Reaction of Arylglyoxals with Electron-Rich Benzenes and π-Excessive Heterocycles. Facile Synthesis of Heteroaryl α-Acyloins

Article abstract of DOI:10.1081/SCC-120027284

The reaction of arylglyoxals and their hydrates with electron-rich benzenes and π-excessive heterocycles, if conducted in the absence of catalysts, affords α-benzoins.

Full text of DOI:10.1081/SCC-120027284

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Reaction of Arylglyoxals with Electron‐Rich Benzenes
and π‐Excessive Heterocycles. Facile Synthesis of
Heteroaryl α‐Acyloins
Sergey P. Ivonin a , Andrey V. Lapandin a , Andrey A. Anishchenko a & Vasilii G. Shtamburg
a
a Department of Organic Chemistry, Dnepropetrovsk National University, Nauchnaya
Street 13, Dnepropetrovsk, 49050, Ukraine
Version of record first published: 16 Aug 2006.
To cite this article: Sergey P. Ivonin, Andrey V. Lapandin, Andrey A. Anishchenko & Vasilii G. Shtamburg (2004): Reaction
of Arylglyoxals with Electron‐Rich Benzenes and π‐Excessive Heterocycles. Facile Synthesis of Heteroaryl α‐Acyloins,
Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic Chemistry, 34:3,
451-461
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 3, pp. 451–461, 2004
Reaction of Arylglyoxals with Electron-Rich
Benzenes and p-Excessive Heterocycles.
Facile Synthesis of Heteroaryl a-Acyloins
*
Sergey P. Ivonin, Andrey V. Lapandin,
Andrey A. Anishchenko, and Vasilii G. Shtamburg
Department of Organic Chemistry, Dnepropetrovsk National University,
Dnepropetrovsk, Ukraine
ABSTRACT
The reaction of arylglyoxals and their hydrates with electron-rich
benzenes and p-excessive heterocycles, if conducted in the absence of
catalysts, affords a-benzoins.
Key Words: Arylglyoxals; Benzoins; p-Excessive heterocycles;
Electrophilic aromatic substitution.
*
Correspondence: Sergey P. Ivonin, Department of Organic Chemistry, Dneprope-
trovsk National University, Nauchnaya Street 13, Dnepropetrovsk 49050, Ukraine;
E-mail: ivonin@dp.ukrtel.net.
451
DOI: 10.1081/SCC-120027284
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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452
Ivonin et al.
INTRODUCTION
Arylglyoxals are soft electrophilic reagents able to react with aromatic
and heterocyclic compounds. Such reactions performed in acid media afford
diarylaroylmethanes.[1–6] In this context, for example, they were applied to
the modelling of corticoid determination. In neutral media, intermediate
benzoins and their heterocyclic analogues[7–11] can be isolated. The resulting
benzoins are less stable a-isomers widely used as synthons in organic
synthesis.[12–18] The use of aluminium chloride as a catalyst is restricted to
halogeno- and methyl-substituted benzenes.[7] Currently available synthetic
routes provide a-benzoins in moderate yields.[7,19–21]
RESULTS AND DISCUSSION
Our interest was attracted by the possibility to condense arylglyoxals and
their hydrates with electron-rich benzenes and p-excessive heterocycles to
obtain a-benzoins and their heterocyclic analogues (Fig. 1).
We have found the condensation of phenylglyoxal with N,N-dimethylani-
line in benzene to furnish a-benzoin 1. The reactivity of a substituted benzene
in this reaction reduces with decreaseing electron-donor ability of the
substituent. For instance, phenylglyoxal condenses with 4-phenylmorpholine
to give a-benzoin 2 in significantly lower yield (Table 1) and no evidence of
the reaction with resorcin dimethyl ether is observable at all. The condensation
of thienylglyoxal with N,N-dialkylanilines proceeds similarly to yield
corresponding a-benzoins 3 and 4.
On boiling less reactive phenylglyoxal hydrate with N,N-dimethylaniline
in benzene, we have isolated not only the condensation product, substituted a-
benzoin 1, but also the product of further N,N-dimethylaniline addition, bis-
adduct 5 (Sch. 1).
Severin et al. used phenylglyoxal in the condensation with alkylpyrroles
to obtain the corresponding a-acyloins in yields not exceeding 50%.[11] We
have shown that an alkyl group at the nitrogen atom sufficiently increases the
reactivity of the pyrrole ring to afford condensation of 1-methylpyrrole and
1,2,5-trimethylpyrrole even with less reactive phenylglyoxal hydrate in
boiling benzene thus obtaining a-acyloins 6 and 9 in higher yields (Table 1).
Electrophilic substitution, namely, acylation, nitration and phosphorila-
tion,[22–24] in N-arylpyrroles is known to run often nonregioselectively giving
a mixture of the products substituted at the positions 2 and 3 of the pyrrole
ring. As found by us, the condensation of N-arylpyrroles with phenylglyoxal
proceeds regioselectively at the position 2 of the pyrrole ring at room temp-
erature. The reaction of less reactive substrates, 1-aryl-2,5-dimethylpyrroles,

ORDER
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Reaction of Arylglyoxals
Table 1. a-Acyloin formation results.
453
Product
R1
R2
Method
Time
Yield (%)
i
3 d
2 h
55
37
1
2
3
4
Ph
Ph
ii
i
i
i
3 d
14
75
46
10 d
11 d
6
7
Ph
Ph
ii
2 h
67
i
12 h
2 h
67
62
ii
i
12 h
2 h
66
54
8
Ph
ii
9
Ph
Ph
ii
2 h
67
i
12 h
2 h
80
50
10
ii
i
12 h
2 h
87
80
11
Ph
ii
i
12 h
2 h
65
62
12
13
ii
ii
2 h
66
14
15
ii
ii
2 h
2 h
58
66
16
17
i
i
12 h
4 d
68
60
18
Ph
i
6 d
49
(continued)

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Ivonin et al.
Table 1 Continued.
Product
R1
R2
Method
Time
Yield (%)
19
20
21
Ph
Ph
i
i
i
12 h
12 d
14 d
82
46
74
with phenylglyoxal leading to 3-substituted products requires elevated
temperature. Introduction of a strong acceptor, nitro-group, into aryl rest
results in an essential decrease of a reactivity of pyrrole substrate in reaction of
a benzoylhydroxymethylation. So N-(p-nitrophenyl)-pyrrole did not react
with phenylglyoxal even during prolonged heating in boiling benzene. Using
less reactive electrophilic agent, phenylglyoxal hydrate, in the condensation
with 1-arylpyrroles and 1-aryl-2,5-dimethylpyrroles results in the reduced
yields of the corresponding acyloins causing no effect on the reaction
regioselectivity (Table 1).
Condensation of (het)arylglyoxal hydrates with indole, always affords
a-acyloins 12–15. Contrary to literature data,[8] no effect of (het)aryl
substituents on the reaction direction and course is observed. Nor is the
process sensitive to using, at room temperature, more reactive phenylglyoxal
instead of its hydrate.
Scheme 1. Benzoylhydroxymethylation with (het)arylglyoxals.

ORDER
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Reaction of Arylglyoxals
455
2-Substituted indoles cannot be reacted with (het)arylglyoxal hydrates.
The condensation proceeds, however, with more reactive (het)arylglyoxals at
room temperature to provide the corresponding a-acyloins 16–19.
Due to lower reactivity of furan compared to pyrrole, 2-methylfuran
enters into the condensation only with anhydrous (het)arylglyoxals. Attempts
to run the condensation with thiophene failed even during prolonged
heating of the reagents in refluxing benzene, due to lower reactivity of this
substrate.
EXPERIMENTAL
1H NMR spectra were recorded in DMSO-D6 on a Varian VXR-300
instrument with TMS as internal standard. The reaction courses and product
purities were controlled by TLC on the Silufol-UV-254 plates using iodine
vapour for visualization. Benzene was freshly distilled over sodium prior to
use.
General Method i
To a solution of arylglyoxal (5.00 mmol) in benzene (4 mL), a solution of
a p-excessive substrate (5.00 mmol) in benzene (4 mL) was added. The
solution obtained was kept at room temperature for a time given in Table 1.
General Method ii
A solution of arylglyoxal hydrate (5.00 mmol) and a p-excessive
substrate (5.00 mmol) in benzene (8 mL) was boiled for 2 h.
Product isolation and purification procedures were performed as follows:
2-(4-Dimethylaminophenyl)-2-hydroxy-1-phenylethanone (1). Ben-
zene was evaporated under vacuum and the residue was recrystallized from
ethanol. Straw-coloured needles. M.p. 161–1628C (159–1608C[19]). 1H
NMR: d ¼ 2.87 (s, 6H), 5.51 (d, J ¼ 7.6, 1H), 5.92 (d, J ¼ 7.6, 1H), 6.62
(d, J ¼ 9.0, 2H), 7.17 (d, J ¼ 8.2, 2H), 7.41 (t, J ¼ 7.6, 2H), 7.52 (d, J ¼ 6.9,
1H), 7.94 (d, J ¼ 7.9, 2H). Anal. Calcd. for C16H17NO2: C, 75.27; H, 6.71; N,
5.49. Found: C, 75.31; H, 6.68; N, 5.51.
2-Hydroxy-2-(4-morpholin-4-yl)phenyl]-1-phenylethanone (2). Ben-
zene was evaporated under vacuum and the residue was recrystallized from
ethanol. Straw-coloured needles. M.p. 163–1648C. 1H NMR: d ¼ 3.04
(t, J ¼ 8.4, 4H), 3.68 (t, J ¼ 8.4, 4H), 5.62 (d, J ¼ 7.6, 1H), 5.93 (d, J ¼ 7.6,

ORDER
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456
Ivonin et al.
1H), 6.86 (d, J ¼ 8.5, 2H), 7.23 (d, J ¼ 8.5, 2H), 7.41 (t, J ¼ 7.2, 2H), 7.52
(d, J ¼ 7.2, 1H), 7.95 (d, J ¼ 7.2, 2H). Anal. Calcd. for C18H19NO3: C, 72.71;
H, 6.44; N, 4.71. Found: C, 72.93; H, 6.56; N, 4.51.
2-(4-Dimethylaminophenyl)-2-hydroxy-1-(thiophen-2-yl)ethanone
(3). The precipitating crystals were filtered off and recrystallized from
benzene. Yellow needles. M.p. 143–1468C. 1H NMR: d ¼ 2.93 (s, 6H), 3.85
(s, 1H), 5.66 (s, 1H), 6.67 (d, J ¼ 9.0, 2H), 7.02 (t, J ¼ 4.3, 1H), 7.22 (d,
J ¼ 9.0, 2H), 7,58 (d, J ¼ 4.3, 1H), 7.63 (d, J ¼ 4.3, 1H). Anal. Calcd. for
C14H15NO2S: N, 5.35; S, 12.27. Found: N, 5.20; S, 12.48.
2-(4-Diethylaminophenyl)-2-hydroxy-1-(thiophen-2-yl)ethanone (4).
Benzene was evaporated under vacuum to 3 mL. The resulting precipitate
was filtered off and recrystallized from benzene. Straw-coloured needles. M.p.
1
128–1318C. H NMR: d ¼ 1.07 (t, J ¼ 7.0, 6H), 3.29 (q, J ¼ 7.0, 4H), 5.59
(s, 1H), 5.79 (s, 1H), 6.57 (d, J ¼ 8.7, 2H), 7.12 (t, J ¼ 5.1, 1H), 7.20 (d,
J ¼ 8.7, 2H), 7.85 (d, J ¼ 5.1, 1H), 7.95 (d, J ¼ 3.9, 1H). Anal. Calcd. for
C16H19NO2S: N, 4.84; S, 11.08. Found: N, 4.71; S, 11.23.
2,2-Bis-(4-dimethylaminophenyl)-1-phenylethanone
(5). Benzene
was evaporated under vacuum and the residue was chromatographed on a
column (alumina, benzene). The products obtained were recrystallized from
ethanol. The yield of bis-adduct 5 (yellow needles) is 19%. M.p. 167–
1688C.[1] 1H NMR: d ¼ 2.86 (s, 12H), 5.97 (s, 1H), 6.63 (d, J ¼ 8.4, 4H), 7.05
(d, J ¼ 8.4, 4H), 7.42 (t, J ¼ 7.8, 2H), 7.52 (d, J ¼ 7.8, 1H), 7.99 (d, J ¼ 7.8,
2H). Anal. Calcd. for C24H26N2O: C, 80.41; H, 7.31; N, 7.81. Found: C, 80.37;
H, 7.33; N, 7.80.
2-Hydroxy-2-(1-methyl-1H-pyrrol-2-yl)-1-phenylethanone (6). Ben-
zene was evaporated under vacuum and the residue was recrystallized from
hexane. Colourless plates. M.p. 91–928C. 1H NMR: d ¼ 3.59 (s, 3H), 5.56 (d,
J ¼ 6.0, 1H), 5.62 (s, 1H), 5.74 (s, 1H), 6.08 (d, J ¼ 6.0, 1H), 6.62 (s, 1H),
7.38 (t, J ¼ 7.5, 2H), 7.49 (d, J ¼ 7.5, 1H), 7.82 (d, J ¼ 7.5, 2H). Anal.
Calcd. for C13H13NO2: C, 72.55; H, 6.09; N, 6.51. Found: C, 72.36; H, 6.12;
N, 6.47.
2-Hydroxy-1-phenyl-2-(1-p-tolyl-1H-pyrrol-2-yl)ethanone (7). Ben-
zene was evaporated under vacuum and the residue was chromatographed
1
on a column (alumina, methylene chloride). Oil. H NMR: d ¼ 2.58 (s, 3H),
5.79 (d, J ¼ 6.7, 1H), 5.87 (d, J ¼ 6.7, 1H), 6.10 (d, J ¼ 3.9, 1H), 6.24
(t, J ¼ 3.9, 1H), 6.39 (d, J ¼ 3.9, 1H), 7.45–7.52 (m, 6H), 7.64 (d, J ¼ 8.1,
1H), 7.73 (d, J ¼ 8.1, 2H). Anal. Calcd. for C19H17NO2: C, 78.33; H, 5.88; N,
4.81. Found: C, 78.25; H, 5.97; N, 4.59.
2-[1-(4-Ethoxyphenyl)-1H-pyrrol-2-yl]-2-hydroxy-1-phenylethanone
(8). Benzene was evaporated under vacuum. The residue was extracted with
boiling hexane (2 Â 5 mL) and hexane was evaporated under vacuum. A
straw-coloured oil crystallizing with time. M.p. 31–328C. 1H NMR: d ¼ 1.39

ORDER
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Reaction of Arylglyoxals
457
(t, J ¼ 7.0, 3H), 4.07 (q, J ¼ 7.0, 4H), 5.59 (s, 1H), 5.72 (s, 1H), 6.24
(d, J ¼ 3.3, 1H), 6.38 (d, J ¼ 3.3, 1H), 6.89 (t, J ¼ 3.3, 1H), 6.95 (d, J ¼ 7.9,
2H), 7.33 (d, J ¼ 7.9, 2H), 7.53 (t, J ¼ 7.1, 2H), 7.70 (d, J ¼ 7.1, 1H), 7.87
(d, J ¼ 7.1, 2H). Anal. Calcd. for C20H19NO3: C, 74.75; H, 5.96; N, 4.36.
Found: C, 74.23; H, 6.01; N, 14.78.
2-Hydroxy-1-phenyl-2-(1,2,5-trimethyl-1H-pyrrol-3-yl)ethanone (9).
Benzene was evaporated under vacuum to 2 mL and the reaction mixture was
allowed to stand at 48C for 24 h. The precipitating crystals were filtered off and
1
recrystallized from benzene. White plates. M.p. 131–1328C (1378C[11]). H
NMR: d ¼ 2.01 (s, 3H), 2.18 (s, 3H), 3.25 (s, 3H), 5.01 (d, J ¼ 6.0, 1H), 5.50
(s, 1H), 5.89 (d, J ¼ 6.0, 1H), 7.42 (t, J ¼ 7.9, 2H), 7.52 (d, J ¼ 7.9, 1H), 7.88
(d, J ¼ 7.9, 2H). Anal. Calcd. for C15H17NO2: C, 74.05; H, 7.04; N, 5.76.
Found: C, 73.87; H, 6.90; N, 5.80.
2-(2,5-Dimethyl-1-p-tolyl-1H-pyrrol-3-yl)-2-hydroxy-1-phenyletha-
none (10). Benzene was evaporated under vacuum. The residue was
chromatographed on a column (alumina, methylene chloride) and recrystal-
lized from 80% aqueous ethanol. A greyish powder. M.p. 88–898C. 1H NMR:
d ¼ 1.94 (s, 3H), 2.36 (s, 3H), 3.34 (s, 3H), 5.24 (d, J ¼ 6.1, 1H), 5.77 (s, 1H),
5.96 (d, J ¼ 6.1, 1H), 7.05 (d, J ¼ 8.5, 2H), 7.28 (d, J ¼ 8.5, 2H), 7.47
(t, J ¼ 8.1, 2H), 7.58 (d, J ¼ 8.1, 1H), 7.96 (d, J ¼ 8.1, 2H). Anal. Calcd. for
C21H21NO2: C, 78.97; H, 6.63; N, 4.39. Found: C, 78.89; H, 6.65; N, 4.34.
2-[1-(4-Bromophenyl)-2,5-dimethyl-1H-pyrrol-3-yl]-2-hydroxy-1-
phenylethanone (11). Benzene was evaporated under vacuum and the
residue was boiled with hexane (10 mL). The undissolved part of the residue
was filtered off and recrystallized from 70% aqueous ethanol. A yellow
1
powder. M.p. 142–1438C. H NMR: d ¼ 1.89 (s, 3H), 2.04 (s, 3H), 5.11
(d, J ¼ 6.1, 1H), 5.69 (s, 1H), 5.88 (d, J ¼ 6.1, 1H), 7.14 (d, J ¼ 8.4, 2H), 7.44
(t, J ¼ 7.3, 2H), 7.54 (d, J ¼ 7.3, 1H), 7.63 (d, J ¼ 8.4, 2H), 7.94 (d, J ¼ 7.3,
2H). Anal. Calcd. for C20H18BrNO2: C, 62.51; H, 4.72; N, 3.64. Found: C,
62.50; H, 4.74; N, 3.60.
2-Hydroxy-2-(1H-indol-3-yl)-1-phenylethanone (12).[8] The yield was
increased by keeping the reaction mixture after boiling at 48C for 24 h. M.p.
170–1728C.[8] 1H NMR: d ¼ 5.53 (d, J ¼ 5.1, 1H), 6.36 (d, J ¼ 5.1, 1H), 6.98
(t, J ¼ 7.0, 1H), 7.06 (t, J ¼ 7.0, 1H), 7.31 (s, 1H), 7.32 (d, J ¼ 7.0, 1H), 7.39
(t, J ¼ 7.5, 2H), 7.62 (d, J ¼ 7.0, 1H), 7.63 (d, J ¼ 7.5, 1H), 8.00 (d, J ¼ 7.5,
2H), 11.06 (s, 1H). Anal. Calcd. for C16H13NO2: C, 76.48; H, 5.21; N, 5.57.
Found: C, 76.42; H, 5.23; N, 5.58.
1-(4-Chlorophenyl)-2-hydroxy-2-(1H-indol-3-yl)ethanone (13). The
resulting crystalline precipitate was filtered off and recrystallized from
benzene. White plates. M.p. 145–1468C. 1H NMR: d ¼ 5.62 (d, J ¼ 5.1, 1H),
6.32 (d, J ¼ 5.1, 1H), 6.98 (t, J ¼ 7.8, 1H), 7.06 (t, J ¼ 7.8, 1H), 7.32
(d, J ¼ 7.8, 1H), 7.34 (s, 1H), 7.47 (d, J ¼ 8.4, 2H), 7.60 (d, J ¼ 7.8, 1H), 8.01

ORDER
REPRINTS
458
Ivonin et al.
(d, J ¼ 8.4, 2H), 11.07 (s, 1H). Anal. Calcd. for C16H12ClNO2: C, 67.26; H,
4.23; N, 4.90. Found: C, 67.17; H, 4.26; N, 4.89.
1-(4-Bromophenyl)-2-hydroxy-2-(1H-indol-3-yl)ethanone (14). The
resulting crystalline precipitate was filtered off and recrystallized from
benzene. White plates. M.p. 159–1608C. 1H NMR: d ¼ 5.64 (d, J ¼ 5.4, 1H),
6.32 (d, J ¼ 5.4, 1H), 6.98 (t, J ¼ 7.5, 1H), 7.06 (t, J ¼ 7.5, 1H), 7.32
(d, J ¼ 7.5, 1H), 7.36 (d, J ¼ 7.5, 1H), 7.37 (s, 1H), 7.60 (d, J ¼ 8.4, 2H), 7.94
(d, J ¼ 8.4, 2H), 11.09 (s, 1H). Anal. Calcd. for C16H12BrNO2: C, 58.20; H,
3.66; N, 4.24. Found: C, 58.16; H, 3.74; N, 4.24.
2-Hydroxy-2-(1H-indol-3-yl)-1-thiophen-2-ylethanone (15).[8] M.p.
178–1808C.[8] 1H NMR: d ¼ 4.27 (d, J ¼ 4.0, 1H), 6.27 (d, J ¼ 4.0, 1H),
6.99 (t, J ¼ 3.2, 1H), 7.15 (t, J ¼ 3.2, 1H), 7.19 (dd, J ¼ 0.8 Hz, J ¼ 3.0, 1H),
7.22 (s, 1H), 7,26 (s, 1H), 7.37 (s, 1H), 7.58 (d, J ¼ 3.0, 1H), 7.70 (d, J ¼ 3.0,
1H), 8.24 (s, 1H). Anal. Calcd. for C14H11NO2S: C, 65.35; H 4.31; N 5.44.
Found: C, 65.92; H, 4.38; N, 5.31.
2-Hydroxy-2-(2-methyl-1H-indol-3-yl)-1-phenylethanone (16). The
solution obtained was kept at 08C for 1 h. The resulting crystalline precipitate
was filtered off and recrystallized from benzene. White plates. M.p. 156–
1
1578C. H NMR: d ¼ 2.27 (s, 3H), 5.16 (d, J ¼ 5.9, 1H), 6.29 (d, J ¼ 5.9,
1H), 6.97 (t, J ¼ 7.1, 1H), 7.05 (t, J ¼ 7.1, 1H), 7.18 (d, J ¼ 7.1, 1H), 7.39
(t, J ¼ 7.6, 2H), 7.45 (d, J ¼ 7.1, 1H), 7.48 (d, J ¼ 7.6, 1H), 7.86 (d, J ¼ 7.6,
2H), 10.86 (s, 1H). Anal. Calcd. for C17H15NO2: C, 76.96; H, 5.70; N, 5.28.
Found: C, 76.95; H, 5.72; N, 5.25.
2-Hydroxy-2-(2-methyl-1H-indol-3-yl)-1-thiophen-2-ylethanone (17).
The crystalline precipitate was filtered off and recrystallized from benzene.
1
Pink plates. M.p. 125–1278C. H NMR: d ¼ 2.46 (s, 3H), 5.49 (d, J ¼ 1.4,
1H), 6.09 (d, J ¼ 1.4, 1H), 6.91 (t, J ¼ 7.2, 1H), 6.98 (t, J ¼ 7.2, 1H), 7.08 (t,
J ¼ 4.2, 1H), 7.23 (d, J ¼ 7.2, 1H), 7.54 (d, J ¼ 7.2, 1H), 7.75 (d, J ¼ 4.0,
1H), 7.84 (d, J ¼ 4.2, 1H), 11.00 (s, 1H). Anal. Calcd. for C15H13NO2S: N
5.16; S 11.82. Found: N 5.04; S 11.93.
2-(1,2-Dimethyl-1H-indol-3-yl)-2-hydroxy-1-phenylethanone
(18).
The crystalline precipitate was filtered off and recrystallized from benzene.
White plates. M.p. 138–1398C. 1H NMR: d ¼ 2.45 (s, 3H), 3.67 (s, 3H), 5.36
(s, 1H), 6.39 (s, 1H), 6.95 (t, J ¼ 7.1, 1H), 7.02 (t, J ¼ 7.1, 1H), 7.19 (d,
J ¼ 7.1, 1H), 7.30 (d, J ¼ 7.1, 1H), 7.45 (t, J ¼ 7.6, 2H), 7.53 (d, J ¼ 7.6,
1H), 7.86 (d, J ¼ 7.6, 2H). Anal. Calcd. for C18H17NO2: C, 77.40; H, 6.13; N,
5.01. Found: C, 77.38; H, 6.15; N, 5.94.
2-Hydroxy-1-phenyl-2-(2-phenyl-1H-indol-3-yl)ethanone (19). Ben-
zene was evaporated under vacuum. The residue was extracted with the
mixture benzene : hexane (1 : 5) and the solvent was evaporated under
vacuum. White plates. M.p. 144–1468C. 1H NMR: d ¼ 5.53 (d, J ¼ 5.1, 1H),
6.15 (d, J ¼ 5.1, 1H), 6.92 (t, J ¼ 7.1, 1H), 7.02 (t, J ¼ 7.1, 1H), 7.20

ORDER
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Reaction of Arylglyoxals
459
(d, J ¼ 7.1, 1H), 7.26 (d, J ¼ 7.1, 1H), 7.30–7.40 (m, 5H), 7.37 (t, J ¼ 7.5,
2H), 7.58 (d, J ¼ 7.5, 1H), 7.74 (d, J ¼ 7.5, 2H), 11.36 (s, 1H). Anal. Calcd.
for C22H17NO2: C, 80.71; H, 5.23; N, 4.28. Found: C, 80.69; H, 5.24; N, 4.25.
2-Hydroxy-2-(5-methylfuran-2-yl)-1-phenylethanone (20). Benzene
was evaporated under vacuum to 1 mL. The precipitating crystals were
filtered off and recrystallized from benzene. Colourless plates. M.p. 1268C. 1H
NMR: d ¼ 2.20 (s, 3H); 3.28 (s, 1H); 5.94 (d, J ¼ 3.3, 1H), 5.98 (s, 1H), 6.20
(d, J ¼ 3.3, 1H), 7.45 (t, J ¼ 8.4, 2H), 7.57 (d, J ¼ 8.4, 1H), 7.95 (d, J ¼ 8.4,
2H). Anal. Calcd. for C13H12O3: C, 72.21; H, 5.59. Found: C, 72.19; H, 5.59.
2-Hydroxy-2-(5-methylfuran-2-yl)-1-thiophen-2-ylethanone (21). The
crystalline precipitate was filtered off and recrystallized from benzene. White
plates. M.p. 141–1428C. 1H NMR: d ¼ 2.24 (s, 3H), 4.26 (s, 1H), 5.75 (s, 1H),
5.94 (d, J ¼ 3.3, 1H), 6.31 (d, J ¼ 3.3, 1H), 7.10 (t, J ¼ 4.3, 1H), 7.67
(d, J ¼ 4.3, 1H) 7.71 (d, J ¼ 4.3, 1H). Anal. Calcd. for C11H10O3S: C 59.44; H
4.53. Found: C 59.52; H 4.41.
ACKNOWLEDGMENT
We acknowledge the financial support of this work provided by the
Ministry of Education and Science of Ukraine (Grant No. 0101U001529).
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Received in Poland July 2, 2003

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