Synthesis and ultraviolet absorption characteristics of 4-arylidene isopinocamphones from α-pinene

Article abstract of DOI:10.14233/ajchem.2014.17781

A new series of 4-arylidene isopinocamphones were synthesized from α-pinene which is a natural chemical from pine tree and their ultraviolet absorption characteristics were investigated. (+)Isopinocamphone was obtained from α-pinene by hydroboration-oxidation and then it was reacted with benzaldehyde, p-methylbenzaldehyde, p -methoxybenzaldehyde, p-chlorobenzaldehyde, furfural and p -nitrobenzaldehyde in the presence of alkali catalysts to get 4-arylidene isopinocamphones including 2-benzylidene-4,6,6-trimethylbicyclo[3.1.1]heptan-3-one (1), 2,6,6-trimethyl-4-(4-methyl benzyl)bicyclo[3.1.1]heptane-3-one (2), 2-(4-methoxybenzylidene)-4,6,6-trimethylbicyclo[3.1.1] heptan-3-one ( 3 ), 2-(4-chlorobenzylidene)-4,6,6-trimethylbicyclo[3.1.1]heptan-3-one (4 ), 2-(furan-2-methylene)-4,6,6-trimethylbicyclic [3.1.1] heptane-3-one (5) and 2,6,6-trimethyl-4-(4-nitrobenzylidene)bicyclo[3.1.1]heptan-3-one (6). he structures of 4-arylidene isopinocamphones were determined by FT-IR, ¹H NMR, ¹³/C NMR and GC-MS technique. Their ultraviolet absorption characteristics and light stability was further examined. The results showed that compounds 1 , 2, 3 and 5 could be used as Btype UV absorbents, compounds 4 and 6 could be used as A-type UV absorbents and compounds 6 had both functions as UV-A and UVB types absorbents. The light stability sequence of these compounds was (2 ) > (1) ≈ (3) ≈ (4) ≈(6) > (5).

Full text of DOI:10.14233/ajchem.2014.17781

Asian Journal of Chemistry; Vol. 26, No. 22 (2014), 7779-7784
ASIAN JOURNAL OF CHEMISTRY
http://dx.doi.org/10.14233/ajchem.2014.17781
Synthesis and UltravioletAbsorption Characteristics of 4-Arylidene Isopinocamphones from
α-Pinene
1
1
1
1
1,2,*
1,2
JIA-YU WANG , PENG-NA WANG , JIN-LAI YANG , JIA SHEN , XU XU
and SHI-FA WANG
1
2
College of Chemical Engineering, Nanjing Forestry University, Nanjing 210037, Jiangsu Province, P.R. China
Jiangsu Key Lab of Biomass-based green Fuels and Chemicals, Nanjing 210037, Jiangsu Province, P.R. China
*
Corresponding author: Tel/Fax: +86 25 85427812; E-mail: xuxu200121@163.com
Received: 8 April 2014; Accepted: 18 June 2014; Published online: 6 November 2014;
AJC-16234
A new series oo ff 44 - -aa r ryy l li idd ee nn ee i is soo pp i inn oo c ca amm pp hh oo nn e es s ww e er re es sy yn nt ht he es si zi ze ed df rf or omm α α- p- pi ni ne en ne ew wh hi ci hc hwi as saan na at ut ur ra al lc chh e emm i ic ca al lf fr roo mm pp i inn ee tree and their
ultraviolet absorption characteristics were investigated. (+) Ii sopinocamphone was obtained from α-pinene by hydroboration-oxidation
and then it ww aa ss rr ee aa cc t tee dd ww i it th hb be en nz za al dl de eh hy yd de e, ,p p- m- me te ht hy yl bl eb ne zn az lad l ed he yh dy ed ,e ,p -pm- me t eh toh xo yx by e bn ez na zl da el dh ey hd ye d, e p, - cp h- cl oh rl o br oe nb ze an lzd ael hd ye dh ey ,d ef u, rfur fa ul ra nl da np d-
pn -i tn r iot rb oe bn ez na zl da le dh ey hdyed ei ni nt h teh ep rpe rs ees ne cn ec eo fo fa lak l ak lai lic ac ta at la yl ys ts st st ot og ge et t4 4- a- ar yr yl il di de en ne ei si so op pi ni no oc ca amm pphhoonneess i inn cc l luu dd ii nn gg 22 -- bb ee nn zylidene-4,6,6-
trimethylbicyclo[3.1.1]heptan-3-one (1), 2,6,6-trimethyl-4-(4-methyl benzyl)bicyclo[3.1.1]heptane-3-one (2), 2-(4-methoxybenzylidene)-
4
,6,6-trimethylbicyclo[3.1.1]heptan-3-one (3), 2-(4-chlorobenzylidene)-4,6,6-trimethylbicyclo[3.1.1]heptan-3-one (4), 2-(furan-2-
methylene)-4,6,6-trimethylbicyclic [3.1.1] heptane-3-one (5) and 2,6,6-trimethyl-4-(4-nitrobenzylidene)bicyclo[3.1.1]heptan-3-one (6).
1
13
The structures of 4-arylidene isopinocamphones were determined by FT-IR, H NMR, C NMR and GC-MS technique. Their ultraviolet
absorption characteristics and light stability was further examined. The results showed that compounds 1, 2, 3 and 5 could be used as B-
type UV absorbents, compounds 4 and 6 could be used as A-type UV absorbents and compounds 6 had both functions as UV-A and UV-
B types absorbents. The light stability sequence of these compounds was (2) > (1)
≈ (3)
≈ (4) ≈ (6) > (5).
Keywords: α-Pinene, (+)isopinocamphone, 4-Arylidene isopinocamphones, Ultraviolet absorbent, Light stability.
process of synthesis routes gives rise to severe environmental
INTRODUCTION
22
pollution .
Nowadays, the increased ultraviolet radiation has been
becoming one of the global environmental problems in recent
Pinene is another natural product and it has been studied
23-26
for years as one kind of most important renewable product
A new series of 4-arylidene-2-hydroxy-3-pinanones synthe-
.
1-3
years is very harmful to human health , which leads to sunburn
cells, premature skin aging, tanning, DNA and an increased
27,28
sized from (-)-α-pinene could be used as ideal UV absorbents
.
4
-12
risk for skin cancers . Sensitive skin in the sun after conti-
nuous UV-B and UV-A radiation can damage DNA to decreased
immunity and even cause skin cancer. So we have no choice
but to protect the body from injury and aging from the defense
In this paper, the low-cost and abundant renewable resource
α-pinene was also used as the raw material to synthesize a
series of 4-arylidene isopinocamphones by hydroboration-
oxidation and aldol condensation with aromatic aldehydes.
The chemical structure, UV absorption and light stability of
the synthesized chemicals were studied. The new compounds
of 4-arylidene isopinocamphones have a wide range of UV
absorption spectra, good stability and high yield.
13
excessive UV-A, UV-B radiation . Cosmetics ideal UV absor-
ber should have the following properties including the ability
to absorb UV 280-360 nm, high extinction coefficient with
less dose, non-toxic light toxicity, no reacting with cosmetics
and skin components, good compatibility, low price, no odor,
14
EXPERIMENTAL
preventing dry skin, etc. . Because of the reasons above, we
need to obtain new and good sunscreen products to protect
The structures of compounds were characterized by
elemental analysis (Elementar, Germany, Vano EL cube). The
1
5-17
the skin from the deleterious effects of the sun
.
20
As a natural product, camphor derivatives have merits of
stable storage, no irritation to skin, no photosensitization, low
toxicity, good stability, chemical inertness and low absorption
raw material α-pinene with a purity of 98.1 % (GC) and [α]
+ 36.8º (c = 1.0, CCl ) was purchased from Deqing Forest
D
3
Chemical Plant of China. Flash column chromatography was
carried out on silica ge l60 (230-400 mesh). All reactions were
performed under a nitrogen atmosphere with magnetic stirring
18-21
to skin, so they are widely used as UV-B filters in cosmetics .
However, natural camphor is very expensive, as well as a long

7
780 Wang et al.
Asian J. Chem.
and the syntheses of 4-arylidene isopinocamphones from
α-pinene were shown in Scheme-I.
was charged with 200 mL tetrahydrofuran, 54.4 g α-pinene,
9.08 g sodium borohydride (purity of 96 %) and cooled with
ice bath to under 5 °C. Then, 69.33 mL oboron trifluoride
etherate (purity of 46.8 %) was added in portions with the
constant of subsection funnel drip in 40 min. The ice bath was
removed when the temperature is under 5 °C after finishing
addition of oboron trifluoride etherate and the reaction was
General procedure
Isopinocampheol: Isopinocampheol was prepared from
23
α-pinene by hydroboration . A 500 mL dried four-necked
flask equipped with a thermometer, a condenser and a stirrer
OH
O
Sodium borohydride
Oxidant
α
-Pinene
Isopinocampheol
Isopinocamphone
O
O
O
Catalyst
R
R
4-Arylidene isopinocamphone
Isopinocamphone
R=H, CH , OCH ,Cl or NO
3
3
2
1, 2, 3, 4, 6
O
O
O
O
Catalyst
O
Isopinocamphone
Furfural
5
O
O
O
O
2-Benzylidene-4,6,6-
trimethylbicyclo-
2,6,6 Trimethyl-4-(4-methyl benzyl)
bicyclo[3.1.1]heptan-3-one (2)
2
-(4-Methoxybenzylidene)-4,6,6-
trimethylbicyclo[3.1.1]heptan-3-
one(3)
[3.1.1]heptan-3-one (1)
O
O
O
O
Cl
NO2
2
4
-(4-Chlorobenzylidene)-
,6,6-trimethylbicyclo[3.1.1
heptan-3-one (4)
2-(Furan-2-methylene)-4,6,6-
trimethylbicyclic[3.1.1]heptan
-3-one(5)
2
,6,6-Trimethyl-4-(4-
nitrobenzylidene)bicyclo-
[3.1.1]heptan-3-one (6)
Scheme-I: Synthetic route for 4-arylidene isopinocamphones from α-pinene

Vol. 26, No. 22 (2014)
Synthesis and Ultraviolet Absorption Characteristics of 4-Arylidene Isopinocamphones from α-Pinene 7781
kept at room temperature for another 3-4 h. Then 38 mL
anhydrous ethanol was dropped into the flask for an hour. The
reaction system was cooled with ice bath to under 5 °C and the
reaction temperature was not higher than 30 °C by controlling
dropping speed. Cooled with ice bath to under 5 °C again after
finishing addition of anhydrous ethanol, then 40.08 mL 3
3
CH -C-C=O), 2-2.03 (m, 1H, -CH-C=O), 2.57-2.76 (m, 1H,
-CH-C-C=O), 2.74-2.76 (t, 1H, J = 2.90 Hz, -CH-C=C-), 7.31-
7.32 (t, 1H, J = 2.19 Hz, -C=CH-), 7.24-7.26 (m, 2H, -CH in
-C
6
H
5
), 7.31 (s, 1H, -CH in -C
6
H
5
), 7.33-7.34 (m, 2H, -CH in
13
-C
6
H
5
); C NMR (500 MHz, CDCl ): δ (ppm) 15.2, 17.0, 21.1,
3
23.2, 26.1, 26.8, 29.1, 33.9, 41.0, 43.1, 44.5, 44.7, 50.0, 49.4,
52.1, 77.0, 128.1, 131.5, 135.4, 141.7, 203.3; FT-IR (KBr,
-1
mol L sodium hydroxide aqueous solution was added for
about 30 min and the reaction was kept for at the temperature
of 40-45 °C by adding 30 mL hydrogen peroxide (purity of
-
1
ν
max, cm ): 2966 (CH
3
, νas C-H), 2927 (CH
-, νas C=C), 747, 696 (C
τC-H); EI-MS m/z (%): 240.2 (M , 14), 225(1), 207(2), 199(1),
2 3
, νas C-H), 2892 (CH ,
ν
s C-H), 1697 (νC=O), 1619, 1446 (C
6 5
H
6 5
H -,
+
3
0 %) and controlling its dropping speed and continued
reacting for 1 h after finishing dropping. When the reaction
system was cooled to room temperature, added 100 mL
n-hexane, mixed fully for 0.5 h, filtered, then extraction were
finished by adding 12 mL saturated sodium thiosulfate to
198(5), 197(20), 195(1), 185(1), 184(2), 183(2), 182(1),
181(1), 180(1), 179(2), 178(1), 1702(1), 169(7), 167(2),
165(3), 158(13), 157(100), 154(6), 153(4), 152(3), 142(4),
141(10), 130(7), 129(64), 128(35), 127(13), 119(2), 115(13),
102(4), 91(10), 83(5), 77(8), 65(3), 63(3), 55(11), 53(3), 51(4);
remove excess H
to neutral. The organic layer was dried over Na
2
O
2
firstly and washing with saturated brine
SO and then
2
4
Anal. Calcd for C17
8.25.
H20O: C 84.96, H 8.39; found C 84.83, H
concentrated by a rotor evaporator to recover n-hexane. The
reaction was monitored by GC until the peak of α-pinene was
disappeared. Finally, the residue was distilled to collect the
fraction at 70-80 °C/266 kPa, a white acicular crystal with a
2,6,6-Trimethyl-4-(4-methyl benzyl)bicyclo[3.1.1]-
heptane-3-one(2): A 100 mL dried flask equipped with an
agitator, a thermometer and a condenser was charged with (+)-
isopinocamphone (1.52 g, 0.01 mol), p-methylbenzaldehyde
(1.20 g, 0.012 mol) and 1.5 g of powdered sodium methoxide
in 15 mL of anhydrous ethanol. The resulting mixture was
refluxed at room temperature for 12-15 h until the conversion
ratio of isopinocamphone reached over 95.1 % (monitored
20
yield over 72 %, purity of 96 % (GC), specific rotation [α]
0.295° (c = 0.05, C OH), melting point: 53-55 °C.
Isopinocamphone: Isopinocamphone was prepared from
D
+
2 5
H
24
isopinocampheol by oxidation .A 250 mL dried three-necked
flask equipped with a thermometer, a condenser and a stirrer
was charged with 10 g of isopinocampheol, 100 mL of dichloro-
methane and cooled with ice bath to 0 °C. Then pyridinium
25
with GC) . The reacted mixture was extracted with 5 % of
hydrochloric acid solution and ethyl acetate and the combined
organic layers were washed with water and saturated brine to
3
chlorochromate (PCC, CrO was 2.32 mol/g) was added in
the mixture and reacted at 20 °C. And it was stopped after the
reaction continued for 2 h when the conversion ratio of isopino-
campheol was no longer change (monitored with GC). The
reacted mixture was diluted with a moderate amount of toluene
and filtered 2 or 3 times and the combined organic layers were
washed with water and saturated brine to neutrality, dried over
2 4
neutrality, dried over Na SO and concentrated to afford the
yellow crude product, which was purified by thin layer silica
gel chromatography column with mixed solvent containing
1000 mL of petroleum ether and 100 mL of cyclohexane to
provide a 99.4 % isolated yield of compound 2 as a pale yellow
2
0
oily liquid (monitored with GC-MS), [α]
D
-135.8° (c = 0.005
-1
1
Na SO
2
4
and concentrated to afford the crude product, which
g mL , CHCl
3H, -CH ), 1.32-1.34 (m, 2H, -CH
3H, J = 5.79 Hz, CH
2.33-2.34 (d, 3H, J = 4.23 Hz, -CH
1H, -CH-C-C=O), 2.74-2.75 (t, 1H, J = 1.41 Hz, -CH-C=C-),
7.53 (t, 1H, -C=CH), 7.14-7.17 (m, 2H, -CH in -C ), 7.18-
); C NMR (500 MHz, CDCl ): δ
(ppm) 21.2, 26.3, 29.3, 41.1, 43.2, 44.8, 76.8, 77.0, 77.3, 129.0,
129.4, 131.8, 132.7, 138.1, 141.3, 203.7; FT-IR (KBr, νmax
3
). H NMR (300 MHz, CDCl
3
): δ (ppm) 0.93 (s,
was purified by thin layer silica gel chromatography column
with mixed solvent containing 1000 mL of petroleum ether
and 50 mL of ethyl acetate to provide a 99.6 % isolated yield
of isopinocamphone as a colourless oily liquid (monitored with
3
2
-C-C=C-), 1.40-1.42 (d,
3
-C-C=O), 2.01-2.04 (m, 1H, -CH-C=O,
3
6 4
-C H -), 2.54-2.59 (m,
20
GC-MS), specific rotation [α]
D
2 5
+ 0.459° (c = 0.05, C H OH).
6 5
H
13
2
-Benzylidene-4,6,6-trimethylbicyclo[3.1.1]heptan-3-
7.25 (m, 2H, -CH in -C
H
6 5
3
one (1): A 100 mL dried flask equipped with an agitator, a
thermometer and a condenser was charged with (+)-isopino-
camphone (1.52 g, 0.01 mol), benzaldehyde (1.06 g, 0.012
mol) and 1.5 g of powdered sodium methoxide in 15 mL of
anhydrous ethanol. The resulting mixture was refluxed at room
temperature for14-16 h until the conversion ratio of isopino-
,
-
1
cm ): 2967 (CH
C-H), 1695 (νC=O), 1615, 1510, 1461 (C
C-H), 814 (C
3
, νas C-H), 2931 (CH
2
, νas C-H), 2876 (CH
3
, ν
s
6
H
5
-, νas C=C), 1370 (-CH
3
,
+
δ
S
6
H
5
-, τC-H); EI-MS m/z (%): 254 (M , 12),
212(3), 211(13), 207(3), 195(2), 191(1), 183(7), 178(2),
172(11), 171(90), 169(3), 168(8), 167(7), 166(4), 165(10),
156(7), 155(13), 154(5), 153(13), 152(11), 151(2), 144(6),
143(47), 142(13), 141(42), 139(7), 129(25), 128(100),
127(25), 126(4), 119(3), 117(7), 116(8), 115(43), 105(9),
103(5), 102(7), 91(18), 89(7), 83(14), 79(8), 78(5), 77(15),
69(4), 67(9), 65(11), 63(7), 55(45), 53(12), 51(7);Anal. Calcd
25
camphone reached over 96.7 % (monitored with GC) . The
reacted mixture was extracted with 5 % of hydrochloric acid
solution and ethyl acetate and the combined organic layers
were washed with water and saturated brine to neutrality, dried
2 4
over Na SO and concentrated to afford the yellow crude
product, which was purified by thin layer silica gel chromato-
graphy column with mixed solvent containing 800 mL of
petroleum ether and 100 mL of ethyl acetate to provide a 99.9 %
isolated yield of compound 1 as a pale yellow oily liquid
for C18H22O: C 84.99, H 8.72; found C 84.82, H 8.84.
2-(4-Methoxybenzylidene)-4,6,6-trimethylbicyclo-
[3.1.1]heptan-3-one(3): A 100 mL dried flask equipped with
an agitator, a thermometer and a condenser was charged with
(+)-isopinocamphone (1.52 g, 0.01 mol), p-methoxybenzal-
dehyde (1.63 g, 0.012 mol) and 1.2 g of powdered sodium
2
0
-1
(
monitored with GC-MS), [α]
D
-140.6° (c = 0.005 g mL ,
). H NMR (300 MHz, CDCl ): 0.91 (s, 3H, -CH ), 1.32-
2
.37 (m, 2H, -CH -C-C=C-), 1.39-1.40 (d, 3H, J = 4.2 Hz,
1
CHCl
3
3
3
1

7
782 Wang et al.
Asian J. Chem.
methoxide in 15 mL of anhydrous toluene. The resulting
mixture was refluxed at room temperature for 12-15 h until
the conversion ratio of isopinocamphone reached over 91.3 %
231(15), 217(1), 207(6), 203(5), 197(1), 196(6), 195(3),
191(100), 181(2), 177(2), 176(1), 168(7), 167(6), 166(5),
165(18), 164(5), 163(36), 162(4), 156(4), 155(4), 153(8),
152(10), 151(5), 149(8), 141(10), 139(6), 129(8), 128(50),
127(35), 126(6), 125(10), 115(11), 77(10), 75(6), 67(5), 63(6),
25
(
monitored with GC) . The reacted mixture was extracted with
% of hydrochloric acid solution and toluene and the com-
bined organic layers were washed with water and saturated
brine to neutrality, dried over Na SO and concentrated to
5
55(28), 53(7), 51(6); Anal. Calcd for C17
6.97; found C 74.15, H 6.78.
H19OCl: C 74.31, H
2
4
afford the yellow crude product, which was purified by thin
layer silica gel chromatography column with mixed solvent
containing 1500 mL of petroleum ether and 100 mL of cyclo-
hexane to provide a 99.4 % isolated yield of compound 3 as a
2-(Furan-2-methylene)-4,6,6-trimethylbicyclic [3.1.1]
heptane-3-one (5): A 100 mL dried flask equipped with an
agitator, a thermometer and a condenser was charged with (+)-
isopinocamphone (1.52 g, 0.01 mol), furfural (1.52 g, 0.012
mol) and 0.8 g of powdered sodium methoxide in 20 mL of
anhydrous ethanol under a nitrogen atmosphere and the resul-
ting mixture was refluxed at room temperature for 14-16 h
until the conversion ratio of isopinocamphone reached over
20
pale yellow oily liquid (monitored with GC-MS), [α]
D
-176°
). H NMR (300 MHz, CDCl ): δ
), 1.26-1.34 (m, 2H, -CH -C-C=C-),
-C-C=O), 2.50-2.53 (m, 1H, -CH-C=O), 2.67-
.69 (m, 1H, -CH-C-C=O) 2.68-2.70 (m, 1H, -CH-C=C-),
.20-7.21 (t, 1H, J = 1.68 Hz, -C=CH), 3.73 (s, 3H, -O-CH ),
.17-7.19 (m, 2H, -CH in -C ), 7.46-7.50 (m, 2H,-CH in
); C NMR (500 MHz, CDCl ): δ (ppm) 15.2, 16.9, 21.1,
3.1, 26.2, 26.8, 29.1, 33.9, 40.9, 43.2, 44.7, 55.0, 77.0, 113.7,
-1
1
(
(
c = 0.005 g mL , CHCl
3
3
ppm) 0.91 (s, 3H, -CH
3
2
1
2
7
7
.34 (d, 3H, CH
3
2
5
93.8 % (monitored with GC) . The reacted mixture was
extracted with 5 % of hydrochloric acid solution and ethyl
acetate and the combined organic layers were washed with
3
6 5
H
13
-C
H
6 5
3
2 4
water and saturated brine to neutrality, dried over Na SO and
2
1
concentrated to afford the yellow crude product, which was
purified by thin layer silica gel chromatography column with
mixed solvent containing 1500 mL of n-hexane and 100 mL
27.8, 130.8, 131.4, 140.2, 159.4, 203.3; FT-IR (KBr, νmax
,
,
,
-
1
cm ): 2966 (CH
3
, νas C-H), 2927 (CH
s C-H), 1697 (νC=O), 1619, 1446 (C -, νas C=C), 1377 (-CH
S C-H), 747, 696 (C
2
, νas C-H), 2892 (CH
3
ν
H
6 5
3
of ethyl acetate to provide a 99.9 % isolated yield of compound
20
5 as a pale yellow oily liquid (monitored with GC-MS), [α]
D
+
δ
2
1
1
1
9
5
H
6 5
-, τC-H); EI-MS m/z (%): 270 (M , 11),
-
1
1
27(5), 207(1), 199(4), 195(1), 188(13), 187(100), 185(2),
84(3), 173(1), 171(4), 159(34), 158(4), 157(3), 153(4),
52(4), 146(2), 145(10), 144(16), 143(4), 141(6), 133(5),
28(23), 127(14), 121(6), 116(14), 115(32), 103(4), 102(9),
1(9), 89(7), 81(5), 79(7), 78(4), 77(11), 65(5), 63(5), 55(27),
-138°(c = 0.005g mL , CHCl
δ (ppm) 0.86 (s, 3H, -CH ), 1.43-1.45 (m, 2H, -CH
1.34-1.36 (d, 3H, J = 6.45 Hz, CH -C-C=O), 2.01-2.03 (m,
3
). H NMR (300 MHz, CDCl
3
):
3
2
-C-C=C-),
3
1H, -CH-C=O), 2.03-2.17 (m, 1H, -CH-C-C=O), 2.59-2.64
(m, 1H, -CH-C=C-), 7.46 (s, 1H, -C-C=CH), 6.42-6.43 (d,
1H, J = 1.05 Hz, CH in furyl), 6.43 (d, 1H, J = 1.08 Hz, CH in
22 2
3(7), 51(4);Anal. Calcd for C18H O : C 79.79, H 8.20; found
13
C 79.65, H 8.16.
-(4-Chlorobenzylidene)-4,6,6-trimethylbicyclo-
3.1.1]heptan-3-one (4):A 100 mL dried flask equipped with
an agitator, a thermometer and a condenser was charged with
furyl), 7.46 (s, 1H, CH in furfuryl); C NMR (500 MHz,
CDCl ): δ (ppm) 15.3, 17.0, 21.1, 23.2, 26.4, 28.8, 33.8, 41.1,
43.8, 44.2, 44.5, 44.8, 45.1, 49.4, 77.0, 115.6, 118.0, 138.8,
2
3
[
-1
143.6, 151.9; FT-IR (KBr, νmax, cm ): 2967 (CH
(CH , νas C-H), 2879 (CH , νs C-H), 1695 (νC=O), 1615, 1551 (C
, νas C=C), 743 (C -, τC-H); EI-MS m/z (%): 230 (M , 22),
3
, νas C-H), 2933
(+)-isopinocamphone (1.52 g, 0.01 mol), p-chlorobenzaldehyde
2
3
6 5
H -
+
(
1.40 g, 0.012 mol) and 1.2 g of powdered sodium methoxide
6 5
H
in 15 mL of anhydrous toluene. The resulting mixture was
refluxed at room temperature for 12-14 h until the conversion
ratio of isopinocamphone reached over 96.3 % (monitored
215(1), 188(3), 187(21), 174(1), 173(2), 159(7), 148(10),
147(100), 145(2), 144(3), 131(6), 120(3), 119(26), 117(4),
116(4), 115(9), 105(7), 104(2), 103(4), 95(1), 92(2), 91(37),
89(4), 81(5), 79(4), 78(4), 77(11), 65(15), 55(19), 53(6), 52(2),
25
with GC) . The reacted mixture was extracted with 5 % of
hydrochloric acid solution and toluene and the combined
organic layers were washed with water and saturated brine to
18 2
51(8);Anal. cald for C15H O : C 78.23, H 7.88; found C 78.09,
H 7.75.
neutrality, dried over Na
2
SO
4
and concentrated to afford the
2,6,6-Trimethyl-4-(4-nitrobenzylidene)bicyclo[3.1.1]-
heptan-3-one (6): A 100 mL dried flask equipped with an
agitator, a thermometer and a condenser was charged with (+)-
isopinocamphone (1.52 g, 0.01 mol), p-nitrobenzaldehyde
(1.51 g, 0.012 mol) and 0.8 g of powdered sodium methoxide
in 20 mL of anhydrous ethanol. The resulting mixture was
refluxed at room temperature for 8-10 h until the conversion
ratio of isopinocamphone reached over 91.7 % (monitored
yellow crude product, which was purified by recrystallization
in mixed solvent containing 24 mL of ethyl acetate and 3 mL
of petroleum ether for several days at room temperature to
afford a 99.9 % isolated yield of compound 4 as a colourless
20
transparent crystal, m.p. 55-57 °C, [α]
D
-190.4° (c = 0.005 g
). H NMR (300 MHz, CDCl ): δ (ppm) 0.91 (s,
), 1.33-1.35 (m, 2H, -CH -C-C=C-), 1.33-1.35 (d,
H, J = 5.58 Hz, CH -C-C=O), 2.03-2.06 (m, 1H, -CH-C=O),
-
1
1
mL , CHCl
3
3
3
3
2
7
H, -CH
3
2
25
3
with GC) . The reacted mixture was extracted with 5 % of
hydrochloric acid solution and ethyl acetate and the combined
organic layers were washed with water and saturated brine to
.57-2.78 (m, 1H, -CH-C-C=O), 2.67-2.69 (m, 1H, -CH-C=C-)
.27-7.32 (t, 1H, J = 5.58 Hz, -C=CH), 7.18-7.26 (m, 2H,
1
3
-
CH in -C
6
H
5
), 7.48 (m, 2H, -CH in -C
): δ (ppm) 15.4, 21.3, 26.3, 29.2, 41.2, 43.2, 44.7,
4.8, 76.7, 77.3, 128.6, 130.5, 134.0, 142.4, 203.5; FT-IR (KBr,
6
H
5
); C NMR (500
2 4
neutrality, dried over Na SO and concentrated to afford the
MHz, CDCl
3
yellow crude product, which was purified by thin layer silica
gel chromatography column with mixed solvent containing
1500 mL of petroleum ether and 100 mL of ethyl acetate to
provide a 96.1 % isolated yield of compound 6 as as a white
4
ν
ν
-1
max cm ): 2964 (CH
s C-H), 1693 (νC=O), 1620, 1487 (C
-, τC-H); EI-MS m/z (%): 274 (M , 13), 233(6), 232(4),
3
, νas C-H), 2935 (CH
2 3
, νas C-H), 2885 (CH ,
6 5
H
-, νas C=C), 899, 822, 803,
+
20
-1
7
68 (C H
6 5
D
crystal, m.p. 121.8-131.8 °C, [α] -197.6° (c = 0.005 g mL ,

Vol. 26, No. 22 (2014)
Synthesis and Ultraviolet Absorption Characteristics of 4-Arylidene Isopinocamphones from α-Pinene 7783
1
CHCl
CH
3.27 Hz, CH
.10 (m, 1H, -CH-C-C=O), 2.61-2.66 (m, 1H, -CH-C=C-),
.27-7.41 (m, 1H, -C-C=CH), 8.20-8.22 (m, 2H, -CH in -C ),
):
3
). H NMR (300 MHz, CDCl
3
): δ (ppm) 0.93 (s, 3H,
-C-C=C-), 1.39-1.40 (d, 3H, J
3
-C-C=O), 2.07-2.08 (m, 1H, -CH-C=O), 2.09-
a 30 m × 0.32 mm i.d., 0.25 mm file thickness HP-5 capillary
column with nitrogen as carrier gas (38 cm/s, 80 °C for 2 min
and then programmed to 280 °C at 10 °C/min and held for 20
min) in the split mode and the split ratio was 50:1. Fourier-
transform infrared (FT-IR) spectra of samples were recorded
from potassium bromide disks prepared with each crystalline
sample on a Nicolet 380 FT-IR spectrophotometer in the scan
-
3 2
), 1.22-1.37 (m, 2H, -CH
=
2
7
7
6 5
H
13
6 5 3
.41-7.54 (m, 2H, -CH in -C H ); C NMR (500 MHz, CDCl
δ (ppm) 15.3, 17.1, 21.4, 23.5, 26.3, 26.9, 29.0, 33.9, 41.4,
-1
4
1
3.5, 44.8, 45.0, 49.7, 77.0, 123.6, 129.0, 130.0, 142.5, 144.8,
range of 4000-400 cm . Melting points and specific rotation
were measured using X-6 microscopic melting point apparatus
and W22-2S digital automatic polarimeter.
-1
47.1, 203.1; FT-IR (KBr, νmax, cm ): 2964 (CH
, νas C-H), 1694 (νC=O), 1617, 1593 (C
-, τC-H); EI-MS m/z (%): 285 (M , 17), 281(3),
3
, νas C-H), 2912
(CH
2
6 5
H -, νas C=C), 911,
+
8
2
2
2
1
1
1
1
1
1
9
7
5
47, 691 (C H
6 5
70(3), 268(3), 256(3), 255(7), 244(3), 243(16), 242(16),
42(21), 229(5), 228(4), 226(6), 215(2), 214(4), 207(8),
04(4), 203(28), 202(26), 197(5), 196(6), 186(8), 181(7),
74(12), 173(6), 172(30), 169(7), 168(18), 167(18), 166(8),
65(19), 157(11), 156(15), 155(10), 154(10), 153(24),
53(24), 152(28), 151(7), 144(18), 143(16), 142(8), 141(34),
40(6), 139(15), 131(6), 130(14), 129(25), 128(98), 127(50),
26(11), 117(15), 116(15), 115(67), 114(10), 113(11), 107(5),
06(10), 105(10), 103(10), 102(28), 101(9), 93(9), 92(5),
1(27), 89(20), 83(65), 81(13), 79(18), 78(18), 77(33), 76(12),
5(11), 69(15), 67(31), 65(18), 63(19), 60(12), 55(100),
RESULTS AND DISCUSSION
UV ray absorption ability analysis of the 4-arylidene
isopinocamphone derivatives: UV ray absorption abilities
of compounds 1 to 6 which are the E-isomers were listed in
Table-1. Table-1showed that the compounds 1 to 6 had strong
UV absorption. For compound 1, its UV absorption range,
λ
max and ε value were 202-313 nm, 295 nm and 24640 L/mol
cm, respectively. It completely meets the requirement of UV-
B absorbent. For compounds 2, 3 and 5 can also be used as
UV-B absorber. For compound 4, it also meet the conditions
of UV-A absorbents because its UV absorption range, λmax
and ε value were 249-490 and 298 nm, 33821 L/mol × cm,
respectively. For compound 6, it had wide range of UV absor-
ption and λmax reached 313 nm, which was suitable for UV-A
and UV-B absorbent. The sequence of UV ray absorption
ability of compounds 1 to 6 was (6) > (4) > (3) > (5) > (2) >
(1) according to the ε value.
3
4(11), 53(28), 51(19); Anal. Calcd for C17H19NO : C 71.56,
H 6.71; found C 71.44, H 6.59.
UV spectroscopy of compounds 1-6: λmax and molar
extinction coefficient (ε) of synthesized compounds 1-6 were
determined as follows. The solutions of 1, 2, 3, 4, 5 and 6 in
-4
-5
the concentration range 10 -10 mol/L (or 0.0015 %, weight
percent) were prepared in 50 % ethanol and their absorbance
(A) was recorded at respective peak wavelengths (λmax) using
TABLE-1
UV ABSORPTION RANGES, λmax AND ε OF THE
-ARYLIDENE ISOPINOCAMPHONE DERIVATIVES
quartz cuvettes of 1 cm path length (L). A plot of A versus
molar concentration at λmax was prepared and ε value was
obtained from the slope of straight line.
4
UV absorption
range (nm)
λ
max
ε
(L/mol cm)
24640
Photodegradation experiments of compounds 1-6:
Photochemical measurements were carried out as follows: three
same conical flasks with stoppers were charged with 50 mL
of the prepared solution, respectively for compound 1 and was
kept in dark place, second one was put indoor and the last one
was shown in sunlight using 50 % ethanol as the blank. The
other compounds were done according to the same procedure
and their UV absorbance was measured at the maximum absor-
ption wavelength lmax at the same time on every day using
the 50 % ethanol as the control. Photo stability of the synthe-
sized compounds was compared by calculating their degrada-
Compounds
(nm)
295
304
310
298
296
313
1
2
3
4
5
6
202-313
238-310
214-318
249-490
202-312
238-536
25888
31115
33821
26687
37453
Photodegradation studies of 4-arylidene isopinocamp-
hone derivatives: The photostability of compounds 1 to 6
was examined by comparing their molar extinction coefficient
change at different conditions including dark, indoor and
sunlight circumstance. The test results were shown in Figs.
2
6,27
tion rate
.
NMR spectra were recorded in CDCl
3
solution on a Bruker
1
AV 500 spectrometer at 300 MHz for H and 500 MHz for
1
-3, respectively.
Fig. 1 showed that all of these compounds were stable in
13
C, respectively. The chemical shifts were expressed in ppm
δ scale) relative to the reference compound tetramethylsilane
TMS). Electronic impact (EI) gas chromatography-mass
dark circumstance because their molar extinct coefficients had
little change even after 7 days. It was found from Figs. 2 and
(
(
3
that the molar extinct coefficients of all the synthesized
spectrometry (GC-MS) was conducted on an Agilent 6890N
GC coupled to an Agilent Technologies 5973 inert mass
selective detector using a 30 m × 0.25 mm i.d., 0.25 mm file
thickness HP-5MS capillary column (Agilent Technologies,
Wilmington, DE) with helium as carrier gas (36 cm/s, 80 °C
for 2 min and then programmed to 280 °C at 15 °C/min and
held for 20 min). A 70 eV electron beam was employed for
sample ionization. GC analyses were performed on anAgilent
compounds were decreased in different extent. ε values of
compounds 4 and 6 were obviously decreased during the first
two days under strong sunlight irradiation and the molar extinct
coefficients was decreased by 6.3 and 6.7 %, respectively.
However, the ε values of compounds 1-6 were scarcely changed
after two days. All of the six compounds were stable after two
days. Therefore, the photostability sequence of the synthesized
compounds was (2) > (1) ≈ (3) ≈ (4) ≈ (6) > (5).
6890 GC equipped with a flame ionization detector (FID) using

7
784 Wang et al.
Asian J. Chem.
4
4
3
3
3
3
3
2
2
.0 × 10
301 nm and ε value was 20500 L/mol cm). More interesting
thing is that 2-(furan-2-methylene)-4,6,6-trimethylbicyclic
4
.8 × 10
[
3.1.1] heptane-3-one is a completely green product because
1
2
3
4
5
6
4
.6 × 10
the starting materials furfural and α-pinene are totally natural
renewable resource. This research results also provide a
completely new pathway for developing new type of UV filter.
4
.4 × 10
4
.2 × 10
ACKNOWLEDGEMENTS
4
.0 × 10
The authors gratefully acknowledge the financial support
received from Forestry Public Sector Research Fund of State
Forestry Administration of China (No. 201104015), National
Natural Science Foundation of China (No. 31170538),
National Undergraduate Training Programs for Innovation and
Entrepreneurship (201310298009), the Doctorate Fellowship
Foundation of Nanjing Forestry University, and the Priority
Academic Program Development of Jiangsu Higher Education
Institutions.
4
.8 × 10
4
.6 × 10
1
2
3
4
Time (d)
5
6
7
Fig. 1. ε Variation of compounds 1 to 6 along with the time in dark
circumstance
4
4.0 × 10
3.8 × 10
3.6 × 10
3.4 × 10
3.2 × 10
3.0 × 10
2.8 × 10
2.6 × 10
2.4 × 10
2.2 × 10
2.0 × 10
1
2
3
4
5
6
4
4
4
4
4
4
4
4
4
4
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In conclusion, the results presented in this paper clearly
illustrated that 4-arylidene isopinocamphone derivatives
prepared from α-pinene possessed not only good UV ray
absorption ability but also good photostability. Furthermore,
their UV absorption abilities were all much better than that of
p-methylbenzylidene camphor (UVmax in 95 % ethanol was
2
7. B.S. Wei, X. Xu,Y.Q.Yang, X.Q. Cao and S.F. Wang, Chin. J. Org. Chem.,
2, 2287 (2012).
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, 314 (2008).
3
2
3