Highly selective catalytic preparation of bis(4-oxo-benzo-2-cyclohexen-1-yl) amine from 1-naphthylamine oxidation over metalloporphyrin catalysts by molecular oxygen under air pressure and by hydrogen peroxide

Article abstract of DOI:10.1016/j.molcata.2006.02.039

In the presence of molecular oxygen or hydrogen peroxide, 1-naphthylamine (1-NA) was catalytically converted into bis(4-oxo-benzo-2-cyclohexen-1-yl) amine (BOBCHA) over metalloporphyrin catalysts through an oxidative-coupling way. UV-vis, IR, NMR, MS, mp determinations and elemental analysis were employed for product characterization. A possible catalytic mechanism based on in situ UV-vis and EPR determinations was proposed. A spectrophotometric method was established for quantitative analysis of the product according to its characteristic absorption at λ_max = 465 nm. The influences of reaction conditions, such as solvents, temperature, reaction time, medium alkalinity, as well as species and amount of the catalysts were discussed in detail.

Full text of DOI:10.1016/j.molcata.2006.02.039

Journal of Molecular Catalysis A: Chemical 252 (2006) 56–62
Highly selective catalytic preparation of bis(4-oxo-benzo-2-cyclohexen-1-yl)
amine from 1-naphthylamine oxidation over metalloporphyrin catalysts by
molecular oxygen under air pressure and by hydrogen peroxide
a
b
a
c
a
a
Tie Chen , Enhua Kang , Guiping Tan , Sijie Liu , Shaodan Zheng , Keer Yang ,
a
c,∗
b,∗
a,∗
Shanling Tong , Chiguang Fang , Fengshou Xiao , Yan Yan
Department of Chemistry & Advanced Material Institute, Shantou University, Shantou, Guangdong 515063, China
a
b
College of Chemistry, State Key Lab of Synthesis & Preparative Chemistry, Jilin University, Changchun, Jilin 130012, China
c
Jilin Provincial Center for Disease Prevention and Control, Changchun, Jilin 130021, China
Received 29 October 2005; received in revised form 10 January 2006; accepted 6 February 2006
Available online 20 March 2006
Abstract
In the presence of molecular oxygen or hydrogen peroxide, 1-naphthylamine (1-NA) was catalytically converted into bis(4-oxo-benzo-2-
cyclohexen-1-yl) amine (BOBCHA) over metalloporphyrin catalysts through an oxidative-coupling way. UV–vis, IR, NMR, MS, mp determinations
and elemental analysis were employed for product characterization. A possible catalytic mechanism based on in situ UV–vis and EPR determinations
was proposed. A spectrophotometric method was established for quantitative analysis of the product according to its characteristic absorption at
λ
max = 465 nm. The influences of reaction conditions, such as solvents, temperature, reaction time, medium alkalinity, as well as species and amount
of the catalysts were discussed in detail.
2006 Elsevier B.V. All rights reserved.
©
Keywords: Metalloporphyrin; 1-Naphthylamine; Selective catalysis; Oxidative-coupling; Molecular oxygen; Hydrogen peroxide; Bis(4-oxo-benzo-2-cyclohexen-
-yl) amine
1
1
. Introduction
oxidant [3–6]. But traditional synthetic metalloporphyrins also
exhibited higher catalytic activities and strong endurance in the
oxidative preparation of 2-hydroxy-1,4-naphthoquinone from
1- or 2-naphthol, as we reported before [7,8]. Metallopor-
phyrin catalysts also exhibited high activities in NO dispro-
portionation [9], photosensitised degradation of 4-chlorophenol
[10] and unique direct oxidative conversion of N-acyl-l-proline
to N-Acyl-l-glutamate [11]. Our primary research indicated
that, under the similar catalytic conditions as literature [8]
stated bis(4-oxo-benzo-2-cyclohexen-1-yl) amine (BOBCHA)
was prepared when the reactants, 1- or 2-naphthol was replaced
by 1-naphthylamine (1-NA) [12]. But, no catalytic mechanis-
tic evidences were provided due to the difficulty in observing
catalytic intermediates between iron porphyrin catalyst and O2
during the reaction.
Metalloporphyrin researches were focused on mimic model
compounds of biological enzymes based on their extremely high
selectivity in catalytic conversions of hydrocarbons. Recently,
water-soluble ferrous porphyrin, with similar structure as heme,
was investigated of thermal and photoinduced properties to
unambiguously prove its sitting-atop structure [1]. In another
report, iron porphyrin complex catalyzed efficiently alcohol
oxidations to the corresponding carbonyl compounds via a
high-valent iron-oxo porphyrin intermediate [2]. For getting
higher anti-oxidative endurance of the catalysts, some met-
alloporphyrins with halogen substituted were prepared as the
third generation catalysts and applied to catalyze the epoxida-
tion and hydroxylation of hydrocarbons using different strong
We presents here, in a methanolic alkaline medium, 1-
naphthylamineisconvertedintobis(4-oxo-benzo-2-cyclohexen-
1-yl) amine over 5,10,15,20-tetraphenyl porphyrinato man-
ganese chloride (MnTPPCl) catalyst by O2 with conversion of
∗
Corresponding authors. Tel.: +86 754 2903388.
E-mail address: yanyan@stu.edu.cn (Y. Yan).
1
381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2006.02.039

T. Chen et al. / Journal of Molecular Catalysis A: Chemical 252 (2006) 56–62
57
7
8.5% and selectivity at 100%, and over 5,10,15,20-tetraphenyl
porphyrinato iron chloride (FeTPPCl) catalyst by H2O2 with
conversion of 79.6% and with the same selectivity. Based on in
situ determinations of FeTPPCl with H2O2, a possible catalytic
mechanism was proposed and the various factors influencing
the catalysis were also discussed. With resembling molecular
structure, BOBCHA should have the similar properties to naph-
thoquinone. It would be used as a receptor to modulate ryanodine
in scarcoplasmic reticulum [13] and as the intermediate of fine
chemicals preparation. For instance, by electrochemical method,
BOBCHA could be polymerized into an oligomer film with
excellentopticalcharacteristics[14–16]toprovideitselfapoten-
tial application future.
Scheme 1. A novel compound of bis(4-oxo-benzo-2-cyclohexen-1-yl) amine
(BOBCHA), is catalytic prepared coupling-oxidation over metalloporphyrin cat-
alysts.
ditions kept constant. After 40 min of reaction, the red powder
was obtained in yield of 79.6%.
2.3. Product characterization
2
. Experimental
The product was quantitatively analyzed by HPLC and
UV–vis techniques. It was also characterized by means of melt-
ing point measurement, element analysis, GC-MS, IR and H
2
.1. Reagents and instrument
1
NMR determination.
Metalloporphyrin catalysts were prepared by the methods of
Bis(4-oxo-benzo-2-cyclohexen-1-yl)amine: (Melting point:
Adler et al. [17] and Lindsey et al. [18]. Molecular oxygen with
purity of 99.99%, methanol, and 1-naphthylamine were pur-
chased with purity higher than 99.99%. An aqueous solution of
hydrogen peroxide (30 wt%) and all other reagents with purities
higher than 99.9% were directly used without further purifica-
tion.
◦
2
32–233 C); (Found: C, 79.46; H 5.08; N 4.52. Calc. for
−1
C20H NO2: C, 79.73; H, 4.98; N, 4.65%); vmax(KBr)/cm
15
3
444(N H); 1691(C O) [19]; δH = 7.25, 7.42, 7.26, 7.69(H-
naph.); 6.88, 6.86(H C C); 2.0(H N) [20]; mass spectrum
m/z = 301 (molecular ion).
The UV–vis spectrum of BOBCHA in CH2Cl2 showed 3
The experiments were monitored by a Shimadzu UV-
4
4
absorptions at 289 nm (ε = 8.2 × 10 ), 345 nm (ε = 4.6 × 10 ),
2
0
40 spectrophotometer (operating conditions: 40 nm/cm,
4
and 490 nm (ε = 2.0 × 10 ), and that in CH3OH showed
.0–1.5 A; wavelength range: 200–800 nm; sample concentra-
4
3
two absorptions at 277 nm (ε = 3.9 × 10 ) and 465 nm
tion: 0.0001–0.1 mol/dm ), a Nicolet FTIR 5-PC spectrometer
4
(
ε = 2.3 × 10 ), respectively. Meanwhile, other substances in
(
4
operating conditions: slow scanning speed; resolution power:
cm ; wave number range: 400–4000 cm , KBr), a VG-
−1
−1
2 2 2
the catalytic system, such as NaOH, O , H O and 1-NA,
with no absorption appeared around 350–800 nm. Therefore,
the absorption of BOBCHA at 465 nm can be directly used
as the characteristic peak to analyze BOBCHA quantitatively.
The linear regressive equation of standard curve for BOBCHA
Quattro series connection mass spectrometer (operating con-
ditions: laser source; 200 C; ionization voltage: 70 eV; ana-
lytic current: 500 ␮A; sample feed: Desorption Electro-Impact
◦
(
DEI), range: 0–300 m/z), a UNTY-400 NMR spectrometer
−6
analysis is as A = 0.02526 + 0.3612 × 10 CBOBCHA (linear cor-
(
operating conditions: 300 MHz, standard substance is CDCl3),
relative coefficient, r = 0.9994). In the concentration range of
a Brucker ER 200D EPR spectrometer (operating conditions: at
room temperature; microwave frequency: 9.67 GHz; microwave
power: 2 mW; midfield: 348.62 mT; scan range: 600.0 mT; scan
time: 200 s; modulation frequency: 100 kHz; field modulation:
−
6
3
(
0.142–4.656) × 10 mol/dm , the standard curve displays a
well linear correlation.
0
.125 mT) and a X4 microscope melting point apparatus.
3. Result and discussion
2
.2. Catalytic reactions
3.1. Catalytic mechanism
For preparing BOBCHA, 0.40 g of 1-NA, 2.50 g of NaOH,
FeTPPCl reacted with H2O2 to form a high valence metallo-
porphyrin complex, an active catalytic intermediate for the oxi-
dationfrom1-and2-naphtholto2-hydroxy-1,4-naphthoquinone
[7]. The catalytic intermediate is the same one in the oxidative-
coupling of 1-NA to form BOBCHA. UV–vis spectrum of FeTP-
PCl shows an absorption peak at 415 nm (Soret band). By adding
H2O2 into this solution, an in situ determination reveals a new
absorption peak at 461 nm [the absorption of O Fe(V)TPPOH,
Soret band], meanwhile the Soret band of FeTPPOH weakens
gradually with an isobestic point emerging at 436 nm (Fig. 1a).
Followed by adding 1-NA into the reaction system, the absorp-
tion at 461 nm assigned to the new species of metalloporphyrin
disappears gradually, possibly owing to the consumption of
−
3
and 1.50 mg (2.13 × 10 mmol) of MnTPPCl were dissolved
in 20 ml of MeOH at 333 K, followed by bubbling of molecular
oxygen with pressure at 1 atm (101.325 kPa). Color of the reac-
tion mixture was changed from straw yellow to red gradually
(
see Scheme 1). After 5 h of reaction under continuous stirring,
the addition of water into the mixture produced red precipitates.
The red product was purified by chromatography (using SiO2 gel
column with toluene as eluant). Finally, 0.63 g of a red powder
was obtained in 78.5% yield.
In another catalytic system with H2O2 as an oxygen
source, the above MnTPPCl catalyst was replaced by 3.0 mg
3
(
4.25 × 10− mmol) of TPPFeCl and at 313 K while other con-

5
8
T. Chen et al. / Journal of Molecular Catalysis A: Chemical 252 (2006) 56–62
Fig. 1. In situ UV–vis spectrum varying, (a) FeTPPCl + H2O2; (b) 1-naphthylamine + (a)-6, after (1) 5 min; (2) 10 min; (3) 15 min.
the intermediate during the formation of BOBCHA (Fig. 1b).
These evidences indicate that the active catalytic intermediate
must be a new species of metalloporphyrin, [O Fe(V)TPPOH].
The formation of O Fe(V)TPPOH is just similar to the high-
valent iron-oxo entities of cytochrome P-450 with H2O2 as
oxygen donating [21,22]. EPR spectra of the catalytic oxida-
tion have confirmed the suggestion. Fig. 2 shows the in situ
EPR determination spectra of FeTPPCl reacting with H2O2 and
EPR signal disappearance means the formation of high valence
of O Fe(V)TPPOH. The high valence species is paramagnetic,
but is “EPR-inert” one giving a broad spectrum, and hence,
is difficult to be detected (see Fig. 2e) [26]. When 1-NA is
added to the methanol solution with O Fe(V)TPPOH, the para-
magnetic signal appears again, possibly due to the reaction of
O Fe(V)TPPOH with 1-NA to produce the product, BOBCHA
and the original catalyst, Fe(III)TPPOH (see Fig. 2f–i).
1
-naphthylamine. Fe(III)TPPCl (presenting in Fe(III)TPPOH
Therefore, a possible catalytic mechanism for oxidative-
coupling of 1-NA by H2O2 is proposed as in Scheme 2.
In the alkaline methanol media, the balance chloric anion
in Fe(III)TPPCl is replayed by hydroxyl anion to form
Fe(III)TPPOH, and Fe(III)TPPOH is coordinated further at the
opposite axial trend by H2O2 to produce (HOOH)Fe(III)TPPOH
form in the methanolic alkaline medium) itself displays a strong
EPR signal at g = 2.225 (Fig. 2a). By adding H2O2 into the
solution, this signal becomes much weaker than before, and
disappears completely after 45-min reaction (Fig. 2b–e). The
(step 1). This unstable (HOOH)Fe(III)TPPOH rapidly dissoci-
ates into a high valence form of O Fe(V)TPPOH, the catalytic
intermediate; by the synergism of dehydration and oxidation
(step 2) [21–25]. Meanwhile, 1-NA can be polymerized into an
oligmer (step 3) in oxidative ambience [27], and the oligmer is
oxidized by O Fe(V)TPPOH (step 4) to form BOBCHA after
deamination (step 5) and oxidation (step 6).
In the molecular oxygen system, the catalytic intermedi-
ate is in accordance with the model of cytochrome P-450 in
hydroxylation of hydrocarbons [21,22]. Therefore, the catalytic
intermediates in both H2O2 and O2 oxidative-coupling of 1-NA
are considered as an O M(V) porphyrin form.
3
3
.2. Catalytic condition optimization
.2.1. Activities of different MTPP catalysts and their
amount selection
Influences of the kind and the amount of metalloporphyrin
catalysts on the oxidative-coupling of 1-NA were examined.
The different effects of metalloporphyrin catalysts are list in
Table 1 (the reacting conditions were given under the table).
Notably, among metalloporphyrin catalysts with same center
metal, M-TPP displays the highest activity in all system of
O2 oxygen donor and H2O2 oxygen donor, excepting Co-T(4-
NO2)PP catalyst in H2O2 system. These indicate the substituent
groups at phenyl rings in metalloporphyrin including both the
electron donating OCH3, OH, and the electron attracting F,
Fig. 2. The in situ EPR spectra of the catalytic system. (a) TPPFeCl + NaOH in
MeOH solution. (b)–(e) H2O2 + (a), 10 min, 20 min, 35 min, and 45 min. (f)–(i)
1-Naphthylamine + (e), 5 min, 15 min, 25 min, and 30 min.
2
NO , are all unfavorable for getting high catalytic activities in

T. Chen et al. / Journal of Molecular Catalysis A: Chemical 252 (2006) 56–62
59
Scheme 2. A possible catalytic mechanism for producing BOBCHA with H2O2 as oxygen donor over FeTPPCl catalyst.
the oxidative-coupling. The special demand to form BOBCHA
may be account for the amounts and stabilities of high valence
metalloporphyrin intermediates in the oxidative-coupling of
the catalytic intermediate amount and meanwhile makes the
catalytic intermediate too stable in kinetics to react with 1-NA.
Therefore, less BOBCHA is produced too. Obviously, both
amount and stabilities of the intermediate come from metallo-
porphyrin without any electron donating or accepting groups,
such as MTPPCl, are more suitable in the catalytic preparation
of BOBCHA. The intermediate spectra change along with
time after adding 1-NA also indicates kinetic stability of the
intermediate. Within 15 min, the intermediate spectrum of
O Fe(V)TPPOH is almost changed into its original spectrum
of FeTPPOH catalyst (see Fig. 1b), while the intermediate
spectrum of O Fe(V)T(p-OCH3)PPOH becoming into that
of Fe(III)T(p-OCH3)PPOH almost takes 40 min. The rate to
consume O Fe(V)TPPOH is rather faster than that to consume
O Fe(V)T(p-OCH3)PPOH based on Fe(III)T(p-OCH3)PPOH,
with 4 methoxyls, the strong electron donating substituents.
The experimental data in Table 1 also indicate that FeTPPCl
and MnTPPCl are with relative higher activities than other ones
in O2 and H2O2 systems, respectively. After metalloporphyrin
catalyst selections, the amount of FeTPPCl and MnTPPCl cat-
alysts for the two catalytic systems were examined (see Fig. 3).
When1.5 mgofMnTPPCl(forO2 system)or3.0 mgofFeTPPCl
1
-NA. In fact, the absorbance peaks of O Fe(V)T(p-F)PPOH,
O Fe(V)TPPOH and Fe(V)T(p-OCH3)PPOH appear at
4
4
λmax = 462 nm (ε = 1.38 × 10 ), λmax = 465 nm (ε = 2.25 × 10 )
4
and λmax = 468 nm (ε = 2.60 × 10 ), respectively. During the
formation of the catalytic intermediates, the electron donating
groups ( OCH3) around porphyrin rings make redox potential
descend while the electron attracting groups ( F) make
that arise. The redox potential arising reduces the catalytic
intermediate amount, and as a result, less BOBCHA is pro-
duced. Contrarily, the redox potential descending increases
Table 1
Activity compare of different metalloporphyrin catalystsa
Metalloporphyrin catalyst
Yield of BOBCHA/%
O2 as oxidant
H2O2 as oxidant
Fe-T(4-OCH3)PPCl
Fe-T(4-OH)PPCl
Fe-TPPCl
Fe-T(4-F)PPCl
Fe-T(4-NO2)PPCl
46.88
38.43
52.31
51.91
32.74
19.71
24.63
51.64
27.03
5.34
(H2O2 system) are added, the highest conversions from 1-NA
into BOBCHA reach at 65.3% and 79.6%, respectively under
the relative reacting conditions. Less or more catalysts than the
best amounts will descend the yield of BOBCHA. The poly-
mer formation of 1-NA may account for the conversion falling
[27]. Meanwhile, high concentration of metalloporphyrin cat-
alyst may accelerate the formation of an inactive species of
␮-oxygen dimmer, [Por-M-O-M-Por], to descend concentration
of the active intermediate of O M(V)TPP. As a result, the yield
of BOBCHA would be reduced consequentially [28,29].
Mn-T(4-OCH3)PPCl
Mn-TPPCl
Mn-T(4-F)PPCl
Mn-T(4-NO2)PPCl
Mn-T(3-NO2)PPCl
29.62
65.32
47.28
56.41
40.94
0.84
19.07
10.94
0.63
1.62
Co-T(4-OCH3)PP
Co-TPP
Co-T(4-NO2)PP
Co-T(4-F)PP
17.94
32.21
29.97
8.16
3.70
2.21
14.86
0.18
a
All catalysts are based on the structure of 5,10,15,20-tetraphenylporphyrin-
metal complexs (M-TPP), and the substituent at the phenyl ring is labeled in
the brackets. Reaction conditions: VMeOH = 30 ml, mNaOH = 2.5 g, m1−NA = 0.4 g.
For H2O2 system: T = 313 k, t = 1 h, mCatalyst = 0.5 mg, VH O = 1.5 ml. For O2
3.2.2. Influence of the amount of sodium hydroxide
Fig. 4 presents the influence of sodium hydroxide amount in
2
2
system: T = 333 k, t = 3 h, mCatalyst = 1.5 mg, PO = 1 atm.
the methanol solution. Alkali reacting medium is beneficial for
2

6
0
T. Chen et al. / Journal of Molecular Catalysis A: Chemical 252 (2006) 56–62
Fig. 5. Reaction time selection, VMeOH = 30 mL, m1−NA = 0.4 g, mNaOH = 2.5 g.
a) H2O2 system: mFeTPPCl = 0.5 mg, VH O = 1.5 mL, T = 313 K. (b) O2 system:
Fig. 3. M-TPPCl catalyst amount selection, VMeOH = 30 mL, mNaOH = 2.5 g,
m1−NA = 0.4 g. Change the amount of M-TPPCl catalysts, (a) H2O2 system:
FeTPPCl as catalyst, t = 40 min, T = 313 K, (b) O2 system: MnTPPCl as cata-
lyst, t = 3 h, T = 333 K.
(
2
2
mMnTPPCl = 1.5 mg, PO = 1 atm, T = 333 K.
2
both decreasing the redox potential and promoting the organic
reaction rate. In the catalytic oxidation of 1-NA, sodium hydrox-
ide displays a very important role. Without sodium hydroxide,
no BOBCHA can be detected. Therefore, the conversion of 1-
NA to BOBCHA also increases with the amount of NaOH in the
reaction solution before its amount reaches 2.5 g for both sys-
tems. The MeOH solution as reaction mediate becomes much
sticky to barrier the collision between the reactants when the
added amount of NaOH is beyond 2.5 g. Under definite reaction
conditions, the highest conversions of 1-NA are at 66.18% and
are different too. Fig. 5 shows the best reacting times are
35–40 min for (FeTPPCl + H2O2) system and 5 h for (MnTP-
PCl + O2) system. Obviously, the strong oxidant H2O2 needs
much shorter time than the weak oxidant O2 does to make the
catalytic oxidative-coupling of 1-NA get equilibrium. Remark-
ably, after long time reaction (especially for the system with
suitable amount of H2O2 as much stronger oxidant), the yields
of BOBCHA do not descend any longer. Then BOBCHA can
be considered as a very stable product under the catalytic con-
ditions.
5
3.20% for O2 and H2O2 systems, respectively.
3
.2.4. Temperature impacting
Temperature is an important factor to accelerate chemical
3
.2.3. Reacting time selections
The oxidants of O2 and H2O2 are with different oxidative
rate, to shorten the equilibrium time and even to change the
reaction direction or to vary the products. For getting its influ-
ences on both H2O2 and O2 systems, the oxidative-couplings
were carried out at different temperatures. Fig. 6a shows the
temperature influencing on (H2O2 + FeTPPCl) system, and the
best temperature range is from 35 C to 40 C (308–313 K).
The yields of BOBCHA are lower when the reaction temper-
ature selected is out of the best range. Below 35 C or above
abilities. So the reaction rates between two catalysis systems
◦
◦
◦
◦
40 C, the reaction rate is small or the BOBCHA may be fur-
ther oxidized by H2O2, and as results to reduce the yield of
BOBCHA. But for (O2 + MnTPPCl) system (Fig. 6b), the yield
of BOBCHA ascends along with the reaction temperature ris-
ing, until reaching the reflux temperature of MeOH solution. So
BOBCHA could not be oxidized by the weaker oxidant of O2 at
the reflux temperature.
3.2.5. Influences of oxidant amount and reacting media for
(H2O2 + FeTPPCl) system
In the (H2O2 + FeTPPCl) system, the oxidant amount influ-
Fig. 4. NaOH dosage selection, VMeOH = 30 mL, m1−NA = 0.4 g. Change the
amount of NaOH. (a) H2O2 system: mFeTPPCl = 0.5 mg, VH O = 1.5 mL,
ence to the catalysis was investigated. Fig. 7 shows the best
amount of H2O2 (30 wt% aqueous solution) in preparing of
BOBCHA is 1.5 mL at adding rate of 1 drop/6 s. Under
2
2
t = 60 min, T = 313 K. (b) O2 system: mMnTPPCl = 1.5 mg, PO = 1 atm, t = 3 h,
2
T = 333 K.

T. Chen et al. / Journal of Molecular Catalysis A: Chemical 252 (2006) 56–62
61
medium should be strictly controlled for getting high conver-
sion from 1-NA to BOBCHA.
Summarizing all above, the optimizing catalytic con-
ditions to prepare BOBCHA are (1) for (O2 + MnTPPCl)
system: mMnTPPCl = 1.5 mg, m1−NA = 0.4 g, VMeOH = 30 mL,
◦
mNaOH = 2.5 g, t = 5 h, T = 333 K (60 C), PO = 1 atm, yield
2
BOBCHA = 78.51%; and (2) for (H2O2 + FeTPPCl) sys-
tem: mFeTPPCl = 3.0 mg, m1−NA = 0.4 g, VMeOH = 30 mL,
◦
◦
mNaOH = 2.5 g, t = 40 min, T = 308–313 K (35 C–40 C),
VH O = 1.5 mL, yieldBOBCHA = 79.62%.
2
2
4. Conclusions
1
-Naphthylamine (1-NA) can be converted into the novel
oxidative-coupling product of bis(4-oxo-benzo-2-cyclohexen-
-yl) amine (BOBCHA) over metalloporphyrin catalysts by
1
Fig. 6. Affirmance of reaction temperature, VMeOH = 30 mL, m1−NA = 0.4 g,
mNaOH = 2.5 g. (a) H2O2 system: mFeTPPCl = 0.5 mg, VH O = 1.5 mL, t = 1 h. (b)
both molecular oxygen and hydrogen peroxide aqueous solution
(30 wt%), respectively. The molecular structure of BOBCHA is
much different from that of 1,1 -bi-2-naphthol with 2-naphthol
2
2
O2 system: mMnTPPCl = 1.5 mg, PO = 1 atm, t = 3 h.
ꢀ
2
as reactant [30], and from that of the cross-coupling product with
2-naphthol and 2-naphthylamine as reactant [31,32], the tra-
ditional oxidative-coupling products. These oxidative-coupling
reactions exhibit characters as below: (1) relative low temper-
ature is needed in preparing BOBCHA with high selectivity
and conversion; (2) both strictly polarity and strong alkali of
the reacting medium is demanded, and more suitable reacting
media are methanol and ethanol; (3) low solubility of BOBCHA
makes it easy to separate from the reacting medium; (4) metallo-
porphyrin catalysts are stable enough to anti-oxidize and can be
reused after seperation; and (5) with a special molecular struc-
ture and color change property in different media, BOBCHA
would be found as a potential useful function material.
the definite conditions, excess amount of H2O2 will oxidize
BOBCHA to descend its yield.
Furthermore, different solvents were employed for selection
of reacting media in catalytic preparation of BOBCHA. Exper-
imental results indicate that both MeOH and EtOH are much
better solvents with suitable polarizing properties. Relatively,
water-soluble solvents, including acetonitrile, acetone and even
water itself, and other water-unsolvable solvents, including
ether, dichloromethane, chloroform, benzene and toluene, are
all unsuitable media for the catalytic oxidative-coupling of 1-
NA. Except methanol and ethanol, although sodium hydroxide
is with enough solubility in the other water-soluble solvents,
they can supply unsuitable polarities for the catalysis. Other-
wise, sodium hydroxide is undissolvable in the water-unsolvable
solvents for supplying the necessary alkaline to the catalysis.
Therefore, both the polarity and the alkaline of the reacting
Acknowledgement
Thanks professor K.P. Dennis Ng (Department of Chemistry,
The Chinese University of Hong Kong) for determination of the
1
H NMR.
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