Synthesis of 2-(ethynyloxy)naphthaene-1-carbaldehyde using 2-hydroxy benzyl alcohol and propargyl bromide in aqueous micellar media

Article abstract of DOI:10.1007/s11164-017-3221-z

A highly convenient method has been developed for the synthesis of 2-(ethynyloxy) napthaene-1-carbaldehyde and its derivatives. Substituted naphthalene derivatives, having hydroxyl and carbonyl group, in the presence of K₂CO₃ base, react with propargyl bromide. Not only the product was obtained in good yield, but also the low cost and easy availability of the starting materials makes this synthesis a convenient one. In micellar solution, organic substrates are pushed away from water molecules towards the hydrophobic core of micelle droplets, thus inducing efficient collisions between organic substrates that eventually enhance the reaction rate and yield, which is ten times greater and two and half hours lesser time than in absence of micellar medium. An electron withdrawing group favours the formation of a stable phenoxide ion, which in turn favours the formation of product. The product is confirmed by FT-IR, ¹H-NMR, and MASS spectroscopy. A green and useful method has been developed for the O-alkylation of aryl in aqueous surfactant media.

Full text of DOI:10.1007/s11164-017-3221-z

Res Chem Intermed
https://doi.org/10.1007/s11164-017-3221-z
Synthesis of 2‑(ethynyloxy)naphthaene‑1‑carbaldehyde
using 2‑hydroxy benzyl alcohol and propargyl bromide
in aqueous micellar media
Sangita Mandal · Swagata Mandal · Satyajit Biswas · Soujanya Banerjee3 ·
1
1
1,2
1
Bidyut Saha
Received: 28 June 2017 / Accepted: 4 December 2017
©
Springer Science+Business Media B.V., part of Springer Nature 2017
Abstract A highly convenient method has been developed for the synthesis of
-(ethynyloxy) napthaene-1-carbaldehyde and its derivatives. Substituted naphtha-
lene derivatives, having hydroxyl and carbonyl group, in the presence of K CO
2
2
3
base, react with propargyl bromide. Not only the product was obtained in good
yield, but also the low cost and easy availability of the starting materials makes this
synthesis a convenient one. In micellar solution, organic substrates are pushed away
from water molecules towards the hydrophobic core of micelle droplets, thus induc-
ing eꢀcient collisions between organic substrates that eventually enhance the reac-
tion rate and yield, which is ten times greater and two and half hours lesser time
than in absence of micellar medium. An electron withdrawing group favours the for-
mation of a stable phenoxide ion, which in turn favours the formation of product.
1
The product is conꢁrmed by FT-IR, H-NMR, and MASS spectroscopy. A green
and useful method has been developed for the O-alkylation of aryl in aqueous sur-
factant media.
Keywords 2-(Ethynyloxy)napthaene-1-carbaldehyde · 2-Hydroxy-1-
naphthaldehyde · Propargyl bromide and micellar catalysis
*
Bidyut Saha
b_saha31@rediꢂmail.com
1
Homogeneous Catalysis Laboratory, Department of Chemistry, The University of Burdwan,
Golapbag, Burdwan 713104, WB, India
2
3
Department of Chemistry, Hooghly Women’s College, Hooghly, WB, India
Department of Chemistry, IIEST, Shibpur, WB, India
1
3

S. Mandal et al.
Introduction
The synthesis and application of new dendrimeric structures have been the focus
of several research teams. Synthetic methodologies, involving convergent [1] and
divergent [2] routes have been reviewed [3]. Other strategies involving ‘hyper-
monomers’ [4], exponential [5], and orthogonal [6], growth, and ‘activated’
monomers [7] have also been reported. Polyether backbones have been widely
used for preparing dendritic architectures by Frechet’s convergent strategies [8].
2
-Hydroxybenzyl alcohol has been used as fundamental reagent for preparing a
large number of dendrons and dendrimers frequently using the Williamson reac-
tion. Naphthalene derivatives, having hydroxyl and carbonyl groups in the neigh-
bouring peri-position, play an important role as potential precursors of perfused
heterocyclic systems [9–11]. Moreover, these compounds are unique models for
studying so-called [12, 13] “peri eꢂects” (hydrogen bonds, electrophilic interac-
tions, ring chain tautomerism and other interactions between the perisubstitu-
ents) [14–21]. It is strongly desirable to know speciꢁc features of the structure
of the perihydroxy carbonyl moiety and the nature of peri eꢂects while studying
the reactivity and predicting chemical properties of perihydroxy carbonyl com-
pounds. The O-hydroxybenzaldehyde has many applications as an intermediate in
chemical industries [22]. Green or sustainable chemistry has now attained the sta-
tus of a major scientiꢁc discipline [23], and the studies in this area have led to the
development of cleaner and relatively less harmful chemical processes with many
new technologies being developed each year [24]. Encouraged by the ‘Green
Chemistry strategies’ of Paul, Anastas and Warner [25], we have attempted to
develop synthetic protocols for an etheriꢁcation reaction. Carrying out the reac-
tion in micellar medium makes the method advantageous over other methods due
to comparatively higher yield and shorter reaction time [26].
Experimental
Materials and reagents
All reagents were purchased from renowned manufacturers and used as received,
unless noted otherwise. The 2-Hydroxy-1-naphthaldehyde (AR, Merck) propargyl
bromide (AR, Qualigens) CTAB (AR, SRL) and double distilled water were used
for the preparation of required solution. All other chemicals used, were purchased in
the highest purity state, available commercially.
Instrumentation
1
Product was conꢁrmed by performing FTIR, H NMR, and MASS Spectroscopy.
The HRMS study was performed in a Thermo Exactive plus HRMS (Thermo Fisher
Scientiꢁc). The FTIR spectra were recorded on a JASCO FTIR-3500 spectrometer.
1
3

Synthesis of 2‑(ethynyloxy)naphthaene‑1‑carbaldehyde…
−
1
The analysis conditions used were 16 scans at a resolution of 4 cm measured
−1
between 500 and 4000 cm .
General procedure for the preparation of the ether
Propargyl bromide (0.05 M) in aqueous CTAB solution (0.4 M, 10 mL) was added
drop wise to a solution of 2-hydroxy-1-naphthaldehyde (0.05 M) taken in a 250 mL
reaction ꢃask. After that, aqueous solution of K CO (0.05 M) was added to it, and
2
3
the progress of the reaction was monitored by TLC. After completion of the reac-
tion, the reaction mixture was diluted with ethyl acetate (20 mL) and extracted
with dilute HCl (2 × 5 mL). The separated organic layer was washed with water
(
3 × 10 mL) and ꢁnally washed with brine solution (2 × 5 mL). The aqueous part
was dried over sodium sulphate. The ether containing the organic part was concen-
trated under reduced pressure to get the crude product. The crude product was puri-
ꢁ
ed by column chromatography (silica gel, 100–200 mesh) using EtOAc-hexane
(
1:9) as eluent to obtain the ꢁnal product. The chemical structures of the phenolic
ether can be referred to in Fig. 1.
The overall stoichiometry of the reaction may be represented as given below:
Results and discussion
A structure of resulting compounds was ꢁrst conꢁrmed by FT-IR spectroscopy,
which plays a vital role in verifying the existence of the typical key functional
OHC
CHO
OH
O
HBr
Br
H O
2
H O
2
Fig. 1 Micellar eꢂect on surfactant catalysed Williamson synthesis of asymmetric ether in aqueous
medium
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S. Mandal et al.
groups. In this case, the infrared spectra displayed characteristic bands in the
−
1
1
070–1150 cm region, which conꢁrmed the presence of the ether functional
group. To compare the IR data of the product with the reactant, it is very much nec-
essary to know the actual data from the commercially available reactant rather than
from a literature survey.
FT‑IR spectrum of the reactant and product
FTIR spectrum of the 2‑hydroxy‑1‑naphthaldehyde
Interpretation of the chemical structure of 2-hydroxy-1-naptahldehyde was done by
means of FT IR Spectroscopy (Fig. 2).
In this case, the spectra displayed characteristic bands in the region of
−1
1
620–1634 cm which conꢁrmed the presence of the aldehydic group (–CHO).
−1
The band found near 2862–3200 cm was due to the –OH group, while the ones
−
1
at 1400–1600 cm corresponded to the aromatic C=C. The band found near
1
3
550–3200 cm− was due to the phenolic –OH group.
FTIR spectrum of the propargyl bromide
Structure of propargyl bromide was ꢁrst conꢁrmed by FT-IR spectroscopy. In
this case, the infrared spectra displayed characteristic bands in the region of
−
1
3
330–3270 cm which conꢁrmed the presence of the acetylenic group. The band
−1
near 500–600 cm was due to the C–Br group. This also indicated the purity of
propargyl bromide (Fig. 3).
100
8
6
4
2
0
0
0
0
4000
3500
3000
2500
2000
1500
1000
500
1
/cm
Fig. 2 FT-IR spectra of 2-Hydroxy-1-naptahldehyde
1
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Synthesis of 2‑(ethynyloxy)naphthaene‑1‑carbaldehyde…
9
8
7
6
5
4
0
0
0
0
0
0
4
000
3500
3000
2500
2000
1500
1000
500
1/cm
Fig. 3 FT-IR spectra of propargyl bromide
FT‑IR spectrum of the product 2‑(ethynyloxy) naphthalene‑1‑carbaldehyde
The FT-IR spectra of the ꢁnal product was also recorded. The peak which appeared
−1
at 1050–1150 cm should be due to the C–O band of the ether group. The carbonyl
group should have a higher stretching frequency due to the absence of the phenolic
−
1
hydroxyl group. Hence, the band which appeared at 1634 cm should be due to the
aldehydic carbonyl group. Therefore, by comparing the obtained spectroscopy data
with the literature data, it is evident that 2-(ethynyloxy) naphthaene-1-carbaldehyde
was produced accompanied by a high conversion rate and selectivity (Fig. 4).
Mass spectra
The high resolution mass spectrum of product is presented in Fig. 5. The mass spec-
tral analysis of the product gave the molecular ion peak at m/z 201 along with the
isotopic peak at m/z 233 in the positive ion mode. All these identiꢁcations indicate
that the product obtained was 2-(ethynyloxy) naphthaene-1-carbaldehyde.
NMR data
1
Spectroscopic measurements- H-NMR and elemental analysis were performed
to determine the identity and purity of 2-(ethynyloxy) naphthaene-1-carbalde-
1
hyde. Based on the H-NMR spectrum (Fig. 6), the structure was conꢁrmed. The
peak appearing at 2.606 ∂ was due to the ethynyl-oxy proton, which was absent
in the reactant (2-hydroxy-1-naphthaldehyde). One characteristic singlet centre
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S. Mandal et al.
9
7
6
4
3
1
0
5
0
5
0
5
4
500
4000
3500
3000
2500
/cm
2000
1500
1000
500
1
Fig. 4 FT-IR spectrum of the Product
Fig. 5 High resolution mass spectrum of product 2-(ethynyloxy)naphthaene-1-carbaldehyde (Product)
1
3

Synthesis of 2‑(ethynyloxy)naphthaene‑1‑carbaldehyde…
Fig. 6 NMR data of product 2-(ethynyloxy) naphthaene-1-carbaldehyde
obtained at 1.87 ∂ was due to the hydroxy proton, and this peak was absent in
2
-(ethynyloxy) naphthaene-1-carbaldehyde. In 2-(ethynyloxy) naphthaene-1-car-
baldehyde, a –CHO proton appeared at 10.916 ∂ (singlet, sharp), an aromatic
C–H proton appeared at 8.091–7.379 ∂ (doublet and multiplet) and an acetylenic
proton appeared at 2.606 ∂ (singlet, sharp).
Conversion rate enhancement in micellar media
Surfactants as amphiphilic molecules in the presence of water and immiscible
organic species tend to mediate between the two phases. If water is present in a
large amount, the hydrophobic eꢂect drives the formation of spontaneous micel-
lar aggregates [27–30] in solution when the surfactant is present above a certain
minimum concentration (cmc). The nanoscale assemblies formed by aggregation
of about 50–100 monomers are in thermodynamic equilibrium where monomers
rapidly exchange among aggregates. The typical life time of a surfactant micelle
−
3
−2
is in the order of 10 –10 s. The use of surfactants under micellar conditions
represents one of the simplest methods to achieve catalysis in water. Micelles
behave like enzymes isolating species from the bulk solvent, favoring compart-
mentalization of reagents with enhancement of the local concentration and reac-
tivity imparting unique chemo, regio and steroselectivities. Organic species added
to micellar media are distributed between bulk water and micelles depending on
their polarity, charge and dimension. Here, 2-Hydroxy benzyl alcohol and propar-
gyl bromide are almost exclusively hosted within micelles that experience a local
concentration in the supramolecular aggregates some order of magnitudes higher
than that calculated considering the entire volume of the solutions.
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S. Mandal et al.
Conclusions
The catalytic eꢂect of the micellar solution of cetyl trimethyl ammonium bromide
CTAB) may be attributed to the hydrophobic nature of organic substrates. In micel-
(
lar solution, organic substrates are pushed towards the hydrophobic core of micelle
droplets, away from water molecules, thus inducing eꢀcient collisions between
organic substrates. This eventually enhances the reaction rate and yield is ten times
greater in two and half hours lesser time than in the absence of micellar medium.
The hydrophobic interior of the micelles swiftly excludes the water molecules gen-
erated during the reaction, thus shifting the equilibrium towards the desired product.
This ultimately leads to an increase in the reaction yield. The target of synthesis of
the compounds and their characterizations were successfully achieved. This method
of synthesis involves readily available starting materials, stable and solid ether and
short reaction times. The FT-IR spectrum of the ꢁnal product was also recorded. The
−1
peak which appeared at 2847 cm should be due to the C–H band of an aldehyde
group. Carbonyl group should have a lower stretching frequency due to the presence
−
1
of a phenolic hydroxyl group. Hence, the band appearing at 1101 cm should be
due to an aldehyde carbonyl group. Therefore, by comparing the obtained spectro-
scopic data with the literature value, it is evident that 2-hydroxy-1-naphthaldehyde
was produced corresponding to the ether. The structure was conꢁrmed by the peaks
appearing at 2.606 ∂.
Acknowledgments SM and SM are grateful to RGNF UGC, New Delhi for ꢁnancially supporting their
research.
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