Selective introducing of aryl and amino groups: Reaction of benzanthrone and organometallic reagents

Article abstract of DOI:10.1016/j.tet.2012.12.013

The reaction of benzanthrone and aryl magnesium bromides produced 6-aryl-substituted benzanthrones in moderate to good yields. Similarly, 6-alkylaminobenzanthrones were selectively prepared by the reaction of benzanthrone and lithium alkylamides. In contrast, for the lithium arylamides, the arylamino groups were selectively introduced at the 4-position of the benzanthrone.

Full text of DOI:10.1016/j.tet.2012.12.013

Tetrahedron xxx (2012) 1e6
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Selective introducing of aryl and amino groups: reaction of benzanthrone and
organometallic reagents
*
Rui Umeda, Teruaki Namba, Tomohiro Yoshimura, Masamichi Nakatsukasa, Yutaka Nishiyama
Department of Chemistry and Material Engineering, Faculty of Chemistry, Material and Bioengineering, Kansai University, Suita, Osaka 564-8680, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of benzanthrone and aryl magnesium bromides produced 6-aryl-substituted benzanthrones
in moderate to good yields. Similarly, 6-alkylaminobenzanthrones were selectively prepared by the re-
action of benzanthrone and lithium alkylamides. In contrast, for the lithium arylamides, the arylamino
groups were selectively introduced at the 4-position of the benzanthrone.
Received 11 September 2012
Received in revised form 5 December 2012
Accepted 5 December 2012
Available online xxx
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Arylation
Amination
Benzanthrone
1. Introduction
On the other hand, the syntheses of 6-substituted benzan-
throne derivatives have been reported.10,11 In the mid-1930s to
The applications of
p
-extendedcompoundshave been intensively
1950, 6-phenylbenzanthrone was prepared by the treatment of 1
with phenyl magnesium bromide or phenyl sodium in moderate
to good yields.10aed After that, Allen found that the yield of
6-phenylbenzanthrone was improved by the use of excess
amounts of phenyl magnesium chloride in the presence of copper
salts.10e Very recently, Hopf and Johannes reported that the 1,4-
addition reaction of biphenyl-2-yl lithium to 1 selectively pro-
ceeded to form the corresponding stable enol, and the enol was
transformed into two intramolecular cyclization products having
spiro and bicyclic structures together with the formation of the 6-
(2-biphenyl)benzanthrone under acidic conditions.10f Direct ami-
nation of 1 by the treatment with the sodium amide derivatives
has also been reported.12 Based on these aminations, the 4- or 6-
aminobenzanthrones have been prepared. However, the limita-
tion of amination and relationship between the selectivity of
products and reagents were not clearly discussed.
studied as organic electronic materials, such as organic field-effect
transistors (OFETs), organic light-emitting diodes (OLEDs), and or-
ganic solar cells.1 It is well-known that benzanthrone (1) and its
derivatives have shown a bright fluorescence and high photostability
and have been used as daylight fluorescent pigments for synthetic
textile materials and mass coloration of polymeric materials.2,3
Recently, their applications as a fluorescent probe for amyloid
fibrils,4 fluorescentdyesinaliquidcrystals,5 OLEDs,6 and green-light-
emitting polymer7 have been reported; however, most of these
reports have appeared based on the utilization of 3-substituted
benzanthrones derived from 3-bromo- and 3-nitrobenzanthrones,
which were easily prepared by the bromination8 and nitration9 of 1.
Therefore, the development of syntheticmethods for the introducing
of functional groups at the other positions of the benzanthrone is still
a challenging topic in organic and material chemistry.
In this paper, to elucidate the scope and limitations of the re-
action of 1 with various organometallic reagents, we investigated
the reaction of 1 with various aryl magnesium bromides and lith-
ium alkylamides and found that the 6-aryl and 6-alkylamino-
substituted benzanthrones were formed, respectively, in moderate
to good yields. Furthermore, it is clearly noted that the 4-aryla-
mino-substituted benzanthrones were selectively prepared by the
reaction of 1 and lithium arylamides.
O
1
2
6
5
4
3
1
* Corresponding author. Tel.: þ81 6 6368 0902; fax: þ81 6 6339 4026; e-mail
address: nishiya@kansai-u.ac.jp (Y. Nishiyama).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.12.013
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2
R. Umeda et al. / Tetrahedron xxx (2012) 1e6
Table 2
2. Results and discussion
Reaction of 1 and lithium di-n-butylamide
First, the reaction of 1 with phenyl magnesium bromide
(2.0 equiv) at room temperature followed by the addition of water
formed the corresponding enol derivative 2a. Although the iso-
lation of the enol 2a was tried by chromatography on SiO2 or a re-
cyclable preparative HPLC, 6-phenylbenzanthrone (3a) instead of
2a was obtained. It was found that even when the solution of the
crude enol 2a in CHCl3 was stirred at room temperature under air,
6-phenylbenzanthrone (3a) was obtained in good yield (86% from
1) (entry 1 in Table 1). Compared to the Allen’s condition10e the
larger amount of Grignard reagents, additive, and heating were not
required in this condition.
n-C4H9
n-C4H9
O
H2O
1
NLi
+
N
n-C4H9
THF
n-C4H9
0 °C to r.t.
(1.0 mmol)
4a
Entry
Amide (mmol)
1, Recoverya (%)
4a, Yielda (%)
1
2
3
1.5
2.0
3.0
5.0
3.0
3.0
99
54
24
25
15
99
Trace
17
62
35
18
4
5b
6c
0
Table 1
a
Isolated yields from 1.
Reaction of 1 and various aryl magnesium bromides
b
c
Reaction was carried out at 80 ꢀC.
Ar-MgBr
n-Bu2NMgBr was used instead of n-Bu2NLi.
(2.0 equiv.)
H2O
HO
O
1
H
Ar
Ar
THF
r.t.
CHCl3
r.t.
R
NLi
R
(1.0 mmol)
2
3
R O
N
(3.0 equiv.)
H2O
Entry
Ar
3, Yielda (%)
1
THF
R
1
2
3
4
5
6
7
C6H5
4-CH3C6H4
4-CH3OC6H4
4-(CH3)2NC6H4
3,5-Di-t-Bu-4-TMSOC6H2
4-FC6H4
3a, 86
3b, 90
3c, 68
3d, 73
3e, 78
3f, 53
3g, 54
0 °C to r.t.
(1.0 mmol)
R
4
i-C3H7
i-C3H7
C2H5
N-
N-
N-
,
=
O
N-
,
R
Bn
4c (39%)
2-Thienyl
4b (35%)
4d (22%)
a
Isolated yields from 1.
Scheme 1. Reaction of 1 and various lithium alkylamides.
To study the scope and limitations of the substrates, benzan-
throne (1) was treated with various aryl magnesium bromides and
these results are shown in Table 1. The 4-methyl derivative 3b was
obtained in 90% yield (entry 2), whereas the yields of the methoxy
and N,N-dimethylamino derivatives 3c,d slightly were decreased
(entries 3 and 4). The di-tert-butylphenoxy trimethylsilane de-
rivative 3e was also obtained in a good yield (entry 5). The arylation
of 1 with the 4-fluorophenyl magnesium bromide occurred to give
3f in a moderate yield (entry 6). For the reaction of the 2-thienyl
magnesium bromide, 6-(2-thienyl)benzanthrone (3g) was ob-
tained in 54% yield (entry 7).
Next, the reaction of 1 with lithium di-n-butylamide was ex-
amined under various conditions and these results are shown in
Table 2. The treatment of 1 with 1.5 equiv of lithium di-n-butyla-
mide gave a trace amount of 6-(N,N-di-n-butylamino)benzan-
throne (4a) and 1 was almost quantitatively recovered (entry 1).
When 2.0 equiv of lithium di-n-butylamide was used, 4a was ob-
tained in 17% (entry 2). In the case of using the 3.0 equiv of lithium
amide, 4a was formed as the sole product in 62% yield together
with the recovered 1 (24%) (entry 3). In this case, 1H NMR spectra of
the crude reaction mixture clearly showed the peaks of 1 and 4a
and did not detect the 1,4-addition product. However, with in-
creasing the amount of lithium amide or under higher reaction
temperature, the yield of 4a was decreased due to the formation of
unidentified products (entries 4 and 5). The use of magnesium di-n-
butylamide instead of lithium di-n-butylamide did not give 4a and
starting material 1 was recovered (entry 6).
afford the 6-aminobenzanthrones, 4c and 4d, in 39% and 22% yields,
respectively.13,14 When other lithium cyclic amides prepared from
pyrrolidine and piperidine were used, no formation of the corre-
sponding amino-substituted benzanthrones was observed.
Notably, in the case of lithium methylphenylamide, the N-
methylphenylamino group was selectively introduced at the 4-
position of 1 to give 5a in 53% yield (Scheme 2).13 The structure
of the product 5a was assigned by 1H, 13C NMR, and COSY experi-
ments (see, Supplementary data). Also, the reaction of 1 with
lithium arylamides, which were generated by the reaction of N,N-
diphenylamine, N,N-di(4-tert-butylphenyl)amine, or carbazole
with n-butyl lithium, selectively formed the corresponding 4-
substituted benzanthrones 5bed.13
Although Hopf and Johannes suggested the reaction pathway
involving the protonation of the enol derivative, 1,4-addition
product, to form the oxionium ion followed by the retro-[2þ4]
R1
NLi
R2
O
H2O
(3.0 equiv.)
1
THF
0 °C to r.t.
(1.0 mmol)
N
R2
R1
5
Next, the reaction of 1 with lithium alkylamides was examined
under the optimized conditions as entry 3 in Table 2 (Scheme 1).
Surprisingly, whenever lithium diisopropylamide (LDA), which is
a well-known hindered amide base with a low nucleophilicity, was
allowed to react with 1, 4b was obtained in 35% yield.13 The reaction
of 1 with lithium benzylamide and a cyclic amide proceeded to
Ph
R1
R2
Ph
4-t-BuC6H4
N-
N-
N-
=
N-
,
,
,
N
H3C
Ph
4-t-BuC6H4
5c (9%)
5a (53%) 5b (11%)
5d (6%)
Scheme 2. Reaction of 1 and various lithium arylamides.
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R. Umeda et al. / Tetrahedron xxx (2012) 1e6
3
cycloaddition leading to the losing hydrogen and proton, no direct
Ph
H3C
43%
experimental evidence was shown in the report.10f To clarify the
reaction pathway of the transformation of 2a into 3a, we carried out
some investigations. First, the production of hydrogen did not
detected by GC after stirring the solution of the crude 2a in CHCl3,
though 3a was formed. Moreover, the transformation of 2a to 3a
was proceeded under basic conditions using Et3N and CHCl3 (1:9)
as the solvent under air. When a solution of crude 2a in degassed
CHCl3 was stirred under a nitrogen atmosphere, no formation of 3a
was observed.15 Thus, it was assumed that dehydrogenated prod-
ucts 3 were formed by the oxidation of the 1,4-addition products 2.
The possible reaction pathways are shown in Scheme 3. First, the
NLi
MgBr
90%
3b
O
1
N
Ph
Ph
CH3
5a
NLi
MgBr
10
H3C
53%
53%
Scheme 5. Synthesis of 4,6-disubstituted benzanthrone 10.
Ar MgBr
HO
3-substituted benzanthrones 8, which were easily prepared by the
coupling reaction of 3-bromobenzanthrone with diphenylamine, 4-
t-butylphenylborane, phenyl acetylene or 4-t-butylphenol, were
allowed to react with p-tolylmagnesium bromide, the corre-
Oxidation
1,4-Addition
3
H
Ar
sponding 3,6-disubstituted benzanthrones
(Scheme 4).
9 were obtained
2
Alk
Next, the synthesis of the 4,6-disubstituted benzanthrone from
1 using two routes was examined. The reaction of 3b, which was
prepared by the reaction of 1 with p-tolylmagnesium bromide,
with lithium methylphenylamide afforded the 4-(N-methyl-
phenylamino)-6-(p-tolyl)benzanthrone (10) in 43% yield. Com-
pound 10 was also successfully synthesized by the reaction of 4-
(N,N-methylphenylamino)benzanthrone (5a) with p-tolylmagne-
sium bromide in 53% yield (Scheme 5).
NLi
Alk
1,4-Addition
HO
H
Oxidation
1
4
Alk
N
Alk
6
Ar
NLi
R
HO
H
1,6-Addition
Oxidation
5
3. Conclusion
In conclusion, we developed the selective synthesis of 6-aryl-
and 6-amino-substituted benzanthrones, 3 and 4, by the reaction of
benzanthrone (1) with the aryl magnesium bromides and the
lithium alkylamides. Interestingly, the reaction of 1 with the lith-
ium arylamides selectively gave the 4-amino-substituted benzan-
thrones 5. This methodology can provide a simple access to a range
of valuable 6- and 4-substituted benzanthrone derivatives. Im-
provement of the yields of the amino-substituted products 4 and 5
and investigation of the difference in reactivity between the lith-
ium alkylamides and arylamides are currently underway. Also, the
preparation of multiple substituted benzanthrones using this
methodology is being undertaken in our laboratories.
N
Ar
R
7
Scheme 3. Plausible reaction pathways.
1,4-addition of aryl magnesium bromides and lithium alkylamides
or 1,6-addition of lithium arylamides toward 1 affords the enols 2,
6, and 7 having the phenanthrene moiety. The enols 2, 6, and 7
were oxidized by oxygen in the air to form the corresponding
substituted products 3e5.16 The difference in reactivity between
lithium alkylamides and lithium arylamides has not been clearly
elucidated yet.17
To demonstrate the application of this methodology, the syn-
theses of the 3,6- and 4,6-disubstituted benzanthrones 9 and 10
were investigated (Schemes 4 and 5). First, when various types of
4. Experimental section
4.1. Reagents
Benzanthrone, aryl bromides, amines, magnesium turnings, n-
BuLi in hexane, and silica gel 60N (Kanto Reagents, 63e210 mesh)
were commercially available and were used without further
purification.
MgBr
O
O
(2.0 equiv.)
4.2. General procedure for synthesis of 6-arylbenzanthrones
3 and 3,6-disubstituted benzanthrones 9
CHCl3
r.t.
THF
r.t.
R
R
A solution of aryl magnesium bromide (2.0 mmol), which was
prepared from Mg turnings (244 mg, 10 mmol) and the corre-
sponding aryl bromide (2.0 mmol) in THF (5.0 mL), was added to
a solution of benzanthrone (1) (230 mg, 1.0 mmol) or 8 (1.0 mmol)
in THF (7.0 mL) at room temperature. After being stirred overnight
at room temperature, to the reaction mixture was added water,
then the resulting mixture was extracted several times with CHCl3
and the organic fraction was washed with brine and dried over
MgSO4. After removal of drying agent, the reaction mixture was
diluted with CHCl3 (30 mL) and was stirred for 5 h at room
8
9
(1.0 mmol)
O
Ph
Ph
N
R =
t-Bu
t-Bu
9d, 65 %
9a, 62 %
9b, 48 %
9c, 63 %
Scheme 4. Synthesis of 3,6-disubstituted benzanthrones 9.
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4
R. Umeda et al. / Tetrahedron xxx (2012) 1e6
temperature under air. The resulting reaction solution was con-
centrated under reduced pressure and the residue was purified by
chromatography on SiO2 followed by a recyclable preparative HPLC
to give the 6-arylbenzanthrone 3 or 3,6-disubstituted benzan-
throne 9.
(d, J¼7.2, Hz, 1H), 8.33e8.30 (m, 2H), 8.17 (d, J¼8.0 Hz, 1H), 8.01 (d,
J¼8.0, Hz, 1H), 7.73e7.70 (m, 2H), 7.54 (d, J¼8.4 Hz, 1H), 7.50 (ddd,
J¼8.0, 7.2, 0.8 Hz, 1H), 7.38e7.34 (m, 2H), 7.21e7.15 (m, 2H). 13C
NMR (100 MHz, CDCl3)
d
184.2, 162.1 (J¼244.5 Hz), 145.8, 139.5
(J¼3.3 Hz), 135.5, 133.9, 133.0, 132.6, 132.2, 131.1, 130.2, 129.5
(J¼8.3 Hz), 128.6, 128.3, 128.1, 127.4, 126.5, 125.4, 124.6, 122.7, 115.3
(J¼21.4 Hz). IR (KBr): 3065, 1651, 1596, 1468, 1218, 1155, 1092, 940,
820, 758 cmꢁ1. MS (FAB): m/z 325 (MþHþ). HRMS (FAB): calcd for
4.2.1. 6-Phenylbenzanthrone (3a). Yield: 263 mg (86%), yellow
solid, mp 166e168 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.52 (dd, J¼7.6,
1.2 Hz, 1H), 8.35e8.32 (m, 2H), 8.19 (d, J¼8.4 Hz, 1H), 8.04 (dd,
J¼8.2, 0.8 Hz, 1H), 7.75e7.70 (m, 2H), 7.59 (d, J¼8.0 Hz, 1H),
C23H14OF: 325.1029. Found 325.1001.
7.52e7.38 (m, 6H). 13C NMR (100 MHz, CDCl3)
d
184.1, 147.0, 143.8,
4.2.7. 6-(2-Thienyl)benzanthrone (3g). Yield: 168 mg (54%), brown
solid, mp 182e183 ꢀC. 1H NMR (400 MHz, CDCl3)
135.5, 133.8, 133.0, 132.5, 132.3, 131.2, 130.2, 128.7, 128.3, 128.22,
128.17, 127.8, 127.5, 127.0, 126.4, 125.3, 124.5, 122.7. IR (KBr): 3053,
1647, 1597, 1557, 1490, 1350, 1264, 939, 845, 762, 694 cmꢁ1. MS
(FAB): m/z 307 (MþHþ). HRMS (FAB): calcd for C23H14O: 307.1123.
Found 307.1444.
d
8.36 (d, J¼7.2, Hz,
1H), 8.33 (dd, J¼8.0, 0.8 Hz, 1H), 8.20 (d, J¼8.0 Hz, 1H), 8.06 (d,
J¼8.4 Hz, 1H), 7.90 (d, J¼8.0 Hz, 1H), 7.67e7.63 (m, 2H), 7.61 (dd,
J¼8.0, 7.2 Hz, 1H), 7.50e7.45 (m, 2H), 7.20e7.15 (m, 2H). 13C NMR
(100 MHz, CDCl3)
d 183.7, 144.4, 138.5, 135.0, 133.4, 132.8, 132.5,
132.0,131.6,129.9,128.3,128.0,127.9,127.1,127.0,126.5,126.1,125.9,
125.8, 124.3, 122.4. IR (KBr) 3096, 3069, 3040, 1650, 1600, 1560,
1435, 1418, 1372, 1340, 1295, 1270, 1217, 1146, 940, 840, 816, 752,
724 cmꢁ1. MS (FAB): m/z 313 (MþHþ). HRMS (FAB): calcd for
4.2.2. 6-(p-Tolyl)benzanthrone (3b). Yield: 288 mg (90%), yellow
solid, mp 165e167 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.52 (d, J¼7.6 Hz,
1H), 8.36e8.32 (m, 2H), 8.17 (d, J¼8.4 Hz, 1H), 8.02 (d, J¼8.4 Hz, 1H),
7.74e7.68 (m, 2H), 7.59 (d, J¼8.0 Hz, 1H), 7.49 (dd, J¼7.6, 7.6 Hz, 1H),
C21H12OS: 313.0687. Found 313.0682.
7.31 (br s, 4H), 2.47 (s, 3H). 13C NMR (100 MHz, CDCl3)
d 184.2, 147.2,
140.8, 136.7, 135.5, 133.8, 132.9, 132.43, 132.40, 131.4, 130.2, 129.1,
128.8, 128.2, 127.8, 127.4, 126.3, 125.4, 124.4, 122.6, 21.4 (one signal
is missing due to overlap). IR (KBr): 3012, 2966, 1646, 1596, 1557,
1501, 1349, 1263, 938, 812, 755 cmꢁ1 MS (FAB): m/z 321 (MþHþ).
HRMS (FAB): calcd for C24H17O: 321.1279. Found 321.1288.
4.2.8. 3-(N,N-Diphenylamino)-6-(p-tolyl)benzanthrone (9a). Yield:
302 mg (62%), red solid, mp>250 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.43(d, J¼8.0 Hz, 1H), 8.34e8.30 (m, 2H), 8.22 (d, J¼8.4 Hz, 1H),
7.67 (dd, J¼8.0, 8.0 Hz,1H), 7.47e7.44 (m, 2H), 7.40 (d, J¼8.8 Hz,1H),
7.26e7.22 (m, 8H), 7.09 (d, J¼8.0 Hz, 4H), 7.00 (dd, J¼7.2, 7.2 Hz, 2H),
2.43 (s, 3H) ppm. 13C NMR (100 MHz, CDCl3)
d 184.4, 148.5, 147.2,
4.2.3. 6-(p-Methoxyphenyl)benzanthrone (3c). Yield: 228 mg (68%),
146.4, 140.6, 136.6, 135.3, 132.9, 131.9, 131.5, 130.6, 130.2, 129.7,
129.3, 129.0, 128.1, 127.9, 127.7, 126.7, 126.0, 125.1, 125.0, 122.6,
122.5, 21.4 ppm (one signal is missing due to overlap). IR (KBr)
3060, 3033, 2918, 2860, 1654, 1587, 1558, 1492, 1465, 1435, 1417,
1369, 1295, 1246, 939, 842, 811, 754, 695 cmꢁ1. MS (FAB): m/z 488
(MþHþ). HRMS (FAB): calcd for C36H26ON: 488.2014. Found
488.2006.
yellow solid, mp 189e191 ꢀC. 1H NMR (400 MHz, CDCl3)
d 8.49 (d,
J¼7.2 Hz, 1H), 8.34 (dd, J¼7.6, 0.8 Hz, 1H), 8.31 (d, J¼8.4 Hz, 1H), 8.15
(d, J¼8.8 Hz, 1H), 8.00 (d, J¼8.0 Hz, 1H), 7.73e7.67 (m, 2H), 7.58 (d,
J¼8.0 Hz, 1H), 7.49 (ddd, J¼7.6, 7.6, 0.8 Hz, 1H), 7.36 and 7.04
(AA0BB0; JAB¼8.8 Hz, 4H), 3.91 (s, 3H). 13C NMR (100 MHz, CDCl3)
d
184.3, 158.8, 146.8, 135.8, 135.5, 133.8, 132.9, 132.4, 132.3, 131.5,
130.2, 129.3, 128.7, 128.13, 128.09, 127.3, 126.2, 125.2, 124.4, 122.6,
113.8, 55.2. IR (KBr): 3054, 2997, 2923, 2834, 1650, 1596, 1557, 1514,
1349, 1241, 1026, 834, 817, 760 cmꢁ1. MS (FAB): m/z 337 (MþHþ).
HRMS (FAB): calcd for C24H17O2: 337.1229. Found 337.1082.
4.2.9. 3-(4-tert-Butylphenyl)-6-(p-tolyl)benzanthrone (9b). Yield:
217 mg (48%), yellow solid, mp 206e208 ꢀC. 1H NMR (400 MHz,
CDCl3)
d
8.53 (d, J¼7.6 Hz, 1H), 8.37e8.32 (m, 3H), 8.33 (d, J¼8.8 Hz,
1H), 7.72 (dd, J¼8.0, 8.0 Hz,1H), 7.58 (d, J¼8.0 Hz, 2H), 7.55e7.49 (m,
4.2.4. 6-[p-(N,N-Dimethylamino)phenyl]benzanthrone (3d). Yield:
255 mg (73%), orange solid, mp 234e237 ꢀC. 1H NMR (400 MHz,
4H), 7.32 (br s, 4H), 2.48 (s, 3H), 1.46 (s, 9H) ppm. 13C NMR
(100 MHz, CDCl3)
d 184.4, 150.8, 146.9, 142.7, 140.9, 136.8, 136.5,
CDCl3)
d
8.49 (d, J¼7.6 Hz, 1H), 8.37 (d, J¼8.0 Hz, 1H), 8.32 (d,
135.5, 132.9, 132.4, 132.1, 131.1, 130.8, 129.9, 129.1, 128.03, 128.00,
127.7, 127.3, 126.3, 125.6, 125.4, 124.1, 122.6, 34.7, 31.4, 21.4 ppm
(one signal is missing due to overlap). IR (KBr) 3062, 3028, 2957,
2898, 1647, 1577, 1451, 1323, 1308, 1273, 1013, 943, 842, 828, 782,
755, 703 cmꢁ1. MS (FAB): m/z 453 (MþHþ). HRMS (FAB): calcd for
J¼8.0 Hz,1H), 8.12 (d, J¼8.8 Hz,1H), 7.98 (d, J¼8.0 Hz,1H), 7.72e7.62
(m, 3H), 7.50 (ddd, J¼8.0, 7.6, 1.2 Hz, 1H), 7.37 and 6.85 (AA0BB0;
JAB¼8.8 Hz, 4H), 3.05 (s, 6H). 13C NMR (100 MHz, CDCl3)
d 184.4,
149.7,147.7,135.5,133.6, 132.7,132.7,132.0,131.8,130.9,130.2,129.5,
129.0, 128.1, 128.0, 127.2, 125.8, 124.9, 124.2, 122.6, 112.1, 40.5. IR
(KBr): 3060, 2919, 1639, 1596, 1349, 1215, 1031, 939, 844, 811,
753 cmꢁ1. MS (EI): m/z 349 (Mþ). HRMS (EI): calcd for C25H19ON:
349.1467. Found 349.1440.
C
34H29O: 453.2218. Found 453.2204.
4.2.10. 3-(Phenylethynyl)-6-(p-tolyl)benzanthrone(9c). Yield: 265 mg
(63%), yellow solid, mp 152e154 ꢀC. 1H NMR (400 MHz, CDCl3)
8.78
d
(d, J¼8.0 Hz, 1H), 8.43 (d, J¼8.0 Hz, 1H), 8.32 (dd, J¼8.0, 1.2 Hz, 1H),
8.28 (d, J¼8.4 Hz, 1H), 7.92 (d, J¼8.0 Hz, 1H), 7.72e7.66 (m, 4H), 7.49
(ddd, J¼7.6, 7.6, 1.2 Hz, 1H), 7.45e7.41 (m, 3H), 7.31 (br s, 4H), 2.48 (s,
4.2.5. 6-[3,5-Di(tert-butyl)-4-(trimethylsilyl)oxyphenyl]benzan-
throne (3e). Yield: 395 mg (78%), yellow solid, mp 195e196 ꢀC. 1H
NMR (400 MHz, CDCl3)
d
8.48 (d, J¼6.8 Hz, 1H), 8.33e8.30 (m, 2H),
3H) ppm. 13C NMR (100 MHz, CDCl3)
d 184.1, 147.5, 140.7, 136.8, 135.1,
8.13 (d, J¼8.4 Hz, 1H), 7.99 (d, J¼7.2 Hz, 1H), 7.73e7.66 (m, 3H), 7.51
(ddd, J¼7.2, 7.6, 0.8 Hz, 1H), 7.39 (s, 2H), 1.46 (s, 18H), 0.49 (s, 9H).
133.0, 132.3, 132.2, 132.05, 131.96, 131.7, 130.5, 129.1, 128.9, 128.7,
128.6,128.5,128.2, 127.75, 127.68,125.6,123.8,123.3, 122.9, 96.9, 87.1,
21.4 ppm (one signal is missing due to overlap). IR (KBr) 3053, 3014,
2884, 2206, 1649, 1597, 1557, 1488, 1434, 1307, 1249, 959, 938, 841,
810, 786, 755, 690 cmꢁ1. MS (FAB): m/z 421 (MþHþ). HRMS (FAB):
calcd for C32H21O: 421.1592. Found 421.1583.
13C NMR (100 MHz, CDCl3)
d 184.9, 152.9, 147.6, 140.4, 135.4, 134.44,
133.42, 133.1, 132.6, 132.0, 131.7, 130.1, 129.0, 128.1, 127.7, 127.3,
126.6, 125.9, 125.6, 124.1, 122.6, 35.2, 31.4, 4.0. IR (KBr): 3036, 2954,
2913, 1652, 1599, 1419, 1262, 1120, 908, 863, 757 cmꢁ1. MS (FAB):
m/z 507 (MþHþ). HRMS (FAB): calcd for C34H39O2Si: 507.2719.
Found 507.2707.
4.2.11. 3-(4-tert-Butylphenoxy)-6-(p-tolyl)benzanthrone (9d). Yield:
305 mg (65%), yellow solid, mp 207e211 ꢀC. 1H NMR (400 MHz,
4.2.6. 6-(p-Fluorophenyl)benzanthrone (3f). Yield: 172 mg (53%),
CDCl3)
J¼8.4 Hz, 1H), 8.16 (d, J¼7.6 Hz, 1H), 7.67e7.65 (m, 1H), 7.63
Please cite this article in press as: Umeda, R.; et al., Tetrahedron (2012), http://dx.doi.org/10.1016/j.tet.2012.12.013
d
8.72 (d, J¼8.0 Hz, 1H), 8.35 (dd, J¼8.0, 1.2 Hz, 1H), 8.32 (d,
yellow solid, mp 225e226 ꢀC. 1H NMR (400 MHz, CDCl3)
d 8.50

R. Umeda et al. / Tetrahedron xxx (2012) 1e6
5
(d, J¼8.0 Hz, 1H), 7.50e7.42 (m, 3H), 7.37e7.33 (m, 4H), 7.13 (d,
J¼8.0 Hz, 2H), 7.00 (d, J¼8.8 Hz, 1H), 2.42 (s, 3H), 1.32 (s, 9H) ppm.
1404, 1375, 1295, 1262, 1219, 1172, 1073, 1020, 937, 831, 814, 787,
755 cmꢁ1. MS (FAB): m/z 364 (MþHþ). HRMS (FAB): calcd for
13C NMR (100 MHz, CDCl3)
d
184.3, 156.2, 153.8, 147.7, 147.4, 140.8,
C26H22ON: 364.1701. Found 364.1678.
136.6,135.4,132.8,131.5,131.0,129.8,129.0,128.0,127.8,127.7,127.3,
126.9, 125.3, 125.2, 125.0, 122.1, 121.7, 119.3, 111.4, 34.4, 31.4,
21.4 ppm. IR (KBr) 3069, 3034, 2961, 2945, 2904, 2860, 1651, 1585,
1561, 1462, 1421, 1371, 1227, 1215, 1172, 1107, 1015, 854, 813, 783,
753 cmꢁ1. MS (FAB): m/z 469 (MþHþ). HRMS (FAB): calcd for
4.3.4. 4-(N-Morpholyl)benzanthrone (4d). Yield: 69 mg (22%), red
viscous oil, 1H NMR (400 MHz, CDCl3)
d
8.54 (dd, J¼8.0, 1.2 Hz, 1H),
8.50 (d, J¼7.6 Hz, 1H), 8.36 (d, J¼8.4 Hz, 1H), 8.02 (d, J¼9.6 Hz, 1H),
7.87 (d, J¼8.0 Hz,1H), 7.71 (ddd, J¼7.6, 8.0,1.6 Hz,1H), 7.57e7.52 (m,
2H), 7.43 (d, J¼9.6 Hz, 1H), 4.03 (t, J¼4.8 Hz, 4H), 3.47 (t, J¼4.8 Hz,
C
34H28O2: 421.469.2168. Found 469.2176.
4H) ppm. 13C NMR (100 MHz, CDCl3)
d 181.3, 154.8, 136.2, 134.8,
4.3. General procedure for synthesis of 6-amino- and
4-aminobenzanthrones 4 and 5
132.9, 131.8, 130.1, 129.7, 127.7, 127.5, 127.3, 125.6, 124.7, 123.2, 122.4,
119.4, 112.8, 67.0, 52.2 ppm. IR (KBr) 3047, 2953, 2923, 2888, 2852,
2834, 1626, 1598, 1570, 1550, 1507, 1437, 1394, 1369, 1355, 1300,
A solution of benzanthrone (1) (230 mg, 1.0 mmol) in THF
(8.0 mL) was added to a solution of the lithium amide (3.6 mmol),
which was prepared by the reaction of n-BuLi (1.6 M in hexane,
2.3 mL, 3.6 mmol) and the corresponding amine (3.0 mmol) in THF
(4.0 mL) at 0 ꢀC, and then the reaction mixture was slowly warmed
to room temperature and stirred overnight. To the reaction mixture
was added water, then the resulting mixture was extracted several
times with EtOAc and the organic fraction was washed with dilute
HCl aq and brine and dried over MgSO4. After removal of drying
agent, the organic solution was concentrated under reduced pres-
sure and the residue was purified by chromatography on SiO2 fol-
lowed by a recyclable preparative HPLC to give the 6-amino- and
4-aminobenzanthrones 4 and 5.
1266,1243,1220, 1177, 1146,1046, 980, 884, 834, 817, 777, 758 cmꢁ1
.
MS (FAB): m/z 316 (MþHþ). HRMS (FAB): calcd for C21H18ON:
316.1338. Found 316.1335.
4.3.5. 4-(N-Methylphenylamino)benzanthrone (5a). Yield: 178 mg
(53%), yellow solid, mp 154e156 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.77 (d, J¼8.0 Hz, 1H), 8.51 (d, J¼8.0 Hz, 1H), 8.32 (d, J¼7.2 Hz, 1H),
8.23 (d, J¼8.0 Hz, 1H), 8.05 (d, J¼8.4 Hz, 1H), 7.69 (dd, J¼7.2, 7.6 Hz,
1H), 7.56 (d, J¼7.6 Hz, 1H), 7.52 (dd, J¼7.2, 7.6 Hz, 1H), 7.47 (dd,
J¼7.6, 8.4 Hz, 1H), 7.22 (dd, J¼7.6, 7.6 Hz, 2H), 6.89 (dd, J¼7.6, 7.6 Hz,
1H), 6.82 (d, J¼7.2 Hz, 2H), 3.50 (s, 3H) ppm. 13C NMR (100 MHz,
CDCl3) d 182.8,152.8,150.0,136.0,133.0,130.92, 130.86, 129.5,129.4,
129.0, 128.1, 127.8, 127.2, 126.6, 126.0, 125.4, 124.2, 123.3, 122.9,
119.8, 116.8, 41.5 ppm. IR (KBr) 3069, 2881, 2816, 1643, 1600, 1571,
1492, 1415, 1381, 1342, 1290, 1274, 1248, 1103, 1030, 1001, 907, 857,
788, 755, 708, 694 cmꢁ1. MS (EI): m/z 335 (Mþ). HRMS (EI): calcd for
4.3.1. 4-(N,N-Di-n-butylamino)benzanthrone (4a). Yield: 222 mg
(62%), red viscous oil, 1H NMR (400 MHz, CDCl3)
d
8.56 (dd, J¼8.0,
1.2 Hz, 1H), 8.44 (d, J¼7.6 Hz, 1H), 8.35 (d, J¼7.6 Hz, 1H), 7.89 (d,
J¼8.8 Hz, 1H), 7.81 (d, J¼8.0 Hz, 1H), 7.68 (ddd, J¼8.0, 8.0, 1.2 Hz,
1H), 7.56 (dd, J¼7.6, 7.6 Hz, 1H), 7.48e7.44 (m, 2H), 3.53 (t, J¼7.5 Hz,
4H), 1.62 (tt, J¼7.5, 7.5 Hz, 4H), 1.28 (tt, J¼7.5, 7.5 Hz, 4H), 0.84 (t,
C24H17ON: 335.1310. Found 335.1309.
4.3.6. 4-(N,N-Diphenylamino)benzanthrone (5b). Yield: 44 mg
(11%), orange solid, mp 200e202 ꢀC. 1H NMR (400 MHz, CDCl3)
J¼7.5 Hz, 6H) ppm. 13C NMR (100 MHz, CDCl3)
d
180.3, 154.6, 134.8,
d
8.73 (d, J¼8.0 Hz,1H), 8.52 (dd, J¼8.0, 1.6 Hz,1H), 8.39 (d, J¼7.2 Hz,
134.7, 133.4, 131.1, 130.2, 129.1, 127.2, 127.1, 126.3, 125.0, 124.0, 122.3,
122.1, 120.5, 111.6, 52.4, 30.1, 20.0, 13.8 ppm. IR (KBr) 3064, 2956,
2929, 2869, 1627, 1596, 1547, 1506, 1432, 1375, 1294, 1264, 1215,
1174, 1144, 1035, 938, 832, 815, 786, 756 cmꢁ1. MS (FAB): m/z 358
(MþHþ). HRMS (FAB): calcd for C25H28ON: 358.2171. Found
358.2175.
1H), 8.31 (d, J¼8.0 Hz, 1H), 8.11 (d, J¼8.0 Hz, 1H), 7.71 (ddd, J¼7.2,
8.4, 1.2 Hz, 1H), 7.55 (dd, J¼8.0, 8.0 Hz, 1H), 7.47 (d, J¼8.0 Hz, 1H),
7.46 (dd, J¼7.6, 7.6 Hz, 1H), 7.28e7.23 (m, 4H), 7.08e7.03 (m,
6H) ppm. 13C NMR (100 MHz, CDCl3)
d 182.9, 151.4, 148.6, 136.2,
133.1, 131.0, 130.8, 130.0, 129.43, 129.41, 128.2, 128.0, 127.4, 127.1,
126.2, 126.1, 125.5, 124.2, 123.6, 123.2, 123.0 ppm. IR (KBr) 3060,
3029, 1646, 1599, 1585, 1571, 1509, 1492, 1415, 1380, 1341, 1308,
1271, 1031, 1018, 924, 854, 786, 767, 753, 694 cmꢁ1. MS (EI): m/z 397
(Mþ). HRMS (EI): calcd for C29H19ON: 397.1467. Found 397.1487.
4.3.2. 4-(N,N-Diisopropyllamino)benzanthrone (4b). Yield: 115 mg
(35%), red viscous oil, 1H NMR (400 MHz, CDCl3)
d
8.48 (dd, J¼8.0,
1.2 Hz, 1H), 8.43 (d, J¼8.0 Hz, 1H), 8.34 (d, J¼8.0 Hz, 1H), 7.86 (d,
J¼9.2 Hz,1H), 7.82 (d, J¼8.0 Hz,1H), 7.69 (ddd, J¼7.6, 7.6,1.2 Hz,1H),
7.61 (d, J¼9.6 Hz, 1H), 7.54 (dd, J¼7.2, 7.6 Hz, 1H), 7.48 (dd, J¼7.6,
8.0 Hz, 1H), 4.04 (sept, J¼6.8 Hz, 2H), 1.42 (d, J¼6.8 Hz, 12H) ppm.
4.3.7. 4-(N,N-Di(4-tert-butylphenyl)amino)benzanthrone (5c). Yield:
46 mg (9%), red solid, mp 231e232 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.70 (d, J¼8.4 Hz, 1H), 8.51 (dd, J¼8.0, 1.6 Hz, 1H), 8.38 (d, J¼7.2 Hz,
13C NMR (100 MHz, CDCl3)
d
181.6, 134.8, 133.5, 133.3, 131.4, 130.3,
1H), 8.30 (d, J¼8.4 Hz, 1H), 8.11 (dd, J¼8.8, 0.8 Hz, 1H), 7.70 (ddd,
J¼7.6, 8.0, 1.6 Hz, 1H), 7.54 (ddd, J¼8.4, 7.2, 1.6 Hz, 1H), 7.44 (ddd,
J¼8.4, 8.0, 0.8 Hz, 1H), 7.44 (d, J¼8.4 Hz, 1H), 7.25e7.22 (m, 4H),
6.98e6.95 (m, 4H), 1.30 (s, 18H) ppm. 13C NMR (100 MHz, CDCl3)
129.2,127.4, 127.2, 126.9,125.2, 124.7, 123.9,122.6, 122.3, 115.2, 52.3,
22.8 ppm. (It seems that one aromatic carbon cannot be observed
due to signal overlap.) IR (KBr) 3064, 2969, 2931, 2871, 1627, 1596,
1547, 1504, 1478, 1461, 1444, 1371, 1293, 1260, 1241, 1222, 1126,
1072, 1036, 1011, 937, 835, 810, 786, 756 cmꢁ1. MS (FAB): m/z 330
(MþHþ). HRMS (FAB): calcd for C23H24ON: 330.1858. Found
330.1844.
d
182.9, 152.0, 146.2, 145.9, 136.2, 133.0, 131.1, 130.9, 130.0, 129.4,
128.2, 127.9, 127.4, 127.2, 126.2, 125.90, 125.86, 125.1, 124.2, 123.03,
122.97, 34.3, 31.4 ppm. IR (KBr) 3062, 3034, 2961, 2902, 2867, 1648,
1601, 1572, 1507, 1463, 1422, 1411, 1380, 1364, 1339, 1315, 1270, 1190,
1113, 1089, 1021, 923, 875, 830, 788, 764, 710, 691 cmꢁ1. MS (FAB):
m/z 510 (MþHþ). HRMS (FAB): calcd for C37H36ON: 510.2797. Found
510.2823.
4.3.3. 4-(N-Ethylbenzylamino)benzanthrone (4c). Yield: 142 mg
(39%), light brown viscous oil, 1H NMR (400 MHz, CDCl3)
d 8.54 (dd,
J¼8.0, 1.2 Hz, 1H), 8.38 (d, J¼7.6 Hz, 1H), 8.28 (d, J¼8.0 Hz, 1H), 7.85
(d, J¼9.2 Hz, 1H), 7.76 (dd, J¼7.6, 1.2 Hz, 1H), 7.64 (ddd, J¼7.6, 8.0,
1.6 Hz, 1H), 7.52 (ddd, J¼7.6, 7.6, 1.2 Hz, 2H), 7.44e7.40 (m, 2H),
7.25e7.10 (m, 5H), 4.62 (s, 2H), 3.54 (q, J¼7.2 Hz, 2H), 1.18 (t,
4.3.8. 4-(N-Carbazolyl)benzanthrone (5d). Yield: 24 mg (6%), yel-
low solid, mp>250 ꢀC. 1H NMR (400 MHz, CDCl3)
d
8.96 (d, J¼8.0 Hz,
1H), 8.57 (dd, J¼8.0, 1.6 Hz, 1H), 8.51 (d, J¼6.4 Hz, 1H), 8.38 (d,
J¼8.4 Hz,1H), 8.23 (dd, J¼8.4, 2.0 Hz, 2H), 7.93 (d, J¼7.6 Hz,1H), 7.79
(ddd, J¼7.6, 8.0, 1.6 Hz, 1H), 7.64e7.52 (m, 3H), 7.40e7.32 (m, 4H),
7.07 (dd, J¼6.8, 2.0 Hz, 2H) ppm. 13C NMR (100 MHz, CDCl3)
J¼7.2 Hz, 3H) ppm. 13C NMR (100 MHz, CDCl3)
d 181.0, 154.3, 137.7,
134.9, 134.8, 133.3, 131.3, 130.0, 129.2, 128.4, 127.8, 127.23, 127.18,
127.1, 126.5, 125.1, 124.1, 122.5, 122.4, 120.5, 112.1, 56.9, 47.1,
13.5 ppm. IR (KBr) 3061, 2901, 2929, 1625, 1595, 1548, 1506, 1433,
d
183.35, 142.07, 140.79, 136.15, 133.71, 130.95, 130.50, 130.14,
Please cite this article in press as: Umeda, R.; et al., Tetrahedron (2012), http://dx.doi.org/10.1016/j.tet.2012.12.013

6
R. Umeda et al. / Tetrahedron xxx (2012) 1e6
129.41, 128.66, 128.62, 128.27, 127.73, 127.37, 127.22, 126.23, 126.07,
124.84, 123.62, 123.22, 120.45, 110.19 ppm. (It seems that one aro-
matic carbon cannot be observed due to signal overlap.) IR (KBr)
3051, 1650, 1598, 1577, 1508, 1490, 1478, 1448, 1416, 1384, 1352,
1335, 1311, 1293, 1277, 1231, 1155, 1030, 1016, 932, 761, 751,
724 cmꢁ1. MS (EI): m/z 395 (Mþ). HRMS (EI): calcd for C29H17ON:
395.1310. Found 395.1229.
Research Bases at Private Universities from the Ministry of Educa-
tion, Culture Sports, Science and Technology of Japan.
Supplementary data
Supplementary data for new compounds of 1H and 13C NMR
spectra. Supplementarydataassociatedwiththisarticlecanbefound
in the online version, at http://dx.doi.org/10.1016/j.tet.2012.12.013.
4.4. Synthesis of 10 in Scheme 5
4.4.1. Synthesis of 10 by the reaction of 5a with Grignard reagent. A
solution of p-tolylmagnesium bromide (1.0 mmol), which was
prepared from Mg turnings (122 mg, 5.0 mmol) and p-bromoto-
luene (171 mg,1.0 mmol) in THF (2.0 mL), was added to a solution of
5a (178 mg, 0.5 mmol) in THF (6.0 mL) at room temperature. After
being stirred overnight at room temperature, to the reaction mix-
ture was added water, then the resulting mixture was extracted
several times with EtOAc and the organic fraction was washed with
brine and dried over MgSO4. After removal of drying agent, the
solution of the crude product in CHCl3 was stirred for 5 h at room
temperature. The resulting reaction solution was concentrated
under reduced pressure and the residue was purified by chroma-
tography on SiO2 followed by a recyclable preparative HPLC to give
10 (91 mg, 43%) as a red solid.
References and notes
1. Forrest, S. R.; Thompson, M. E. Chem. Rev. 2007, 107, 923e925.
2. Krasovitskii, B. M.; Bolotin, B. M. Organic Luminescent Materials; VCH: 1988.
3. For selected examples, see: (a) Carlini, F. M.; Paffoni, C.; Boffa, G. Dyes Pigments
1982, 3, 59e69; (b) Konstantinova, T.; Meallier, P.; Konstantinov, H. R.; Staneva,
D. Polym. Degrad. Stab. 1995, 48, 161e166.
4. Gorbenko, G.; Trusova, V.; Kirilova, E.; Kirilov, G.; Kalnina, I.; Vasilev, A.;
Kaloyanova, S.; Deligeorgiev, T. Chem. Phys. Lett. 2010, 495, 275e279.
5. For selected examples, see: (a) Grabchev, I.; Moneva, I.; Wolarz, E.; Bauman, D.
Dyes Pigments 2003, 58, 1e6; (b) Grabchev, I.; Bojinov, V.; Moneva, I. Dyes
Pigments 2001, 48, 143e150; (c) Grabchev, I.; Moneva, I. Dyes Pigments 1998, 37,
155e164.
6. Yu, M. X.; Chang, L. C.; Lin, C. H.; Duan, J. P.; Wu, F. I.; Chen, L. C.; Cheng, C. H.
Adv. Funct. Mater. 2007, 17, 369e378.
7. Lu, B.; Xu, J.; Fan, C.; Miao, H.; Shen, L. J. Phys. Chem. B 2009, 113, 37e48.
8. (a) Starikov, A. V.; Yakobi, V. A.; Ponomarev, B. A.; Evstaf’eva, O. V.; Zelenskii, L. I.;
Karpukhin,P. P.;Kuznetsov, A.M.;Maslosh, V.Z.;Shuliko, N.I.;Starodubtseva,L.P. U.
S.S.R. SU508517A119760330,1976. (b)Rogovik, V.I.;Gutnik, L. F.;Struzhevskaya,V.
E. U.S.S.R. SU 1004343 A119830315, 1983.
9. (a) Enya, T.; Suzuki, H.; Hisamatsu, Y. Bull. Chem. Soc. Jpn. 1998, 71, 2221e2228;
(b) Ohshima, S.; Onozato, M.; Fujimaki, Y.; Hisamatsu, Y. Polycyclic Aromat.
Compd. 2008, 28, 93e101.
10. (a) Charrier, G.; Ghigi, E. Chim. Ital. 1932, 62, 928e936; (b) Allen, C. F. H.;
Overbaugh, S. C. J. Am. Chem. Soc. 1935, 57, 740e744; (c) Allen, C. F. H.;
Overbaugh, S. C. J. Am. Chem. Soc. 1935, 57, 1322e1325; (d) Bradley, W.; Sutcliffe,
F. K. J. Chem. Soc. 1954, 708e711; (e) Allen, C. F. H. Can. J. Chem. 1973, 51,
382e387; (f) Debeaux, M.; Brandhorst, K.; Jones, P. G.; Hopf, H.; Grunenberg, J.;
Kowalsky, W.; Johannes, H. H. Beilstein J. Org. Chem. 2009, 5, http://dx.doi.org/
10.3762/bjoc.5.31
11. Reaction of analogous benzanthrone derivatives with organometallic reagents,
see (a) Suenaga, M.; Miyahara, Y.; Inazu, T. J. Org. Chem. 1993, 58, 5846e5848;
(b) Martins, C. I.; Coelho, P. J.; Carvalhoa, L. M.; Oliveira-Campos, A. M. F.; Samat,
A.; Guglielmetti, R. Helv. Chim. Acta 2003, 86, 570e578.
4.4.2. Synthesis of 10 by the reaction of 3b with lithium arylamide. A
solution of the lithium amide (0.9 mmol), which was prepared by
the reaction of n-BuLi (1.6 M in hexane, 0.55 mL, 0.9 mmol) and the
N-methylphenylamine (96 mg, 0.9 mmol) in THF (2.0 mL), was
added to a solution of 3b (96 mg, 0.3 mmol) in THF (5.0 mL) at 0 ꢀC
and then the reaction mixture was slowly warmed to room tem-
perature and stirred overnight. To the reaction mixture was added
water, then the resulting mixture was extracted several times with
EtOAc and the organic fraction was washed with dilute HCl aq and
brine and dried over MgSO4. After removal of drying agent, the
organic solution was concentrated under reduced pressure and the
residue was purified by chromatography on SiO2 followed by a re-
cyclable preparative HPLC to give 10 (68 mg, 53%) as a red solid.
12. Direct amination of 1: see, (a) Bradley, W. J. Chem. Soc. 1937, 1091e1096; (b)
Bradley, W. J. Chem. Soc. 1948, 1175e1181; (c) See Ref. 10d. For other related
works: see, (d) Bradley, W.; Jadhav, G. V. J. Chem. Soc. 1948, 1622e1626; (e)
Bradley, W. J. Chem. Soc. 1949, 2712e2715; (f) Backhouse, A. J.; Bradley, W.;
Sutcliffe, F. K. J. Chem. Soc. 1955, 91e95; (g) Vaidyanathan, T.; Seshadri, S. Dyes
Pigments 1984, 5, 431e436.
4.4.2.1. 4-(N-Methylphenylamino)-6-(p-tolyl)benzanthrone
(10). Red solid, mp 157e159 ꢀC. 1H NMR (400 MHz, CDCl3)
d 8.44
(d, J¼7.2 Hz, 1H), 8.34 (d, J¼7.6 Hz, 1H), 8.27 (d, J¼8.4 Hz, 1H), 8.09
(d, J¼8.0 Hz, 1H), 7.66 (dd, J¼8.0, 7.6 Hz, 1H), 7.53 (dd, J¼8.0, 7.6 Hz,
1H), 7.46 (dd, J¼8.0, 7.6 Hz, 1H), 7.39 (s, 1H), 7.31e7.26 (m, 4H), 7.20
(dd, J¼7.2, 7.2 Hz, 2H), 6.87e6.80 (m, 3H), 3.48 (s, 3H), 2.43 (s,
13. 1H NMR spectra of the crude reaction mixture clearly showed the peaks of
benzanthrone (1) as starting material and 4 or 5.
14. For the reaction of 1 with the lithium ethylbenzylamide, uncharacterized
products were formed along with the 6-substituted product 4c and 1.
15. A dehydrogenation reaction of the phenalenone derivative smoothly occurred
by DDQ as an oxidative reagent to give the corresponding dehydrogenated
products; see Ref. 11a.
3H) ppm. 13C NMR (100 MHz, CDCl3)
d 183.4, 151.2, 150.0, 148.4,
140.6, 136.7, 135.5, 132.7, 132.3, 130.6, 129.1, 129.03, 128.96, 128.1,
128.0, 127.9, 127.7, 126.6, 125.9, 124.6, 122.7, 122.6, 119.9, 116.9, 41.5,
21.4 ppm. (It seems that one aromatic carbon cannot be observed
due to signal overlap.) IR (KBr) 3023, 2920, 2889, 2817, 1644, 1598,
1575, 1551, 1490, 1433, 1386, 1344, 1294, 1273, 1233, 1123, 1112,
1032, 920, 876, 817, 764, 700 cmꢁ1. MS (FAB): m/z 426 (MþHþ).
HRMS (FAB): calcd for C31H24ON: 426.1858. Found 426.1815.
16. Although the formation of the intermediates 6 and 7 were not detected in the
1H NMR of the crude reaction mixtures, it was reported that the amination of 1
with sodium amides was accelerated under oxygen; see, Refs. 12aec
17. To obtain more information for the selectivity, the reactions of 1 and other
organic metal reagents were examined. For example, the reaction of 1 and
phenyl lithium (1.2 equiv) was carried out at room temperature in THF. After
the workup, the reaction mixture in CHCl3 was stirred at room temperature and
the 1,2-addition product (10%) and 3a (35%) were formed. On the other hand, in
the case of lithium reagent (1.2 equiv), which was prepared by the reaction of
4-bromo-2,6-di-tert-butylphenoxy trimethylsilane and n-butyl lithium, 3e was
selectively formed in 76% yield. Moreover, the reaction of 1 with n-butyl
magnesium bromide (2.0 equiv) and n-butyl lithium (2.0 equiv) gave 6-n-bu-
tylbenzththrone as main product in 31% and 32%, respectively, together with
some of other regioisomers. These anomalous behaviors are not clearly eluci-
dated so far.
Acknowledgements
This research was supported by a Grant-in-Aid for Science
Research, and Strategic Project to Support the Formation of
Please cite this article in press as: Umeda, R.; et al., Tetrahedron (2012), http://dx.doi.org/10.1016/j.tet.2012.12.013