysis gave the desired product with (ES, 4000 V) on Perkin Elmer GC-MS. High-resolution mass spectra
concurrent liberation of β-CD for next catalytic cycle. In these (HRMS) were obtained on
a Brüker micrOTOF™-Q II mass
reactions, β-CD was recycled and reused.
spectrometer (ESIMS).
Microwave Irradiation Experiment. All microwave experiments
were carried out in dedicated Anton Paar Monowave-300
a
reactor®, operating at a frequency of 2.455 GHz with continuous
irradiation power of 0 to 850 W. The reactions were performed in a
G-30 Borosilicate glass vial sealed with Teflon septum and placed in
a microwave cavity. Initially, microwave of required power was
used and temperature was being ramped from room temperature
to a desired temperature. Once this temperature was attained, the
process vial was held at this temperature for required time. The
reactions were continuously stirred. Temperature was measured by
an IR sensor. After the experiments a cooling jet cooled the reaction
vessel to ambient temperature.
Fig. 1 Mechanistic Rationale of β-cyclodextrin induced deprotection
of phenolic ether and concomitant cyclization.
General procedure for the microwave-assisted deprotection of
THP, MOM, acetyl and tosyl ethers and concomitant cyclization of
chalcone epoxides and 2’-aminochalcones: The substrate (1 mmol)
dissolved in water (2 mL) was added to an aqueous solution of β-
cyclodextrin (10 mol % in 10 mL of water) kept in a G-30 process vial
and capped with Teflon septum. After a pre-stirring for one minute,
the vial was subjected to microwave irradiation with the holding
temperature of 60 °C for the prescribed time (Table 3 and 4). After
completion of reaction, the mixture was cooled to room
temperature and extracted with EtOAc (3 × 15 mL) and the catalyst
was filtered off and washed with EtOAc (2×10 ml), filterate was
dried over anhydrous Na2SO4 and concentrated under reduced
pressure. The crude product was purified by silica gel column
chromatography using hexane/ethyl acetate (8:2) as an eluent if
required otherwise compounds were pure enough for the spectral
elucidation.
Scheme 1. Plausible reaction mechanism of β-cyclodextrin induced
deprotection of phenolic THP ether and concomitant intramolecular
Friedel–Crafts alkylation.
Characterization data for representative compounds:
Conclusions
(E)-3-(4-chlorophenyl)-1-(4-hydroxyphenyl)prop-2-en-1-one (5a):
1H NMR (CDCl3, 500 MHz, ppm) δ 7.99 ( d, J = 8 Hz, 2H), 7.77 (d, J =
15.5 Hz, 1H), 7.63 (t, J = 8Hz, 2H), 7.46 (d, J = 15.5 Hz, 1H), 7.10 (t, J
= 8.5 Hz, 2H), 6.95 (d, J = 8 Hz, 2H), 5.38 (s, 1H, D2O exchangeable).
13C NMR (CDCl3, 125 MHz, ppm) δ 186.88, 162.05, 141.32, 131.41,
130.90, 130.83, 128.92, 121.85, 115.81, 115.21. IR (KBr, νmax = cm-1):
3410, 2926, 2875, 1686, 1599, 1265, 1078, 862, 730. GC-MS (m/z):
302 [M+., C15H11BrO2], 304 [M+2].
(E)-3-(4-bromophenyl)-1-(4-hydroxyphenyl)prop-2-en-1-one (6a):
1H NMR (CDCl3, 500 MHz, ppm) δ 7.99 ( d, J = 8 Hz, 2H), 7.77 (d, J =
15.5 Hz, 1H), 7.63 (t, J = 8Hz, 2H), 7.46 (d, J = 15.5 Hz, 1H), 7.10 (t, J
= 8.5 Hz, 2H), 6.95 (d, J = 8 Hz, 2H), 5.48 (s, 1H, D2O exchangeable).
13C NMR (CDCl3, 125 MHz, ppm) δ 186.88, 162.05, 141.32, 131.41,
130.90, 130.83, 128.92, 121.85, 115.81, 115.21. IR (KBr, νmax = cm-1):
3410, 2926, 2875, 1686, 1599, 1265, 1078, 862, 730. GC-MS (m/z):
302 [M+., C15H11BrO2], 304 [M+2].
Thus, we have developed for the first time the successful use of β-
cyclodextrin in water for the deprotection of THP/MOM/Ac/Ts
ethers and concomitant regioselective ring opening of chalcone
epoxides via intramolecular Friedel-Krafts alkylation to produce 2-
hydroxyindanones and cyclization of 2’-aminochalcone to aza-
flavanone under supramolecular catalysis affording the products in
excellent yields (59–99%) within 8-22 min and therefore represent a
novel methodology. This high regioselectivity was achieved due to
the inclusion complex formation of epoxides with β–CD. This
method precludes the use of organic solvents, toxic metals, acid or
base catalysts. Some important features of the method include high
yields, shorter reaction time, green conditions, reusability of
catalyst and easy workup.
Experimental
All the required chemicals were purchased from Merck and Aldrich
Chemical Company. Pre-coated aluminium sheets (silica gel 60
(E)-3-(4-hydroxyphenyl)-1-(4-methoxyphenyl)prop-2-en-1-one
(7a): 1H NMR (CDCl3, 500 MHz, ppm) δ 8.03 (d, J = 8 Hz, 2H), 7.74 (d,
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J = 15.5 Hz, 1H), 7.56 (d, J = 8.5 Hz, 2H), 7.51 (d, J = 16 Hz, 1H), 7.38 1685, 1593, 1266, 1083, 864, 727. GC–MS (m/z): 318 [M+,
(d,
J = 8.5 Hz, 2H), 6.98 (d, J = 9
Hz, 2H), 5.48 (s, 1H, C15H11BrO3], 320 [M+2]+.
D2Oexchangeable), 3.89 (s, 3H). 13C NMR (CDCl3, 125 MHz, ppm) δ 2,6-diphenyltetrahydro-2H-pyran-4-ol (22a): 1H NMR (500 MHz,
188.2, 163.9, 142.7, 131.4, 131.3, 130.1, 121.5, 116.8, 116.6, 114.2, CDCl3, ppm): δ 7.19-7.41 (m, 8H), 4.51-4.43 (m, 2H), 4.07 (tt, J = 4.5,
55.1. IR νmax (KBr, cm-1): 3410, 2928, 2880, 1684, 1599, 1265. GC-MS 11.5 Hz, 1H), 2.28 (s, br, D2O exchangeable, 1H, OH), 2.21 (dd, J = 4,
(m/z): 254 [M+, C16H14O3].
(E)-1-(4-hydroxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one
11.5Hz, 2H), 1.53 (q, J = 11.5 Hz, 2H). 13C NMR (125 MHz, CDCl3,
ppm): δ 131.4, 128.3, 127.5, 125.8, 77.8, 68.6, 42.9. IR (KBr, cm-1):
(8a): 1H NMR (CDCl3, 500 MHz, ppm) δ 8.03 (d, J = 8 Hz, 2H), 7.77 (d, 3433, 2965, 2921, 2852, 1634, 1452, 1382, 1265, 1156, 1065, 900,
J = 16 Hz, 1H), 7.55 (d, J = 8Hz, 2H), 7.42 (d, J = 15.5 Hz, 1H), 6.98 (d, 760, 700. GC-MS (m/z): 410 [M+, C17H18O2].
J = 8 Hz, 2H), 6.89 (d, J = 8 Hz, 2H), 5.82 (s, 1H, D2O exchangeable), 2,6-bis(4-chlorophenyl)tetrahydro-2H-pyran-4-ol (23a): 1H NMR
3.89 (s, 3H). 13C NMR (CDCl3, 125 MHz, ppm) δ 188.7, 163.6, 142.8, (500 MHz, CDCl3, ppm): δ 7.29-7.24 (m, 8H), 4.47 (d, J = 11.5 Hz,
131.2, 131.0, 130.4, 121.7, 116.3, 116.2, 114.0, 55.7. IR (KBr, νmax
=
2H), 4.06 (tt, J = 4.5, 11.5 Hz, 1H), 2.19 (dd, J = 4, 11.5 Hz, 2H), 1.48
cm-1): 3410, 2926, 2875, 1686, 1599, 1265. GC-MS (m/z): 254 [M+, (q, J = 11.5 Hz, 2H). 13C NMR (125 MHz, CDCl3, ppm): δ 139.2, 132.3,
C16H14O3].
127.5, 126.2, 77.8, 67.4, 41.9. IR (KBr, cm-1): 3447, 2960, 2886,
1652, 1543, 1088, 804. GC-MS (m/z): 323 [M+, C17H16Cl2O2].
(E)-1-(2-hydroxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one
1
(9a): H NMR (CDCl3, 400 MHz, ppm) δ 7.91-7.86 (m, 2H), 7.61 (d, J (E)-3-(4-(6-(4-chlorophenyl)-4-hydroxytetrahydro-2H-pyran-2-
= 8.8 Hz, 2H), 7.52 (d, J = 15.6 Hz, 1H), 7.49-7.45 (m, 2H), 7.00 (dd, J yl)phenyl)-1-(4-fluorophenyl)prop-2-en-1-one (24a): 1H NMR (500
= 1.2, 8.8 Hz, 1H), 6.93 (d, J = 8.4 Hz, 2H), 3.84 (s, 3H), 1.68 (s, 1H, MHz, CDCl3, ppm): δ 8.18 (d, J = 8 Hz, 1H), 7.95 (d, J = 8 Hz, 2H), 7.59
D2O exchangeable). 13C NMR (CDCl3, 100 MHz, ppm) δ 193.8, 163.7, (d, J = 9 Hz, 3H), 7.48 (d, J = 8 Hz, 2H), 7.41 (d, J = 9 Hz, 2H), 7.36 (d,
162.1, 145.5, 136.3, 130.7, 129.7, 127.4, 120.2, 118.9, 118.7, 117.7, J = 8.5 Hz, 2H), 7.01 (d, J = 9 Hz, 2H), 4.66 (t, J = 3 Hz, 2H), 4.14 (tt, J
114.6, 55.6. IR (KBr, νmax = cm-1): 3410, 2926, 2875, 1686, 1599, = 11, 3 Hz, 1H), 2.22-2.85 (m, 2H), 2.04 (s, br, D2O exchangeable,
1265. GC-MS (m/z): 254 [M+, C16H14O3].
1H), 1.73-1.84 (m, 2H). 13C NMR (125 MHz, CDCl3, ppm): δ 188.8,
(E)-1-(4-chlorophenyl)-3-(2-hydroxyphenyl)prop-2-en-1-one (12a): 166.7, 164.6, 144.6, 143.7, 140.8, 134.5, 134.3, 131.2, 130.0,
1H NMR (CDCl3, 400 MHz, ppm) δ 7.92-7.84 (m, 2H), 7.64-7.58 (m, 128.7, 127.7, 126.5, 125.9, 121.6, 115.9, 78.0, 77.7, 69.4, 40.0. IR
3H), 7.53-7.49 (m, 1H), 7.41 (d, J = 8.8 Hz, 2H), 7.01 (d, J = 8.4 Hz, (KBr, cm-1): 3434, 3010, 2922, 2843, 1734, 1626, 1456, 1256, 1069,
1H), 6.95 (d, J = 7.2 Hz, 2H), 4.84 (s, 1H, D2O exchangeable). 13C 808.8. HRMS (ESIMS): for C26H22ClFNaO3 (M+Na)+ Anal. calcd.
NMR (CDCl3, 100 MHz, ppm) δ 193.6, 163.8, 144.1, 136.7, 133.2, 459.1139; found 459.1150.
131.7, 130.0, 129.8, 129.5, 129.0, 120.7, 119.1, 118.9. IR (KBr, νmax
=
(E)-1-(4-bromophenyl)-3-(4-(6-(4-bromophenyl)-4-
cm-1): 3410, 2926, 2875, 1686, 1599, 1265. GC-MS (m/z): 258 [M+, hydroxytetrahydro-2H-pyran-2-yl)phenyl)prop-2-en-1-one (25a):
C15H11ClO2], 260 [M+2]+.
1H NMR (500 MHz, CDCl3, ppm): δ 7.88 (d, J = 8 Hz, 2H), 7.82 (d, J =
8.5 Hz, 2H), 7.78 (s, 1H), 7.61-7.66 (m, 4H), 7.47 (s, 1H), 7.35 (d, J = 8
2,5-dihydroxy-3-(4-methoxyphenyl)-2,3-dihydro-1H-inden-1-one
1
(16a): H NMR (CDCl3, 500 MHz, ppm) δ 7.92 (dd, J = 1.5, 7 Hz, 2H), Hz, 2H), 7.31-7.32 (m, 2H), 4.45 (d, J = 32, 11.5 Hz, 2H), 4.07 (tt, J =
7.55-7.52 (m, 2H), 7.07-7.01 (m, 3H), 5.31 (d, J = 2 Hz, 1H), 5.22 (d, J 10.5, 3 Hz, 1H), 2.30-2.35 (m, 2H), 2.20 (s, br, D2O exchangeable,
= 2 Hz, 1H), 4.19 (s, 1H, D2O exchangeable), 3.91 (s, 3H), 1.61 (s, 1H, 1H), 1.77-1.86 (m, 2H). 13C NMR (125 MHz, CDCl3, ppm): δ 189.8,
D2O exchangeable). 13C NMR (CDCl3, 125 MHz, ppm) δ 195.9, 162.6, 143.7, 140.7, 135.4, 134.4, 134.1, 129.8, 129.2, 128.5, 128.4, 127.8,
162.2, 136.8, 134.8, 131.4, 129.3, 128.9, 125.6, 116.7, 115.8, 75.4, 127.5, 126.2, 125.7, 122.0, 77.8, 77.4, 67.2, 39.8. IR (KBr, cm-1):
63.6, 53.7. IR (KBr, νmax = cm-1): 3408, 2925, 2879, 1685, 1595, 1266, 3454, 2961, 2878, 1651, 1541, 1091, 801. HRMS (ESIMS): for
1089, 858, 731. GC-MS (m/z): 270 [M+, C16H14O4].
C26H22Br2NaO3 (M+Na)+ Anal. calcd. 562.9833; found 562.9853.
3-(4-bromophenyl)-2,5-dihydroxy-2,3-dihydro-1H-inden-1-one
2-(4-(4-hydroxy-6-phenyltetrahydro-2H-pyran-2-yl)phenyl)-4H-
(18a): H NMR (CDCl3, 500 MHz, ppm) δ 7.93 (m, 2H), 7.70-7.67 (m, chromen-4-one (26a): 1H NMR (500 MHz, CDCl3, ppm): δ 7.74 (d, J =
1H), 7.58-7.53 (m, 2H), 7.08-7.04 (m, 2H), 6.10 (s, 1H, D2O 8 Hz, 2H), 7.37 (dd, J = 6, 3 Hz, 2H), 7.27 (d, J = 8.5 Hz, 2H), 7.17-7.21
exchangeable), 5.37 (d, J = 2 Hz, 1H), 5.22 (d, J = 2.5 Hz, 1H), 4.15 (s, (m, 3H), 7.15 (d, J = 8.5 Hz, 2H), 6.92 (s, 1H), 6.79 (dd, J = 6.5, 3 Hz,
1H, D2O exchangeable). 13C NMR (CDCl3, 125 MHz, ppm) δ 195.6, 2H), 4.40 (t, J = 11.5 Hz, 2H), 3.90 (tt, J = 11, 3 Hz, 1H), 2.15-2.22 (m,
161.9, 137.4, 132.4, 131.9, 131.5, 130.0, 129.8, 126.0, 123.1, 116.3, 2H), 1.68-1.77 (m, 2H). 13C NMR (125 MHz, CDCl3, ppm): δ 190.0,
75.4, 63.6. IR (KBr, νmax = cm-1): 3433, 2935, 2877, 1687, 1585, 1266, 163.0, 156.0, 139.8, 135.5, 134.1, 131.6, 129.9, 129.3, 128.6, 128.6,
1
1088, 862, 733. GC-MS (m/z): 318 [M+, C15H11BrO3], 320 [M+2]+.
127.6, 127.5, 126.3, 122.2, 121.8, 77.1, 76.9, 65.0, 39.8, 39.7. IR
(KBr, cm-1): 3446, 2971, 2880, 1652, 1513, 1208, 799. HRMS
5-chloro-2-hydroxy-3-(4-hydroxyphenyl)-2,3-dihydro-1H-inden-1-
one (20a): 1H NMR (CDCl3, 500 MHz, ppm) δ 7.92 (m, 2H), 7.68 (d, J (ESIMS): for C26H21NaO4 (M+Na)+ Anal. calcd. 421.1416; found
= 7.5 Hz, 1H), 7.58-7.50 (m, 2H), 7.43 (d, J = 8.5 Hz, 2H), 5.36 (d, J = 421.1441.
1.5 Hz, 1H), 5.19 (d, J = 2 Hz, 1H), 4.13 (s, 1H, D2O exchangeable), 2-(2-chlorophenyl)-2,3-dihydroquinolin-4(1H)-one (29a): 1H NMR
1.81 (s, 1H, D2O exchangeable). 13C NMR (CDCl3, 125 MHz, ppm) δ (500 MHz, CDCl3, ppm) δ 11.34 (s, 1H, D2O exchangeable), 8.58 (d, J
195.7, 162.4, 161.5, 136.7, 134.7, 131.4, 130.5, 129.4, 128.8, 125.3, = 6 Hz, 1H), 7.87 (dd, J = 10, 2.5 Hz, 1H), 7.75-7.79 (m, 1H), 7.59 (d, J
116.2, 75.4, 63.6. IR (KBr, νmax = cm-1): 3417, 2931, 2871, 1681, = 10 Hz, 1H), 7.44-7.48 (m, 1H), 7.26-7.29 (m, 1H), 6.98-7.03 (m,
1597, 1263, 1081, 860, 737. GC-MS (m/z): 274 [M+, C15H11ClO3], 276 2H), 5.60 (dd, J = 13.5, 6.5 Hz, 1H), 3.06-3.16 (m, 2H). 13C NMR (125
[M+2]+.
MHz, CDCl3, ppm) δ 191.2, 160.8, 157.1, 148.4, 138.3, 136.2, 127.1,
123.8, 121.9, 121.4, 121.2, 118.1, 79.1, 42.8. IR (KBr, cm-1): 3164,
5-bromo-2-hydroxy-3-(4-hydroxyphenyl)-2,3-dihydro-1H-inden-1-
one (21a): H NMR (CDCl3, 500 MHz, ppm) δ 7.91 (dd, J = 1, 8 Hz, 2926, 1693, 1606, 1462, 1305, 763. GC-MS (m/z): 257 [M+,
1
2H), 7.70-7.67 (m, 1H), 7.58-7.54 (m, 2H), 7.43 (t, J = 8.5 Hz, 2H), C15H12ClNO], 259 [M+2]+.
6.10 (s, 1H, D2O exchangeable), 5.38 (d, J = 2 Hz, 1H), 5.22 (d, J = 2.5 2-(3,4-dimethoxyphenyl)-2,3-dihydroquinolin-4(1H)-one (33a): 1H
Hz, 1H), 4.15 (s, 1H, D2O exchangeable). 13C NMR (CDCl3, 125 MHz, NMR (500 MHz, CDCl3, ppm) δ 12.17 (s, 1H, D2O exchangeable),
ppm) δ 197.7, 163.9, 161.9, 134.5, 134.2, 133.6, 130.1, 130.0, 129.3, 7.93 (d, J = 10 Hz, 1H), 7.51 (t, J = 10.5 Hz, 1H), 7.01-7.08 (m, 4H),
128.7, 115.7, 76.1, 63.1. IR (KBr, νmax = cm-1): 3427, 2937, 2875, 6.91 (d, J = 10 Hz, 1H), 5.43 (dd, J = 16.5, 2.5 Hz, 1H), 3.93 (s, 3H),
8 | J. Name., 2012, 00, 1-3
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5, 68; (k) N. Ahmed, N. K. Konduru, S. Ahmad and M. Owais,
Eur. J. Med. Chem., 2014, 75, 233.
3.91 (s, 3H), 3.13 (dd, J = 21, 17 Hz, 1H), 2.88 (dd, J = 21, 2.5 Hz, 1H).
13C NMR (125 MHz, CDCl3, ppm) δ 192.2, 161.6, 149.4, 149.3, 136.2,
131.2, 127.1, 120.9, 121.6, 118.8, 118.2, 111.1, 109.4, 79.6, 56.0,
55.9, 44.6. IR (KBr, cm-1): 3110, 2837, 1687, 1598, 1026. GC-MS
(m/z): 283 [M+, C17H17NO3].
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Acknowledgements
The authors wish to express their gratitude to the BRNS, India for
financial support, DST, New Delhi for providing HRMS facility and
CSIR, New Delhi for awarding SRF to S.K.
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A catalytic method for the deprotection of THP/MOM/Ac/Ts ethers and concomitant cyclization
of epoxy chalcone to 2-hydroxyindanone and 2’-aminochalcone to aza-flavanone is reported.
This method is “green” and milder but more advanced than those earlier reported.
10 | J. Name., 2012, 00, 1-3
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