Synthesis and characterization of chiral aza-macrocycles and study of their enantiomer recognition ability for organo-phosphoric acid and phosphonic acid derivatives by 31P NMR and fluorescence spectroscopy

Article abstract of DOI:10.1039/c5ob02616d

Two diastereomers of optically active N,O-containing new macrocycles with dual chirality of the ring and pendent group were synthesized and characterized. The difference in the accessibility of the cavity was explored to discriminate the enantiomers of the derivatives of organo-phosphoric and phosphonic acids by ³¹P NMR and fluorescence spectroscopy.

Full text of DOI:10.1039/c5ob02616d

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Manuscript for Article for Organic and Biomolecular Chemistry
Synthesis, characterization of chiral aza-macrocycles and study of their enantiomer
recognition ability of organo phosphoric acid and phosphonic acid derivatives by
3
1
P NMR and fluorescence spectroscopy
Aditya N. Khanvilkar and Ashutosh V. Bedekar*
Department of Chemistry
Faculty of Science
M.S. University of Baroda, Vadodara 390 002
India
*
Telephone number: +91-0265-2795552; Email: avbedekar@yahoo.co.in
ABSTRACT: Two diastereomers of optically active N,O-containing new macrocycles with duel chi-
rality of the ring and pendent group were synthesized and characterized. Difference in accessibility
of the cavity was explored to discriminate enantiomers of derivatives of organo phosphoric and
3
1
phosphonic acids by P NMR and fluorescence spectroscopy.

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Introduction:
Crown ethers and other macrocyclic compounds have a unique place in the field of supramo-
lecular chemistry. These host molecules interact with guest entities by predictable and non-covalent
1
manner. This phenomena has been well studied over the last several decades. Importance of optical-
ly active molecules in the field of medicine, fragrance and flavours, material science and supramole-
cular chemistry has already been well established. The supramolecular interactions in biological sys-
tems between the chiral receptors and guest substrates are in general more enantiospecific. Many
studies have been conducted on large complex biological assemblies and their interactions based on
2
supramolecular principles. Optically active crown ethers and other macrocyclic compounds can be
prepared by introducing chirality in the backbone of the ring itself or by attaching chiral pendent
groups to the achiral framework of the crown. Chiral macrocyclic hosts can selectively recognize
isomers of optically active guest molecules based on supramolecular interactions. Few such macro-
3
4
cyclic compounds with chiral ring or with suitable chiral pendent groups have been reported and
their molecular recognition ability with chiral guests has been investigated.
Optical purity of chiral materials is usually confirmed by more than one analytical methods
such as chromatography (GC or HPLC with chiral stationary phase), spectroscopy (NMR, CD), ca-
pillary electrophoresis etc. For accurate determination of the ratio of enantiomers by NMR spectros-
copy, it is necessary to convert the analyte to the diastereomers, quantitatively. This can be achieved
by making diastereomeric derivatives of the analyte with appropriate chiral derivatizing agents
5
(
CDA), such as Mosher’s acid, involving a covalent bond. In other approach, chiral solvating agent
6
(
CSA) can be mixed during the NMR analysis where it may bind temporarily with the chiral ana-
lyte, creating in situ diastereomers. Their ratio can be established by detecting the signals. This has
7
8
been achieved by chiral crown ethers or macrocyclic CSAs capable of supramolecular interactions
with optically active analytes. Also some crown ethers with chiral pendent groups have been used as
9
CSA for determination of optical purity. The molecular recognition of chiral macrocycles with opti-
1
0
cally active guests has also been measured by analyzing the change in their fluorescence properties.
Here we report synthesis of new macrocycles 1 with chiral backbone along with chiral pendent
groups. We evaluate their ability to discriminate chiral organic compounds by NMR and fluores-
cence spectroscopy (Scheme 1). Two chiral elements will allow the study of match, mismatch effect
to fine tune the CSA for such applications for different analytes. In this report we have screened
derivaties of 1,1′-binaphthyl-2,2′-diyl hydrogenphosphate, α-hydroxy phosphonic acid and α -amino
3
1
phosphonic acid as analytes employing P NMR analysis. Chiral BINOL deived phosphoric acid
derivatives have acquired significant interest in asymmetric catalysis. Chiral phosphoric acids have

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1
1
cemented their status as an efficient synthetic tool in Bronsted acid catalysis. α-Hydroxy
phosphonic acids and α-amino phosphonic acids have received considerable attention in the field of
medicinal chemistry. Aminophosphonic acid derivatives, being structurally analogous to amino
acids, have been incorporated in to many drug molecules due to their physiological activity as
1
1a
antiviral, antibacterial, anticancer and neuroactive compounds.
Scheme 1 New macrocycles with chiral backbone and chiral pendent group
O
O
O
O
O
O
O
O
N
N
N
N
N
N
Me
Ph
Ph
Me
Me
Ph
Ph
Me
(S,S,S)-1a
(R,R,S)-1b
Result and Discussion:
The two diastereomers of the aminocyclohexanol, 3a and 3b, were obtained by ring opening
1
2
reaction of cyclohexene oxide 2 with (S)-2-phenylethyl amine (Scheme 2).
Scheme 2 Preparation of amino alcohols from cyclohexeneoxide
Me
(S)
(R)
OH
OH
O
H2N (S) Ph
+
EtOH, reflux
72 h, 65 %
(S) NH
(R) NH
2
Me (S) Ph
Me (S) Ph
(
S,S,S)-3a
(R,R,S)-3b
The two separated diastereomers were condensed with m-xylene dibromide to afford two di-
astereomers of diol 4a and 4b (Scheme 3). The final eighteen member macrocycles were prepared by
transesterification with dimethyl 2,6-pyridinedicarboxylate by a slightly modified procedure.

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Scheme 3 Synthesis of the macrocycle
Br
Br
OH
N
HO
N
(
S,S,S)-3a
K2CO3, CH3CN,
reflux
24 h, 68 %
Me
Ph
Ph
Me 4a
5
7 %
4 %
O
O
(
S,S,S)-1a
N
(R,R,S)-1b
OMe
OMe
5
NaH, KI
toluene, reflux, 48 h
HO
Br
Br
OH
N
(
R,R,S)-3b
K2CO3, CH3CN,
reflux
24 h, 79 %
N
Me
Ph
Ph
Me 4b
Single crystal X-ray analysis of both the diastereomers of macrocycles revealed interesting
features. In case of (S,S,S)-1a the phenyl unit of the pendent groups were seen to lie on the top and
cover the bottom of the macrocyclic cavity while in case of (R,R,S)-1b they appear to be away (Fig-
ure 1).
Figure 1 X-ray structure of (S,S,S)-1a [top] (CCDC N0. 1004162) and (R,R,S)-1b [bottom] (CCDC
N0. 1016922).

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Recently chiral Brønsted acids such as phosphoric acid derivative 1,1′-Binaphthyl-2,2′-diyl
1
1b,c
hydrogenphosphate 5a and its analogues have found wide uses as chiral catalysts.
There can be
three different types of chiral organic phosphorous containing acid derivatives (Chart 1).
O
P
O
P
O
P
HO
TsHN
O
*
OH
*
OH
OH
*
O
OMe
OMe
R
R
*
Type A
Phosphoric acid
Type B
Type C
Phosphonic acid
Chart 1 Types of phosphorous containing analytes
The two derivatives of 1 were screened to study their ability to discriminate the P NMR
3
1
1
3
signals of derivatives of 5 by measuring the chemical shift non-equivalence (∆∆δ) (Table 1). A
clear pattern of better discrimination for (R,R,S)-1b was observed in all the examples, while the other
derivative (S,S,S)-1a, with closed cavity was found ineffective (Figure 2).
a
Table 1 Discrimination of Binaphthyl phosphoric acids 5
R1
O
O
O
R2
R2
P
OH
R1
5
No Comd. R1
No.
R2
∆∆δ (ppm)
(S,S,S)- (R,R,S)-
1
a
1b
1
2
3
4
5
5a
5b
5c
5d
5e
H
H
H
OMe
O-iPr
H
0.03
0.74
b
--
0.68
0.76
0.81
0.40
b
H
--
b
NO2
Br
--
b
H
--
a
31
In CDCl (20 mM), 162 MHz ( P NMR), ratio of 5:1 (2:1);
Not resolved.
3
b

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3
1
Figure 2 P NMR signals for (±)-5a with 1a and 1b.
The separation of signals was further studied to establish linear relationship between experi-
mental and actual values of optical purity for establishing practical utility of CSA (see ESI).
The nature of complex between 5 and the isomers of macrocycle was determined by IR spec-
-1
14
troscopy. Complex of 5 with 1a showed a weak band at 1098 cm for phosphoryl bond stretching,
but appears much stronger for 1b (see ESI). This may indicate a better complexation in case of 1b
supporting the observation.
Use of fluorescence spectroscopy for understanding the recognition of chiral molecules has
1
5
received considerable attention. Many chiral fluorescent host molecules have been known to exhi-
1
5c
15g
bit enantioselective quenching or enhancement on interaction with chiral guests. In this study
the fluorescence property of the analyte 5a was utilized to evaluate the interactions with the two
isomers of macrocycle. Such chirality dependent quenching of both enantiomers of 5a in presence of
macrocycles 1a and 1b have been investigated. The recognition ability of macrocycles towards the
phosphoric acid was evident from the extent of quenching (Figure 3). The static quenching is proba-
bly attributed to the deprotonation of phosphoric acid 5a, which is indicated by appearance of new
1
5c
peak in the UV-Vis spectra (at the higher wavelength at 327 nm; see ESI).
The response of quenching the emission of enantiomers of 5a with 1a follows the Stern-
R-5a
S-5a
Völmer equation. The florescence quenching efficiency can be expressed as a ratio of Ksv /Ksv
which was observed to be 1.05 (Figure 3, A-2). On the other hand quenching of enantiomers of 5a
R-5a
S-5a
with the other macrocycle 1b indicated the ratio Ksv /Ksv to be 1.40 (Figure 3, B-2), indicating

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1
6
31
its higher quenching ability. This data confirms the recognition observed in P NMR analysis.
These observations substantiate the assumption that the relatively open cavity of 1b facilitates effi-
cient complexation between protonated macrocycle and phosphate ion as well as - interaction of
naphthyl ring of 5 (see ESI for geometrical model).
-5
Figure 3 Quenching study: A-1) Fluorescence spectra of 5a (10 M, CHCl ); (±)-5a, (S)-5a and (R)-
3
5
a in presence of 1a (λ = 305 nm); A-2) Stern-Völmer plots of (S)-5a and (R)-5a with 1a; B-1)
ex
-5
Fluorescence spectra of 5a (10 M, CHCl ); (±)-5a, (S)-5a and (R)-5a in presence of 1b (λ = 305
3
ex
nm); B-2) Stern-Völmer plots of (S)-5a and (R)-5a with 1b.
Preliminary investigation was made to determine effective stoichiometric ratio of host-guest
association in the present system (Table 2). Although each macrocycle contains three basic sites, out

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of which the two tertiary nitrogens undergo protonation to generate ion pairs, as evident from entry 2
of Table 2. While the third site of pyridine is expected to show - interaction with the naphthyl ring
of guest molecule.
Table 2 Determination of stoichiometry of host (1b) and guest (5a) association.
a
No
Ratio
∆∆δ (ppm)
1
b : 5a
1 : 3
1
2
3
4
0.58
0.74
0.66
0.63
1 : 2
1 : 1
1 : 0.5
a
31
In CDCl (20 mM), 162 MHz ( P NMR).
3
Chiral phosphonic acid derivatives which resemble closely have also been found useful in
17
medicinal chemistry and in asymmetric transformations. It was noteworthy to see a reverse trend
for a second group of analytes of -substituted phosphonic acids (6 to 10) with the same set of ma-
crocyclic CSAs (Table 3). These analytes, being smaller in size are better accommodated in the par-
tially closed cavity of macrocycle 1a. Presence of hydrogen bond donor group at the position of
phosphonic acid is essential to effect the discrimination. In case of -chloro derivative 8 both the
macrocycles are found to be ineffective in the discrimination.

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a
Table 3 Discrimination of monomethyl esters of substituted phosphonic acids 6 to 10
OH
OH
Cl
O
O
O
P
P
P
OH
OH
OH
MeO
MeO
MeO
R
6
7
8
No
Comd.
No.
R
∆∆δ (ppm)
S,S,S)- (R,R,S)-
(
1
a
1b
1
2
3
4
5
6a
6b
6c
7
H
Me
Cl
--
0.17
0.19
0.16
0.17
0.04
b
--
b
--
b
--
b
b
8
--
--
--
NHTs
O
NHTs
O
P
P
OH
OH
MeO
MeO
R
9
10
b
6
7
8
9
9a
9b
9c
9d
9e
10
H
Me
Cl
0.40
--
b
0.42
0.45
0.43
0.40
0.37
--
0.10
b
OMe
NO2
--
--
1
1
0
1
0.12
b
--
a
31
In CD OD (5%) in CDCl (20 mM), 162 MHz ( P NMR),
3
3
b
ratio of 6 to 10:4 (2:1); Not resolved.
In both the cases protonation of nitrogen of macrocycles result in electrostatic interactions
holding the diastereomers together effecting the chiral discrimination. In the second set of analytes
there could be additional H-bonding interaction working in tandem. The formation of H-bond be-

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tween phosphonic acid analyte and H-bond acceptor sites of macrocyclic CSA are probably favored
by partially close cavity of 1a. This could also explain better discrimination for the -amino deriva-
tives (9 and 10) where the H-bonding will be stronger.
In summary, two diastereomers of eighteen member N,O-macrocycles are synthesized and
31
evaluated as CSA for effective discrimination of P NMR signals and fluorescence quenching of
several organo phorphoric and phosphonic acid derivatives. Combination of chirality on the back-
bone of macrocycle and of the pendant group was explored for molecular recognition of optically
active hosts for quantifiable discrimination. Further studies on the binding between isomers of ma-
crocycles and two sets of guest molecules are in progress.
Experimental Section:
Reagents were purchased from Sigma-Aldrich Chemicals Limited, SD Fine, Sisco, Qualigens, Avara
Chemicals Limited etc. All the glassware were flame dried before experiment. All solvents that were
used were stored on oven dried molecular sieves (4Å). All commercial products were used without
further purification. Toluene was distilled and dried by passing Sodium wire. Thin Layer Chromato-
graphy was performed on Merck 60 F254 Aluminium coated plates. The spots were visualized under
UV light or with iodine vapour. All the compounds were purified by column chromatography using
SRL silica gel (60-120 mesh). All reactions were carried out under an inert atmosphere (nitrogen)
1
13
31
unless other conditions are specified. H, C and P NMR spectra are recorded on a 400 MHz
1
3
31
Bruker Avance 400 Spectrometer (100 MHz for C and 162 MHz for P respectively) spectrometer
with CDCl as solvent and TMS as internal standard. Signal multiplicity is denoted as singlet (s),
3
doublet (d), doublet of doublet of doublets (ddd), triplet (t), doublet of triplet (dt), quartet (q) and
multiplet (m). Mass spectra were recorded on Thermo-Fischer DSQ II GCMS instrument. IR spectra
were recorded on a Perkin-Elmer FTIR RXI spectrometer as KBr pallets or neat in case of liquids.
UV-vis spectra were recorded on Perkin-Elmer Lambda
Fluorescence spectra were recorded on
Jasco FP-6300 Spectrofluorometer. The 1,1’-Binaphthyl-2,2’-diylhydrogen phosphate derivatives
1
8a
5
a-5e were synthesized by reported procedure. Monomethyl esters of -hydroxy and -amino
1
8b
31
phosphonic acids 6-10 were synthesized by following literature procedure. All P CSA NMRs
were recorded by mixing 1equiv (10 mmol) of 1a or 1b and 2 equiv (20mmol) of hosts (5-10) in
0
.6ml CDCl or indicated otherwise.
3

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Synthesis of (1S,2S)-trans-2-(N-Benzoyl-N-methyl)amino-1-cyclohexanol (3a)
A mixture of (S)-phenylethyl amine (1.0g, 8.3mmol) and cyclohexenoxide (0.97g, 9.9mmol), in
5mL dry ethanol, was refluxed under nitrogen atmosphere for 72 h. The solvent was then evapo-
1
rated under vacuum and the reaction mixture was subjected to column chromatography (ethyl ace-
tate/petroleum ether, 3:7) yielding compound 3a as colourless oil. (0.63g, 35 %);
1
2
=
+11.5 (c = 1.0 in MeOH) (Lit +20.9 c = 1.64, MeOH)
1
H NMR (400 MHz, CDCl ): 0.80-0.91 (1H, m), 1.15-1.35 (3H, m), 1.34-1.36 (3H, d, J = 6.4 Hz),
3
1
3
.66-1.73 (2H, m), 1.94-1.98 (1H, m), 2.09-2.06 (1H, m), 2.32-2.38 (1H, ddd, J = 13.2, 9.2, 4.0 Hz),
.08-3.14 (1H, dt, J = 9.2, 4.4), 3.91-3.96 (1H, q, J = 6.4 Hz), 7.24-7.28, (1H, m), 7.32-7.36 (4H, m).
1
3
C NMR (100 MHz, CDCl3):
IR (neat):
Mass (ESI): m/z 242 (30), 221 (50), 220 (94), 158 (30), 116 (99), 106 (24), 105 (100).
Synthesis of (1R,2R)-trans-2-[(S)-(α-Methylbenzyl)amino]-1-cyclohexanol (3b)
As described above, the compound 3b was obtained from the later fractions from column chromato-
graphy (ethyl acetate/petroleum ether, 2:3) as white solid. (0.54g, 30%);
o
Mp: 53-54 C
1
2.
=
-99.6 (c = 1.0 in MeOH) (Lit -100.2 c = 1.20, MeOH)
1
H NMR (400 MHz, CDCl3):
-
m), 1.07-1.13 (2H, m), 1.19-1.30 (1H, m), 1.36-1.38
(3H, d, J = 6.4 Hz) 1.64-1.69 (2H, m), 1.99-2.05 (2H, m), 2.14-2.20 (1H, m), 3.14-3.20 (1H, m)
3
.99-4.04 (1H, q, J = 6.4 Hz), 7.25-7.27 (1H, m), 7.31-7.35 (4H, m)
C NMR (100 MHz, CDCl3):
1
3
IR (KBr): 3480, 2924, 1452, 1368, 1350, 1127, 1064, 762, 698.
Mass (ESI): m/z 242 (7), 221 (48), 220 (96), 116 (96), 106 (24), 105 (100).

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(1S,1’S,2S,2’S)-2,2’-((S)-(1,3-phenylenebis(methylene))bis(((S)-1-phenylethyl)azanediyl))-
dicyclohexanol (4a)
A solution of amino alcohol 3a (0.5g, 2.2mmol) in 10mL acetonitrile was added K CO (0.69g,
2
3
5
.0mmol) and
’-dibromo-m-xylene (0.33g, 1.3mmol). The mixture was then refluxed under ni-
trogen for 24 h. The solvent was then evaporated under vacuum and the mixture was poured in cold
water and extracted from ethyl acetate (3 x 50 mL) and the combined extracts were washed with wa-
ter (2 x 25mL). The organic layer was dried over anh. Na SO , evaporated under vacuum and then
2
4
subjected to column chromatography on silica gel (ethyl acetate/ petroleum ether, 1:4) to afford
compound 4a as white solid.(0.42g, 68%);
o
Mp: 58-60 C.
=
+83.9 (c = 1.0 in CHCl3).
1
H NMR (400 MHz, CDCl3):
m), 1.27-1.39 (1H, m), 1.47-1.49 (3H, d, J = 6.4 Hz),
.64-1.66 (1H, m), 1.76-1.78 (1H, m), 1.92-1.93 (1H, m), 1.96- 2.03 (1H, m), 2.34-2.39 (1H, m)
.33-3.68 (1H, m), 3.64-3.67 (1H, d, J = 13.6 Hz), 3.86-3.89 (1H, d, J = 13.6 Hz), 4.02-4.07 (1H, q,
1
3
J = 6.8 Hz) 7.13-7.25 (6H, m), 7.29-7.38 (1H, m)
1
3
C NMR (100 MHz, CDCl3):
IR (KBr): 3465, 2934, 1603, 1450, 1374, 1218, 1076, 759, 701.
Mass (ESI): m/z 542 (40), 541 (100), 349 (10), 348 (46), 234 (13).
HRMS: Calculated for C H N O (M+1) = 541.3788. Found 541.3789.
3
6
49
2
2
(1R,1’R,2R,2’R)-2,2’-((S)-(1,3-phenylenebis(methylene))bis(((S)-1-phenylethyl)azanediyl))-
dicyclohexanol (4b)
The title compound was obtained by following the same procedure as for compound 4a from the cor-
responding amino alcohol 3b. The organic extract was column chromatographed (ethyl acetate/ pe-
troleum ether, 1:4) to yield compound 4b as white solid. (0.49g, 79%);
o
Mp: 111-112 C.
=
-161.4 (c = 1.0 in CHCl3).

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1
H NMR (400 MHz, CDCl3):
, m), 1.45-1.47 (3H, d, J = 6.8 Hz), 1.70-1.71 (1H, m)
.77-1.99 (1H, m), 1.95-1.98 (1H, m), 2.09-2.11 (1H, m), 2.59-2.65 (1H, m), 3.41-3.47 (1H, m),
.67-3.69 (1H, d, J = 13.2 Hz), 3.96-4.02, (2H, m), 5.34 (1H, s), 6.67-6.69 (1H, d, J = 8.0), 7.09-7.17
1
3
(3H, m), 7.19-7.22 (2H, m), 7.25-7.29 (1H, m).
1
3
C NMR (100 MHz, CDCl3):
IR (KBr): 3440, 2928, 1603, 1449, 1373, 1349, 1198, 1084, 761, 699.
Mass (ESI): m/z 542 (37), 541 (100), 523 (5).
HRMS: Calculated for C H N O (M+1) = 541.3788. Found 541.3789.
3
6
49
2
2
Synthesis of Aza-macrocycle (1a)
In a three neck round bottom flask fitted with septa, a mixture of diamino diol 4a (0.4g, 0.74mmol),
NaH (0.15g, 3.7mmol) and KI (0.13g, 0.74mmol) was heated to reflux under nitrogen in 30mL dry
toluene for 0.5 h. To this mixture a solution of dimethyl 2,6-pyridinedicarboxylate (0.17g,
0
.89mmol) in 10mL dry toluene was added dropwise with a syringe over a period of 0.5 h. The mix-
ture was then refluxed for 48 h. After completion of reaction the solvent was removed under vacuum
and the reaction mixture was subjected to column chromatography (ethyl acetate/petroleum ether,
1
:9) resulting in white solid. (0.28g, 57%);
o
Mp: >200 C.
=
-162.7 (c = 1.0 in CHCl3).
1
H NMR (400 MHz, CDCl ): 0.9-1-1.10 (2H, m), 1.26-1.42 (4H, m), 1.53-1.54 (1H, m), 1.57-1.59
3
(6H, d, J = 6.4 Hz), 1.59-1.69 (5H, m), 1.69-1.99 (2H, m), 2.29-2.31 (2H, m), 3.04-3.10 (2H, dt, J =
1
6
7
0.8, 3.2 Hz), 4.01-4.04 (2H, d, J = 13.6 Hz), 4.07-4.10 (2H, d, J = 13.6 Hz), 4.28- 4.30 (2H, q, J =
.4 Hz), 5.12-5.16 (2H, dt, J = 10.8, 3.6 Hz), 6.98-7.01 (6H, m), 7.17-7.26 (3H, m), 7.64 (4H, s),
.87-7.91 (1H, t, J = 4.0 Hz), 8.22-8.24 (2H, d, J = 7.6 Hz), 8.51 (1H, s).
1
3
C NMR (100 MHz, CDCl3):
IR (KBr): 2940, 1704, 1602, 1585, 1448, 1368, 1330, 1243, 1144, 957, 701.
Mass (ESI): m/z 672 (100), 568 (60), 464 (70) 462(20), 105(20).

Organic & Biomolecular Chemistry
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DOI: 10.1039/C5OB02616D
HRMS: Calculated for C H N O (M+1) = 672.3790. Found 672.3796.
4
3
50
3
4
Synthesis of Aza-macrocycle (1b)
The title compound was obtained by following the same procedure as for compound 1a from the cor-
responding diamino diol 4b. The organic extract was column chromatographed (ethyl acetate/ petro-
leum ether, 1:9) to yield compound 1b as white solid. (0.27g, 54%);
o
Mp: >200 C.
=
+36.8 (c = 1.0 in CHCl3).
1
13
The H and C NMR spectra of compound 1b exhibit broad signals. This type of observation for
3
i
macrocyclic system has been reported earlier by Periasamy et al.
1
H NMR (400 MHz, CDCl ): 1.26-1.28 (4H, m), 1.30-1.43 (7H, m), 1.59-1.69 (9H, m), 2.23 (2H,
3
s), 2.97-3.32 (2H, m), 3.61-3.64 (2H, d, J = 13.6 Hz) 4.26 (4H, m), 5.31 (2H, s), 7.07 (2H , br s),
7
.19-7.20 (4H, m), 7.28-7.30 (4H, m), 7.54 (3H, s), 8.04-8.08 (1H, t, J = 8 Hz), 8.47 (3H, m).
1
3
C NMR (100 MHz, CDCl3):
IR (KBr): 2941, 1705, 1559, 1449, 1369, 1333, 1245, 1082, 700.
Mass (ESI): m/z 695 (45), 694 (80), 672 (M+1, 100), 568 (10).
HRMS: Calculated for C H N O (M+1) = 672.3790. Found 672.3797.
4
3
50
3
4
Supporting Information
The supporting Information is available free of charge on the RSC Publication website at DOI:
This includes copies of the spectral data, details of crystal structure including cif files, spectra of
CSA study (as PDF).
ACKNOWLEDGMENT
We wish to thank Council and Scientific and Industrial Research (CSIR), New Delhi for the
award of fellowship to ANK (JRF and SRF) and Department of Science and Technology (DST-

Page 15 of 17
Organic & Biomolecular Chemistry
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DOI: 10.1039/C5OB02616D
FIST), New Delhi for the grant to purchase single crystal X-ray diffraction facility in the faculty. We
also thank Dr S. Sahoo of Sun Pharma Industries for some NMR analysis. We are also grateful to
Prof. Jean-Marie Lehn, University of Strasbourg, Strasbourg for his helpful discussion and sugges-
tions.
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