Synthesis of aromatic triols and triacids from oleic and erucic acid: separation and characterization of the asymmetric and symmetric isomers

Article abstract of DOI:10.1016/j.chemphyslip.2007.11.002

Hexasubstituted benzene derivatives, aromatic triols 4, 9 and triacids 5, 10 have been synthesized from oleic and erucic acid derivatives followed by a cyclotrimerization step catalyzed by palladium-on-carbon (Pd/C) and chlorotrimethylsilane (TMSCl). The asymmetric isomer, which is the main product, was isolated from its symmetric isomer by flash chromatography. All the products were fully characterized by IR, ¹H NMR, ¹³C NMR and mass spectrometry. The products are suitable monomers for the production of polyurethanes, polyesters and polyamides.

Full text of DOI:10.1016/j.chemphyslip.2007.11.002

Available online at www.sciencedirect.com
Chemistry and Physics of Lipids 152 (2008) 1–8
Synthesis of aromatic triols and triacids from oleic and
erucic acid: separation and characterization of the
asymmetric and symmetric isomers
Jin Yue, Suresh S. Narine∗
Alberta Lipid Utilization Program, Department of Agricultural Food and Nutritional Science,
4-10 Agriculture/ Forestry Centre, University of Alberta, Edmonton, Alberta, Canada T6G 2P5
Received 28 June 2007; received in revised form 6 November 2007; accepted 7 November 2007
Available online 13 November 2007
Abstract
Hexasubstituted benzene derivatives, aromatic triols 4, 9 and triacids 5, 10 have been synthesized from oleic and erucic acid derivatives followed
by a cyclotrimerization step catalyzed by palladium-on-carbon (Pd/C) and chlorotrimethylsilane (TMSCl). The asymmetric isomer, which is the
main product, was isolated from its symmetric isomer by flash chromatography. All the products were fully characterized by IR, 1H NMR, 13
NMR and mass spectrometry. The products are suitable monomers for the production of polyurethanes, polyesters and polyamides.
© 2007 Elsevier Ireland Ltd. All rights reserved.
C
Keywords: Aromatic triol; Aromatic triacid; Mono-unsaturated fatty acid; Fatty alkynes; Cyclotrimerization
1. Introduction
research group, a new method of producing polyols with ter-
minated primary hydroxyl groups from vegetable oils has been
developed (Narine et al., 2007c) and polyurethane elastomers
and foams have been synthesized from these polyols (Narine et
al., 2007a,b).
As oil reserves are depleting and prices continue to rise, there
is a growing worldwide interest in the development of renew-
able raw materials which are economical and environmentally
friendly. Vegetable oils and fats are one of the most important
sources of renewable raw materials for the chemical indus-
try, since they are inexpensive, abundant, and provide versatile
opportunities for transformation to meet specific applications.
Twenty years ago, more than 90% of oleochemical reactions
wereperformedonthefattyacidcarboxylgroup(Baumannetal.,
1988), these include hydrolysis of fats to make soaps (Sonntag,
1982), and synthesis of fatty amines from fatty acids (Billenstein
and Blaschke, 1984). Recently, increasing interest in industrial
and academic research has been focused towards reactions on
the hydrocarbon chains of fatty acids, especially on the double
bonds of unsaturated fatty acids. An example being the epoxida-
tion of the double bonds of fatty acids, followed by nucleophilic
ring opening of the epoxide to make polyols for polyurethanes
based on renewable raw materials (Guo et al., 2000). In our
Cyclotrimerization of alkynes to make benzene derivatives
has been intensively investigated since 1948, when Reppe et
al. (1948) reported that acetylene cyclized to form benzene in
the presence of nickel. A large number of transition metals and
their complexes have been applied as catalysts in these types
of reactions (Alphonse et al., 1988; Breschi et al., 2000; Chio
et al., 1998; Fehlner, 1980; Ladipo et al., 2004). Among these
catalysts, palladium or palladium chloride are the most eco-
nomical and convenient. In Li’s studies, under the induction
of copper chloride, palladium chloride was utilized to catalyze
the cyclotrimerization of terminal and substituted alkynes in the
presence and absence of carbon dioxide (Li et al., 2001, 2004; Li
and Xie, 2004). In Jhingan’s study, substituted benzenes were
synthesized from alkynes with high yield in the presence of
palladium-on-carbon (Jhingan and Maier, 1987).
Of all the reported studies, cyclotrimerization has only been
performed on short chain alkynes. A review paper (Biermann
et al., 2000) reported that Austin did some work on making
some aromatic polyol compounds from fatty materials in his
∗
Corresponding author. Tel.: +1 780 492 9081; fax: +1 780 492 7174.
E-mail address: Suresh.narine@ualberta.ca (S.S. Narine).
0009-3084/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved.
doi:10.1016/j.chemphyslip.2007.11.002

2
J. Yue, S.S. Narine / Chemistry and Physics of Lipids 152 (2008) 1–8
PhD thesis. A US patent (Renga et al., 1990) in 1990 claimed
that polyfunctional hexasubstituted benzene derivatives could
be obtained from fatty disubstituted alkynes, including fatty
alcohols, fatty acids and fatty esters, but the end products were
a mixture of symmetric and asymmetric benzene derivatives.
Recently, Galia and co-workers reported the synthesis and char-
acterization of fatty acid-based aromatic triols (Lligadas et al.,
2007). In this paper, they report the synthesis of aromatic triols
from the esters of oleic and 10-undecenoic acid and their uses,
withoutseparationoftheasymmetricandsymmetricproducts, in
the formation of polyurethane networks. This work highlights
the potential importance of aromatic compounds synthesized
from fatty acids which can function as monomers to create new
polymers. Given the successful demonstration of the synthe-
ses of polyurethanes from aromatic triols reported in the work
of Galia and co-workers, we report here our work based on the
cyclotrimerizationofoleicanderucicacidtoformboththecorre-
spondingasymmetricandsymmetricaromatictriolsandtriacids.
These triols and triacids are potentially versatile monomers to
many polymer molecules, such as, polyurethanes, polyesters and
polyamides. Our group has successfully separated and charac-
terized the corresponding asymmetric and symmetric aromatic
triols and triacids, which previously have not been reported.
ice chips, filtered and washed in the cold mixture. After dry-
ing, a white powder, 2, was obtained (8.2 g, 29.2 mmol, 86.9%).
IR (thin film) 2750–3050 (OH), 1690 (C O); 918 (OH) cm−1
;
1H NMR (CDCl3, 400 MHz): δ 11.2 (br s, 1H, COOH), 2.35
(t, J = 7.6 Hz, 2H, CH2CO), 2.14 (t, J = 6.4 Hz, 4H, CH2CC),
1.64 (q, J = 7.2 Hz, 2H, CH2CH2CO), 1.48 (q, J = 6.8 Hz, 4H,
CH2CH2CC), 1.24–1.43 (m, 16H, CH2), 0.89 (t, J = 6.8, 3H,
CH3); 13C NMR (CDCl3 100 MHz): δ 179.787 (COOH), 80.254
(CC), 79.951 (CC), 33.887, 31.745, 29.120, 29.067, 29.026,
28.956, 28.854, 28.772, 28.657, 28.505, 24.520, 22.559, 18.655,
18.618, 13.986 (CH3); LRMS (ESI) calcd for C18H32O2Na
([M + Na]+) 303.2, found 303.2.
2.1.2. Stearolyl alcohol 3
Stearolic acid, 2 (1.2 g, 4.3 mmol) was dissolved in 20 mL
diethyl ether. LiAlH4 (0.2 g, 5.1 mmol) was then added. The
mixture was stirred at RT for 1 h. Distilled water (10 mL) was
added followed by 2N HCl (20 mL). The organic layer was sep-
arated, washed with brine (20 mL) and dried over MgSO4. The
solvent was evaporated by reduced pressure to give oil, which
was purified by flash chromatography (silica gel; hexane/EtOAc
6:1) to afford 1.1 g (4.0 mmol, 93%) of stearolyl alcohol, 3,
as a pale yellow oil. IR (thin film) 3156 (OH), 2850–3000
(CH), 1052 (C–O) cm−1; 1H NMR (CDCl3, 500 MHz): δ 3.64
(t, J = 6.5 Hz, 2H, CH2OH), 2.14 (t, J = 7.0 Hz, 4H, CH2CC),
1.56 (q, J = 7.0 Hz, 2H, CH2CH2OH), 1.48 (q, J = 6.5 Hz, 4H,
CH2CH2CC), 1.24–1.41 (m, 18H, CH2), 0.88 (t, J = 7.0, 3H,
CH3); 13C NMR (CDCl3 125.3 MHz): δ 80.286 (CC), 80.150
(CC);63.042(CH2OH), 32.789, 31.846, 29.320, 29.221, 29.176,
29.139, 29.131, 29.118. 28.871, 28.780, 25.702, 22.657, 18.747,
14.091 (CH3); LRMS (ESI) calcd for C18H34ONa ([M + Na]+)
289.3, found 289.3.
2. Experimental
Oleic acid (90%), erucic acid (90%), and all other chem-
icals and reagents were purchased from Sigma–Aldrich Co.
USA. Silica gel (230–400 mesh) was obtained from Rose Sci-
entific Ltd., AB, Canada. TLC plate (250 ␮m) was obtained
from Silicycle Chemistry Division, QC, Canada. FTIR spectra
were measured with a Mattson Galaxy Series FT-IR 3000 spec-
trophotometer. 1H NMR and 13C NMR were recorded on Varian
500 MHz or 400 MHz spectrometers (Varian, Inc., CA, USA)
with CDCl3 or C6D6 as a solvent. Mass spectra were acquired on
a Mariner Biospectrometry ESI system (PerSeptive Biosystems,
Inc., MA, USA) or Kratos Analytical MS-50 (Kratos Analytical
Ltd., Manchester, UK) EI high-resolution spectrometer.
2.1.3. Aromatic triols 4(a) and 4(b)
Stearoyl alcohol, 3 (1.05 g, 4.0 mmol) was dissolved in THF
(20 mL). 0.25 g of Pd/C (10%) and TMSCl (0.75 mL, 6.0 mmol)
were then added. The mixture was refluxed for 8 h then cooled
to RT. The mixture was filtered to remove the Pd/C. Distilled
water (20 mL) was then added. The resulting mixture was further
extracted with diethyl ether and the organic layer was washed
with brine (20 mL) and dried over MgSO4. The solvent was
evaporated under reduced pressure and the residue purified by
flash chromatography (silica gel; hexane/EtOAc 5:1, 3:1, 2:1,
1:1) to afford yellow oils 4a (178.5 mg, 0.22 mmol, 17.0%) and
4b (635.3 mg, 0.80 mmol, 60.5%).
2.1. Synthesis of aromatic triol 4 and triacid 5 from oleic
acid
2.1.1. Stearolic acid 2
Stearolic acid 2 was prepared according to the literature
(Silbert, 1984). A solution of oleic acid (10.6 g, 90% purity,
33.6 mmol) in diethyl ether (50 mL) was cooled to 0 ◦C in an
ice-water bath. Bromine (2.7 mL, 52.3 mmol) was added drop-
wise (30 min for addition). The ice-water bath was then removed
and the solution was stirred for another 30 min at RT. Satu-
rated Na2S2O3 solution (10 mL) was added to reduce the excess
bromine. The organic layer was separated, washed with brine
(20 mL) and dried over MgSO4. The solvent was evaporated
by reduced pressure to give a pale yellow oil (1). The dibromo
intermediate (1) was then dissolved in 1-propanol (150 mL).
KOH(20 g, 0.36 mol)andDMSO(18 mL, 0.25 mol)wereadded.
The mixture was heated under reflux for 1 h. The mixture was
cooled to RT, poured into ice-cold 2N HCl (190 mL) containing
4a: IR (thin film) 3328 (OH), 2850–3000 (CH), 1465
(C C of benzene), 1057 (C–O) cm−1 1H NMR (CDCl3,
;
500 MHz): δ 3.63 (t, J = 6.5 Hz, 6H, CH2OH), 2.46 (t, J = 7.5 Hz,
12H, CH2Ph), 1.28–1.58 (m, 72H, CH2), 0.88 (t, J = 6.5, 9H,
CH3); 13C NMR (CDCl3 125.3 MHz): δ 136.840 (CH2Ph),
136.810 (CH2Ph), 136.686 (CH2Ph), 136.642 (CH2Ph), 63.118
(CH2OH), 32.884, 32.015, 31.545, 30.747, 30.654, 29.833,
29.516, 29.412, 25.854, 22.769, 14.202(CH3);HRMS(EI)calcd
for C54H102O3 798.7829, found m/z 798.7852.
1H NMR (C6D6, 500 MHz): δ 3.36 (t, J = 6.5 Hz, 6H,
CH2OH), 2.86 (t, J = 6.5 Hz, 12H, CH2Ph), 1.80–1.72 (m, 12H,
CH2CH2Ph), 1.60–1.50 (m, 12H, CH2CH2CH2Ph), 1.45–1.24

J. Yue, S.S. Narine / Chemistry and Physics of Lipids 152 (2008) 1–8
3
(m, 38H, CH2), 0.55 (t, J = 7.0 Hz, CH3); 13C NMR (C6D6,
125 MHz): δ 137.081, 137.049, 62.682, 33.206, 32.538, 32.323,
31.137, 31.025, 30.451, 30.415, 29.872, 29.858, 29.854, 29.820,
29.774, 26.180, 23.068, 14.340.
(CH2Ph), 136.616 (CH2Ph), 34.186, 34.151, 34.061, 32.001,
31.587, 31.544, 31.514, 31.502, 31.066, 30.737, 30.691, 30.525,
30.049, 30.007, 29.841, 29.829, 29.798, 29.400, 29.391, 29.374,
29.144, 29.064, 28.812, 28.771, 28.611, 28.599, 24.741, 24.536,
22.747, 14.183 (CH3), 14.176 (CH3); LRMS (ESI) calcd for
C54H95O6 ([M − H]−) 839.7, found 839.7.
4b: IR (thin film) 3333 (O–H), 2850–3000 (CH), 1465
(C C of benzene), 1057 (C–O) cm−1 1H NMR (CDCl3,
;
500 MHz): δ 3.63 (t, J = 6.5 Hz, 6H, CH2OH), 2.46 (t, J = 7.5 Hz,
12H, CH2Ph), 1.25–1.58 (m, 72H, CH2), 0.88 (t, J = 7.0, 9H,
CH3); 13C NMR (CDCl3 125.3 MHz): δ 136.798 (CH2Ph),
136.783 (CH2Ph), 136.745 (CH2Ph), 136.731 (CH2Ph),
136.693 (CH2Ph), 136.673 (CH2Ph), 63.148 (CH2OH), 63.116
(CH2OH), 32.897, 32.884, 32.008, 31.568, 30.743, 30.671,
30.654, 29.848, 29.527, 29.514, 29.505, 29.438, 29.414, 29.403,
25.846, 25.831, 22.754, 14.189 (CH3); 14.181 (CH3); HRMS
(EI) calcd for C54H102O3 798.7829, found m/z 798.7830.
1H NMR (C6D6, 500 MHz): δ 3.45 (t, J = 6.5 Hz, 2H,
CH2OH), 3.45 (t, J = 6.5 Hz, 2H, CH2OH), 3.40 (t, J = 6.5 Hz,
2H, CH2OH), 2.88–2.78 (m, 12H, CH2Ph), 1.80–1.70 (m, 12H,
CH2CH2Ph), 1.59–1.50 (m, 12H, CH2CH2CH2Ph), 1.49–1.24
(m, 38H, CH2), 0.55 (t, J = 7.0 Hz, 9H, CH3); 13C NMR (C6D6,
125 MHz): δ 137.074, 137.066, 137.040, 137.027, 62.675,
62.650, 33.213, 33.206, 32.524, 32.451, 32.435, 32.333, 31.135,
31.068, 31.020, 30.432, 30.389, 29.966, 29.944, 29.902, 29.882,
29.859, 29.852, 29.848, 29.809, 29.796, 29.788, 29.780, 26.271,
26.264, 26.219, 23.076, 14.358, 14.350.
2.2. Synthesis of aromatic triol 9 and triacid 10 from erucic
acid
2.2.1. Behenolic acid 7
A solution of erucic acid (10.1 g, 90% purity, 26.8 mmol)
in diethyl ether (20 mL) was cooled to 0 ◦C in the ice-water
bath. Bromine (1.9 mL, 36.8 mmol) was added drop-wise over
30 min. The ice-water bath was removed and the solution was
stirred for another 30 min at RT. Saturated Na2S2O3 solution
(10 mL) was added to reduce the excess bromine. The organic
layer was separated, washed with brine (20 mL) and dried over
MgSO4. The solvent was evaporated by reduced pressure to
give a pale yellow oil (6). The dibromo intermediate (6) was
then dissolved in 1-propanol (100 mL). KOH (12.1 g, 0.22 mol)
and DMSO (10.6 mL, 0.15 mol) were added. The mixture was
heated under the reflux for 1 h. The mixture was cooled to RT,
poured into ice-cold 2N HCl (150 mL) containing ice chips, fil-
tered and washed in the cold mixture. After drying, a white
powder, 7, was obtained (7.8 g, 23.2 mmol, 86.6%): m.p. 52.5-
53.1 ◦C; IR (microscope) 2750–3050 (OH), 1713 (C=O), 916
2.1.4. Aromatic triacids 5(a) and 5(b)
1
Stearolic acid, 2 (1.91 g, 6.8 mmol) was dissolved in THF
(OH) cm−1; H NMR (CDCl3, 400 MHz): δ 11.2 (br s, 1H,
(20 mL). 0.35 g of Pd/C (10%) and TMSCl (1.1 mL, 8.7 mmol)
were then added. The mixture was refluxed for 8 h and cooled
to RT. The mixture was filtered to remove the Pd/C. Distilled
water (20 mL) was then added. The resulting mixture was further
extracted with diethyl ether and the organic layer was washed
with brine (20 mL) and dried over MgSO4. The solvent was
evaporated under reduced pressure and the residue purified by
flash chromatography (silica gel; hexane/EtOAc 6:1, 5:1, 3:1,
2:1) to afford orange oils 5a (240 mg, 0.29 mmol, 12.6%) and
5b (1.23 g, 1.46 mmol, 64.4%).
COOH), 2.35 (t, J = 7.6 Hz, 2H, CH2CO), 2.14 (m, 4H, CH2CC),
1.64 (q, J = 7.2 Hz, 2H, CH2CH2CO), 1.48 (q, J = 7.2 Hz, 4H,
CH2CH2CC), 1.26–1.39 (m, 24H, CH2), 0.89 (t, J = 6.8, 3H,
CH3); 13C NMR (CDCl3 100 MHz): δ 178.756 (COOH), 80.314
(CC), 80.288 (CC), 33.845; 31.909, 29.754, 29.592, 29.571,
29.473, 29.286, 29.232, 29.216, 29.194, 29.118, 28.931, 28.916,
24.744, 22.722, 18.820, 14.156 (CH3); LRMS (ESI) calcd for
C22H39O2 ([M − H]−) 335.3, found 335.3.
2.2.2. Behenolyl alcohol 8
5a: IR (microscope) 2700–3200 (OH), 1710 (C O), 1465
(C C of benzene) cm−1; 1H NMR (CDCl3, 500 MHz): δ 11.2
(br s, 1H, COOH), 2.46–2.49 (m, 12H, CH2Ph), 2.35–2.39 (m,
6H, CH2CO), 1.65 (q, J = 6.5 Hz, 6H, CH2CH2CO), 1.26–1.50
(m, 60H, CH2), 0.89 (t, J = 7.0, 9H, CH3); 13C NMR (CDCl3
100 MHz): δ 180.276 (COOH), 136.863 (CH2Ph), 136.827
(CH2Ph), 136.641 (CH2Ph), 136.620 (CH2Ph), 34.159, 34.034,
32.003, 31.534, 30.982, 30.738, 30.511, 29.968, 29.838, 29.751,
29.397, 29.175, 28.982, 28.715, 28.538, 24.723, 24.520, 22.752,
14.179 (CH3); LRMS (ESI) calcd for C54H95O6 ([M − H]−)
839.7, found 839.7.
5b: IR (microscope) 2700–3200 (OH), 1710 (C O), 1465
(C C of benzene) cm−1; 1H NMR (CDCl3, 500 MHz): δ 11.2
(br s, 1H, COOH), 2.46–2.49 (m, 12H, CH2Ph), 2.35–2.39
(m, 6H, CH2CO), 1.65 (q, J = 6.5 Hz, 6H, CH2CH2CO),
1.27–1.51 (m, 60H, CH2), 0.89 (m, 9H, CH3); 13C NMR
(CDCl3 100 MHz): δ 180.461 (COOH), 180.383 (COOH),
180.265 (COOH), 179.897 (COOH), 179.902 (COOH), 136.813
(CH2Ph), 136.799 (CH2Ph), 136.688 (CH2Ph), 136.626
Behenolic acid, 7 (1.7 g, 5.1 mmol) was dissolved in 20 mL
diethyl ether. LiAlH4 (0.24 g, 6.3 mmol) was then added. The
mixture was stirred at RT for 1 h. Distilled water (10 mL) was
added followed by 2N HCl (20 mL). The organic layer was
separated, washed with brine (20 mL) and dried over MgSO4.
The solvent was evaporated by reduced pressure to give a
solid, which was purified by recrystallization from petroleum
ether to afford 1.5 g (4.7 mmol, 91.3%) of behenolyl alco-
hol, 8, as a white power. m.p. 43.9–44.5 ◦C; IR (thin film)
1
3160 (OH), 2840–3000 (C–H), 1055 (OH) cm−1; H NMR
(CDCl3, 500 MHz): δ 3.64 (t, J = 6.5 Hz, 2H, CH2OH), 2.14
(m, 4H, CH2CC), 1.57 (q, J = 7.0 Hz, 2H, CH2CH2OH), 1.47
(q, J = 7.0 Hz, 4H, CH2CH2CC), 1.26–1.38 (m, 26H, CH2),
0.88 (t, J = 7.0, 3H, CH3); 13C NMR (CDCl3 125.7 MHz): ␦
80.311 (CC), 80.298 (CC), 63.173 (CH2OH), 32.884, 31.911,
29.665, 29.660, 29.636, 29.607, 29.492, 29.285, 29.237, 29.230,
29.195, 28.932, 28.927, 25.796, 22.723, 18.823, 14.159 (CH3);
LRMS (ESI) calcd for C22H42ONa ([M + Na]+) 345.3, found
345.3.

4
J. Yue, S.S. Narine / Chemistry and Physics of Lipids 152 (2008) 1–8
29.832, 29.774, 29.766, 29.756, 29.741, 29.707, 29.702, 29.526,
2.2.3. Aromatic triols 9(a) and 9(b)
29.517, 29.508, 29.447, 29.398, 25.833, 25.820, 25.807, 22.751,
14.184 (CH3), 14.176 (CH3), 14.171 (CH3); LRMS (ESI) calcd
for C66H126O3Na ([M + Na]+) 990.0, found 990.0.
Behenolyl alcohol, 8 (1.0 g, 3.1 mmol) was dissolved in THF
(20 mL). 0.20 g of Pd/C (10%) and TMSCl (0.59 mL, 4.6 mmol)
were then added. The mixture was refluxed for 8 h and cooled
to RT. The mixture was filtered to remove the Pd/C. Distilled
water (20 mL) was then added. The resulting mixture was further
extracted with diethyl ether and the organic layer was washed
with brine (20 mL) and dried over MgSO4. The solvent was
evaporated under reduced pressure and the residue purified by
flash chromatography (silica gel; hexane/EtOAc 5:1, 3:1, 2:1)
to afford yellow oils 9a (90.0 mg, 0.09 mmol, 9.0%) and 9b
(720.0 mg, 74.5 mmol, 72.0%).
9b: IR (microscope) 3330 (OH), 2850–3000 (C–H), 1466
(C C of benzene), 1056 (OH) cm−1 1H NMR (CDCl3,
;
500 0 δ 3.64 (t, J = 6.5 Hz, 6H, CH2OH), 2.49 (m, 12H,
CH2Ph), 1.30–1.60 (m, 72H, CH2), 0.90 (t, J = 7.0, 9H,
CH3); 13C NMR (CDCl3 125.3 MHz): δ 136.758 (CH2Ph),
136.749 (CH2Ph), 136.744 (CH2Ph), 63.097 (CH2OH), 63.090
(CH2OH), 63.078 (CH2OH), 63.074 (CH2OH), 32.856, 31.991.
31.527, 30.718, 29.822, 29.756, 29.746, 29.737, 29.730, 29.722,
29.698, 29.687, 29.511, 29.500, 29.445, 29.434, 29.386, 25.815,
25.800, 22.742, 14.173(CH3), 14.167(CH3); LRMS(ESI)calcd
for C66H126O3Na ([M + Na]+) 990.0, found 990.0.
9a: IR (microscope) 3330 (OH), 2850–3000 (C–H), 1466
(C C of benzene), 1057 (OH) cm−1 1H NMR (CDCl3,
;
500 MHz): δ 3.63 (t, J = 6.5 Hz, 6H, CH2OH), 2.48 (m, 12H,
CH2Ph), 1.30–1.59 (m, 96H, CH2), 0.88 (t, J = 7.0, 9H,
CH3); 13C NMR (CDCl3 125.7 MHz): δ 136.777 (CH2Ph),
136.755 (CH2Ph), 136.742 (CH2Ph), 63.137 (CH2OH), 63.116
(CH2OH), 63.102 (CH2OH), 32.877, 32.000, 31.537, 30.729,
2.2.4. Aromatic triacids 10(a) and 10(b)
Behenolic acid, 7 (1.0 g, 3.0 mmol) was dissolved in THF
(20 mL). 0.20 g of Pd/C (10%) and TMSCl (0.5 mL, 4.2 mmol)
Scheme 1. Synthesis of aromatic triols and triacids from oleic acid and erucic acid.

J. Yue, S.S. Narine / Chemistry and Physics of Lipids 152 (2008) 1–8
5
were then added. The mixture was refluxed for 8 h and cooled
to RT. The mixture was filtered to remove the Pd/C. Distilled
water (20 mL) was then added. The resulting mixture was further
extracted with diethyl ether and the organic layer was washed
with brine (20 mL) and dried over MgSO4. The solvent was
evaporated under reduced pressure and the residue purified by
flash chromatography (silica gel; hexane/EtOAc 8:1, 7:1, 6:1)
to afford orange oils 10a (70 mg, 0.07 mmol, 7.0%) and 10b
(800 mg, 0.8 mmol, 80.0%).
to produce hexasubstituted benzene derivatives. The symmet-
ric and asymmetric isomers of the triols and triacids shown
above (Scheme 1) have been isolated and fully characterized.
The asymmetric isomer, a less stable compound, is the main
product. Under the conditions discussed, this indicates that
cyclotrimerization is kinetically controlled (Jhingan and Maier,
1987; Lligadas et al., 2007).
The symmetric and asymmetric isomers, such as aromatic
triols 4(a) and 4(b), have almost identical IR or 1H NMR spec-
tra in CDCl3, but their 13C NMR spectra show some visible
differences, which confirm the identity of each isomer. Fig. 1
shows the expanded 13C NMR spectra including the chemical
shifts for the aromatic carbons of triols 4(a) and 4(b). Look-
ing at the planar structure of triol 4(a) (Fig. 2), two chemically
different carbons on the benzene ring were expected due to the
symmetry of the molecule, this would produce two signals at
approximately 140 ppm in the 13C NMR spectrum.
10a: IR (microscope) 2700–3200 (OH), 1710 (C O), 1466
(C C of benzene) cm−1 1H NMR (CDCl3, 500 MHz): δ
;
2.47–2.50 (m, 12H, CH2Ph), 2.36 (t, 6H, J = 7.5 Hz, CH2CO),
1.64 (q, J = 7.0 Hz, 6H, CH2CH2CO), 1.26–1.51 (m, 60H,
CH2), 0.89 (t, J = 7.0, 9H, CH3); 13C NMR (CDCl3 100 MHz):
δ 180.279 (COOH), 136.767 (CH2Ph), 136.748 (CH2Ph),
34.111, 32.008, 31.535, 30.738, 29.845, 29.740, 29.604, 29.594,
29.568, 29.458, 29.401, 29.391, 29.354, 29.269, 29.239, 29.038,
29.013, 24.716, 22.757, 14.183 (CH3); LRMS (ESI) calcd for
C66H119O6 ([M − H]−) 1007.9, found 1007.9.
In reality, the long saturated carbon side chains are freely
rotating which causes the six aromatic carbons to be chemically
different from each other. It was observed that there was only
a slight chemical shift difference between the six aromatic car-
bons, hence the 13C NMR spectrum for triol 4a (Fig. 1) shows
an overlap of some signals resulting in only four peaks being
observed. Although a decoupled 13C NMR experiment is not
quantitative, it is visible from the first spectrum in Fig. 1 that the
ratio (intensities) of the four peaks of 4(a) is 1:2:2:1 indicating
that the peaks at 136.686 and 136.810 ppm represent two car-
bons each. Triol 4(b), because of its unsymmetrical structure,
produces a spectrum that shows the six aromatic carbons to be
all chemically different from each other resulting in six peaks
within the range 136–137 ppm and approximately the same peak
intensities.
10b: IR (microscope) 2700–3200 (OH), 1711(C O), 1466
(C C of benzene ring) cm−1; H NMR (CDCl3, 500 MHz):
1
δ 2.49 (t, J = 8.0 Hz, 12H, CH2Ph), 2.36 (t, 6H, J = 7.5 Hz,
CH2CO), 1.64 (q, J = 7.0 Hz, 6H, CH2CH2CO), 1.31–1.51 (m,
60H, CH2), 0.89 (t, J = 7.0, 9H, CH3); 13C NMR (CDCl3
100 MHz): δ 180.419 (COOH), 180.292 (COOH), 180.191
(COOH), 136.762 (CH2Ph), 136.749 (CH2Ph), 34.157, 34.141,
34.107, 32.005, 31.552, 30.732, 29.843, 29.691, 29.676, 29.655,
29.647, 29.613, 29.592, 29.503, 29.461, 29.451, 29.432, 29.400,
29.318, 29.299, 29.116, 29.101, 29.078, 24.731, 24.723, 24.717,
22.754, 14.180 (CH3); LRMS (ESI) calcd for C66H119O6
([M − H]−) 1007.9, found 1007.9.
1
In order to solidify our arguments, a H NMR experiment
3. Results and discussion
in C6D6 was carried out. The signals for the methylene pro-
tons adjacent to the hydroxyl group occur between 3.30 and
3.50 ppm, as expected (Fig. 3). It can be seen in C6D6, the three
A similar method as reported by Galia and co-workers
has been applied for the cyclotrimerization of fatty alkynes
Fig. 1. Chemical shifts of aromatic carbons on aromatic triols 4(a) and 4(b) in CD3Cl.

6
J. Yue, S.S. Narine / Chemistry and Physics of Lipids 152 (2008) 1–8
1:1 intensity ratio, whereas four distinct peaks were observed
for the asymmetric triol 4(b) with an intensity ratio of 2:1:2:1.
This further establishes our assignment of the symmetric and
asymmetric triols 4(a) and 4(b).
When 4(a) and 4(b) were analyzed on a TLC plate with hex-
ane and ethyl acetate (1:1) as the eluent, the Rf of 4(a) and
4(b) were 0.45 and 0.55, respectively. The symmetric isomer
is more polar than the asymmetric isomer, this could be as a
result of intra-molecular hydrogen bonding. Triol 4(b) has two
adjacent side chains with terminal hydroxyl groups, which could
potentially increase the formation of intra-molecular hydrogen
bonding between the two hydroxyl groups, resulting in a little
lower polarity of the molecule.
Fig. 2. Structures of aromatic triols 4(a) and 4(b).
different methylene protons in the asymmetric triol 4(b) occur
in the 1H NMR spectrum as three triplet peaks. Also from 13
NMR of the aromatic carbons in 4(a) and 4(b) (Fig. 4), only two
separate peaks were observed for the symmetric triol 4(a) in a
In the IR spectra of the fatty alkynes, the carbon–carbon
triple bond stretch which usually occurs at 2150 cm−1 was not
observed. Infra-red absorption spectra result from changes of
C
Fig. 3. 1H NMR splitting patterns of methylene protons (CH2OH) on aromatic triols 4(a) and 4(b) in C6D6.

J. Yue, S.S. Narine / Chemistry and Physics of Lipids 152 (2008) 1–8
7
Fig. 4. 13C NMR splitting patterns of aromatic carbons on aromatic triols 4(a) and 4(b) in C6D6.
the molecular dipole caused by bond vibration (stretching, bend-
ing, scissoring, etc.) in a molecule. The greater the changes in
dipole, the more intense the peaks become. However, the disub-
stituted fatty alkynes possess two long saturated carbon chains
on either side of the centrally located triple bond, so that the
triple bond stretch changes very little of the molecular dipole,
making detection of the triple bond stretch difficult by infra-red
spectroscopy.
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ate the reaction rate. This method was developed by Silbert,
1984, who found that a 3–5 mol ratio of DMSO to dibro-
mostearic acid (DBSA) at a reaction temperature of 100 ◦C
favorably converted the dibromide to stearolic acid within 2 h.
In our study, a higher ratio was used considering that the start-
ing oleic acid or erucic acid was 90% pure, and the impurities
could be some polyunsaturated fatty acids, which could lead to
poly-brominated substrates.
In conclusion, we have reported a general strategy for the syn-
thesis and purification of symmetric and asymmetric aromatic
triols and triacids along with the analytical techniques useful for
isomer-specific analysis. This general synthetic scheme should
also prove useful for the synthesis of hexasubstituted benzene
derivatives from other fatty alkynes.
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Acknowledgements
Li, J.H., Jiang, H.F., Chen, M.C., 2001. CuCl2-induced regiospecifical synthe-
sis of benzene derivatives in the palladium-catalyzed cyclotrimerization of
alkynes. J. Org. Chem. 66, 3627–3629.
The financial support of NSERC, Bunge Corp., AVAC Ltd.
and Archer Daniels Midland are gratefully acknowledged.
Li, J.H., Liang, Y., Xie, Y.X., 2004. Mild and selective palladium-catalyzed
dimerization of terminal alkynes to form symmetrical (Z,Z)-1,4-dihalo-1,3-
dienes. J. Org. Chem. 69, 8125–8127.
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