Synthesis of aryl and heterocyclic polyenes and their activity in free radical scavenging

Article abstract of DOI:10.3184/174751918X15199929401287

Aryl polyenes and heterocyclic polyenes with the same central C₂₀ unit of β,β-carotene but different terminal groups were synthesised. Their free radical scavenging activity was measured by a 1,1-diphenyl-2-picrylhydrazinyl spectrophotometric method. The results indicated that all the new compounds have free radical scavenging activity.

Full text of DOI:10.3184/174751918X15199929401287

JOURNAL OF CHEMICAL RESEARCH 2018
VOL. 42 MARCH, 129–132
RESEARCH PAPER 129
Synthesis of aryl and heterocyclic polyenes and their activity in free radical
scavenging
Kaini Deng, Zuxing Yang, Juan Luo and Kaiqun Wu*
College of Chemistry, Sichuan University, Chengdu 610064, P.R. China
Aryl polyenes and heterocyclic polyenes with the same central C unit of β,β-carotene but different terminal groups were synthesised.
Their free radical scavenging activity was measured by a 1,12-0diphenyl-2-picrylhydrazinyl spectrophotometric method. The results
indicated that all the new compounds have free radical scavenging activity.
Keywords: aryl polyenes, heterocyclic polyenes, β,β-carotene, antioxidant activity, C20 crocetindial
Carotenoids are a type of conjugated polyene pigments widely
found in nature. Their conjugated polyene chain gives them
their yellow–orange–red colours.1 The antioxidant properties of
carotenoids2 are also related to their conjugated chromophore3,4
and are considered beneficial to human health.5,6 Like
carotenoids, the apo-carotenoids are commercially important
in the nutraceutical industry, as food additives, vitamin
supplements and food products, and the cosmetic industry.7,8
To date, a large number of carotenoids have been synthesised,
which have been obtained by modifying the terminal groups
or polyene9 of carotenoids such as β,β-carotene (1) (Fig. 1),
10′-apo-β-carotenal, lycopene, etc. However, there are few
syntheses of new carotenoids10,11 with phenyl or heterocyclic end
groups, and especially syntheses of asymmetrical carotenoids,
and they do not have follow-up studies of their oxidisability. In
this study, a series of new aryl and heterocyclic polyenes with
an asymmetrical structure were synthesised by condensation of
C20 crocetindial with an aryl or heterocycle and phosphonium
salt. The structure of the new carotenoids were characterised
by NMR, IR and HRMS. The free radical scavenging activity
of the new compounds was tested using a WD-2012 automatic
enzyme instrument with 1,1-diphenyl-2-picrylhydrazyl (DPPH)
as the organic free radical.
Results and discussion
Synthesis of 2,6,11,15-tetramethylhexadecahepta-2,4,6,8,10,12,14-
enedial (2)
Isoprene was used as a starting material. The protected C5
phosphonium salt was synthesised from isoprene according to the
literature.12–16 The protected C20 crocetindial was prepared by the
reaction of C5 phosphonium salt with a dienedial, and hydrolysed to
obtain the crocetindial 2 according to our previous work.17
Synthesis of the Wittig salt a–d
Phosphonium salts a–d were prepared by the stirring of the
four chloro compounds and triphenylphosphine in toluene as
the solvent for 12 h under a nitrogen atmosphere to obtain the
products in about 85% yield (Scheme 1).18
Synthesis of the new carotenoids
The synthesis of the new carotenoids included two stages. The
target compounds 3–6 were synthesised by the reaction of
a, b, c or d with 2 and NaOCH3 at 40 °C (Scheme 1).19 The
asymmetric carotenoids 3b–d and 4c were prepared from the
condensation of the target compounds 3 or 4 as the starting
material with phosphonium salt b, c or d and NaOCH3 at 40 °C
Fig. 1 Structure of β,β-carotene.
Scheme 1
* Correspondent. E-mail: 867122800@qq.com

130 JOURNAL OF CHEMICAL RESEARCH 2018
Scheme 2
45.00%
40.00%
35.00%
30.00%
25.00%
20.00%
15.00%
10.00%
5.00%
SADPPH
0.00%
c
c
4
e
3
4
5
6
b
d
3
3
n
3
e
t
o
r
a
c
-
β
,
β
Fig. 2 DPPH radical scavenging capacity of the target compounds.
(Scheme 2).19 The yellow–orange–red crystals of the products
were purified by silica column chromatography.
absorbance of the reaction mixture indicated a greater free
radical scavenging capacity. The DPPH radical scavenging
capacity (SADPPH) is defined as:
The eight new compounds 3–6, 3b–d and 4c were
characterised by NMR, IR and HRMS. 1H NMR spectra showed
the corresponding olefins and terminal groups with a chemical
shift of 6–8 ppm. 13C NMR spectra showed the corresponding
number of carbons and peaks of the methyl group carbon atoms
(15–25 ppm). 13C NMR spectra of 4, 3c, 3d and 4c indicated
that these compounds are a mixture of cis and trans isomers.
As the polarity of cis and trans isomers is very similar and they
can interconvert to make a relatively stable state, they cannot be
separated by chromatography like some natural carotenoids.20
The target compounds, especially the apocarotenals, are
sensitive to light and high temperatures.21
SADPPH = (1 − AS / AC) × 100%
where AC is the absorbance of the blank control reaction and AS
is the absorbance in the presence of samples.
All new compounds and the standard sample β,β-carotene
showed DPPH radical scavenging effects. The effects of the
carotenoids decreased in the order of β,β-carotene > 3c > 3
> 4c > 5 > 6 > 4 > 3d > 3b, and were 40.9%, 35.4%, 33.1%,
25.0%, 21.8%, 20.8%, 19.9%, 19.7%, 19.6% in 30 min,
respectively. Compound 3c had the strongest antioxidant
activity and compound 3b had the weakest antioxidant activity.
Furthermore, the radical scavenging capacity of the new
compounds was lower than that of β,β-carotene (Fig. 2). For the
new apocarotenals, the order of antioxidant activity was 3 > 5 >
6 > 4. It seems that a longer chain does not increase the radical
scavenging capacity for 6. For the asymmetric carotenoids, the
order of antioxidant activity was 3c > 4c > 3d > 3b. It appears
that the existence of furan is helpful for the radical scavenging
capacity. However, we need more evidence to support this.
Determination of DPPH radical scavenging capacity
DPPH is a synthetic stable free radical. Free radical scavengers
can conjugate to the single electron of DPPH, which results
a colour change from purple to yellow and a decrease in
absorbance.22 The degree of fading is quantitatively related to
the number of conjugated electrons. A DPPH experiment was
implemented in 30 min according to the literature.23 A lower

JOURNAL OF CHEMICAL RESEARCH 2018 131
Conclusion
11.91, 11.70, 8.64, 8.60. HRMS calcd for C28H32O [M]+: 384.2453;
found: 384.2453.
We used phosphonium salts with an aryl or heterocycle
and crocetindial to synthesise eight new carotenoids. Their
structures were verified by NMR, IR and HRMS. All new
compounds showed free radical scavenging capacity in a DPPH
experiment.
17-Furan-2-yl-2,6,11,15-tetramethylheptadeca-2,4,6,8,10,12,14,16-
octaenal (5): Dark red powder; yield 94%; m.p. 137–141 °C; IR (KBr)
(υ cm−1): 3041, 2919, 1679 (C=O), 1616 (C=C), 1565, 1518, 1403,
1
1265, 1126s, 1016, 961, 882, 739, 617s; H NMR (400 MHz, CDCl3):
δ 9.45 (s, 1H), 7.37 (d, J = 1.5 Hz, 1H), 6.94 (d, J = 10.6 Hz, 1H), 6.82
(d, J = 15.7 Hz, 1H), 6.77–6.61 (m, 6H), 6.44 (d, J = 16.5 Hz, 2H),
6.41–6.38 (m, 2H), 6.33 (d, J = 10.5 Hz, 1H), 6.29 (d, J = 3.3 Hz, 1H),
2.00 (d, J = 4.1 Hz, 9H, 3 × CH3), 1.90 (s, 3H, CH3); 13C NMR (101
MHz, CDCl3): δ 193.56, 152.79, 148.31, 144.90, 141.00, 137.46, 136.84,
136.51, 135.70, 134.90, 134.37, 131.96, 131.91, 131.56, 131.01, 128.47,
124.98, 121.68, 114.58, 110.68, 107.17, 11.88, 11.71, 11.62, 8.64. HRMS
calcd for C25H28O2 [M]+: 360.2089; found: 360.2085.
Experimental
All reagents were provided by a chemical reagent company, Sichuan
Kelun Pharmaceutical Co. Ltd., and used without further purification
unless otherwise stated. All reactions were carried out under a nitrogen
atmosphere. The IR spectra were recorded on a PerkinElemer 16
PC-FT spectrometer. NMR spectra were recorded on a Varian unity
Inova-400 spectrometer (Varian Inc., Palo Alto, CA, USA) with
CDCl3 as the solvent and tetramethylsilane (TMS) as the internal
standard. Mass spectra (MS) were obtained with a LCMS-IT-TOF
spectrometer (Shimadzu, Japan) using electrospray ionisation (ESI).
Flash chromatography was performed on >300 mesh silica gel. Melting
points were determined using a XRC-1 melting point apparatus
(Sichuan University Instrument Inc., Chengdu, China) and were
uncorrected.
2,6,11,15-Tetramethyl-19-phenylnonadeca-2,4,6,8,10,12,14,16,18-
nonaenal (6): Red powder; yield 63%; m.p. 136–141 °C; IR (KBr) (υ
cm−1): 2973, 2921, 1643 (C=O), 1614 (C=C), 1572, 1552, 1535, 1486,
1
1382, 1126s, 802, 616s; H NMR (400 MHz, CDCl3): δ 9.45 (s, 1H),
7.41 (d, J = 7.5 Hz, 2H), 7.30 (d, J = 7.8 Hz, 2H), 7.21 (t, J = 7.3 Hz, 1H),
6.96–6.93 (m, 1H), 6.90–6.86 (m, 1H), 6.77–6.74 (m, 1H), 6.72–6.65
(m, 4H), 6.61 (t, J = 10.8 Hz, 2H), 6.48 (d, J = 10.9 Hz, 2H), 6.41 (d,
J = 14.9 Hz, 1H), 6.29 (t, J = 12.3 Hz, 2H), 2.00 (d, J = 3.8 Hz, 9H,
3 × CH3), 1.90 (s, 3H, CH3); 13C NMR (101 MHz, CDCl3): δ 194.56,
149.28, 145.90, 138.53, 138.01, 137.89, 137.57, 137.52, 136.80, 136.51,
135.43, 132.94, 132.87, 132.61, 132.26, 129.72, 129.53, 128.95, 128.66,
127.41, 126.30, 126.09, 122.79, 12.92, 12.89, 12.74, 9.68. HRMS calcd
for C29H32ONa [M + Na]+: 419.2351; found: 419.2342.
Synthesis of crocetindial 2 and phosphonium salts a–d
The crocetindial 2 was prepared from isoprene according to the
literature and our previous work.12–17 The intermediate trienedial was
provided by Guangzhou Juyuan Bio Chem Co. Ltd. The phosphonium
salts a–d were prepared by the reaction of the corresponding four
chloro compounds and triphenylphosphine according to the literature.18
Synthesis of asymmetrical compounds 3b–d and 4c; general
procedure
Synthesis of target compounds 3–6; general procedure
Sodium methoxide (0.162 g, 0.003 mol) was added to a solution of the
corresponding phosphonium salt b, c or d (0.002 mol) in dry methanol
(5 mL) at 0 °C, and stirred for 15 min to obtain the phosphorus ylide
completely. A solution of 3 or 4 (0.0013 mol) in dry CH2Cl2 (15 mL)
was added dropwise to the mixture, and the mixture was heated to 40
°C and stirred under a nitrogen atmosphere about for 24 h. Then, the
reaction mixture was washed with the saturated NH4Cl (30 mL) and
extracted with CH2Cl2 (3 ×30 mL). The organic layer was washed
with saturated NaCl (20 mL). Finally, the organic layer was dried over
anhydrous sodium sulfate and CH2Cl2 was removed under vacuum to
obtain the target compounds.
Sodium methoxide (1.62 g, 0.03 mol) was added to a solution of the
corresponding phosphonium salt (7.78 g 0.02 mol) dissolved in dry
methanol (20 mL) at 0 °C and the mixture was stirred about for 15 min.
Crocetindial 2 (3.95 g, 0.013 mol) was dissolved in dry CH2Cl2 (10 mL)
and added dropwise to the mixture, and the mixture was heated to
40 °C and stirred under a nitrogen atmosphere for about 24 h. Then,
the reaction mixture was washed with the saturated NH4Cl (50 mL)
and extracted with CH2Cl2 (3 × 50 mL). The organic layer was washed
with saturated NaCl (50 mL). Finally, the organic layer was dried over
anhydrous sodium sulfate and the CH2Cl2 was removed under vacuum
to obtain the target compounds, which were purified by silica column
chromatography (petroleum ether:ethyl acetate = 25:1).
3,7,12 ,16 -Tet ra m ethyl-1- ph e nyl-18 -p - tolylo ct a d ec a -
1,3,5,7,9,11,13,15,17-nonaene (3b): Orange red powder; yield 16%;
m.p. 188–191 °C: IR (KBr) (υ cm−1): 3026, 2922, 1644 (C=C), 1509,
2,6,11,15-Tetramethyl-17-phenylheptadeca-2,4,6,8,10,12,14,16-
octaenal (3): Dark red powder; yield 32%; m.p. 136–140 °C; IR (KBr)
(υ cm−1): 3036, 2918, 1667 (C=O), 1619 (C=C), 1568, 1517, 1382,
1
1450, 1403, 1265, 1118s, 965s, 803, 748, 684, 617m; H NMR (400
1
MHz, CDCl3): δ 7.36 (d, J = 7.4 Hz, 2H), 7.25 (t, J = 7.8 Hz, 4H), 7.13 (t,
J = 7.8 Hz, 1H), 7.06 (d, J = 8.0 Hz, 2H), 6.88–6.74 (m, 3H), 6.63–6.47
(m, 6H), 6.30 (ddd, J = 27.3, 16.1, 6.4 Hz, 5H), 2.27 (s, 3H, CH3), 1.95
(d, J = 18.1 Hz, 12H, 4 × CH3); 13C NMR (101 MHz, CDCl3): δ 137.25,
136.91, 136.14, 136.04, 135.63, 135.37, 134.26, 133.99, 133.94, 133.58,
132.53, 131.99, 131.75, 131.64, 131.53, 129.24, 128.97, 128.36, 127.62,
126.76, 126.66, 126.42, 126.20, 126.13, 125.32, 125.29, 125.26, 125.22,
124.09, 123.88, 20.22, 11.88, 11.81. HRMS calcd for C35H38 [M]+:
458.2974; found: 458.2972.
1125s, 964, 616s; H NMR (400 MHz, CDCl3): δ 9.45 (s, 1H), 7.44
(d, J = 7.5 Hz, 2H), 7.32 (t, J = 7.6 Hz, 2H), 7.21 (t, J = 7.3 Hz, 1H),
6.92 (dd, J = 15.5, 13.4 Hz, 2H), 6.83–6.72 (m, 3H), 6.68 (dd, J = 11.0,
5.4 Hz, 2H), 6.61 (d, J = 15.9 Hz, 1H), 6.44 (t, J = 12.4 Hz, 2H), 6.33
(t, J = 12.7 Hz, 2H), 2.06–2.00 (m, 9H, 3 × CH3), 1.91 (s, 3H, CH3);
13C NMR (101 MHz, CDCl3): δ 194.56, 149.28, 145.90, 138.44, 137.91,
137.71, 137.51, 136.80, 136.32, 135.42, 133.52, 132.98, 132.93, 132.58,
129.53, 128.68, 127.90, 127.31, 126.38, 126.02, 122.80, 12.96, 12.93,
12.74, 9.68. HRMS calcd for C27H30ONa [M + Na]+: 393.2194; found:
393.2194.
3,7,12,16-Tetramethyl-1-phenyl-18- (furan-2-yl) octadeca-
1,3,5,7,9,11,13,15,17-nonaene (3c): Orange red powder; yield 35%;
m.p. 176–179 °C; IR (KBr) (υ cm−1): 3029, 2918, 1631 (C=C), 1489,
2,6,11,15-Tetramethyl-17-p-tolylheptadeca-2,4,6,8,10,12,14,16-
octaenal (4): Red powder; yield 36%; m.p. 143–147 °C; IR (KBr) (υ
cm−1): 3030, 2922, 1667 (C=O), 1612 (C=C), 1536, 1391, 1122s, 964,
1
1442, 1398, 1256, 1122s, 1019, 968s, 739, 688, 616s; H NMR (400
1
MHz, CDCl3): δ 7.36 (d, J = 7.6 Hz, 2H), 7.29 (s, 1H), 7.24 (t, J = 7.6
Hz, 2H), 7.13 (t, J = 7.2 Hz, 1H), 6.82 (dd, J = 16.0, 2.8 Hz, 1H), 6.75
(dd, J = 15.9, 2.8 Hz, 1H), 6.64–6.49 (m, 5H), 6.39–6.17 (m, 9H), 1.94
(dd, J = 23.1, 6.7 Hz, 12H, 4 × CH3); 13C NMR (101 MHz, CDCl3): δ
153.97, 153.93, 141.99, 141.92, 138.27, 138.24, 137.83, 137.78, 136.61,
136.02, 135.65, 135.54, 135.16, 133.67, 133.53, 133.19, 133.07, 132.99,
132.97, 132.24, 132.07, 130.32, 130.29, 130.18, 130.15, 128.66, 127.77,
127.44, 127.24, 127.17, 126.37, 126.33, 125.04, 125.01, 115.57, 115.30,
111.79, 111.75, 108.15, 107.95, 12.91, 12.84, 12.60, 12.53. HRMS calcd for
C32H34OH [M + H]+: 435.2688; found: 435.2661.
806, 621s; H NMR (400 MHz, CDCl3): δ 9.46 (d, J = 1.0 Hz, 1H),
7.34 (d, J = 8.0 Hz, 2H), 7.14 (d, J = 8.0 Hz, 2H), 7.07–6.97 (m, 1H),
6.94 (dd, J = 9.2, 1.2 Hz, 1H), 6.88–6.81 (m, 2H), 6.80–6.76 (m, 1H),
6.73–6.59 (m, 4H), 6.45 (d, J = 12.8 Hz, 1H), 6.39 (d, J = 11.4 Hz,
1H), 6.33 (d, J = 11.7 Hz, 1H), 2.34 (s, 3H, CH3), 2.04 (dd, J = 10.4,
8.2 Hz, 9H, 3 × CH3), 1.90 (d, J = 5.7 Hz, 3H, CH3); 13C NMR (101
MHz, CDCl3): δ 193.54, 148.27, 147.83, 144.93, 140.64, 137.07, 136.65,
136.54, 136.50, 136.44, 136.01, 135.95, 135.77, 134.21, 133.77, 133.72,
131.87, 131.40, 131.28, 131.12, 131.06, 130.24, 128.41, 128.22, 127.83,
127.48, 126.57, 126.51, 125.39, 125.35, 121.64, 20.24, 12.04, 11.97,

132 JOURNAL OF CHEMICAL RESEARCH 2018
3,7,12,16-Tetramethyl-1,20-diphenylicosa-1,3,5,7,9,11,13,15,17,19-
decaene (3d): Orange red powder; yield 26%; m.p. 183–188 °C; IR (KBr)
(υ cm−1): 3025, 2926, 1647 (C=C), 1512, 1450, 1122s, 972, 747, 688, 621s;
1H NMR (400 MHz, CDCl3): δ 7.35 (t, J = 8.5 Hz, 4H), 7.24 (t, J = 6.6 Hz,
4H), 7.12 (d, J = 7.1 Hz, 2H), 6.84 (d, J = 3.0 Hz, 1H), 6.82–6.80 (m, 1H),
6.65–6.55 (m, 4H), 6.52 (dd, J = 15.6, 3.3 Hz, 2H), 6.43–6.17 (m, 8H), 1.94
(dd, J = 22.8, 6.5 Hz, 12H, 4 × CH3); 13C NMR (101 MHz, CDCl3): δ 137.21,
137.14, 136.98, 136.76, 136.71, 136.59, 136.56, 135.62, 135.59, 135.18,
135.01, 134.71, 134.53, 132.60, 132.47, 132.16, 132.04, 132.00, 131.97,
131.93, 131.09, 130.89, 129.28, 129.19, 129.13, 128.77, 128.73, 127.81, 127.61,
127.48, 126.74, 126.41, 126.33, 126.28, 126.21, 126.18, 126.14, 125.32,
125.29, 125.25, 125.23, 11.88, 11.81, 11.74. HRMS calcd for C36H38 [M]+:
470.2974; found: 470.2980.
3,7,12,16-Tetramethyl-1-p-tolyl-18- (furan-2-yl) octadeca-
1,3,5,7,9,11,13,15,17-nonaene (4c): Red powder; yield 30%; m.p. 190–193
°C; IR (KBr) (υ cm−1): 3025, 2922, 1631 (C=C), 1512, 1450, 1402, 1260,
1015, 964s, 929, 885, 841, 806, 735s, 668, 589, 534; 1H NMR (400 MHz,
CDCl3): δ 7.37–7.31 (m, 3H), 7.13 (d, J = 7.9 Hz, 2H), 6.84 (ddd, J = 15.8,
13.2, 2.8 Hz, 2H), 6.72–6.61 (m, 4H), 6.57 (dd, J = 16.0, 4.6 Hz, 1H),
6.43–6.26 (m, 9H), 2.34 (s, 3H, CH3), 2.01 (dd, J = 20.4, 6.3 Hz, 12H, 4
× CH3); 13C NMR (101 MHz, CDCl3): δ 152.90, 152.86, 140.95, 140.87,
137.23, 136.92, 136.12, 136.03, 135.62, 135.37, 135.17, 134.67, 134.53,
134.05, 133.98, 133.93, 132.17, 132.04, 132.00, 131.78, 131.66, 131.55,
131.19, 131.02, 129.28, 129.21, 129.02, 128.98, 128.36, 126.73, 126.39,
125.24, 125.20, 124.06, 123.88, 114.47, 114.20, 110.75, 110.72, 107.12,
106.92, 20.22, 11.88, 11.81, 11.78, 11.57, 11.50. HRMS calcd for C33H36O
[M]+: 448.2766; found: 448.2745.
References
1
2
3
4
5
B.F. Lutnaes, G. Kildahl-Andersen, J. Krane and S. Liaaen-Jensen, J. Am.
Chem. Soc., 2004, 126, 8981.
M. Heliövaara, P. Knekt, K. Aho, R.K. Aaran, G. Alfthan and A. Aromaa.
Ann. Rheum. Dis., 1994, 53, 51.
R. Álvarez, B. Vaz, H. Gronemeyer and Á.R. de Lera, Chem. Rev. 2014, 114,
1.
A.M. Badr, E.F. Shabana, H.H. Senousy and H.Y. Mohammad, J. Food
Agric. Environ., 2014, 121, 24.
B.P. Arathi, P.R. Sowmya, G.C. Kuriakose, K. Vijay, V. Baskaran, C.
Jayabaskaran and R. Lakshminarayana, Food Chem. Toxicol., 2016, 97, 265.
G. Markou and E. Nerantzis, Biotechnol. Adv., 2013, 31, 1532.
P.V. Reddy, R.S. Monsterrat and B. Babak, J. Labelled Compd Radiopharm.,
2002, 45, 79.
6
7
8
9
C.I. Cazzonelli, Funct. Plant Biol., 2011, 38, 833.
W. Klyne and IUPAC-IUB Joint Commission on Biochemical Nomenclature
(JCBN). Pure Appl. Chem,. 1975, 41, 407.
10 G.W. Francis, B. Lüning, C.R. Enzell, M.J. Tricker and S. Svensson, Acta
Chem. Scand., 1972, 26, 2969.
11 H.R. Brahmana, K. Katsuyama, J. Inanaga, T. Katsuki and M. Yamaguchi,
Tetrahedron Lett., 1981, 22, 1695.
12 G. Eletti-Bianchi, F. Centini and L. Re, J. Org. Chem., 1976, 41, 1648.
13 Y. Satake, T. Nishikawa, T. Hiramatsu, H. Araki and M. Isobe, Synthesis,
2010, 12, 1992.
14 S. Hecht, S. Amslinger, J. Jauch, K. Kis, V. Trentinaglia, P. Adam, W.
Eisenreich, A. Bacher and F. Rohdich, Tetrahedron Lett., 2002, 43, 8929.
15 M. Ihara, Y. Ishida, M. Abe, M. Toyota, K. Fukumoto and T. Kametani, J.
Chem. Soc. Perkin. Trans. 1, 1988, 5, 1155.
Acknowledgement
16 W.L. Dai, B. Jin, S.L. Luo, X.B. Luo, X.M. Tu and C.T. Au, Appl. Catal. A,
2014, 470, 183.
We are grateful to the College of Chemistry, Sichuan University for
providing the comprehensive training platform of the professional
laboratory for NMR, IR and HRMS analysis.
17 J. Luo, A.G. Zhang and Y.L. Wang, Patent: CN201610032227, issued 4 May
2016.
18 T.G. Traylor and K.J. Stewart, J. Am. Chem. Soc., 1986, 108, 6977.
19 S.F. Lockwood, G. Nadolski and B.J. Foss, U.S. Patent: 20090099061, issued
16 April 2009.
Electronic Supplementary Information
The ESI (1HNMR, 13CNMR and HRMS spectra of compounds
3–6, 3b–d and 4c) is available through:
20 A.S. Jeevarajan, C.-C. Wei and L.D. Kispert, J. Chem. Soc. Perkin Trans.
2, 1994, 861.
http://ingentaconnect.com/content/stl/jcr/2018/00000042/00000003/art00003
21 Y. Hu, H.Hashimoto, C. Moine, U. Hengartner and Y. Koyama, J. Chem. Soc.
Perkin Trans. 2, 1997, 2699.
Received 12 December 2017; accepted 23 February 2018
Paper 1705155
https://doi.org/10.3184/174751918X15199929401287
Published online: 14 March 2018
22 T.N. Van and N.D. Kimpe, Tetrahedron, 2000, 56, 7969.
23 K.-Z. Zhang, K. Deng, H.-B. Luo, J. Zhou, Z.-Y. Wu and W.-X. Zhang, J. Inst.
Brew., 2013, 119, 182.