A new method for the synthesis of iminoquinones via DMP-mediated oxidative reaction

Article abstract of DOI:10.1055/s-0030-1258202

Iminoquinones were synthesized by oxidation of primary and secondary amines with hypervalent iodine reagent Dess-Martin periodinane in average to good yields, and possible mechanisms were postulated. This methodology is convenient to establish a library of diversified iminoquinone compounds and has great significance for their potential application in the field of pharmaceuticals.

Full text of DOI:10.1055/s-0030-1258202

PAPER
3295
A New Method for the Synthesis of Iminoquinones via DMP-Mediated
Oxidative Reaction
S
ynthesis of Imino
e
quinone
s
ngchang Ma,*a Shang Wu,a Qiangsheng Sun,a Hongyan Li,a Yannan Chen,a Wenqing Zhao,a Bihui Ma,a
Qing Guo,a Ziqiang Lei,*a Jun Yanb
a
Key Laboratory of Polymer Materials of Gansu Province, Key Laboratory of Eco-Environment-Related Polymer Materials Ministry of
Education, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. of China
Zhejiang HISUN Pharmaceut Co. Ltd, Taizhou, Zhejiang 318000, P. R. of China
Fax +86(931)7970359; E-mail: mahc@nwnu.edu.cn
b
Received 20 May 2010; revised 17 June 2010
The iminoquinone moiety is important in a large number
of antineoplastic drugs and plays a significant role in the
nucleus of actinomycins, which are powerful, highly tox-
ic, natural antibiotics that target DNA as intercalating
Abstract: Iminoquinones were synthesized by oxidation of prima-
ry and secondary amines with hypervalent iodine reagent Dess–
Martin periodinane in average to good yields, and possible mecha-
nisms were postulated. This methodology is convenient to establish
a library of diversified iminoquinone compounds and has great sig- agents.17 Recently, we reported an efficient synthetic ap-
nificance for their potential application in the field of pharmaceuti-
cals.
proach to iminoquinone compounds via hypervalent io-
dine oxidation of primary amines. A variety of substituted
Key words: iodine, amines, oxidation, electron transfer, quinones,
quinone monoimines
primary amines were tested, and series of 2-amino-1,4-
benzoquinone 4-phenylimines were obtained in excellent
yields under mild conditions.18,19 In particular cases, two
useful compounds 4,4¢-diazenediyldianiline and 1-amino-
Hypervalent iodine compounds have proved to be mild 5-aza-10,11-dithiadibenza[a,d]cyclohepten-2-one were
and selective oxidizing agents in an impressive array of obtained, which are of great potential application in the
synthetic methodologies and have received much atten- fields of chemosensors and photochemical switches as
tion in recent years. 2-Iodoxybenzoic acid [IBX, 1-hy- well as pharmaceuticals.
droxy-1,2-benziodoxol-3(1H)-one 1-oxide] was first
Our first attempts to establish the generality of DMP oxi-
dized primary amine systems were inspiring. In ongoing
synthesized in 1893;1 however, it was rarely used in or-
ganic synthesis until 1983 when Dess and Martin trans-
research programs, we discerned that tetrabutylammoni-
formed IBX into the highly soluble Dess–Martin
um bromide (TBAB) is useful in some cases of IBX- or
DMP-involved oxidation transformations; it can be used
periodinane.2
Dess–Martin periodinane [DMP, 1,1,1-triacetoxy-1,1-di- as an activator for hypervalent iodine reagents. Initially,
hydro-1,2-benziodoxol-3(1H)-one] has emerged as the re- we applied tetrabutylammonium bromide as an additive in
agent of choice for the oxidation of primary and the 4-chloroaniline (1a)/DMP reaction system; thin-layer
secondary alcohols to aldehydes and ketones. The syn- chromatography (TLC) indicated that the starting material
thetic applications of DMP have been highlighted in a had been consumed within two hours. Much to our inter-
number of reviews.3 Its unique oxidizing properties and est, a different transformation had occurred. After isola-
convenience of use have ensured the advance DMP to a tion and characterization, the new compound was
widely employed reagent in the synthesis of biologically identified as brominated benzoquinone 2a (Scheme 1).
important natural products. Recently DMP was used Encouraged by this result, we next explored the scope of
in the key oxidation steps in the total syntheses of our newly developed process using various primary
cyclotheonamide B,4 ( )-deoxypreussomerin A,5 ra- amines 1; the results are summarized in Figure 1. It was
cemic brevioxime,6 erythromycin B,7 (+)-discoder- demonstrated that several p-substituted anilines 1a–f were
molide,8 (+)-cephalostatin 7,9 (+)-cephalostatin 12,9 (+)- smoothly converted into the corresponding brominated
ritterazine K,9 3-O-galloyl-(2R,3R)-epicatechin-4b,8-[3- benzoquinones 2a–f in average to good yields. In particu-
O-galloyl-(2R,3R)-epicatechin],10 fredericamycin A,11 in- lar, in the case of p-halo-substituted anilines 1a,d–f, the
dolizidine alkaloids (–)-205A, (–)-207A, and (–)-235B,12 one-step of oxidation and bromination was of excellent
1,19-aza-1,19-desoxy-avermectin B1a,13 angucytcline an- chemoselectivity. However, the limitation of our method-
tibiotics,14 tricyclic b-lactam antibiotics,15 and the platelet ology was obvious. The position of substitution has a de-
aggregation-inhibiting g-lactam PI-091.16
cisive impact on the transformation. With the exception of
p-substituted anilines, other substituted anilines gave ex-
clusively nonbrominated benzoquinone products or a
mixture of both products.
SYNTHESIS 2010, No. 19, pp 3295–3300
x
x.
x
x
.
2
0
1
0
Advanced online publication: 13.08.2010
DOI: 10.1055/s-0030-1258202; Art ID: F08410SS
© Georg Thieme Verlag Stuttgart · New York

3296
H. Ma et al.
PAPER
formation of tetrabutylammonium diacetoxybromate I.
Similarly, in our reaction system, it is envisaged that the
bromate I22 is formed in the first instance and it undergoes
addition to the double bond in II to form bromoacetoxy-
lated intermediate III. The acetate ion formed in the reac-
tion acts as a base to abstract hydrogen, which is acidic
due as a result of C=N conjugation and the electronegativ-
ity of bromine atom, to furnish the final product brominat-
ed benzoquinone IV (Scheme 2).
Recognizing that the scope and versatility of the reaction
could be enhanced if the library of starting materials was
expanded to other available compounds, our further ex-
plorations focused on the reaction of diphenylamines in
the presence of DMP. Despite great efforts, the most high-
ly substituted diphenylamine gave very complicated re-
sults under a variety of reaction conditions. Attempts to
further improve the yield of the major products were
thwarted by the increased production of side products.
Conversely, in special cases, iminoquinones could be
formed predominately by correct choice of the designated
position and the nature of the specific functional group.
When the diphenylamine contains a p-methoxy group, the
reaction could be carried out successfully. Apart from this
particular case, other alkoxy-substituted diphenylamines
gave poor results, for instance, ethoxy, phenoxy, and vi-
nyloxy. As a result, the remarkable collaboration of both
NH and OMe groups renders this methodology to be one
with unique chemoselectivity.
Scheme 1 Synthesis and X-ray crystal structure of 2a20
Br
Br
N
NH2
O
N
NH2
O
Cl
Cl
2a
2b
2 h, 75%
4.5 h, 54%
Br
Br
N
NH2
O
N
NH2
Br
Br
MeO
O
O
Me
2c
6 h, 43%
2d
3 h, 73%
Our initial screening experiments chose 4-methoxy-2-
methyl-N-(2-tolyl)aniline (3a) as a model substrate
(Table 1). Investigations on a variety of reaction condi-
tions established that in the presence of a small amount of
water (20% mol), 3a (1 mmol) and DMP (1.8 mmol) dis-
solved in dichloromethane (2 mL) and stirred at room
temperature for five hours gave the desired product 4a in
87% yield (entry 10). We reasoned that the DMP partially
hydrolyzed by small amount water is of stronger nucleo-
philicity. However, in aqueous media formation of com-
pound 4a was suppressed, resulting in a more complicated
product mixture. It also should be noted that when tetrabu-
tylammonium bromide was applied as an additive, no bro-
minated compound was observed, and also no apparent
promotion effect was detected.
Br
Br
N
NH2
N
F
NH2
O
I
I
O
F
2e
4 h, 66%
2f
5 h, 67%
Figure 1
Akamanchi and co-workers reported a one-step procedure
for preparation of brominated unsaturated carbonyl com-
pounds.21 In this case, the acetate ligand of DMP is prob-
ably transferred to tetrabutylammonium bromide forming
an orange-yellow solution, which may be attributed to the
OAc
AcO
OAc
OAc
I
I
OAc
OAc
Q+Br–
O
+
Q+Br–
+
O
Q = Bu4N
O
O
Ac-IBA
I
– OAc
Br
Br
H
N
NH2
O
N
NH2
O
N
NH2
OAc
O
– AcOH
Q+
OAc–
+
I
+
Cl
Cl
Cl
Cl
Cl
Cl
IV (2a)
III
II
Scheme 2 The postulated mechanism
Synthesis 2010, No. 19, 3295–3300 © Thieme Stuttgart · New York

PAPER
Synthesis of Iminoquinones
3297
Table 1 Optimization of the Reaction Conditionsa
on the benzene ring. Electron-donating groups have evi-
dent positive effects. Methyl-substituted substrate 3c was
converted into iminoquinone 4c in 65% yield (entry 3);
however, for the chlorinated substrate 3h, the reaction was
not only relatively sluggish (12 h), but also the isolated
yield of 4h was less than 50% (entry 8). For the multiply
substituted p-methoxy-substituted diphenylamines, high
steric hindrance around the NH group demonstrated no
negative effect and compounds 3a,e–g reacted to give the
corresponding products 4a,e–g in high isolated yields in
less than five hours.
Based on a previous report,23 we proposed a pathway
based on single electron transfer (SET) mechanism
(Scheme 3). The hydrolyzed DMP reagent Ac-IBX acts as
an extraordinary oxidant which then initiates the single
electron transfer from substrate 3b to give intermediate V.
After releasing the hydrogen proton, V should rapidly
lead to species VI, the resultant free radical VI was prob-
ably less stable than its resonance form VII, with the sin-
gle electron located at the methoxy-attached carbon.
Consequently, because of the potential urgency to form a
larger conjugative effect, the methyl radical was freed
from intermediate VII, and the final product 4b was
achieved.
H
N
N
DMP, solvent
r.t.
O
OMe
4a
3a
Entry
DMP (mmol) Solvent
Additive (mmol) Yield (%)
1
2
1.0
1.0
1.0
1.0
1.0
1.0
1.2
1.4
1.6
1.8
CH2Cl2
CHCl3
acetone
CH2Cl2
H2O
–
27
15
20
35
–
3
–
4
H2O (0.2)
–
b
5
–
6
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
TBAB (1.0)
H2O (0.2)
H2O (0.2)
H2O (0.2)
H2O (0.2)
26
64
74
70
87
7
8
9
10
a 3a (1.0 mmol), solvent (2 mL), air atmosphere, r.t., 5 h.
b No reaction.
In conclusion, from the transformation of two classes of
amines, iminoquinones were obtained; in particular the
brominated products lend themselves to establish easily a
library of diversified iminoquinones. The significance of
this reaction gives iminoquinones a more important place
in the field of potential pharmaceuticals applications.
Meanwhile, the apparent collaboration of the specific
structure and designated position of functional groups in
the aromatic rings gives this methodology unique
chemoselectivity.
Having established suitable reaction conditions for the ox-
idation of diphenylamines with DMP, we proceeded to in-
vestigate the scope and limitation of this new
methodology. A variety of p-methoxy-substituted diphe-
nylamines 3 were employed, a selection of pertinent ex-
amples is displayed in Table 2. All diphenylamines 3a–i
employed were converted into the corresponding imino-
quinones 4a–i in good yields. In general, yields were
higher for the multiply substituted diphenylamines than
those for less-substituted diphenylamines. For instance, 4-
methoxy-N-phenylaniline (3a), 4-methoxy-2-methyl-N-
phenylaniline (3d), and N-(2-chlorophenyl)-4-methoxy-
aniline (3h) as well as 4-methoxy-N-(biphenyl-4-
yl)aniline (3i) gave the corresponding products 4 with av-
erage yields. Notably, the reactions were also significant-
ly affected by the electronic properties of the substituents
All NMR spectra were recorded on a Brüker Avance Digital spec-
trometer [400 MHz (1H), 100 MHz (13C)]; TMS as the internal ref-
erence in CDCl3. IR spectra were recorded on a Shimadzu IR-408
spectrometer. Mass spectra were recorded on a HP5989B mass
spectrometer. Melting points were uncorrected. Room temperature =
15–25°C.
OAc
–O
OAc
AcO
I
OAc
H2O
I
O
H
N
O
[SET]
Ac-IBX
O
O
ref. 23
MeO
V
H
N
– [H]+
MeO
3b
N
N
N
_
Me
MeO
MeO
VI
O
4b
VII
Scheme 3 The postulated mechanism
Synthesis 2010, No. 19, 3295–3300 © Thieme Stuttgart · New York

3298
H. Ma et al.
PAPER
Table 2 Scope of the Substrates 3 for the Formation of Iminoquinones 4a
Entry
1
Substrateb
Time (h)
5
Product
Yieldc (%)
H
N
N
N
87
OMe
OMe
O
O
4a
4b
3a
H
N
2
3
8
5
56
65
3b
3c
H
N
N
O
OMe
4c
H
N
N
4
5
6
7
4
3
3
3
54
78
80
84
OMe
O
3d
3e
4d
4e
H
N
N
OMe
O
H
N
N
MeO
OMe
MeO
O
4f
3f
H
N
N
N
OMe
OMe
O
O
4g
3g
Cl
H
Cl
N
8
9
12
12
47
54
3h
4h
H
N
N
O
OMe
4i
3i
a Substrates are commercially available and used without further purification.
b Conditions: substrate 3 (1.0 mmol), DMP (1.8 mmol), CH2Cl2 (2 mL), H2O (0.2 mmol), r.t.
c Yields indicate product obtained after column chromatography.
Brominated Benzoquinones 2; General Procedure
to afford a soln 2, which was volatilized at r.t. for period during
which time crystallized compounds were formed.
To a soln of DMP (1.3 g, 2.64 mmol) in CH2Cl2 (5 mL) was added
TBAB (0.64 g, 2.0 mmol) and aniline 1 (1.5 mmol). The mixture
was stirred at r.t. until complete consumption of the aniline (TLC).
The soln was washed with H2O (3 × 5 mL) and the organic phase
was dried (anhyd Na2SO4). After filtration, the solvent was removed
and the residue was purified by column chromatography (silica gel)
Benzoquinones 4; General Procedure
To a soln of DMP (0.89 g, 1.8 mmol) in CH2Cl2 (5 mL) was added
aniline 3 (1.0 mmol) and H2O (0.2 mmol) was added dropwise. The
mixture was stirred at r.t. until complete consumption of the aniline
Synthesis 2010, No. 19, 3295–3300 © Thieme Stuttgart · New York

PAPER
Synthesis of Iminoquinones
MS (FAB): m/z = 211.1 [M + H]+.
3299
(TLC), and purified by column chromatography (silica gel) to af-
ford 4.
4-(Phenylimino)cyclohexa-2,5-dienone (4b)
2-Amino-3-bromo-5-chloro-4-(4-chlorophenylimino)cyclo-
hexa-2,5-dienone (2a)
Red solid; mp 150–152 °C.
Red oil.
IR (KBr): 3358, 1650, 1600, 1580, 1453, 1432, 875, 863 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.40–7.39 (t, J = 8.0, 7.6 Hz, 2 H),
7.32–7.22 (m, 2 H), 7.10–7.07 (dd, J = 2.4 Hz 1 H), 6.89–6.87 (d,
J = 8.0 Hz, 2 H), 6.71–6.68 (dd, J = 2.0 Hz 1 H), 6.55–6.52 (m, 1
H).
13C NMR (100 MHz, CDCl3): d = 187.5, 157.3, 149.3, 141.8, 133.4,
128.9, 126.1, 120.6.
IR (KBr): 3477, 3385, 1650, 1618, 1575, 1460, 1200, 1055, 1021,
975, 868 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.32–7.27 (m, 2 H), 6.89 (s, 1 H),
6.76–6.72 (m, 2 H), 5.21 (s, 2 H).
13C NMR (100 MHz, CDCl3): d = 181.2, 157.3, 150.8, 147.2, 132.8,
130.2, 123.7, 119.6, 117.6, 110.5.
MS (FAB): m/z = 345.9 [M + H]+.
MS (FAB): m/z = 183.1 [M + H]+.
4-(4-Tolylimino)cyclohexa-2,5-dienone (4c)
Red oil.
IR (KBr): 3346, 1648, 1612, 1580, 1467, 1438, 981, 865, 821 cm–1.
Anal. Calcd for C12H7BrCl2N2O: C, 41.65; H, 2.04; N, 8.10. Found:
C, 41.68; H, 2.08; N, 7.93.
2-Amino-3-bromo-5-methyl-4-(4-tolylimino)cyclohexa-2,5-di-
enone (2b)
Red solid; mp 138–140 °C.
1H NMR (400 MHz, CDCl3): d = 7.50 (s, 1 H), 7.39–7.37 (m, 1 H),
7.24–7.22 (d, J = 8.0 Hz, 1 H), 7.16–7.13 (m, 1 H), 6.96–6.93 (dd,
J = 2.4 Hz, 1 H), 6.83–6.81 (d, J = 8.0 Hz, 1 H), 6.73–6.67 (m, 1 H),
6.55–6.52 (m, 1 H), 2.37 (S, 3 H).
13C NMR (100 MHz, CDCl3): d = 187.7, 158.4, 145.3, 133.4, 129.6,
128.2, 121.0, 120.5, 20.5.
IR (KBr): 3485, 3364, 1650, 1612, 1545, 1460, 1210, 1165, 1080,
865, 838 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.14–7.12 (d, J = 8.0 Hz, 2 H),
6.68–6.66 (d, J = 8.0 Hz, 2 H), 6.48 (s, 1 H), 5.10 (s, 2 H), 2.34 (s,
6 H).
MS (FAB): m/z = 197.1 [M + H]+.
13C NMR (100 MHz, CDCl3): d = 179.8, 150.8, 143.9, 133.4, 129.1,
126.2, 118.8, 118.6, 117.7, 117.6, 29.6, 20.9.
3-Methyl-4-(phenylimino)cyclohexa-2,5-dienone (4d)
Red oil.
MS (FAB): m/z = 304.0 [M + H]+.
IR (KBr): 3346, 1648, 1612, 1580, 1467, 1438, 981, 865, 821 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.40–7.36 (t, J = 7.6 Hz, 2 H),
7.22–7.18 (t, J = 8.0 Hz, 1 H), 7.08–6.94 (m, 1 H), 6.84–6.82 (d,
J = 7.6 Hz, 2 H), 6.55 (s, 1 H), 6.44–6.41 (m, 1 H), 2.27 (s, 3 H).
13C NMR (100 MHz, CDCl3): d = 187.7, 157.7, 149.5, 149.4, 132.6,
130.8, 128.8, 128.5, 125.6, 119.9, 18.0.
2-Amino-3,5-dibromo-4-(4-bromophenylimino)cyclohexa-2,5-
dienone (2d)
Red solid; mp 147–149 °C.
IR (KBr): 3476, 3380, 1662, 1620, 1580, 1460, 1210, 1010, 1000,
985, 856 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.35–7.29 (m, 2 H), 6.87 (s, 1 H),
6.74–6.70 (m, 2 H), 5.24 (s, 2 H).
13C NMR (100 MHz, CDCl3): d = 182.2, 156.4, 155.8, 143.2, 130.8,
130.2, 124.8, 119.2, 116.6, 110.4.
MS (FAB): m/z = 197.1 [M + H]+.
4-(2,4-Dimethylphenylimino)-3-methylcyclohexa-2,5-dienone
(4e)
Red oil.
MS (FAB): m/z = 433.8 [M + H]+.
IR (KBr): 3348, 1658, 1600, 1580, 1478, 1369, 1002, 756, 654
cm–1.
2-Amino-3-bromo-5-iodo-4-(4-iodophenylimino)cyclohexa-2,5-
dienone (2e)
Red solid; mp 155–157 °C.
1H NMR (400 MHz, CDCl3): d = 7.09 (s, 1 H), 7.02–6.99 (d, J = 9.6
Hz, 2 H), 6.57 (s, 1 H), 6.49–6.42 (m, 2 H), 2.35 (s, 3 H), 2.33 (s, 3
H), 2.15 (s, 3 H).
IR (KBr): 3480, 3370, 1650, 1600, 1575, 1458, 1232, 1000, 975,
862 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.42–7.32 (m, 2 H), 6.77 (s, 1 H),
6.75–6.72 (m, 2 H), 5.35 (s, 2 H).
13C NMR (100 MHz, CDCl3): d = 188.0, 157.1, 149.6, 145.9, 135.8,
132.3, 131.4, 130.6, 129.6, 128.7, 126.6, 118.8, 20.9, 18.1, 17.9.
MS (FAB): m/z = 225.1 [M + H]+.
13C NMR (100 MHz, CDCl3): d = 182.2, 156.4, 155.8, 143.2, 130.8,
130.2, 124.8, 119.2, 116.6, 110.4.
4-(4-Methoxy-2-methylphenylimino)-3-methylcyclohexa-2,5-
dienone (4f)
Red oil.
MS (FAB): m/z = 527.8 [M + H]+.
IR (KBr): 3356, 1660, 1612, 1585, 1450, 1365, 1012, 778, 754
cm–1.
3-Methyl-4-(2-tolylimino)cyclohexa-2,5-dienone (4a)
Red oil.
1H NMR (400 MHz, CDCl3): d = 7.07 (s, 1 H), 7.02–6.99 (d, J = 9.6
Hz, 2 H), 6.57 (s, 1 H), 6.48–6.42 (m, 2 H), 3.73 (s, 3 H), 2.36 (s, 3
H), 2.13 (s, 3 H).
IR (KBr): 3356, 1650, 1612, 1570, 1480, 1356, 1034, 766, 654
cm–1.
1H NMR (400 MHz, CDCl3): d = 7.11 (s, 1 H), 7.01–6.98 (d, J = 9.6
13C NMR (100 MHz, CDCl3): d = 187.0, 156.1, 148.6, 145.5, 136.8,
Hz, 2 H), 6.57 (s, 1 H), 6.49–6.42 (m, 3 H), 2.33 (s, 3 H), 2.16 (s, 3
H).
134.3, 131.4, 130.4, 129.2, 128.4, 126.6, 116.8, 54.9, 18.1, 17.9.
MS (FAB): m/z = 241.1 [M + H]+.
13C NMR (100 MHz, CDCl3): d = 178.0, 156.1, 148.6, 145.5, 135.3,
133.3, 131.4, 130.4, 129.4, 128.7, 123.6, 118.8, 20.9, 17.9.
Synthesis 2010, No. 19, 3295–3300 © Thieme Stuttgart · New York

3300
H. Ma et al.
PAPER
4-(2,6-Dimethylphenylimino)-3-methylcyclohexa-2,5-dienone
(4g)
References
(1) Hartmann, C.; Meyer, V. Ber. Dtsch. Chem. Ges. 1893, 26,
1727.
Red oil.
IR (KBr): 3350, 1648, 1600, 1570, 1488, 1374, 1012, 764, 664
cm–1.
1H NMR (400 MHz, CDCl3): d = 7.07–7.05 (d, J = 8.0 Hz, 2 H),
6.99–6.97 (m, 1 H), 6.63–6.60 (d, J = 10.0 Hz, 1 H), 6.56 (s, 1 H),
6.37–6.34 (m, 1 H), 2.36 (s, 3 H), 1.96 (s, 6 H).
13C NMR (100 MHz, CDCl3): d = 187.6, 158.8, 149.0, 147.8, 132.6,
130.9, 128.3, 127.8, 124.8, 124.3, 18.1, 17.9.
(2) Dess, B. D.; Martin, J. C. J. Org. Chem. 1983, 48, 4155.
(3) (a) Speicher, A.; Bomm, V.; Eicher, T. J. Prakt. Chem. 1996,
338, 588. (b) Chaudhari, S. S. Synlett 2000, 278.
(c) Ladziata, U.; Zhdankin, V. V. ARKIVOC 2006, (ix), 26.
(4) Bastiaans, H. M. M.; Van der Baan, J. L.; Ottenheijm, H. C.
J. J. Org. Chem. 1997, 62, 3880.
(5) Wipf, P.; Jung, J.-K. J. Org. Chem. 1998, 63, 3530.
(6) Clive, D. L. J.; Hisaindee, S. Chem. Commun. 1999, 2251.
(7) Martin, S. F.; Hida, T.; Kym, P. R.; Loft, M.; Hodgson, A. J.
Am. Chem. Soc. 1997, 119, 3193.
(8) Paterson, I.; Florence, G. J.; Gerlach, K.; Scott, J. P.;
Sereinig, N. J. Am. Chem. Soc. 2001, 123, 9353.
(9) Jeong, J. U.; Guo, C.; Fuchs, P. L. J. Am. Chem. Soc. 1999,
121, 2071.
(10) Tueckmantel, W.; Kozikowski, A. P.; Romanczyk, L. J. Am.
Chem. Soc. 1999, 121, 12073.
(11) Kita, Y.; Higuchi, K.; Yoshida, Y.; Lio, K.; Kitagaki, S.;
Ueda, K.; Akai, S.; Fujioka, H. J. Am. Chem. Soc. 2001, 123,
3214.
(12) Comins, D. L.; LaMunyon, D. H.; Chen, X. J. Org. Chem.
1997, 62, 8182.
(13) Meinke, P. T.; Arison, B.; Culberson, J. C.; Fisher, M. H.;
Mrozik, H. J. Org. Chem. 1998, 63, 2591.
(14) Larsen, D. S.; O’Shea, M. D. J. Org. Chem. 1996, 61, 5681.
(15) Niu, C.; Pettersson, T.; Miller, M. J. J. Org. Chem. 1996, 61,
1014.
MS (FAB): m/z = 225.1 [M + H]+.
4-(2-Chlorophenylimino)cyclohexa-2,5-dienone (4h)
Red oil.
IR (KBr): 3358, 1652, 1600, 1589, 1478, 1465, 1121, 876, 769, 664
cm–1.
1H NMR (400 MHz, CDCl3): d = 7.49–7.47 (m, 1 H), 7.39–7.36 (m,
1 H), 7.32–7.28 (m, 1 H), 7.20–7.15 (m, 1 H), 6.91–6.88 (m, 1 H),
6.79–6.77 (m, 1 H), 6.74–6.71 (m, 1 H), 6.55–6.52 (m, 1 H).
13C NMR (100 MHz, CDCl3): d = 187.2, 158.8, 146.5, 141.2, 133.6,
133.2, 130.1, 128.3, 127.1, 126.6, 124.6, 120.7.
MS (FAB): m/z = 217.0 [M + H]+.
4-(Biphenyl-4-ylimino)cyclohexa-2,5-dienone (4i)
Red oil.
IR (KBr): 3358, 1650, 1610, 1586, 1478, 1454, 1006, 965, 875
cm–1.
1H NMR (400 MHz, CDCl3): d = 7.67–7.62 (m, 4 H), 7.49–7.45 (t,
J = 7.6 Hz, 2 H), 7.40–7.32 (m, 2 H), 7.21–7.18 (m, 1 H), 7.01–6.99
(d, J = 8.4 Hz, 2 H), 6.74–6.71 (dd, J = 2.0 Hz, 1 H), 6.59–6.56 (dd,
J = 2.4 Hz, 1 H).
13C NMR (100 MHz, CDCl3): d = 187.6, 157.4, 148.5, 141.8,
140.0, 139.3, 133.4, 132.8, 128.9, 127.7, 126.9, 121.5.
MS (FAB): m/z = 259.1 [M + H]+.
(16) Shiraki, R.; Sumino, A.; Tadano, K.-I.; Ogawa, S. J. Org.
Chem. 1996, 61, 2845.
(17) (a) Bolognese, A.; Scherillo, G.; Schäfer, W. J. Heterocycl.
Chem. 1986, 23, 1003. (b) Bolognese, A.; Piscitelli, C.;
Scherillo, G. J. Org. Chem. 1983, 48, 3649. (c) Nan’ya, S.;
Maekawa, E.; Hayakawa, H.; Kitaguchi, Y.; Ueno, Y.
J. Heterocycl. Chem. 1985, 22, 1483. (d) Ueno, Y.
Pharmazie 1986, 41, 144.
(18) Ma, H.-C.; Jiang, X.-Z. Synthesis 2007, 412.
(19) Ma, H.-C.; Jiang, X.-Z. Synlett 2007, 1679.
(20) CCDC 643540 contains supplementary crystallographic
data for compound 2a; data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
Acknowledgment
We are grateful for the financial support of the National Natural
Science Foundation of China (No.20376071, No. 20674063 and
20774074) and Young Teacher Research Foundation of Northwest
Normal University (NWNU-LKQN-08-8, NWNU-kjcxgc-03-73).
We also thank Key Laboratory of Eco-Environment-Related Poly-
mer Materials (Northwest Normal University), Ministry of Educa-
tion, for financial support.
(21) Ramanarayanan, G. V.; Shukla, V. G.; Akamanchi, K. G.
Synlett 2002, 2059.
(22) Sourkouni-Argirusi, G.; Kirschning, A. Org. Lett. 2000, 2,
3781.
(23) Nicolaou, K. C.; Baran, P. S.; Kranich, R.; Zhong, Y.-L.;
Sugita, K.; Zou, N. Angew. Chem. Int. Ed. 2001, 40, 202.
Synthesis 2010, No. 19, 3295–3300 © Thieme Stuttgart · New York