Phase Transfer Catalysis with Quaternary Ammonium Type Gemini Surfactants: O-Alkylation of Isovanillin

Article abstract of DOI:10.1007/s11743-016-1821-z

In this paper, O-alkylation of isovanillin with unusual phase transfer catalysts alkandiyl-α,ω-bis(dimethylalkylammonium bromide) dimeric surfactants (also known as gemini surfactants) is described. Some dimeric surfactants with simple hydrophobic alkyl chains and others with hydrophobic alkyl chains containing ester functionalities with different lengths were synthesized and characterized in our laboratory. The alkylation of isovanillin with alkyl halide was successively carried out in the presence of potassium carbonate and a phase transfer catalyst in tetrahydrofuran. The same reactions were also performed with both the traditional phase transfer catalyst tetrabutylammonium bromide and without any catalyst. The results were compared with those of dimeric surfactants. Consequently, it was expressed that alkandiyl-α,ω-bis(dimethylalkylammonium bromide) dimeric surfactants successively exhibit the character of phase transfer catalysts through environmentally friendly procedures under mild conditions. The most significant feature of this work is that dimeric surfactants have been determined to act as phase transfer agents.

Full text of DOI:10.1007/s11743-016-1821-z

J Surfact Deterg
DOI 10.1007/s11743-016-1821-z
ORIGINAL ARTICLE
Phase Transfer Catalysis with Quaternary Ammonium Type
Gemini Surfactants: O-Alkylation of Isovanillin
Mesut Boz1 Sedat Semih Bas¸tu¨rk1
•
Received: 3 February 2016 / Accepted: 21 April 2016
Ó AOCS 2016
Abstract In this paper, O-alkylation of isovanillin with unu-
sual phase transfer catalysts alkandiyl-a,x-bis(dimethylalky-
lammonium bromide) dimeric surfactants (also known as
gemini surfactants) is described. Some dimeric surfactants
with simple hydrophobic alkyl chains and others with
hydrophobic alkyl chains containing ester functionalities with
different lengths were synthesized and characterized in our
laboratory. The alkylation of isovanillin with alkyl halide was
successively carried out in the presence of potassium carbonate
and a phase transfer catalyst in tetrahydrofuran. The same
reactions were also performed with both the traditional phase
transfer catalyst tetrabutylammonium bromide and without
any catalyst. The results were compared with those of dimeric
surfactants. Consequently, it was expressed that alkandiyl-
a,x-bis(dimethylalkylammonium bromide) dimeric surfac-
tants successively exhibit the character of phase transfer cat-
alysts through environmentally friendly procedures under mild
conditions. The most significant feature of this work is that
dimeric surfactants have been determined to act as phase
transfer agents.
starting materials, a number of chemicals are usually used,
such as additional reagents, solvents and catalysts. Many
waste materials are produced in addition to the desired
products of the organic synthesis reactions. The develop-
ment of new synthetic methodologies holds the key to
minimize these wastes which create a heavy burden on the
environment [1]. Bringing together a water soluble nucle-
ophile and an electrophilic organic water-insoluble reagent
in the reaction media is difficult. This problem has been
traditionally solved by addition of a solvent which has
hydrophilic and lipophilic character together such as
ethanol that is both water-like and organic-like. Even so,
the rate of the reaction is not sufficiently fast due to
excessive solvation of the nucleophile. Alternatively,
dipolar aprotic solvents like dimethyl formamide (DMF) or
dimethyl sulfoxide (DMSO) can be used, but they suffer
from some drawbacks such as difficulty in the isolation and
recovery of solvents [2].
Phase transfer catalysis (PTC) seems to be the most
general, efficient and environmentally friendly methodol-
ogy to perform reactions in which organic and inorganic
anions react with organic substrates [3]. According to this
methodology, reactions are performed in immiscible two-
phase systems. Phase transfer catalysts are chemical agents
that facilitate the transfer of a molecule or an ion from one
phase to another and in doing so can greatly accelerate the
rate of biphasic reaction processes. PTC can be used widely
in the organic synthesis reactions of various organic
chemicals in both liquid–liquid and solid–liquid systems.
The simplest examples of these processes are normal
biphasic phase transfer reactions in which the catalyst
facilitates reactions by solubilizing a reagent or ion in the
organic phase. One phase is a reservoir of reacting anions
or a base for generation of organic anions, whereas the
organic reactants and catalysts are located in the second,
Keywords Phase transfer catalysis Á O-Alkylation Á
Gemini surfactants Á Green methodology
Introduction
Organic synthesis is the principal way to produce various
chemical products such as pharmaceuticals, dyes, mono-
mers, etc. In the synthesis of desired final products from
& Mesut Boz
mesutboz@trakya.edu.tr
1
Department of Chemistry, Faculty of Science, Trakya
University, 22030 Edirne, Turkey
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J Surfact Deterg
organic phase. In 1971, Starks introduced the term ‘‘phase
transfer catalysis’’ to explain the critical role of tetraalky-
lammonium or phosphonium salts in the reaction between
two substances located in different immiscible phases [4,
5]. This methodology was discovered and introduced into
laboratory practice in the late 1960s by Makosza [1, 6–10].
The most commonly used PTCs in organic synthesis
reactions are quaternary ammonium compounds (QACs).
QACs are usually inexpensive and biodegradable [11–13].
Various organic solvents can be used and product isolation
is effortless in the phase tranfer catalysis. Because of these
advantages, phase transfer reactions have been recognized
as ‘‘green’’ alternatives to many homogeneous reaction
processes, and they have found widespread application in
synthetic organic chemistry. Furthermore, increasing
attention has focused on the development of asymmetric
phase transfer processes in recent years [14–22].
than conventional surfactants at the same molar concen-
tration. Gemini surfactants have better solubilizing, wetting
and foaming abilities, and stronger biological activity and
lime soap dispersing properties compared to conventional
surfactants. These surfactants are made up of two
hydrophobic tails and two polar heads separated by a
spacer group, which considerably changes the physical and
chemical properties of the gemini surfactant. The quater-
nary ammonium dimeric surfactants [CmH2m?1(CH3)2–
N?–CsH2s–N?(CH3)2CmH2m?1], 2X- (X- = counter-ion),
are abbreviated as m–s–m, where m and s denote respec-
tively, the number of carbon atoms in the alkyl chain and
the spacer. Recently, many articles and books have been
published about the synthesis and physicochemical prop-
erties of these surfactants [23–37].
In organic synthesis, the alkylation of various com-
pounds such as imines and phenols with phase transfer
catalysis has great importance and attraction in recent
years. PTC is a significant methodology for alkylation of a
large variety of organic anions derived from OH, NH, CH,
SH, etc. Among these, O-alkylation of isovanillin has
critical importance as 3-cyclopentyloxy-4-methoxyben-
zaldehyde is an intermediate in the synthesis of phospho-
diesterase IV isoenzyme inhibitor PDA-641 used for the
treatment of asthma, inflammatory disorders, and depres-
sion and can be prepared by O-alkylation of isovanillin
with cyclopentyl bromide in a liquid–solid PTC system
[38]. Although many types of phase transfer catalysts such
as quaternary ammonium and phosphonium salts, crown
ethers, cryptands, etc. can be used in organic synthesis, the
examples of phase transfer catalysis with quaternary
ammonium type-gemini surfactants in two-phase reactions
are exiguous [39–41]. So, we aimed to investigate experi-
mentally the behavior of cationic dimeric surfactants as
phase transfer catalysts in the alkylation of isovanillin. For
this purpose, we synthesized some quaternary ammonium
dimeric surfactants with both simple and ester functional
hydrophobic alkyl chains with different lengths. We
Phase transfer-catalyzed reactions of organic anions are
mechanistically more complicated. In these cases, the
inorganic phase contains a base such as conc. aqueous or
solid NaOH or KOH or solid K2CO3, whereas the organic
phase contains the anion precursor, an electrophilic reac-
tant and eventually a solvent [1]. In this state, the organic
anions with metal ions (–C-Na?) are very unreactive, as
they are able to react only with very strong electrophiles. In
the presence of a catalyst (Q?, Quaternary ammonium
compound such as tetrabutylammonium cation), the ion
exchange results in the formation of lipophilic ion pairs
(–C-Q?) which are then transferred into the organic phase
[3]. Further reactions, for instance, alkylations, occur in the
organic phase (Fig. 1).
On the other hand, a new class of quaternary ammonium
compounds, referred to as dimeric surfactants (also known
as gemini surfactants), has attracted increasing attention in
current studies due to their superior surface activity com-
pared to that of the conventional (monomeric) surfactants.
They tend towards a much lower critical micelle concen-
tration (CMC), which can produce lower surface tension
Na+
C
C
Q+
C H
C H
C
(org)
organic phase
Na+OH-(int)
(org)
Q+X-
Na+X-
Q+
C
Na+
+
+
+
H2O (int)
(int)
(int)
(aq)
(int)
interfacial region
inorganic phase
Na+X-
Na+OH-(aq)
Q+
Na+
C
H2O (aq)
C
(aq)
(aq)
Fig. 1 Mechanism of the phase transition in two-phase systems
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J Surfact Deterg
intended to use these dimeric surfactants as phase transfer
agents and to determine the dimeric surfactants as phase
transfer agents.
Mercury Plus 300 MHz spectrometer. 13C spectra were
recorded at 75 MHz. Mass spectra were recorded on an
UPLC-UHR-Q/TOF ABSCIEX Triple TOF 4600 and
Thermo Trace GC Ultra DSQ II instrument with electron
impact at 70 eV. Only isolated yields were reported.
Experimental Section
Materials
Methods for Synthesis of Dimeric Quaternary
Ammonium Compounds
Some dimeric quaternary ammonium compounds, e.g., alka-
nediyl-a-x-bis(alkyl dimethylammonium bromide), were
synthesized in our laboratory. For the synthesis of these
dimeric quaternary ammonium compounds, 1-bromooctane,
1-bromodecane, 1-bromododecane, 1-bromohexadecane,
bromocyclopentane, N,N,N0,N0-tetramethylethylenediamine,
dimethylaminopyridine (DMAP) 1,6-dibromo hexane, 1,10-
dibromodecane, a,a0-dibromo-p-xylene, N,N-dimethylhex-
adecylamine, isovanillin, potassium carbonate, tetrahydrofu-
ran(THF) and acetone were commercially supplied andall the
required fine chemicals were directly used without further
purification. These dimeric surfactantswereusedin alkylation
of isovanillin as phase transfer catalysts. Column chro-
matography was performed on silica gel (0.063–0.200 mm)
with EtOAc–hexane (1:5). Thin layer chromatography (TLC)
was performed on silica gel 60F-254 precoated sheets. Infra-
red (IR) spectra were recorded with Shimadzu IR 470 or ATI
Unicam Mattson 1000 Fourier transform IR spectropho-
tometers and are reported in reciprocal centimeter (cm-1).
Proton nuclear magnetic resonance (1H NMR) spectra were
recorded in deuteriochloroform solution with a Varian
There are two general methods, method I and method II,
for the synthesis of the dimeric quaternary ammonium
compounds [26].
Method I
A mixture of N,N,N0,N0-tetramethylethylenediamine and a
corresponding alkyl bromide were refluxed in acetone for
24 h to synthesize 10-2-10, 12-2-12 and 16-2-16 type
cationic gemini surfactants (Fig. 2). The white solid was
filtered after cooling and then was recrystallized from
acetone at least two times.
Method II
A mixture of N,N-dimethylhexadecylamine and a corre-
sponding dihaloalkane were refluxed in acetone for 24 h to
synthesize 16-6-16 and 16-10-16 type gemini cationic
surfactants (Fig. 3). The white solid was filtered after
Fig. 2 Synthesis of R-2-R type
dimeric quaternary ammonium
compounds
N
Br
+
n
N
1-bromodecane, n= 1
N,N,N',N'-tetramethylethylenediamine
1-bromododecane, n= 3
1-bromohexadecane, n= 7
Acetone
Δ
N
Br
Br
n
N
n
N,N'-didecyl-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide(10-2-10), n= 1
N,N'-didodecyl-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide(12-2-12), n= 3
N,N'-dihexadecyl-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide(16-2-16), n= 7
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N
Br
Br
n
N,N-dimethylhexadecylamine
1,6-dibromohexane, n= 4
1,10-dibromodecane, n= 8
Acetone
Δ
N
Br
n
Br
N
N,N'-dihexadecyl-N,N,N',N'-tetramethyl-N,N'-hexanediyl-diammonium dibromide(16-6-16), n= 4
N,N'-dihexadecyl-N,N,N',N'-tetramethyl-N,N'-decanediyl-diammonium dibromide(16-10-16), n= 8
Fig. 3 Synthesis of 16-s-16 type dimeric quaternary ammonium compounds
Fig. 4 Synthesis of
R-CH2ArCH2-R type dimeric
quaternary ammonium
compounds
BrH2C
CH2Br
N
α,α'-Dibromo-p-xylene
N
n
n
N,N-dimethyldodecylamine, n= 6
N,N-dimethylhexadecylamine, n= 10
Br-
Br-
N
H2C
CH2
N
n
n
N,N'-didodecyl-N,N,N',N'-tetramethyl-N,N'-p-Xylenediyl-diammonium dibromide 12-CH2-Ar-CH2-12 n= 6
N,N'-dihexadecyl-N,N,N',N'-tetramethyl-N,N'-p-Xylenediyl-diammonium dibromide 16-CH2-Ar-CH2-16 n= 10
cooling and was then recrystallized from acetone at least
two times.
alkyl a-bromo acetates derived from bromoacetyl bromide
and corresponding alcohols as shown on Fig. 5 [42].
Products were recrystallized from acetone.
Dimeric surfactants with simple hydrophobic alkyl
chains were synthesized according to method I and II as
shown on Figs. 2 and 3. On the other hand, dimeric qua-
ternary ammonium compounds containing an aromatic
spacer were synthesized according to method II as shown
on Fig. 4.
Method for O-Alkylation of Isovanillin Using
Phase Transfer Catalysis
Synthesis of dimeric quaternary ammonium compounds
containing ester functional groups was carried out by
treatment of N,N,N0,N0-tetramethylethylenediamine with
O-Alkylation of isovanillin was carried out in a THF-
K2CO3 liquid–solid, two-phase system. Bromocyclopen-
tane and 1-bromooctane were used as alkyl halide in
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O
Br
OH
Br
n
Bromoacetyl bromide
1-decanol, n= 1
1-dodecanol, n= 3
1-hexadecanol, n= 7
DMAP
Pyridine
CH2Cl2
O
N
Br
N
O
n
N,N,N',N'-tetramethylethylenediamine
Decyl bromoacetate, n= 1
Dodecyl bromoacetate, n= 3
Hexadecyl bromoacetate, n= 7
Acetone
Δ
O
Br
O
N
n
n
Br
O
N
O
N,N'-bis(decyloxycarbonylmethyl)-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide, n= 1
N,N'-bis(dodecyloxycarbonylmethyl)-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide, n= 3
N,N'-bis(heksadecyloxycarbonylmethyl)-N,N,N',N'-tetramethyl-N,N'-ethanediyl-diammonium dibromide, n= 7
Fig. 5 Synthesis of dimeric quaternary ammonium compounds with ester functionality
Fig. 6 O-Alkylation of
isovanillin with phase transfer
catalysis
O
C
O
C
OH
PTC
K2CO3,
H
O R
R Br
H
THF
OCH3
OCH3
R= cyclopentyl or octyl group
alkylation reactions. Tetrabutylammonium bromide and
dimeric quaternary ammonium compounds were added to
the reaction mixture as phase transfer agents (Fig. 6). For
the purpose of confirming the results, the same reaction
was performed without any catalyst. Products were purified
with column chromatography. Yields of the reactions were
calculated after column chromatography.
was refluxed for 12 h. Then the mixture was cooled
and was left for 12 h in cold conditions. The crude
product was precipitated in the form of white crystals.
It was recrystallized two times from acetone then
filtered and dried in air, yielding 10.4 g of white
crystals (47 %).
1H NMR (300 MHz, CDCl3): d = 0.87 (t, 6H),
1.22–1.41 (m, 28H), 1.80 (m, 4H), 3.48 (s, 12H), 3.70 (m,
4H), 4.72 (s, 4H).
Synthesis of Simple Dimeric Quaternary
Ammonium Compounds
13C NMR (75 MHz, CDCl3): d = 14.4, 22.9, 23.3, 26.5,
29.5, 29.7, 32.1, 51.3, 57.0, 66.1.
General Procedure
N,N0-Didodecyl-N,N,N0,N0-Tetramethyl-N,N0-Ethanediyl-
Diammonium Dibromide (12-2-12) Yield: 82 %
N,N0-Didecyl-N,N,N0,N0-Tetramethyl-N,N0-Ethanediyl-
Diammonium Dibromide (10-2-10)
1H NMR (300 MHz, CDCl3): d = 0.86 (t, 6H), 1.17–1.30
(m, 36H), 1.81 (m, 4H), 3.47 (s, 12H), 3.70 (m, 4H), 4.70
(s, 4H).
13C NMR (75 MHz, CDCl3): d = 14.4, 22.9, 23.3, 26.5,
29.4, 29.6, 29.77, 29.80, 29.88, 32.2, 51.3, 57.0, 66.1.
A magnetically stirred solution of N,N,N0,N0-tetram-
ethylethylenediamine (4.64 g, 40 mmol) and 1-bro-
modecane (17.68 g, 80 mmol) in 200 mL of acetone
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N,N0-Dihexadecyl-N,N,N0,N0-Tetramethyl-N,N0-Ethanediyl-
Diammonium Dibromide (16-2-16) Yield: 90 %
Synthesis of the Alkyl a-Bromoacetates
General Procedure: Decyl a-Bromoacetate
1H NMR (300 MHz, CDCl3): d = 0.86 (t, 6H), 1.23–1.34
(m, 52H), 1.82 (m, 4H), 3.46 (s, 12H), 3.70 (m, 4H), 4.69
(m, 4H).
13C NMR (75 MHz, CDCl3): d = 14.4, 22.9, 23.3, 26.5,
28.4, 29.0, 29.4, 29.60, 29.62, 29.67, 29.79, 29.83, 29.92,
29.98, 32.2, 51.3, 57.1, 66.0.
To a magnetically stirred solution of 1-decanol (4.75 g,
30 mmol), DMAP (0.366 g, 3 mmol), and pyridine
(2.38 g, 30 mmol) in dichloromethane (100 mL) was
added bromoacetylbromide (12.12 g, 60 mmol) under
nitrogen atmosphere at 0 °C. The reaction mixture was
warmed after 2 h of cooling and stirred for 12 h at room
temperature. The mixture was extracted with water, a sat-
urated solution of NaHCO3 and brine, respectively. The
organic extracts were dried over anhydrous calcium chlo-
ride. Then dichloromethane was evaporated giving 7.6 g of
crude product as brown oil. It was pure enough to use in the
synthesis of quaternary ammonium compounds (98 %).
IR (KBr, cm-1): 2953, 2876, 1753, 1472, 1293, 1165,
1114.
N,N0-Dihexadecyl-N,N,N0,N0-Tetramethyl-N,N0-
Hexanediyl-Diammonium Dibromide (16-6-16)
Yield: 49 %
1H NMR (300 MHz, CDCl3): d = 0.86 (t, 6H), 1.23–1.33
(m, 52H), 1.57 (m, 4H), 1.70 (m, 4H), 2.0 (m, 4H), 3.37 (s,
12H), 3.40–3.47 (m, 4H), 3.69–3.72 (m, 4H).
13C NMR (75 MHz, CDCl3): d = 14.4, 21.8, 22.9, 23.1,
24.4, 26.5, 27.7, 27.9, 29.50, 29.59, 29.62, 29.70, 29.83,
29.85, 29.88, 29.91, 32.2, 51.3, 64.4, 65.1.
1H NMR (300 MHz, CDCl3): d 0.88 (t, 3H), 1.25–1.30
(m, 14H), 1.61–1.68 (quin, 2H), 3.84 (s, 2H), 4.17 (t, 2H).
13C NMR (75 MHz, CDCl3): d 14.3, 22.9, 25.9, 26.2,
28.6, 29.4, 29.5, 29.8, 32.1, 66.7, 167.6.
N,N0-Dihexadecyl-N,N,N0,N0-Tetramethyl-N,N0-
Decanediyl-Diammonium Dibromide (16-10-16)
Yield: 30 %
MS (EI): m/z = 278–280 (M?).
Dodecyl a-Bromoacetate Yield: 96 %
1H NMR (300 MHz, CDCl3): d = 0.88 (t, 6H), 1.23-1.32
(m, 48H), 1.35 (m, 8H), 1.44 (m, 8H), 1.74 (m, 8H), 3.35
(s, 12H), 3.43–3.49 (m, 4H), 3.75–3.80 (m, 4H).
13C NMR (75 MHz, CDCl3): d = 14.4, 22.7, 22.9, 23.1,
26.1, 26.5, 28.4, 28.7, 29.49, 29.58, 29.64, 29.71, 29.83,
29.87, 29.91, 32.1, 51.2, 64.4, 64.5.
IR (KBr, cm-1): 2953, 2876, 1752, 1471, 1295, 1163,
1112.
1H NMR (300 MHz, CDCl3): d 0.86 (t, 3H), 1.24–1.30
(m, 18H), 1.59–1.67 (quin, 2H), 3.82 (s, 2H), 4.15 (t, 2H).
13C NMR (75 MHz, CDCl3): d 14.4, 22.9, 26.0, 26.2,
28.6, 29.4, 29.6, 29.75, 29.85, 29.9, 32.2, 66.7, 167.6.
MS (EI): m/z = 306–308 (M?).
N,N0-Didodecyl-N,N,N0,N0-Tetramethyl-N,N0-(p-
xylenediyl)-Diamonyum Dibromide (12-Ar(8)-12)
Yield: 99 %
Hexadecyl a-Bromoacetate Yield: 93 %
1H NMR (300 MHz, CDCl3): d 0.88 (t, 6H), 1.22-1.38 (m,
36H), 1.82 (m, 4H), 3.20 (s, 12H), 3.50 (m, 4H), 5.10 (s,
4H), 7.75 (s, 4H).
IR (KBr, cm-1): 2953, 2876, 1752, 1472, 1294, 1164,
1114.
1H NMR (300 MHz, CDCl3): d 0.87 (t, 3H), 1.23–1.29
(m, 26H), 1.60–1.67 (quin, 2H), 3.81 (s, 2H), 4.15 (t, 2H).
13C NMR (75 MHz, CDCl3): d 14.4, 22.9, 26.0, 26.2,
28.6, 29.4, 29.6, 29.7, 29.8, 29.9, 32.2, 66.7, 167.6.
MS (EI): m/z = 362–364 (M?).
13C NMR (75 MHz, CDCl3): d 14.4, 22.9, 23.2, 26.7,
29.6, 29.8, 29.9, 32.1, 49.8, 64.9, 66.6, 130.1, 134.2.
N,N0-Dihexadecyl-N,N,N0,N0-Tetramethyl-N,N0-(p-
xylenediyl)-Diamonyum Dibromide (16-Ar(8)-16)
Yield: 96 %
Synthesis of the Dimeric Quaternary Ammonium
Compounds with Ester Tails
1H NMR (300 MHz, CDCl3): d 0.85 (t, 6H), 1.14-1.34 (m,
52H), 1.85 (m, 4H), 3.19 (s, 12H), 3.50 (m, 4H), 5.23 (s,
4H), 7.75 (s, 4H).
13C NMR (75 MHz, CDCl3): d 14.4, 22.9, 23.2, 26.7,
29.6, 29.8, 29.9, 30.0, 32.2, 50.0, 65.0, 66.5, 130.2, 134.3.
All dimeric quaternary ammonium compounds containing
ester functionality were synthesized similarly to those
simple dimeric quaternary ammonium compounds from
corresponding alkyl a-bromo acetate.
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N,N0-Bis(decyloxycarbonylmethyl)-N,N,N0,N0-Tetramethyl-
N,N0-Ethanediyl-diammonium Dibromide (10E-2-10E),
Yield: 57 %
chromatographed on silica gel packed in ethyl
acetate:hexane (1:3), yielding a yellowish liquid.
3-(Cyclopentyloxy)-4-Methoxy Benzaldehyde
IR (KBr, cm-1): 2927, 2876, 1753, 1472, 1191.
1H NMR (300 MHz, CDCl3): d 0.88 (t, 6H), 1.22–1.35
(m, 28H), 1.62–1.75 (quin, 4H), 3.78 (s, 12H), 4.20–4.25 (t,
4H), 4.90 (s, 4H), 5.08 (s, 4H).
13C NMR (75 MHz, CDCl3): d 14.3, 22.9, 25.9, 28.5,
29.4, 29.5, 29.7, 29.8, 32.1, 52.6, 57.2, 62.3, 67.8, 164.4.
IR (KBr, cm-1): 3080, 2978, 2876, 2748, 1702, 1600,
1446, 1268, 1140.
1H NMR (300 MHz, CDCl3): d 1.5–2.1 (m, 8H), 3.96 (s,
3H), 4.8–4.9 (quin, 1H), 6.97–7.42 (m, 3H), 9.83 (s, 1H).
13C NMR (75 MHz, CDCl3): d 24.3, 32.9, 56.4, 80.6,
110.9, 112.2, 126.5, 130.2, 148.5, 155.6, 191.2.
HRMS (ESI) m/z calcd. for C13H16O3 (M ? H)?
221.1177, found 221.1233.
N,N0-Bis(dodecyloxycarbonylmethyl)-N,N,N0,N0-
Tetramethyl-N,N0-Ethanediyl-diammonium Dibromide
(12E-2-12E), Yield: 53 %
3-(Octyloxy)-4-Methoxy Benzaldehyde
IR (KBr, cm-1): 2928, 2876, 1752, 1472, 1190.
1H NMR (300 MHz, CDCl3): d 0.88 (t, 6H), 1.22–1.37
(m, 36H), 1.61–1.74 (quin, 4H), 3.77 (s, 12H), 4.19–4.25 (t,
4H), 4.91 (s, 4H), 5.08 (s, 4H).
13C NMR (75 MHz, CDCl3): d 14.3, 22.9, 25.8, 28.4,
29.4, 29.6, 29.7, 29.8, 32.1, 52.5, 57.2, 62.2, 67.8, 164.5.
IR (KBr, cm-1): 3080, 2927, 2876, 1702, 1600, 1472,
1293, 1165, 1140.
1H NMR (300 MHz, CDCl3): d 0.87 (t, 3H), 1.25–1.46
(m, 10H), 1.85 (quin, 2H), 3.94 (s, 3H), 4.06 (t, 2H),
6.99–7.41 (m, 3H), 9.85 (s, 1H).
13C NMR (75 MHz, CDCl3): d 14.3, 22.9, 26.1, 29.2,
29.4, 29.5, 32.0, 56.4, 69.2, 110.3, 110.7, 126.9, 130.2,
149.3, 155.0, 191.2.
N,N0-Bis(hexadecyloxycarbonylmethyl)-N,N,N0,N0-
Tetramethyl-N,N0-Ethanediyl-Diammonium Dibromide
(12E-2-12E), Yield: 59 %
HRMS (ESI) m/z calcd. for C16H24O3 (M ? H)?
265.1804, found 265.1869.
IR (KBr, cm-1): 2927, 2876, 1753, 1472, 1190.
1H NMR (300 MHz, CDCl3): d 0.88 (t, 6H), 1.20–1.37
(m, 52H), 1.62–1.75 (quin, 4H), 3.77 (s, 12H), 4.20–4.25 (t,
4H), 4.88 (s, 4H), 5.17 (s, 4H).
13C NMR (75 MHz, CDCl3): d 14.4, 22.9, 25.9, 28.5,
29.4, 29.6, 29.7, 29.9, 32.2, 52.5, 57.2, 62.2, 67.8, 164.4.
Results and Discussion
Some dimeric surfactants with simple hydrophobic alkyl
chains and others with hydrophobic alkyl chains containing
ester functionalities with different lengths were synthesized
and characterized in our laboratory. Then, they were used
in O-octylation and O-cyclopentylation of isovanillin as
phase transfer catalysts. The alkylation of isovanillin with
alkyl halide was successively carried out in tetrahydrofuran
in the presence of potassium carbonate and a phase transfer
catalyst. The same reactions were also performed with both
the traditional phase transfer catalyst tetrabutylammonium
bromide and without any catalyst. When carbonate was
used in the absence of PTC, the result was a low conversion
of isovanillin. When carbonate was used in the presence of
PTC, lipophilic ion pairs (Q? ArO-) are likely to form
because the deprotonation of the phenol occurs at the
surface of the carbonate. Wilk et al. found that successful
completion of the alkylation of isovanillin depends on the
particle size of potassium carbonate under PTC conditions.
According to Wilk’s results, the carbonates with particle
size 30–50 lm give quantitative conversion of isovanillin,
whereas those with larger particle size (520–570 lm) result
in incomplete conversion [38]. We did not change the
Phase Transfer Catalysis with Dimeric Quaternary
Ammonium Compounds: O-Alkylation
of Isovanillin
General Procedure
A magnetically stirred boiling solution of isovanillin
(0.76 g, 5 mmol), K2CO3 (1.04 g, 7.5 mmol) and PTC (0.1
equivalent dimeric quaternary ammonium compounds) in
THF (25 mL) was cooled to 40 °C after 1.5 h of refluxing.
The mixture was refluxed for 12 h after a solution of alkyl
halide (7.5 mmol) in 10 mL THF was added to the mix-
ture. It was poured into 20 mL of water after cooling of the
reaction mixture, and then the mixture was extracted with
20 mL of diethylether two times. The organic extracts were
combined, washed with 30 mL of brine and dried over
anhydrous calcium chloride. Then, organic solvents were
evaporated giving crude products which were then
123

J Surfact Deterg
yield were aimed for in all studies. In our work, a cat-
alytic amount of a gemini as a phase transfer agent and a
relatively harmless base K2CO3 was used in all alkylation
reactions and, additionally, the solvent THF was recycled.
Consequently, we used dimeric quaternary ammonium
compounds in phase transfer catalysis and determined the
value of the dimeric surfactants as phase transfer agents.
We established a facile and environmentally friendly
synthesis of 3-(cyclopenthyloxy)-4-methoxy benzaldehyde
and 3-(octyloxy)-4-methoxy benzaldehyde with phase
transfer catalysis.
Table 1 O-Alkylation of isovanillin with phase transfer catalysis
Octylation reaction
Catalysts
Cyclopentylation reaction
Yields (%)
Catalyst
Yields (%)
Without catalyst
TBAB
2
76
44
47
77
29
75
60
79
57
36
37
Without catalyst
TBAB
1
65
27
22
45
33
46
42
41
28
25
17
10-2-10
10-2-10
12-2-12
12-2-12
16-2-16
16-2-16
16-6-16
16-6-16
16-10-16
16-10-16
In summary, we have demonstrated that dimeric qua-
ternary ammonium compounds can be used in organic
synthesis as phase transfer catalysts. Due to the low cost of
dimeric quaternary ammonium compounds, this method
provides a simplified way to synthesize various organic
compounds with O-alkylation, N-alkylation, condensation
reactions, etc. The presented methodology delivers an
attractive alternative to classical procedures, and environ-
mental problems can be circumvented. Additionally, an
environmental advantage can be provided through the
hydrolysable and biodegradable properties of dimeric
quaternary ammonium compounds having biological
motifs like amides, amino acids and esters. Our study will
smooth the path for steadily increasing usage of geminis in
phase transfer catalysis.
16-Ar(8)-16
12-Ar(8)-12
E10-2-10E
E12-2-12E
E16-2-16E
16-Ar(8)-16
12-Ar(8)-12
E10-2-10E
E12-2-12E
E16-2-16E
original partical size of potassium carbonate in the present
study. The results are compared in Table 1. Table 1 shows
that especially 16-2-16, 16-10-16, 16-Ar(8)-16, 12-Ar(8)-
12 and its ester derivative E10-2-10E from geminis syn-
thesized have remarkably exhibited the character of a phase
transfer catalyst in the alkylation of isovanillin. The results
denoted that the phase transfer character of dimeric qua-
ternary ammonium compounds with long hydrophobic
alkyl chains (16-s-16) was sometimes as strong as tetra-
butylammonium bromide. On the other hand, geminis with
an ester functional tail did not produce a good catalytic
effect as much as simple geminis. Johnstone and Rose
reported that alkylation of phenols with primary alkyl
halides is more effective than that of secondary alkyl
halides [43]. Because of the SN2 rules, yields of the reac-
tions with the secondary alkyl halide, 1-bromocyclopen-
tane, were lower than those of the primary alkyl halide,
1-bromooctane, in accordance with Johnstone and Rose’s
study.
Acknowledgments The authors would like to acknowledge financial
support from the Scientific Research Project Unit of Trakya Univer-
sity (Project No: 2011/135).
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Mesut Boz is an assistant professor of organic chemistry in the
Chemistry Department at Trakya University. He received his B.Sc.
(1996) in Chemistry and M.Sc (1999) in Organic Chemistry from
Trakya University. He completed his Ph.D (2005) in Organic
Chemistry at Trakya University Institute of Natural Science. His
main research area focuses on organic synthesis, characterization,
spectroscopy, and recently, gemini surfactants.
28. Zana R, Benraou M, Rueff
R (1991) Alkanediyl-a, x-
bis(dimethylalkylammonium bromide) surfactants. 1. Effect of
the spacer chain length on the critical micelle concentration and
micelle ionization degree. Langmuir 7:1072–1075
29. Akbas¸ H, Elemenli A, Boz M (2012) Aggregation and thermo-
dynamic properties of some cationic gemini surfactants. J Surfact
Deterg 15:33–40
30. Akbas¸ H, Boz M, Elemenli A (2010) Study on cloud points of
Triton X-100-cationic gemini surfactants mixtures: a spectro-
scopic approach. Spectrochimica Acta Part A 75:671–677
Sedat Semih Bas¸tu¨rk was a master’s student of organic chemistry in
the Chemistry Department at Trakya University. He received his
B.Sc. in Chemistry from Trakya University in 2010, and his M.Sc. in
Chemistry from the Institute of Natural Sciences at Trakya University
in 2013. His research interests include synthesis of gemini surfactants
and phase transfer catalysis.
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