One-pot synthesis of unsymmetrical benzils by oxidative coupling using selenium dioxide and p-toluenesulfonic acid monohydrate

Article abstract of DOI:10.1002/ejoc.201101012

The oxidative coupling of the α-carbon atom of aromatic ketones with unactivated arenes in the presence of selenium dioxide and p-toluenesulfonic acid monohydrate is described. A number of unsymmetrical benzils have been prepared in good yields (38-75 % with high regioselectivity. The generality and functional tolerance of this new protocol is demonstrated. The mechanistic pathway for the oxidative coupling reaction is also described. The reaction displays superiority in terms of minimization of steps with the C-C bond formation promoted by SeO₂ and pTsOH·H₂O. This method is advantageous as the reactants used as the solvent can be recovered. Copyright

Full text of DOI:10.1002/ejoc.201101012

FULL PAPER
DOI: 10.1002/ejoc.201101012
One-Pot Synthesis of Unsymmetrical Benzils by Oxidative Coupling Using
Selenium Dioxide and p-Toluenesulfonic Acid Monohydrate
Md. Rumum Rohman,[a] Icydora Kharkongor,[a] Mantu Rajbangshi,[a] Hormi Mecadon,[a]
Badaker M. Laloo,[a] Priti R. Sahu,[a] Iadeishisha Kharbangar,[a] and Bekington Myrboh*[a]
Keywords: Ketones / Synthetic methods / C–C coupling / Oxidative coupling / Selenium
The oxidative coupling of the α-carbon atom of aromatic
ketones with unactivated arenes in the presence of selenium
dioxide and p-toluenesulfonic acid monohydrate is de-
scribed. A number of unsymmetrical benzils have been pre-
pared in good yields (38–75%) with high regioselectivity.
The generality and functional tolerance of this new protocol
is demonstrated. The mechanistic pathway for the oxidative
coupling reaction is also described. The reaction displays su-
periority in terms of minimization of steps with the C–C bond
formation promoted by SeO2 and pTsOH·H2O. This method
is advantageous as the reactants used as the solvent can be
recovered.
of acetophenone with SeO2 in the presence of pTsOH·H2O
in benzene, which resulted in the formation of benzil 3a.
In this approach, an intermolecular C–C bond is formed
between the α-carbon atom and the unactivated arene by
the initial oxidation of the corresponding methyl aryl
ketone with SeO2 in the presence of pTsOH·H2O. The over-
all attractiveness of preparing benzils in such a straightfor-
ward manner has motivated us to carry out a detailed study
of this method. Furthermore, the advantage of this method
also lies in the fact that the excess arenes used as reactants
can be recovered, purified, and reused. Although the initial
oxidation of aryl methyl ketones to glyoxal is well
known,[15,16] we wish to report the first one-pot synthesis
of benzils from the oxidative coupling of aryl methyl
ketones and unactivated arenes using SeO2 and
pTsOH·H2O (Scheme 1).
Introduction
Synthetic studies of symmetrical, unsymmetrical, and
heteroaryl 1,2-diketones have long been of interest as they
are precursors for important ligands such as dioximes and
dithiolenes in the field of discotic metallomesogens or poly-
meric mesogens and for the synthesis of heterocyclic com-
pounds.[1,2] Some benzils exhibit the potential for biological
activities, which includes the inhibition of mammalian car-
boxylesterases.[3] A number of synthetic pathways for the
preparation of aryl/heteroaryl 1,2-diketones involve the oxi-
dation of precursors such as olefins with selenium diox-
ide[4,5] or potassium permanganate,[6,7] methylene ketones
by selenium dioxide,[8,9] bismuth nitrate–copper(II) acet-
ate,[10] or oxygen in the presence of FeIII–ethylenediamine-
tetraacetic acid.[11]
Recently, we conducted a literature survey of the syn-
thetic utility of SeO2 oxidation processes in synthetic chem-
istry, in particular, the use of SeO2 in the presence of acids
to promote new C–C bond formation to synthesize unsym-
metrical benzils. Surprisingly, except for the work by Fuson
et al., which relates to the intramolecular condensation of
2-biphenylyl-glyoxal to give phenanthrenequinone and the
synthesis of mixed benzoins by the oxidation of acetophe-
nones to glyoxals with a modification of Riley and Gray’s
method,[12,13] there was no report of one-pot oxidative cou-
pling with SeO2 for the synthesis of 1,2-diketones from ace-
tophenones. As part of our continued efforts to develop
new synthetic methodologies,[14] we carried out the reaction
Scheme 1. Synthesis of unsymmetrical benzils by the oxidative cou-
pling of aryl/heteroaryl methyl ketones with arenes.
[a] Department of Chemistry,
North-Eastern Hill University, Permanent Campus,
Umshing, Mawlai, Shillong, 793002, India
Fax: +91-364-255-0076
E-mail: bmyrboh@nehu.ac.in
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101012.
This methodology proved to be versatile as hitherto un-
known benzils were easily prepared. Of particular interest
320
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Unsymmetrical Benzils by Oxidative Coupling
Table 1. Optimization of reaction conditions and screening of various oxidants and acids for the synthesis of 3b.
Entry
Reagents [mmol] and conditions[a]
Yield [%][b]
1
2
3
4
5
6
7
8
9
SeO2 (5.0), pTsOH·H2O (2.5), 40 °C, 24 h
17
60
23
–
–
–
–
5
5
SeO2 (5.0), pTsOH·H2O (2.5), 40 °C, 4 h then at 80 °C, 12 h
SeO2 (2.5), pTsOH·H2O (2.5), 23–100 °C, 48 h
SeO2 (5.0), 23–100 °C, 48 h
pTsOH·H2O (5.0), 23–100 °C, 48 h
SeO2 (5.0), CH3COOH (2.5), 23–100 °C, 24 h
SeO2 (5.2), AlCl3(2.5), 23–100 °C, 24 h
KMnO4 (2.5), SeO2 (2.5), pTsOH·H2O (2.5), 23–100 °C, 48 h
KMnO4 (5.0), SeO2 (2.5) pTsOH·H2O (2.5), 23–100 °C, 48 h
[a] Substrate 1b (2.5 mmol), 2a (8 mL). [b] Isolated yields.
is the coupling of acetophenones with polynuclear hydro-
Similarly, the oxidative coupling of 1a and 1c with 2a
carbons, which results in the formation of a new series of under the optimized conditions proceeded smoothly to give
unsymmetrical benzils.
3a and 3c in 59 and 60% yields, respectively (Table 2, En-
tries 1 and 3). The generality of the method was further
established by the reaction between substituted acetophe-
nones, which contain electron withdrawing or donating
groups, with arenes other than benzene and extended ar-
enes. Irrespective of the nature of the substituents on the
ring, all the reactions proceeded fairly well to afford unsym-
metrical benzils in moderate to good yields (Table 2, Entries
4–9). The substituted acetophenones with a nitro or N-ace-
tyl group in either meta or para positions appear to offer
cleaner reactions and higher yields of the products without
affecting the N-acetyl group (Table 2, Entries 3 and 6–8).
Notably, the substrates 2b and 2c effectively provided 3d–h
Results and Discussion
In a preliminary experiment, when a mixture of 1-(4-bro-
mophenyl)ethanone (1b) (2.5 mmol), SeO2 (5.0 mmol) and
pTsOH·H2O (2.5 mmol) in benzene (2a, 8 mL) was heated
at 40 °C for 24 h, 3b was obtained in very low yield. How-
ever, when the same reaction mixture was heated initially at
40 °C for 4 h and then at 80 °C for 12 h the yield signifi-
cantly increased to 60% (Table 1, Entries 1–2). The forma-
tion of 3b was confirmed by 1H and 13C NMR (two distinct
carbonyl carbon signals) and IR spectroscopy.
In a control experiment, the use of either SeO2 or
pTsOH·H2O alone failed to give the desired product
(Table 1, Entries 4–5). When SeO2 and pTsOH·H2O were
used in stoichiometric amounts (1 equiv. of each), 3b was
isolated in only 23% yield after 48 h, which showed that the
optimum amount of SeO2 is 2.0 equiv. (Table 1, Entry 3).
The use of other acids instead of pTsOH·H2O, e.g. acetic
acid or a Lewis acid such as AlCl3 in the presence of
pTsOH·H2O, under varying reaction conditions either gave
no reaction or resulted in the formation of intractable prod-
ucts (Table 1, Entries 6–7).
To establish the unique properties of SeO2 that affects
the transformation, we carried out the reaction of acetophe-
nones with various oxidants, such as potassium dichromate,
vanadium pentoxide, and manganese dioxide, in the pres-
ence of pTsOH·H2O and found that in all cases the desired
product was not formed. However, potassium permanga-
nate (1 equiv.) in the presence of SeO2 (1 equiv.) and
pTsOH·H2O (1 equiv.) gave 3b in 5% yield (Table 1, Entry
8). When the amount of potassium permanganate was in-
creased (2 equiv.) in the presence of SeO2 (1 equiv.) and
pTsOH·H2O (1 equiv.), no significant increase in the yield
of the product was observed even with prolonged reaction
times (Table 1, Entry 9).
Table 2. Synthesis of substituted benzils by the oxidative coupling
of substituted acetophenones 1 with arenes 2.[a]
Entry Substrate 1 (R1)
Substrate 2 (R2, R3)
Product Yield
3
[%][b]
1
2
3
4
5
6
7
8
9
C6H5 (1a)
4-BrC6H4 (1b)
4-NO2C6H4 (1c)
4-ClC6H4 (1d)
1b
R2 = R3 = H (2a)
2a
3a[c]
3b
59
58
60
2a
3c[c]
3d[c]
3e
R2 = H, R3 = CH3 (2b)
60[d]
61[d]
62[d]
62
2b
2b
1c
3f
3g
3h
3-NO2C6H4 (1e)
3-NHCOCH3C6H4 (1f) 2b
1f
R2 = R3 = CH3 (2c)
67
70
R2 = H, R3 = OCH3 (2d) 3i
[a] Reaction conditions: (i)
pTsOH·H2O (2.5 mmol), 2a–2c (6–8 mL), 30Ǟ80 °C, 16–20 h. (ii)
(2.5 mmol), SeO2 (5.0 mmol), pTsOH·H2O (2.5 mmol), 2d
1 (2.5 mmol), SeO2 (5.0 mmol),
1
(2.5 mmol), CH3CN (6 mL), 35 °C, 14–16 h. [b] Isolated yields. [c]
Commercially available. [d] Combined yield of the ortho and para
isomers.
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B. Myrboh et al.
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at 35 °C without the need to raise the temperature (Table 2, Entries 11, 12, and 16). The same acetophenones reacted
Entries 4–8). The excess arene substrates used in all the ex- with benzene and its derivatives to give 3b–f in 58, 60, 60,
periments were recovered and reused. In the case of sub- 61, and 62% overall yields, respectively (Table 2, Entries 2–
strate 2d, acetonitrile was used as the solvent when it was 6). This may be attributed to the more reactive nature of
found that stoichiometric amounts (1 equiv.) of the reac- the polynuclear hydrocarbons. As summarized in Table 3,
tants at 35 °C were sufficient to furnish the corresponding of the two polynuclear hydrocarbons, 4 gave slightly better
1,2-diketone (3i) in 70% yield (Table 2, Entry 9).
yields of products than 5 when reacted with aryl methyl
A striking feature of the reaction is the high regioselectiv- ketones that bear substituents, such as hydroxy, nitro, and
ity, which is evident from the fact that only one regioisomer, N-acetyl groups, on the ortho, meta or para positions. For
3g and 3i, was obtained when ortho-xylene (2c) and anisole example, 1h, 1i, 1c, and 1f reacted with 4 to give 6b–e in
(2d) were treated with 1e and 1f, respectively. The electro- 69–75% yield. Reaction of the same aryl methyl ketones
philic substitution appears to be sensitive to steric hin- with 5, however, provided 6m–n and 6p–q in 50–57 and 66–
drance. However, 1H NMR spectroscopy revealed that tolu- 73% yields, respectively (Table 3, Entries 2–5, 13–14, and
ene did show the formation of trace amounts of the ortho 16–17). Similarly, methyl and methoxy substituted aceto-
isomer with the para isomer predominating in a ratio of phenones afforded moderate to good yields when subjected
about 0.5:9.5 (Table 2, Entries 4–6).
to the same reaction conditions with 4 and 5 (Table 3, En-
Encouraged by these results, the scope of this oxidative tries 1, 6–9, and 18–19).
coupling reaction was extended to the reaction of polynu-
Only the products substituted at C1 and C9 were isolated
clear hydrocarbons with aryl methyl ketones that bear a from reactions with 4 and 5, respectively (Table 3). The
wide range of substituents (Table 3). Significantly, naphtha- presence of other isomers was not observed. Disappoint-
lene (4) and anthracene (5) gave better yields of the unsym- ingly, the reactions of chlorobenzene, bromobenzene, and
metrical benzils 6 when reacted with acetophenones that nitrobenzene with various acetophenones with this protocol
contain electron-withdrawing substituents, such as chloro, did not provide any of the isomers, even under different
bromo, and nitro groups, on the ring at 35 °C with acetoni- reaction conditions. This is thought to be due to the ring
trile as the solvent, compared to benzene and its derivatives. deactivating effect of the halide and the nitro group.
For example, 6d was obtained in 70% yield when 4 was
The broad scope of this procedure was further demon-
treated with 1c (Table 3, Entry 4). Similarly, substituted ace- strated by the reactions of fused aromatic methyl or het-
tophenones 1d, 1b, and 1c reacted with 5 to give 6k, 6l, and eroaryl methyl ketones with arenes to give the correspond-
6p in 68, 62, and 66% overall yields, respectively (Table 3, ing 1,2-diketones (Table 4). The same reaction trend was
Table 4. Synthesis of unsymmetrical benzils by the oxidative cou-
Table 3. Synthesis of unsymmetrical benzils 6 by the oxidative cou-
pling of extended/hetero aryl ketones 7 with arenes 8, 4, and 5.[a]
pling of substituted acetophenones 1 with 4 and 5.[a]
Entry
Substrate 1 (R1)
Substrate
4 or 5
Product
Yield
[%][b]
6
1
2
3
4
5
6
7
8
3-CH3O-C6H4 (1g)
2-OH-C6H4 (1h)
4-OH-C6H4 (1i)
1c
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
5
5
5
6a
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6o
6p
6q
6r
6s
65
69
67
70
75
62
60
57
55
63
68
62
50
57
64
66
73
58
53
1f
2,4-(CH3)2-C6H3 (1j)
2-CH3-C6H4 (1k)
4-CH3-C6H4 (1l)
1g
2-Cl-C6H4 (1m)
1d
1b
1h
1i
1e
1c
1f
Entry
Substrate 7 (R4) Substrate 8
(R5, R6, R7, R8), 4 or 5 9/10
Product Yield
[%][b]
9
10
11
12
13
14
15
16
17
18
19
1
2
3
2-naphthyl (7a)
7a
7a
2a (8a)
9a
9b
9c
59
2b (8b)
51[c]
61
R6 = R7 = H, R5 =
R8 = CH3 (8c)
4
5
6
7
8
7a
7a
2d (8d)
9d
70
69
38
57
46
4
4
4
5
10a
10b
10c
10d
2-furanyl (7b)
2-thiophenyl (7c)
7c
1j
2,4,6-(CH3)3-C6H2 (1n)
[a] The reaction conditions are same those used for the reactions
in Tables 2 and 3. For substrate 8c, reaction conditions (i) were
[a] Reaction conditions: (i)
1
(2.5 mmol), SeO2 (5.0 mmol),
pTsOH·H2O (2.5 mmol), 4/5 (2.5 mmol), CH3CN (6 mL), 35 °C, used. [b] Isolated yields. [c] Combined yield of the ortho and para
12–16 h. [b] Isolated yields.
isomers.
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Unsymmetrical Benzils by Oxidative Coupling
observed when the method was applied to the oxidative pTsOH·H2O. The method is regioselective and is also ad-
coupling of 1-(naphthalen-2-yl)ethanone (7a), 1-(furan-2- vantageous as the reactants used as solvent can be reco-
yl)ethanone (7b), and 1-(thiophen-2-yl)ethanone (7c) with vered.
arenes 4, 5, and 8, which gave consistently moderate to
good yields of 9 and 10 (Table 4, Entries 1–8).
A plausible mechanism is shown in Scheme 2. The oxi-
Experimental Section
dation of 1b to glyoxal (11)[15] (isolated, m.p. 50–51 °C; lit.
General: All reactions were carried out in oven-dried glassware at
30–80 °C. The following reagents were purchased and used without
purification: p-toluene sulfonic acid (MERCK), acetophenone, 1-
(4-chlorophenyl)ethanone, 1-(4-bromophenyl)ethanone, 1-(3-nitro-
51–52 °C)[13] by SeO2 is followed by the preferential forma-
tion of an O–Se bond through the carbonyl oxygen atom
of the aldehyde group in the presence of pTsOH·H2O to
give the intermediate 12. The activating effect of the keto
phenyl)ethanone, 1-(4-nitrophenyl)ethanone, N-(3-acetylphenyl)-
group and the formation of the O–Se bond generate a
strong electrophilic center at the aldehyde carbon atom of
12, which is highly susceptible to attack from electron-rich
arenes to give the selenite intermediate 13.[16,17] Oxidative
decomposition of 13 led to 3b.
acetamide, 1-(3-methoxyphenyl)ethanone, 1-(2-hydroxyphenyl)eth-
anone, 1-(4-hydroxyphenyl)ethanone, 1-(2,4-dimethylphenyl)etha-
none, 1-(naphthalen-2-yl)ethanone, 1-(thiophen-2-yl)ethanone, 1-
(furan-2-yl)ethanone, naphthalene, anthracene (Aldrich), and ani-
sole (Aldrich). The following reagents were purified before use:
SeO2 (Aldrich), benzene, toluene, o-xylene, and p-xylene.
1H NMR and 13C NMR analyses were recorded with a 400 MHz
spectrometer and are reported in parts per million from tetrameth-
ylsilane with the solvent resonance as the internal standard. Data
are reported as follows: chemical shift, multiplicity (s = singlet, d
= doublet, dd = double doublet, t = triplet, m = multiplet and br.
= broad). Mass spectra were performed with a GC–MS, LC–MS,
and mass spectrometer equipped with ESI and APCI mass detec-
tor. IR analyses were carried out with an FT-FIR spectrometer.
Melting points were recorded with the open capillary tube method.
Elemental analyses were carried out with a CHN analyzer.
General Experimental Procedure for the Preparation of Aryl/Het-
eroaryl Ethane-1,2-dione. Method A: To a stirring mixture of aceto-
phenone (2.5 mmol) and resublimed SeO2 (5.0 mmol) in benzene
(8 mL) was added pTsOH·H2O (2.5 mmol) in one portion at 30 °C.
The reaction mixture was allowed to stir at 40 °C for 4 h and then
gradually heated to 80 °C. The reaction mixture was stirred at
80 °C for 16–20 h. The reaction mixture was concentrated under
reduced pressure at 40 °C, and the residue was diluted with ethyl
acetate and filtered through celite. The celite was washed with ethyl
acetate (3ϫ5 mL). The combined filtrate was washed with satu-
rated aqueous sodium hydrogen carbonate solution, water (10 mL),
and brine (10 mL). The organic layer was separated, dried with
anhydrous Na2SO4 and concentrated. The benzil was purified by
column chromatography on silica gel (100–200 mesh) using ethyl
acetate and hexane as eluent.
Scheme 2. Proposed mechanism for the one-pot synthesis of un-
symmetrical benzils.
The proposed mechanism was supported by the reactions
of 2-(4-bromophenyl)-2-oxoacetaldehyde (11) and 2-hy-
droxy-1,2-diphenylethanone (14) with 2a to give 3a and 3b
in good yields (Scheme 3). The concerted reaction of gly-
oxals and arenes with SeO2 as the active oxidant appears
to be the major mechanistic pathway for these reactions.
Method B: The procedure is the same as Method A except for reac-
tants such as toluene, o-xylene, and p-xylene the reactions were
performed at 35 °C for 12–16 h and for reactants such as anisole,
naphthalene, and anthracene the reactions were performed at 35 °C
for 12–16 h in acetonitrile (6 mL).
Scheme 3. Reactions of 11 and 14 with 2a.
Benzil (3a): Prepared from acetophenone (300.4 mg, 2.5 mmol),
SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol),
and benzene (8 mL) over 20 h following Method A. Eluent: ethyl
acetate 3% in hexane; yellow solid (310.1 mg, 59%). The 1H NMR
spectrum matched that of a commercial sample.
Conclusions
We have reported a direct and efficient protocol for the
preparation of unsymmetrical and heteroaryl 1,2-diketones
through oxidative coupling between the α-carbon atom of
the aromatic ketone with unactivated arenes in the presence
of SeO2 and pTsOH·H2O. The mechanistic pathway for the
oxidative coupling reaction has been described. The reac-
tion displays superiority in terms of minimization of steps
1-(4-Bromophenyl)-2-phenylethane-1,2-dione (3b): Prepared from 1-
(4-bromophenyl)ethanone (497.6 mg, 2.5 mmol), SeO2 (554.8 mg,
5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and benzene (8 mL)
over 20 h following Method A. Eluent: ethyl acetate 5% in hexane;
light yellow solid (419.2 mg, 58%); m.p. 71–73 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.90–7.89 (m, 2 H), 7.79–7.77 (m, 2 H),
7.63–7.59 (m, 3 H), 7.48–7.44 (m, 2 H) ppm. 13C NMR (100 MHz,
with a C–C bond formation promoted by SeO2 and CDCl3): δ = 193.9, 193.3, 135.1, 132.7, 132.5, 131.7, 131.3, 130.5,
Eur. J. Org. Chem. 2012, 320–328
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B. Myrboh et al.
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130.0, 129.1 ppm. IR (KBr film): ν = 3089, 3064, 2959, 2924, 2852,
7.6 Hz, 1 H), 8.31 (d, J = 7.6 Hz, 1 H), 7.77–7.72 (m, 3 H) 7.30 (d,
J = 8.0 Hz, 1 H), 2.37 (s, 3 H), 2.34 (s, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 192.2, 191.3, 148.1, 145.4, 137.4, 135.3,
134.8, 134.0, 130.4, 130.0, 129.8, 128.2, 127.5, 124.1, 19.9,
˜
1669, 1582, 1569, 1483, 1450, 1399, 1321, 1301, 1261, 1211, 1174,
1071, 1011 cm–1. C14H9BrO2 (289.13): calcd. C 58.16, H 3.14;
found C 58.23, H 3.09.
19.3 ppm. IR (KBr film): ν = 3082, 2951, 2920, 2870, 1682, 1655,
˜
1-(4-Nitrophenyl)-2-phenylethane-1,2-dione (3c): Prepared from 1-
(4-nitrophenyl)ethanone (412.9 mg, 2.5 mmol), SeO2 (554.8 mg,
5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and benzene (8 mL)
over 20 h following Method A. Eluent: ethyl acetate 15% in hex-
ane; yellow solid (382.8 mg, 60%); m.p. 140–142 °C. The 1H NMR
1607, 1578, 1569, 1534, 1437, 1350, 1279, 1232, 1208, 1173, 1135,
1090 cm–1. LC–MS: m/z = 284.0 [M + H]+. C16H13NO4 (283.28):
calcd. C 67.84, H 4.63, N 4.94; found C 67.79, H 4.68, N 4.96.
N-[3-{2-Oxo-2-(p-tolyl)acetyl}phenyl]acetamide (3h): Prepared from
spectrum matched that of
a
commercial sample. 1H NMR
N-(3-acetylphenyl)acetamide
(443.0 mg,
2.5 mmol),
SeO2
(400 MHz, CDCl3): δ = 8.37 (m, 2 H), 8.18 (m, 2 H), 8.00–7.99
(m, 2 H), 7.74–7.70 (m, 1 H), 7.58–7.54 (m, 2 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 192.9, 192.1, 151.1, 137.3, 135.5, 132.4,
(554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and tolu-
ene (6 mL) over 16 h following Method B. Eluent: ethyl acetate
25% in hexane; light yellow solid (471.2 mg, 67%); m.p. 117–
119 °C. 1H NMR (400 MHz, CDCl3): δ = 7.99 (d, J = 7.6 Hz, 1
H), 7.93–7.86 (m, 2 H), 7.76–7.74 (m, 2 H), 7.56 (d, J = 7.6 Hz, 1
H), 7.38–7.34 (m, 1 H), 7.22 (m, 2 H), 2.35 (s, 3 H), 2.06 (s, 3 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 193.5, 193.2, 167.9, 145.5,
137.9, 133.0, 132.1, 131.6, 129.0, 128.8 125.4, 124.7, 119.2, 23.4,
131.0, 130.1, 129.2, 124.1 ppm. IR (KBr film): ν = 3108, 3082,
˜
2925, 2853, 1676, 1663, 1604, 1596, 1528, 1451, 1410, 1348, 1324,
1207, 1182, 1173 cm–1. C14H9NO4 (255.23): calcd. C 65.88, H 3.55,
N 5.49; found C 65.97, H 3.50, N 5.50.
1-(4-Chlorophenyl)-2-(p-tolyl)ethane-1,2-dione (3d): Prepared from
1-(4-chlorophenyl)ethanone (386.5 mg, 2.5 mmol), SeO2 (554.8 mg,
5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and toluene (6 mL)
over 15 h following Method B. Eluent: ethyl acetate 10% in hexane;
yellowish solid (388.1 mg, 60%); m.p. 121–123 °C. The 1H NMR
21.0 ppm. IR (KBr film): ν = 3287, 3200, 3145, 3119, 3103, 2925,
˜
2857, 2828, 1685, 1665, 1606, 1594, 1571, 1488, 1441, 1372, 1330,
1308, 1290, 1270, 1246, 1180, 1159 cm–1. GC–MS: m/z (%) = 281
(9) [M]+, 239 (12), 162 (60), 134 (22), 119 (100), 91 (98). C17H15NO3
(281.31): calcd. C 72.58, H 5.37, N 4.98; found C 72.81, H 5.29, N
4.89.
spectrum matched that of
a
commercial sample. 1H NMR
(400 MHz, CDCl3): δ = 7.92–7.91 (m, 2 H), 7.87–7.85 (m, 2 H),
7.50–7.84 (m, 2 H), 7.33–7.31 (m, 2 H), 2.44 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 193.7, 193.3, 146.5, 141.5, 131.4,
N-[3-{2-(4-Methoxyphenyl)-2-oxoacetyl}phenyl]acetamide (3i): Pre-
pared from N-(3-acetylphenyl)acetamide (443.0 mg, 2.5 mmol), an-
isole (270.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
14 h following Method B. Eluent: ethyl acetate 30% in hexane; yel-
lowish solid (520.3 mg, 70%); m.p. 130–132 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.00–8.82 (m, 5 H), 7.58 (d, J = 7.2 Hz, 1
H), 7.37 (t, J = 7.6 Hz, 1 H), 6.89–6.87 (m, 2 H), 3.81 (s, 3 H), 2.07
(s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 194.6, 193.1,
169.0, 165.2, 138.8, 133.6, 132.4, 129.8, 126.4, 125.8, 125.7, 120.4,
131.2, 130.3, 130.1, 129.8, 129.4, 22.0 ppm. IR (KBr film): ν =
˜
3093, 3066, 2924, 2854, 1663, 1605, 1587, 1573, 1486, 1457, 1402,
1319, 1215, 1185, 1174 cm–1. GC–MS: m/z (%) = 258 (8) [M]+, 139
(72), 119 (100), 111 (69), 91 (98). C15H11ClO2 (258.70): calcd. C
69.64, H 4.29; found C 69.57, H 4.31.
1-(4-Bromophenyl)-2-(p-tolyl)ethane-1,2-dione (3e): Prepared from
1-(4-bromophenyl)ethanone (497.6 mg, 2.5 mmol), SeO2 (554.8 mg,
5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and toluene (6 mL)
over 16 h following Method B. Eluent: ethyl acetate 8% in hexane;
yellowish solid (462.3 mg, 61%); m.p. 92–94 °C. 1H NMR
(400 MHz, CDCl3): δ = 7.88–7.68 (m, 6 H), 7.33–7.31 (m, 2 H),
2.45 (s, 3 H) ppm.13C NMR (100 MHz, CDCl3): δ = 193.6, 193.5,
146.5, 134.0, 132.4, 131.8, 131.2, 130.4, 130.1, 129.8, 22.0 ppm. IR
114.5, 55.7, 24.5 ppm. IR (KBr film): ν = 3289, 3199, 3145, 3103,
˜
2924, 2851, 1684, 1668, 1654, 1599, 1571, 1509, 1487, 1441, 1425,
1310, 1261, 1246, 1177, 1159, 1021 cm–1. MS (ES+): m/z = 298.0
[M + H]+, 320.0 [M + Na]+. C17H15NO4 (297.31): calcd. C 68.68,
H 5.09, N 4.71; found C 68.56, H 5.13, N 4.79.
(KBr film): ν = 3090, 3061, 3031, 2925, 2854, 1665, 1605, 1584,
˜
1-(3-Methoxyphenyl)-2-(naphthalen-1-yl)ethane-1,2-dione (6a): Pre-
pared from 1-(3-methoxyphenyl)ethanone (375.4 mg, 2.5 mmol),
naphthalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 15% in hexane; yel-
low solid (471.7 mg, 65%); m.p. 93–95 °C. 1H NMR (400 MHz,
CDCl3): δ = 9.30 (d, J = 8.8 Hz, 1 H), 8.12 (d, J = 8.0 Hz, 1 H),
7.95–7.89 (m, 2 H), 7.75 (t, J = 7.6 Hz, 1 H), 7.65–7.60 (m, 2
H),7.55–7.47 (m, 2 H), 7.40 (t, J = 8.0 Hz, 1 H), 7.20 (dd, J = 2.4,
J = 8.4 Hz, 1 H), 3.86 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 197.0, 194.5, 160.1, 135.9, 135.0, 134.7, 134.1, 131.0,130.1,
129.5, 128.8, 128.7, 127.1, 126.0, 124.4, 123.3, 121.8, 113.0,
1483, 1458, 1400, 1319, 1310, 1206, 1174, 1069 cm–1. MS (ES+):
m/z = 325.0 [M + Na]+. C15H11BrO2 (303.15): calcd. C 59.43, H
3.66; found C 59.57, H 3.63.
1-(4-Nitrophenyl)-2-(p-tolyl)ethane-1,2-dione (3f): Prepared from 1-
(4-nitrophenyl)ethanone (412.9 mg, 2.5 mmol), SeO2 (554.8 mg,
5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and toluene (6 mL)
over 16 h following Method B. Eluent: ethyl acetate 15% in hexane;
light yellow solid (417.4 mg, 62%); m.p. 145–147 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.37–8.16 (m, 4 H), 7.89–7.88 (m, 2 H),
7.36–7.34 (m, 2 H), 2.47 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 192.6, 192.3, 147.0, 137.4, 134.4, 132.8, 131.0, 130.2,
55.6 ppm. IR (KBr film): ν = 3070, 3012, 2964, 2940, 2922, 2837,
˜
130.0, 124.1, 22.0 ppm. IR (KBr film): ν = 3106, 3080, 3052, 2924,
˜
1672, 1655, 1594, 1572, 1509, 1485, 1465, 1431, 1339, 1299, 1268,
1245, 1211, 1172, 1161, 1104 cm–1. GC–MS: m/z (%) = 290 (22)
[M]+, 155 (100), 135 (86), 127 (98), 107 (39), 101 (20), 92 (58).
C19H14O3 (290.32): calcd. C 78.61, H 4.86; found C 78.51, H 4.89.
2854, 1677, 1661, 1603, 1570, 1525, 1411, 1348, 1323, 1207, 1184,
1174 cm–1. GC–MS: m/z (%) = 269 (15) [M]+, 239 (19), 150 (27),
119 (100), 104 (26), 91 (94). C15H11NO4 (269.26): calcd. C 66.91,
H 4.12, N 5.20; found C 66.86, H 4.22, N 5.26.
1-(3,4-Dimethylphenyl)-2-(3-nitrophenyl)ethane-1,2-dione (3g): Pre-
pared from 1-(3-nitrophenyl)ethanone (412.9 mg, 2.5 mmol), SeO2
(554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and o-
xylene (6 mL) over 16 h following Method B. Eluent: ethyl acetate
20% in hexane; yellow solid (439.2 mg, 62%); m.p. 105–107 °C. 1H
1-(2-Hydroxyphenyl)-2-(naphthalen-1-yl)ethane-1,2-dione (6b): Pre-
pared from 1-(2-hydroxyphenyl)ethanone (340.4 mg, 2.5 mmol),
naphthalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 30% in hexane; yel-
1
NMR (400 MHz, CDCl3): δ = 8.81 (s, 1 H), 8.50 (dd, J = 1.6, J = low solid (476.6 mg, 69%); m.p. 120–122 °C. H NMR (400 MHz,
324
www.eurjoc.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 320–328

Unsymmetrical Benzils by Oxidative Coupling
CDCl3): δ = 11.48 (s, 1 H), 9.32 (d, J = 8.4 Hz, 1 H), 8.16 (d, J = hexane; yellow solid (446.9 mg, 62%); m.p. 87–89 °C. 1H NMR
8.0 Hz, 1 H), 7.97–7.93 (m, 2 H), 7.77 (t, J = 7.6 Hz, 1 H), 7.67–
7.50 (m, 4 H), 7.11 (d, J = 8.4 Hz, 1 H), 6.89 (t, J = 7.6 Hz, 1 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 199.4, 194.4, 163.4, 137.9,
136.4, 135.5, 134.1, 132.5, 131.0, 129.7, 128.9, 128.1, 127.3, 125.9,
(400 MHz, CDCl3): δ = 9.30 (d, J = 8.8 Hz, 1 H), 8.11 (d, J =
8.0 Hz, 1 H), 7.95–7.92 (m, 2 H), 7.73 (t, J = 7.6 Hz, 1 H), 7.65–
7.60 (m, 2 H), 7.49 (t, J = 7.6 Hz, 1 H), 7.17 (s, 1 H), 7.06 (d, J =
8.0 Hz, 1 H), 2.73 (s, 3 H), 2.38 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 197.6, 196.3, 144.8, 141.9, 135.6, 134.8, 134.1, 133.6,
133.5, 131.1, 129.4, 129.3, 128.9, 128.7, 127.0, 126.8, 126.0, 124.4,
124.4, 119.8, 118.4, 117.1 ppm. IR (KBr film): ν = 3241, 3174,
˜
3087, 3062, 3010, 2957, 2924, 2852, 1660, 1631, 1591, 1575, 1509,
1486, 1454, 1397, 1309, 1251, 1230, 1182, 1156, 1100, 1084 cm–1.
C18H12O3 (276.29): calcd. C 78.25, H 4.38; found C 78.33, H 4.42.
22.0, 21.7 ppm. IR (KBr film): ν = 3089, 3028, 2963, 2924, 2854,
˜
1663, 1611, 1571, 1508, 1451, 1436, 1378, 1314, 1221, 1214, 1181,
1148, 1100 cm–1. GC–MS: m/z (%) = 288 (25) [M]+, 155 (90), 133
(100), 127 (98), 105 (76), 89 (36). C20H16O2 (288.35): calcd. C 83.31,
H 5.59; found C 83.23, H 5.61.
1-(4-Hydroxyphenyl)-2-(naphthalen-1-yl)ethane-1,2-dione (6c): Pre-
pared from 1-(4-hydroxyphenyl)ethanone (340.4 mg, 2.5 mmol),
naphthalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
1-(Anthracen-9-yl)-2-(o-tolyl)ethane-1,2-dione (6g): Prepared from
1-(o-tolyl)ethanone (335.5 mg, 2.5 mmol), anthracene (445.6 mg,
15 h following Method B. Eluent: ethyl acetate 35% in hexane; yel-
1
low solid (462.8 mg, 67%); m.p. 115–117 °C. H NMR (400 MHz, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg,
CDCl3): δ = 9.28 (d, J = 8.0 Hz, 1 H), 8.12 (d, J = 8.0 Hz, 1 H),
2.5 mmol), and acetonitrile (6 mL) over 14 h following Method B.
7.95–7.89 (m, 4 H), 7.74 (t, J = 8.0 Hz, 1 H), 7.63 (t, J = 7.6 Hz, Eluent: ethyl acetate 5% in hexane; yellow solid (486.6 mg, 60%);
1
1 H), 7.49 (t, J = 7.6 Hz, 1 H), 6.89–6.87 (m, 2 H), 5.31 (s, 1 H) m.p. 128–130 °C. H NMR (400 MHz, CDCl3): δ = 8.55 (s, 1 H),
ppm. 13C NMR (100 MHz, CDCl3): δ = 197.6, 193.5, 162.0, 136.0,
135.1, 134.1, 132.8, 130.9, 129.4, 128.8, 128.7, 127.1, 126.2, 125.9,
8.20 (d, J = 7.6 Hz, 1 H), 8.03–7.97 (m, 4 H), 7.51–7.31 (m, 7 H),
2.54 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 197.3, 192.5,
141.2, 132.5, 131.8, 131.7, 130.8, 129.9, 129.9, 129.4, 129.1, 128.1,
124.4, 116.0 ppm. IR (KBr film): ν = 3280, 3056, 2962, 2821, 2681,
˜
1663, 1645, 1598, 1566, 1510, 1462, 1437, 1397, 1371, 1317, 1296,
1264, 1225, 1185, 1165, 1148, 1108, 1086 cm–1. C18H12O3 (276.29):
calcd. C 78.25, H 4.38; found C 78.29, H 4.46.
126.8, 124.9, 124.5, 123.4, 20.9 ppm. IR (KBr film): ν = 3053, 3029,
˜
2979, 2929, 1660, 1600, 1556, 1486, 1452, 1382, 1305, 1249, 1179,
1100 cm–1. MS (ES+): m/z = 347.0 [M + Na]+. C23H16O2 (324.38):
calcd. C 85.16, H 4.97; found C 85.09, H 5.11.
1-(Naphthalen-1-yl)-2-(4-nitrophenyl)ethane-1,2-dione (6d): Pre-
pared from 1-(4-nitrophenyl)ethanone (412.9 mg, 2.5 mmol), naph-
thalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 30% in hexane; yel-
1-(Anthracen-9-yl)-2-(p-tolyl)ethane-1,2-dione (6h): Prepared from
1-(p-tolyl)ethanone (335.4 mg, 2.5 mmol), anthracene (445.6 mg,
2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg,
2.5 mmol), and acetonitrile (6 mL) over 15 h following Method B.
Eluent: ethyl acetate 5% in hexane; light yellow solid (462.3 mg,
1
low solid (534.3 mg, 70%); m.p. 150–152 °C. H NMR (400 MHz,
1
CDCl3): δ = 9.20 (d, J = 8.4 Hz, 1 H), 8.31–8.29 (m, 2 H), 8.15–
8.10 (m, 3 H), 7.91 (d, J = 8.4 Hz, 1 H), 7.82 (d, J = 7.2 Hz, 1 H),
7.71 (t, J = 8.0 Hz, 1 H), 7.60 (t, J = 7.6 Hz, 1 H), 7.46 (t, J =
7.6 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 195.4, 192.2,
151.1, 137.7, 136.7, 135.3, 134.1, 131.0, 130.9, 129.8, 129.0, 128.0,
57%); m.p. 138–140 °C. H NMR (400 MHz, CDCl3): δ = 8.55 (s,
1 H), 8.16–8.14 (m, 2 H), 7.99–7.95 (m, 4 H), 7.44–7.34 (m, 6 H),
2.44 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 198.5, 191.0,
146.1, 134.1, 131.8, 131.0, 130.9, 130.0, 130.0, 129.1, 127.8, 127.2,
125.6, 124.5, 22.0 ppm. IR (KBr film): ν = 3045, 2923, 2850, 1672,
˜
127.4, 125.8, 124.4, 124.2 ppm. IR (KBr film): ν = 3108, 3087,
1661, 1601, 1445, 1411, 1333, 1301, 1285, 1259, 1160, 1112 cm–1.
MS (ES+): m/z = 347.1 [M + Na]+. C23H16O2 (324.38): calcd. C
85.16, H 4.97; found C 85.20, H 4.90.
˜
3075, 3050, 2920, 2853, 1674, 1651, 1602, 1572, 1526, 1511, 1466,
1436, 1399, 1371, 1345, 1322, 1307, 1262, 1220, 1179, 1110 cm–1.
GC–MS: m/z (%) = 305 (6) [M]+, 155 (98), 150 (100), 127 (99), 92
(44). C18H11NO4 (305.29): calcd. C 70.82, H 3.63, N 4.59; found C
70.67, H 3.72, N 4.64.
1-(Anthracen-9-yl)-2-(3-methoxyphenyl)ethane-1,2-dione (6i): Pre-
pared from 1-(3-methoxyphenyl)ethanone (375.4 mg, 2.5 mmol),
anthracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
N-[3-{2-(Naphthalen-1-yl)-2-oxoacetyl}phenyl]acetamide (6e): Pre-
pared from N-(3-acetylphenyl)acetamide (443.0 mg, 2.5 mmol), 14 h following Method B. Eluent: ethyl acetate 5% in hexane; light
naphthalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), yellow solid (468.1 mg, 55%); m.p. 123–125 °C. 1H NMR
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
(400 MHz, CDCl3): δ = 8.52 (s, 1 H), 7.98–7.94 (m, 4 H), 7.85 (d,
J = 7.6 Hz, 1 H), 7.68–7.67 (m, 1 H), 7.44–7.38 (m, 5 H), 7.18 (dd,
J = 2.0, J = 8.4 Hz, 1 H), 3.77 (s, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 198.1, 191.2, 160.1, 134.1, 132.0, 131.0, 130.2, 130.1,
129.2, 128.0, 127.2, 125.6, 124.4, 123.7, 121.8, 113.9, 55.5 ppm. IR
15 h following Method B. Eluent: ethyl acetate 25% in hexane; yel-
1
low solid (595.0 mg, 75%); m.p. 145–147 °C. H NMR (400 MHz,
CDCl3): δ = 9.27 (d, J = 8.8 Hz, 1 H), 8.13–8.07 (m, 2 H), 7.94–
7.87 (m, 3 H), 7.75–7.60 (m, 4 H), 7.50–7.43 (m, 2 H), 2.09 (s, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 196.9, 194.2, 168.7,
138.8, 136.1, 135.2, 134.1, 133.9, 130.9, 129.9, 129.5, 128.8, 128.4,
127.2, 126.3, 125.9, 125.8, 124.4, 120.4, 24.5 ppm. IR (KBr film):
(KBr film): ν = 3073, 3012, 2971, 2933, 2832, 1679, 1665, 1593,
˜
1482, 1462, 1452, 1422, 1332, 1274, 1262, 1229, 1156, 1111 cm–1.
MS (ES+): m/z = 363.0 [M + Na]+. C23H16O3 (340.38): calcd. C
81.16, H 4.74; found C 81.29, H 4.89.
ν = 3292, 3251, 3186, 3135, 3090, 2926, 2856, 1678, 1665, 1600,
˜
1558, 1509, 1487, 1412, 1371, 1326, 1304, 1269, 1236, 1202, 1176,
1162, 1109 cm–1. MS (ES+): m/z = 317.9 [M + H]+, 340
[M + Na]+. C20H15NO3 (317.34): calcd. C 75.70, H 4.76, N 4.41;
found C 75.76, H 4.68, N 4.39.
1-(Anthracen-9-yl)-2-(2-chlorophenyl)ethane-1,2-dione (6j): Pre-
pared from 1-(2-chlorophenyl)ethanone (386.5 mg, 2.5 mmol), an-
thracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
1-(2,4-Dimethylphenyl)-2-(naphthalen-1-yl)ethane-1,2-dione
Prepared from 1-(2,4-dimethylphenyl)ethanone (370.5 mg,
(6f): 14 h following Method B. Eluent: ethyl acetate 5% in hexane; yel-
1
low solid (543.1 mg, 63%); m.p. 138–140 °C. H NMR (400 MHz,
2.5 mmol), naphthalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, CDCl3): δ = 8.52 (s, 1 H), 8.22 (d, J = 7.6 Hz, 1 H), 7.95–7.94 (m,
5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile
4 H), 7.66–7.372 (m, 7 H) ppm. 13C NMR (100 MHz, CDCl3): δ
(6 mL) over 15 h following Method B. Eluent: ethyl acetate 10% in
= 198.3, 191.2, 134.8, 132.2, 132.0, 131.0, 130.7, 130.3, 130.1, 129.2,
Eur. J. Org. Chem. 2012, 320–328
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
325

B. Myrboh et al.
FULL PAPER
129.2, 128.0, 125.6, 124.4 ppm. IR (KBr film): ν = 3057, 2924,
(445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O
(475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over 15 h following
Method B. Eluent: ethyl acetate 20% in hexane; light orange solid
˜
2852, 1663, 1622, 1577, 1555, 1487, 1452, 1303, 1247, 1103 cm–1.
MS (ES+): m/z = 345.1 [M + H]+, 366.9 [M + Na]+. C22H13ClO2
(344.80): calcd. C 76.64, H 3.80; found C 76.48, H 3.96.
1
(568.5 mg, 64%); m.p. 132–134 °C. H NMR (400 MHz, CDCl3):
δ = 9.08 (s, 1 H), 8.60–8.57 (m, 2 H), 8.51 (d, J = 7.6 Hz, 1 H),
8.02–8.00 (m, 2 H), 7.89–7.87 (m, 2 H), 7.76 (t, J = 7.6 Hz, 1 H),
7.45–7.43 (m, 4 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 197.0,
188.5, 148.7, 136.1, 133.6, 132.7, 131.0, 130.5, 130.2, 129.4, 129.0,
1-(Anthracen-9-yl)-2-(4-chlorophenyl)ethane-1,2-dione (6k): Pre-
pared from 1-(4-chlorophenyl)ethanone (386.5 mg, 2.5 mmol), an-
thracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 5% in hexane; yel-
128.8, 128.3, 125.8, 125.5, 124.1 ppm. IR (KBr film): ν = 3056,
˜
2923, 2852, 1676, 1649, 1609, 1554, 1533, 1441, 1354, 1249, 1079
cm–1. MS (ES+): m/z = 378.1 [M + Na]+. C22H13NO4 (355.35):
calcd. C 74.36, H 3.69, N 3.94; found C 74.53, H 3.55, N 3.89.
1
low solid (586.2 mg, 68%); m.p. 165–167 °C. H NMR (400 MHz,
CDCl3): δ = 8.55 (s, 1 H), 8.20–8.19 (m, 2 H), 7.99–7.89 (m, 4 H),
7.53–7.51 (m, 2 H), 7.42–7.40 (m, 4 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 196.8, 188.8, 140.5, 131.1, 131.0, 129.9, 129.5,
129.0,128.9, 128.6, 128.2, 127.0, 124.6, 123.2 ppm. IR (KBr film):
1-(Anthracen-9-yl)-2-(4-nitrophenyl)ethane-1,2-dione (6p): Prepared
from 1-(4-nitrophenyl)ethanone (412.9 mg, 2.5 mmol), anthracene
(445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O
(475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over 15 h following
Method B. Eluent: ethyl acetate 20% in hexane; yellowish solid
ν = 3046, 2926, 2851, 1672, 1657, 1622, 1584, 1568, 1401, 1252
˜
cm–1. MS (ES+): m/z = 345.1 [M + H]+, 366.9 [M + Na]+.
C22H13ClO2 (344.80): calcd. C 76.64, H 3.80; found C 76.58, H
3.92.
1
(586.3 mg, 66%); m.p. 187–189 °C. H NMR (400 MHz, CDCl3):
δ = 8.67 (s, 1 H) 8.50–8.40 (m, 4 H), 8.09–8.07 (m, 2 H), 7.95–7.93
(m, 2 H), 7.52–7.50 (m, 4 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 197.0, 189.1, 151.1, 136.8, 132.6, 131.7, 130.9, 130.2, 129.4,
1-(Anthracen-9-yl)-2-(4-bromophenyl)ethane-1,2-dione (6l): Pre-
pared from 1-(4-bromophenyl)ethanone (497.6 mg, 2.5 mmol), an-
thracene (554.8 g, 5.0 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
12 h following Method B. Eluent: ethyl acetate 10% in hexane; light
yellow solid (603.0 mg, 62%); m.p. 168–170 °C. 1H NMR
(400 MHz, CDCl3): δ = 8.55 (s, 1 H) 8.12–8.10 (m, 2 H), 7.99–7.88
(m, 4 H), 7.69–7.67 (m, 2 H), 7.42–7.40 (m, 4 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 197.8, 190.1, 132.6, 132.1, 132.1, 131.0,
130.5, 130.1, 129.9, 129.2, 128.0, 125.7, 124.2 ppm. IR (KBr film):
129.0, 128.3, 125.8, 124.2, 124.0 ppm. IR (KBr film): ν = 3113,
˜
3074, 3054, 2925, 2855, 1678, 1624, 1598, 1555, 1525, 1444, 1408,
1353, 1345, 1321, 1266, 1254 cm–1. GC–MS: m/z (%) = 355 (11)
[M]+ 355, 205 (80), 177 (100), 150 (92), 104 (62). C22H13NO4
(355.35): calcd. C 74.36, H 3.69, N 3.94; found C 74.47, H 3.71, N
3.98.
N-[3-{2-(Anthracen-9-yl)-2-oxoacetyl}phenyl]acetamide (6q): Pre-
pared from N-(3-acetylphenyl)acetamide (443.0 mg, 2.5 mmol), an-
thracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 25% in hexane; yel-
ν = 3083, 3045, 2955, 2924, 2853, 1674, 1657, 1581, 1555, 1482,
˜
1443, 1397, 1252 cm–1. MS (ES+): m/z = 389.4 [M + H]+.
C22H13BrO2 (389.25): calcd. C 67.88, H 3.37; found C 67.79, H
3.43.
1
low solid (670.5 mg, 73%); m.p. 181–183 °C. H NMR (400 MHz,
1-(Anthracen-9-yl)-2-(2-hydroxyphenyl)ethane-1,2-dione (6m): Pre-
pared from 1-(2-hydroxyphenyl)ethanone (340.4 mg, 2.5 mmol),
anthracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
14 h following Method B. Eluent: ethyl acetate 15% in hexane; light
CDCl3): δ = 8.56 (s, 1 H), 8.13–7.88 (m, 7 H), 7.50–7.36 (m, 6 H),
1.99 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 197.8, 190.8,
168.7, 138.8, 132.6, 132.1, 130.9, 130.1, 130.1, 130.0, 129.2, 128.1,
126.6, 126.5, 125.7, 124.3, 121.1, 24.5 ppm. IR (KBr film): ν =
˜
1
3305, 3087, 3054, 2925, 2854, 1668, 1612, 1587, 1554, 1514, 1485,
1368, 1304, 1250, 1175 cm–1. MS (ES+): m/z = 390.0 [M + Na]+.
C24H17NO3 (367.40): calcd. C 78.46, H 4.66, N 3.81; found C
78.58, H 4.51, N 3.92.
orange solid (407.9, 50%); m.p. 135–137 °C. H NMR (400 MHz,
CDCl3): δ = 11.31 (s, 1 H), 8.58 (s, 1 H) 8.21 (d, J = 7.6 Hz, 1 H),
8.01–7.97 (m, 4 H), 7.59 (t, J = 7.6 Hz, 1 H), 7.45–7.43 (m, 4 H),
7.07–7.00 (m, 2 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 196.5,
195.6, 164.5, 138.2, 132.6, 132.3, 130.9, 130.2, 129.7, 129.3, 128.2,
1-(Anthracen-9-yl)-2-(2,4-dimethylphenyl)ethane-1,2-dione (6r): Pre-
pared from 1-(2,4-dimethylphenyl)ethanone (370.5 mg, 2.5 mmol),
anthracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 8% in hexane; yel-
125.7, 124.2, 120.0, 119.1, 115.7 ppm. IR (KBr film): ν = 3054,
˜
3026, 3002, 2957, 2925, 2854, 1662, 1622, 1578, 1578, 1486, 1452,
1303, 1246 cm–1. MS (ES+): m/z = 327.0 [M + H]+, 349.0 [M +
Na]+. C22H14O3 (326.35): calcd. C 80.97, H 4.32; found C 80.87,
H 4.12.
1
low solid (490.7 mg, 58%); m.p. 134–136 °C. H NMR (400 MHz,
CDCl3): δ = 8.50 (s, 1 H), 8.11 (d, J = 8.0 Hz, 1 H), 8.03–7.93 (m,
4 H), 7.41–7.30 (m, 4 H), 7.15–7.11 (m, 2 H), 2.50 (s, 3 H), 2.33 (s,
3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 198.6, 193.3, 144.7,
142.7, 133.8, 133.3, 131.8, 131.0, 130.7, 130.1, 129.1, 128.1, 127.8,
1-(Anthracen-9-yl)-2-(4-hydroxyphenyl)ethane-1,2-dione (6n): Pre-
pared from 1-(4-hydroxyphenyl)ethanone (340.4 mg, 2.5 mmol),
anthracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
16 h following Method B. Eluent: ethyl acetate 20% in hexane; yel-
low solid (465.0, 57%); m.p. 215–217 °C. 1H NMR [400 MHz,
(CD3)2CO]: δ = 8.85 (s, 1 H), 8.28–8.06 (m, 6 H), 7.61–7.56 (m, 4
H), 7.16–7.14 (m, 2 H), 5.05 (s, 1 H) ppm. 13C NMR [100 MHz,
(CD3)2CO]: δ = 198.6, 189.7, 163.8, 133.3, 131.3, 131.0, 129.7,
129.2, 127.8, 127.7, 125.9, 125.7, 124.3, 116.2 ppm. IR (KBr film):
126.7, 125.5, 124.5, 22.1, 21.8 ppm. IR (KBr film): ν = 3079, 3059,
˜
2926, 1670, 1658, 1594, 1554, 1522, 1449, 1253, 1119 cm–1. MS
(ES+): m/z = 361.0 [M + Na]+. C24H18O2 (338.41): calcd. C 85.18,
H 5.36; found C 85.27, H 5.42.
1-(Anthracen-9-yl)-2-mesitylethane-1,2-dione (6s): Prepared from 1-
mesitylethanone (405.6 mg, 2.5 mmol), anthracene (445.6 mg,
2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg,
2.5 mmol), and acetonitrile (6 mL) over 16 h following Method B.
Eluent: ethyl acetate 10% in hexane; orange solid (466.9 mg, 53%);
ν = 3384, 3056, 2926, 1692, 1649, 1595, 1569, 1514, 1445, 1296,
˜
1227, 1162, 1111 cm–1. MS (ES+): m/z = 349.0 [M + Na]+.
C22H14O3 (326.35): calcd. C 80.97, H 4.32; found C 80.73, H 4.23.
1
1-(Anthracen-9-yl)-2-(3-nitrophenyl)ethane-1,2-dione (6o): Prepared
m.p. 108–110 °C. H NMR (400 MHz, CDCl3): δ = 8.52 (s, 1 H),
from 1-(3-nitrophenyl)ethanone (412.9 mg, 2.5 mmol), anthracene
8.00–7.98 (m, 2 H), 7.76–7.74 (m, 2 H), 7.44–7.42 (m, 4 H), 6.85
326
www.eurjoc.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 320–328

Unsymmetrical Benzils by Oxidative Coupling
(s, 2 H), 2.26 (s, 3 H), 2.21 (s, 6 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 198.4, 193.2, 140.3, 135.5, 133.6, 132.2, 131.0, 130.4,
129.3, 129.0, 129.0, 127.2, 125.7, 125.6, 124.7, 21.3, 20.5 ppm. IR
Na]+. C19H14O3 (290.32): calcd. C 78.61, H 4.86; found C 78.70,
H 4.90.
1-(Naphthalen-1-yl)-2-(naphthalen-2-yl)ethane-1,2-dione (10a): Pre-
pared from 1-(naphthalen-2-yl)ethanone (425.5 mg, 2.5 mmol),
naphthalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
15 h following Method B. Eluent: ethyl acetate 15% in hexane;
brownish yellow solid (535.3 mg, 69%); m.p. 128–130 °C. 1H NMR
(KBr film): ν = 3057, 3003, 2917, 2853, 1697, 1670, 1613, 1445,
˜
1371, 1242, 1152, 1104 cm–1. MS (ES+): m/z = 375.0 [M + Na]+.
C25H20O2 (352.43): calcd. C 85.20, H 5.72; found C 85.23, H 5.94.
1-(Naphthalen-2-yl)-2-phenylethane-1,2-dione (9a): Prepared from
1-(naphthalen-2-yl)ethanone
(425.5 mg,
2.5 mmol),
SeO2
(554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and ben- (400 MHz, CDCl3): δ = 9.28 (d, J = 8.8 Hz, 1 H), 8.41 (s, 1 H),
zene (8 mL) over 18 h following Method A. Eluent: ethyl acetate
10% in hexane; light yellow solid (384.0 mg, 59%); m.p. 76–78 °C.
1H NMR (400 MHz, CDCl3): δ = 8.41 (s, 1 H), 8.11–7.89 (m, 6
8.08–8.05 (m, 2 H), 7.92–7.82 (m, 5 H), 7.72–7.68 (m, 1 H), 7.59–
7.55 (m, 2 H), 7.47 (t, J = 7.6 Hz, 1 H), 7.41 (t, J = 7.6 Hz, 1 H)
ppm. 13C NMR (100 MHz, CDCl3): δ = 197.2, 194.7, 136.3, 136.0,
H), 7.69–7.51 (m, 5 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 135.2, 134.1, 133.5, 132.4, 131.0, 130.7, 129.9, 129.5, 129.5, 129.2,
194.7, 136.4, 134.9, 133.6, 133.1, 132.3, 130.3, 130.0, 129.9, 129.6,
128.8, 128.7, 127.9, 127.2, 127.1, 126.0, 124.5, 123.9 ppm. IR (KBr
129.2, 129.1, 128.0, 127.2, 123.6 ppm. IR (KBr film): ν = 3084, film): ν = 3063, 3048, 2926, 2855, 1679, 1660, 1623, 1594, 1571,
˜
3057, 3031, 2973, 2927, 1671, 1659, 1626, 1596, 1580, 1466, 1449,
1438, 1396, 1371, 1354, 1325, 1307, 1276, 1251, 1211, 1190, 1176,
1153, 1126 cm–1. MS (ES+): m/z = 260.9 [M + H]+, 282.9 [M +
Na]+. C18H12O2 (260.29): calcd. C 83.06, H 4.65; found C 83.19,
H 4.71.
˜
1508, 1464, 1437, 1387, 1370, 1357, 1290, 1261, 1243, 1218, 1198,
1165, 1098 cm–1. MS (ES+): m/z = 333.0 [M + Na]+. C22H14O2
(310.35): calcd. C 85.14, H 4.55; found C 85.16, H 4.39.
1-(Furan-2-yl)-2-(naphthalen-1-yl)ethane-1,2-dione (10b): Prepared
from 1-(furan-2-yl)ethanone (275.3 mg, 2.5 mmol), naphthalene
1-(Naphthalen-2-yl)-2-(p-tolyl)ethane-1,2-dione (9b): Prepared from (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O
1-(naphthalen-2-yl)ethanone
(425.5 mg,
2.5 mmol),
SeO2
(475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over 16 h following
Method B. Eluent: ethyl acetate 15% in hexane; brownish yellow
solid (237.7 mg, 38%); m.p. 64–66 °C. 1H NMR (400 MHz,
CDCl3): δ = 9.13 (d, J = 8.4 Hz, 1 H), 8.11 (d, J = 8.0 Hz, 1 H),
7.98 (d, J = 7.2 Hz, 1 H), 7.92 (d, J = 8.0 Hz, 1 H), 7.75–7.69 (m,
(554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), and tolu-
ene (6 mL) over 16 h following Method B. Eluent: ethyl acetate
10% in hexane; yellow solid (350.0 mg, 51%); m.p. 90–92 °C. 1H
NMR (400 MHz, CDCl3): δ = 8.40 (s, 1 H), 8.09 (d, J = 8.0 Hz, 1
H), 7.96–7.87 (m, 5 H), 7.63 (t, J = 6.8 Hz, 1 H), 7.54 (t, J = 2 H), 7.60 (t, J = 7.6 Hz, 1 H), 7.50 (t, J = 8.0 Hz, 1 H), 7.41 (d,
8.0 Hz, 1 H), 7.31 (d, J = 8.0 Hz, 2 H), 2.43 (s, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 194.9, 194.4, 146.3, 136.3, 133.5,
132.6, 132.3, 130.1, 129.9, 129.8, 129.5, 129.1, 127.9, 127.2, 126.1,
J = 3.6 Hz, 1 H), 6.62–6.61 (m, 1 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 194.2, 181.3, 150.3, 149.3, 135.9, 134.5, 134.1, 131.1,
129.3, 128.8, 128.4, 127.1, 125.8, 124.4, 124.0, 113.7 ppm. IR (KBr
123.7, 22.0 ppm. IR (KBr film): ν = 3063, 2924, 2853, 1666, 1625,
film): ν = 3163, 3139, 3123, 3058, 3045, 3009, 2924, 2853, 1658,
˜
˜
1602, 1572, 1464, 1353, 1316, 1249, 1216, 1187, 1171, 1124 cm–1.
C19H14O2 (274.32): calcd. C 83.19, H 5.14; found C 83.36, H 5.29.
1651, 1595, 1570, 1558, 1509, 1463, 1399, 1315, 1268, 1243, 1231,
1215, 1193, 1159, 1080, 1031 cm–1. MS (ES+): m/z = 272.9 [M +
Na]+. C16H10O3 (250.25): calcd. C 76.79, H 4.03; found C 76.86,
H 4.13.
1-(2,5-Dimethylphenyl)-2-(naphthalen-2-yl)ethane-1,2-dione
(9c):
Prepared from 1-(naphthalen-2-yl)ethanone (425.5 mg, 2.5 mmol),
SeO2 (554.8 mg, 5.0 mmol), pTsOH·H2O (475.6 mg, 2.5 mmol), 1-(Naphthalen-1-yl)-2-(thiophen-2-yl)ethane-1,2-dione (10c): Pre-
and p-xylene (6 mL) over 16 h following Method B. Eluent: ethyl pared from 1-(thiophen-2-yl)ethanone (315.5 mg, 2.5 mmol), naph-
acetate 10% in hexane; yellowish solid (439.7 mg, 61%); m.p. 75– thalene (320.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
77 °C. 1H NMR (400 MHz, CDCl3): δ = 8.36 (s, 1 H), 8.04–8.02 pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
(m, 1 H), 7.92–7.83 (m, 3 H), 7.58 (t, J = 7.2 Hz, 1 H), 7.50 (t, J
= 7.2 Hz, 1 H), 7.40 (s, 1 H), 7.24 (d, J = 7.6 Hz, 1 H), 7.18 (d, J
= 6.4 Hz, 1 H), 2.63 (s, 3 H), 2.21 (s, 3 H) ppm. 13C NMR
16 h following Method B. Eluent: ethyl acetate 15% in hexane; yel-
low sticky solid (379.5 mg, 57%). H NMR (400 MHz, CDCl3): δ
= 9.16 (d, J = 8.4 Hz, 1 H), 8.12 (d, J = 8.0 Hz, 1 H), 8.00 (d, J =
1
(100 MHz, CDCl3): δ = 197.0, 195.1, 138.4, 136.3,135.8, 134.7, 7.2 Hz, 1 H), 7.94 (d, J = 8.0 Hz, 1 H), 7.86–7.83 (m, 2 H), 7.75–
133.5, 133.4, 132.5, 132.4, 130.5, 129.9, 129.5, 129.1, 128.0, 127.1,
7.71 (m, 1 H), 7.62 (t, J = 7.6 Hz, 1 H), 7.52 (t, J = 7.6 Hz, 1 H),
7.20 (t, J = 4.4 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
194.7, 186.3, 140.3, 136.7, 136.6, 135.9, 134.8, 134.0, 131.1, 129.3,
123.9, 21.5, 20.8 ppm. IR (KBr film): ν = 3061, 3023, 2957, 2924,
˜
2855, 1678, 1665, 1623, 1596, 1570, 1497, 1466, 1438, 1387, 1380,
1361, 1309, 1277, 1249, 1221, 1196, 1162, 1129 cm–1. GC–MS: m/z
= 288 [M]+. C20H16O2 (288.35): calcd. C 83.31, H 5.59; found C
83.46, H 5.63.
128.8, 128.8, 128.5, 127.1, 125.8, 124.4 ppm. IR (Neat): ν = 3091,
˜
3052, 3011, 2953, 1654, 1591, 1572, 1508, 1461, 1435, 1409, 1353,
1304, 1291, 1263, 1226, 1178, 1106, 1078, 1053 cm–1. MS (ES+): m/z
= 267.2 [M + H]+, 288.9 [M + Na]+. C16H10O2S (266.31): calcd. C
72.16, H 3.78, S 12.04; found C 72.29, H 3.79, S 11.97.
1-(4-Methoxyphenyl)-2-(naphthalen-2-yl)ethane-1,2-dione (9d): Pre-
pared from 1-(naphthalen-2-yl)ethanone (425.5 mg, 2.5 mmol), ani-
sole (270.4 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
14 h following Method B. Eluent: ethyl acetate 15% in hexane; yel-
lowish solid (508.1 mg, 70%); m.p. 69–71 °C. 1H NMR (400 MHz,
1-(Anthracen-9-yl)-2-(thiophen-2-yl)ethane-1,2-dione (10d): Pre-
pared from 1-(thiophen-2-yl)ethanone (315.5 mg, 2.5 mmol), an-
thracene (445.6 mg, 2.5 mmol), SeO2 (554.8 mg, 5.0 mmol),
pTsOH·H2O (475.6 mg, 2.5 mmol), and acetonitrile (6 mL) over
CDCl3): δ = 8.34 (s, 1 H), 8.03 (d, J = 8.8 Hz, 1 H) 7.94–7.82 (m, 14 h following Method B. Eluent: ethyl acetate 20% in hexane; yel-
5 H), 7.57 (t, J = 7.2 Hz, 1 H), 7.49 (t, J = 7.2 Hz, 1 H), 6.93–6.91 lowish solid (363.9 mg, 46%); m.p. 145–147 °C. 1H NMR
(m, 2 H), 3.82 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
195.0, 193.3, 165.0, 136.3, 133.4, 132.4, 132.4, 130.5, 129.9, 129.9,
129.1, 128.0, 127.1, 126.2, 123.7, 114.4, 55.7 ppm. IR (KBr film):
(400 MHz, CDCl3): δ = 8.55 (s, 1 H), 8.23 (d, J = 3.6 Hz, 1 H),
8.00–7.98 (m, 2 H), 7.86–7.84 (m, 3 H), 7.44–7.40 (m, 4 H), 7.25
(t, J = 4.4 Hz, 1 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 197.7,
182.3, 138.1, 137.7, 137.2, 134.1, 133.5, 131.4, 130.9, 130.2, 129.8,
ν = 3058, 3006, 2933, 2839, 1663, 1628, 1599, 1574, 1509, 1464,
˜
1422, 1313, 1252, 1219, 1167 cm–1. MS (ES+): m/z = 312.9 [M +
129.1, 129.1, 127.7, 127.2, 125.6, 124.4 ppm. IR (KBr film): ν =
˜
Eur. J. Org. Chem. 2012, 320–328
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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327

B. Myrboh et al.
FULL PAPER
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3133, 3091, 3052, 2926, 1696, 1678, 1637, 1592, 1445, 1407, 1354,
1343, 1262, 1108 cm–1. MS (ES+): m/z = 338.9 [M + Na]+.
C20H12O2S (316.37): calcd. C 75.93, H 3.82, S 10.14; found C 75.81,
H 3.80, S 10.23.
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1
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Acknowledgments
The authors are thankful to the University Grants Commission
(UGC), India for research fellowships and the Sophisticated Ana-
lytical Instrument Facility (SAIF), North-Eastern Hill University
for NMR and mass spectral analysis and acknowledge the Univer-
sity Grants Commission (UGC) for financial assistance under pro-
ject number 40-83/2011(SR).
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Received: July 12, 2011
Published Online: November 11, 2011
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