Oxidation of aromatic compounds: XVII. Oxidative cross-dimerization of diarylacetylenes in the system CF3CO2H-CH 2Cl2-PbO2. Characteristic of cation-radicals of diarylacetylenes by cyclic voltammetry and ESR spectroscopy

Article abstract of DOI:10.1134/S1070428010090034

The oxidation of mixtures of diarylacetylene ArC≡CAr and Ar′C≡CAr′ in a system CF₃CO₂H-CH ₂Cl₂-PbO₂ (0°C, 1.5 h) results in products of cross-dimerization, (Z)-1,2,3,4-tetraarylbut-2-ene-1,4-diones Ar(ArCO) C=C(COAr′)Ar′. The routes of transformation of intermediate cation-radicals of diarylacetylenes [ArC≡CAr]^+? into the final products of oxidative dimerization are elucidated. By cyclic voltammetry and ESR spectroscopy the high reactivity of the diarylacetylene cation-radicals is demonstrated, the character of their singly occupied molecular orbitals (a₂ or b₁) has been revealed by ESR method.

Full text of DOI:10.1134/S1070428010090034

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2010, Vol. 46, No. 9, pp. 1282−1289. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © A.V. Vasil’ev, A.P. Rudenko, 2010, published in Zhurnal Organicheskoi Khimii, 2010, Vol. 46, No. 9, pp. 1286−1292.
Dedicated to Full Member of the Russian Academy of Sciences
N.S. Zefirov on occasion of his 75th anniversary
Oxidation of Aromatic Compounds: XVII.*
Oxidative Cross-Dimerization of Diarylacetylenes
in the System CF3CO2H–CH2Cl2–PbO2. Characteristic
of Cation-Radicals of Diarylacetylenes
by Cyclic Voltammetry and ESR Spectroscopy
A.V. Vasil’ev and A.P. Rudenko
State Forestry Academy, St. Petersburg, 194021 Russia
e-mail: aleksvasil@mail.ru
Received May 7, 2010
Abstract—The oxidation of mixtures of diarylacetyleneArC≡CAr andAr'C≡CAr' in a system CF3CO2H–CH2Cl2–
PbO2 (0°C, 1.5 h) results in products of cross-dimerization, (Z)-1,2,3,4-tetraarylbut-2-ene-1,4-diones Ar(ArCO)
C=C(COAr')Ar'. The routes of transformation of intermediate cation-radicals of diarylacetylenes [ArC≡CAr]+·
into the final products of oxidative dimerization are elucidated. By cyclic voltammetry and ESR spectroscopy
the high reactivity of the diarylacetylene cation-radicals is demonstrated, the character of their singly occupied
molecular orbitals (a2 or b1) has been revealed by ESR method.
DOI: 10.1134/S1070428010090034
The oxidation of diarylacetylenes with the lead di-
oxide in various acids (CF3CO2H [2–4], HF [5], HSO3F
[6, 7]) gives products of the oxidative dimerization, (Z)-
(cis)-1,2,3,4-tetraarylbut-2-ene-1,4-diones (unsaturated
γ-diketones) Ar(ArCO)C=C(COAr)Ar, (E,E)-1,2,3,4-
tetraaryl-1,4-difluoro(or dichloro)butadienes (Ar)
XC=C(Ar)–(Ar)C=CX(Ar) (X = F, Cl) formed as a result
of the closure of a new carbon-carbon bond through the
acetylene carbon atoms of the diarylacetylenes. It was
shown by ESR spectroscopy that the primary interme-
diates in these reactions were diarylacetylene cation-
radicals [7]. The extension of the synthetic potential of
these reaction consists in the oxidation of mixtures of
various diarylacetylenes for the preparation of products
of their mixed (cross-) oxidative dimerization.
PbO2, and also characterizing of the diarylacetylene
cation-radicals by electrochemical analysis and ESR
spectroscopy.
The oxidation of a mixture of diphenylacetylene
(tolane) (I) and its monomethyl-substituted derivative
II in the system CF3CO2H–CH2Cl2–PbO2 is presented
in Scheme 1.
The products of this reaction III–V, VIa–VIc, and
also γ-diketones VIII, IX and XI, XII (Schemes 2, 3),
inseparable by column chromatography on silica gel were
analyzed by GC-MS method like in [3]. The identification
of separate components was performed by the presence
in the mass spectra of characteristic ions [ArCO]+ and
[M – ArCO]+ (see Experimental).
Alongside compounds V (oxidation product of
compound I [2]) and VIa–VIc (a mixture of three
oxidation products of compound II [3]) we observed the
formation of γ-diketones III and IV, the products of the
oxidative cross-dimerization of diarylacetylenes I and
The goal of this work was the study of substrate, regio,
and stereoselectivity in the oxidative cross-dimerization
of diarylacetylenes in the system CF3CO2H–CH2Cl2–
* For Communication XVI, see [1].
1282

1283
OXIDATION OF AROMATIC COMPOUNDS: XVII.
Scheme 1.
Scheme 2.
Me
Me
Me
Me
Ph
C
CF3CO2H_CH2Cl2_PbO2
0°C, 1.5 h
Ph
C
C
C
+
V (20%)
+
+
C C
O O
C C
O O
C
Ph
C
Me
Me
C
C
Me
Ph
I
VIII (5%)
IX (9%)
Me
VII
II (Scheme 1). The overall yield of compounds III–V,
VIa–VIc was 46%. Therewith the cross-coupling prod-
ucts III and IV formed in approximately equal quantity
(8 and 7% respectively).
IX, XII, 34 and 35% respectively (Schemes 2, 3).
As a result of the oxidation of the mixture of dialkyl-
substituted diarylacetylenes VII and XIII alongside the
corresponding γ-diketones IX and XV the cross-coupling
product XIV was obtained in 8% yield (Scheme 4). The
latter was isolated by chromatography in the individual
state (see Experimental).
We ascribed to compounds III and IV and to the
other related structures VIII, IX, XIV (Schemes 2–4)
the Z-(cis)-location of substituents at the C=C bond by
the analogy to the stereochemical structure of γ-diketones
obtained from alkyl(or halo)-substituted diarylacetylenes
in the system CF3CO2H–CH2Cl2–PbO2 [2, 3].
The attempts of cooxidation of tolane (I) with sub-
strates possessing higher oxidation potential, 1,2-bis(4-
nitrophenyl)acetylene (XVI) and 1,2-bis(3-ethoxycar-
bonylphenyl)acetylene (XVII), did not afford the cross-
dimerization products. Thus the cross-coupling products
formed only in the mixed oxidation of diarylacetylenes
possessing close oxidation potentials (close HOMO ener-
gies) (Schemes 1–4).
The oxidation of tolane (I) in the mixture with
1,2-bis(4-methylphenyl)acetylene (VII) or 1,2-bis(4-fluo-
rophenyl)acetylene (X) also provided the cross-dimeriza-
tion products VIII, XI in 5 and 7% yields at the overall
yield of all reaction products, including γ-diketones V,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

VASIL’EV, RUDENKO
1284
dimerization of the cation-radicals into dication C. Fur-
O2N
C C
NO2
ther transformations of intermediates B and C result in
γ-diketones XIX. These two routes may lead to the prod-
ucts of the oxidative cross-dimerization (Schemes 1–4).
However the now available experimental data are insuf-
ficient for distinguishing these two reaction routes (cf.
with the data of [1] on reactions of cation-radicals of
acetylene compounds with electron-withdrawing groups).
XVI
C C
EtO2C
XVII
CO2Et
It is hardly possible that in the studied system
CF3CO2H–CH2Cl2–PbO2 an alternative route c materi-
alizes for cation-radicals A (Scheme 5), since the tolane
(I) oxidation in the presence of a nucleophilic additive
ыodium or silver trifluoroacetates in the systems CF-
3CO2H–CF3CO2Na (or CF3CO2Ag–PbO2) results in
The cation-radicals A arising from the one-electron
oxidation of diarylacetylenes XVIII (Scheme 5) may
react along the following most probable routes leading
to the formation of a new carbon-carbon bond. The first
route a consists in the reaction with the initial substrate
XVIII to give cation-radical B, the second route b is the
Scheme 3.
F
F
F
F
Ph
C
Ph
C
CF3CO2H_CH2Cl2_PbO2
0°C, 1.5 h
C
C
C C
O O
C C
O O
+
+
V (23%)
+
C
F
C
C
F
Ph
C
F
Ph
XII (5%)
XI (7%)
F
X
Scheme 4.
Me
Bu-t
Me
Bu-t
C
C
CF3CO2H_CH2Cl2_PbO2
0°C, 1.5 h
C
C
+
C C
O O
+
Me
C
C
Bu-t
XIV (8%)
Bu-t
Me
VII
t-Bu
Bu-t
XIII
+
IX (7%)
+
C C
O O
t-Bu
C
C
Bu-t
XV (10%)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

OXIDATION OF AROMATIC COMPOUNDS: XVII.
1285
Scheme 5.
Ar C C Ar
a:
XVIII
Ar C C Ar
B
Ar
Ar
CF3CO2H_CH2Cl2_PbO2
_e
C C
Ar C C Ar
Ar C C Ar
b:
A
Ar
C
C Ar
XVIII
A
c:
O O
CF3CO2H,
_H+
Ar C C Ar
XIX
Ar C C Ar
Ar
C
Ar C C
OOCCF3
D
obtaining benzil PhCOCOPh. Only traces of γ-diketone
V were found in the reaction product, whereas it is the
main (yield 60%) product of tolane (I) oxidation in the
system CF3CO2H–CH2Cl2–PbO2 [2]. This shows that
the vinyl radical Ph(CF3COO)C·=CPh (species D, Ar =
Ph, Scheme 5) formed by the reaction of the nucleophile
CF3CO2 with tolane cation-radical suffers further oxida-
tion into benzil and did not take part in the formation of
the carbon-carbon bond.
high reactivity of the corresponding cation-radicals. For-
merly an irreversible electrochemical oxidation was also
observed for the other methyl- and methoxy-substituted
diarylacetylenes [8, 9].
The increase in the extent of the alkyl substitution
favors the stabilization of cation-radicals. A pseudo-
reversible electron transfer was observed in oxidation of
hexa- and decamethyl derivatives XXII and XX (Fig. 1),
since the difference between the potentials of the anode
and cathode peaks 149 and 82 mV respectively exceeded
the theoretical value for reversible processes of 57 mV.
The easily oxidizable substrates XXV, XXVII have two
half-waves of oxidation (Table 1). However even at high
scanning rate (4 V/s) the oxidation of diarylacetylene
XXV was not completely reversible. It means that in
the given electrochemical conditions the cation-radicals
gradually reacted.
–
Diarylacetylene cation-radicals A were additionally
studied in this work by electrochemical analysis and ESR
spectroscopy.
The characteristics of oxidation of acetylene com-
pounds XX–XXVII are compiled in Table 1 obtained
by cyclic voltammetry, and a typical voltammogram is
shown in Fig. 1.
As follows from voltammograms, in oxidation of
compounds XXI, XXIII, XXIV, XXVI, XXVII a totally
irreversible electron transfer occurs demonstrating the
Fig. 1. Cyclic voltammogram of bis-(pentamethylphenyl)acety-
lene (XX) oxidation (concentration 2 mmol l−1 ) in CH2Cl2–
Bu4N+PF6– (0.1 mol l−1) at 25°C, saturated calomel electrode,
scanning rate 0.1 V/s.
Fig. 2. ESR spectrum of cation-radical XX+· generated by
oxidation of bis(pentamethylphenyl)acetylene XX in a system
NO+SbCl6 –CH2Cl2 at –70°C.
–
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

VASIL’EV, RUDENKO
1286
Table 1. Voltampere characteristics of oxidation of acetylene compounds XX–XXVII (concentration 2–5 mmol l−1 ) in CH2Cl2–
Bu4N+PF6– (0.1 mol l−1) at 25°C, saturated calomel electrode
Anode
potential
Epa, C
Cathode
potential
EpC, C
Potential difference
ΔE = Epa–EpC, MC
Compound no.
Scanning rate,V/s
XX
1.362
1.567
1.280
82
–
0.1
0.5
0.2
0.2
0.1
4
XXI
–
XXII
XXIII
XXIV
XXV
1.541
1.392
149
–
1.538
–
1.414
–
–
1.292
1.030
262
437
–
1.633a
1.196a
XXVI
1.473 (1.37 [8])
1.300 (1.17 [8])
1.453a
–
–
–
0.1
0.1
XXVII
–
–
a Second half-wave.
Cation-radicals XX+·, XXII+·, XXVIII+· were char-
acterized by ESR spectra registered at the oxidation
of the corresponding acetylene compounds XX, XXII,
ylbiphenyl (bimesityl) with the following parameters
aHO-Me 2.1 (2.19) Gs (12H), aHm-arom <0.13 (0.5) Gs (4H),
aHp-Me 6.99 (8.79) Gs (6H) [10, 11]. The largest hyperfine
interaction constant in the ESR spectra of species XX+·,
XXII+·, XXVIII+· and the bimesityl cation-radical was
observed for the protons of the para-methyl groups,
aH ~ 7...10 Gs. The very small value aH ≤ 0.5 Gs charac-
terized the moieties in the meta-position of the aromatic
rings for protons, methyl and nitro groups. These values
XXVIII in the systems NO+SbCl6 –CH2Cl2 (–70°C) and
–
HSO3F–PbO2 (–75°C) (Table 2).
The ESR spectra of these cation-radicals are similar
and consist of multiplets of over 20 equidistant peaks
(Fig. 2). The spectra of these species are also like the
spectrum of a cation-radical of 2,2',4,4',6,6'-hexameth-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

OXIDATION OF AROMATIC COMPOUNDS: XVII.
1287
Table 2. ESR spectra of cation-radicals XX+·, XXII+·, XXVIII+· generated from compounds XX, XXII, XXVIII) respectively
in systems NO+SbCl6 –CH2Cl2 (–70°C) and HSO3F–PbO2 (–75°C) (g-factors ~2.000)
–
Cation-radical
Oxidation system
Constants of hyperfine interactiona
Me
Me
Me
Me
aHo-Me 2 Gs (12H),
aHm-Me < 0.5 Gs (12H),
aHp-Me 8 Gs (6H)
Me
Me
C C
Me
Me
NO+SbCl6 –CH2Cl2, –70°C
–
Me
H
Me
Me
Me
Me
H
XX+·
Me
aHo-Me 2 Gs (12H),
aHm-arom < 0.5 Gs (4H),
aHp-Me 8 Gs (6H)
C C
NO+SbCl6 –CH2Cl2, –70°C
–
H
H
Me
Me
Me
XXII+·
H
H
Me
aHo-Me 2.5 Gs (12H),
aHm-arom < 0.5 Gs (2H),
aHNO2 < 0.5 Gs (2N),
aHp-Me 10 Gs (6H)
Me
C C
Me
HSO3F–PbO2, –75°C
O2N
Me
Me
NO2
XXVIII+·
a Ortho, meta, and para positions with respect to the acetylene substituent.
of hyperfine interaction constants indicate the singly oc-
cupied molecular orbitals (SOMOs), previous HOMOs
of the neutral molecules, of the b1 type in the aromatic
systems of these species. In the cation-radicals of diary-
lacetylenes with the singly occupied molecular orbital
b1 the acetylene bond transmits well the spin density
between the aromatic rings and is essentially involved
in its delocalization (Fig. 3) (see also the data of [1] on
the characteristic by ESR of cation-radicals of acetylene
compounds with electron-withdrawing groups). The pres-
ence of the spin density on the acetylene carbon atoms
results in the formation of the new carbon-carbon bond
just at thgese atoms (Scheme 5).
We failed to register the ESR spectrum at the oxidation
of octamethyl-substituted diarylacetylene XXI in the sys-
tem NO+SbCl6 –CH2Cl2 (–70°C) since the corresponding
–
cation-radical XXI+· proved to be exclusively unstable
that was also confirmed by the irreversible character of the
electrochemnical oxidation of compound XXI (Table 1).
The singly occupied molecular orbital characteristic of
cation-radical XXI+· is a2 with a weak involvement of
the acetylene fragment into the delocalization of the spin
density (Fig. 3).
Hence we demonstrated the high reactivity of diary-
Fig. 3. Character of singly occupied molecular orbital in cation-radicals XXI+ and XXII+ substituent..
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

VASIL’EV, RUDENKO
1288
lacetylene cation-radicals by cyclic voltammetry and ESR
spectroscopy. By ESR method we established the SOMO
type a2 or b1 of these species governing the direction of
reaction of the cation-radicals [2–4].
δ, ppm: 2.24 s (6H, 2Me), 3.81 s (6H, 2MeO), 3.89 s
(6H, 2MeO), 6.71 s (2Harom), 6.98 s (2Harom). Found,
%: C 73.58; H 6.88. C20H22O4. Calculated, %: C 73.60;
H 6.79.
Oxidation of mixtures of diarylacetylenes I, II, VII,
X, XIII, XVI, XVII in the system CF3CO2H–CH2Cl2–
PbO2. To a solution of 0.43 ml of CF3CO2H in 4 ml of
CH2Cl2 was added while vigorous stirring at 0°C 1 mmol
of each diarylacetylene. Then 478 mg (2 mmol) of PbO2
was added, and the mixture was stirred for 1.5 h. On
completion of the reaction the mixture was poured into
50 ml of chloroform, the extract was washed with water,
with saturated solution of NaHCO3, again with water,
and dried with Na2SO4. The solvents were distilled off,
the residue was subjected to column chromatography
on silica gel (eluent petroleum ether–ethyl ether) or was
analyzed by GC-MS method.
EXPERIMENTAL
1H NMR spectra were registered on a spectrometer
Bruker AM-500 (operating frequency 500 MHz) from
solution of compounds in CDCl3 and (CD3)2CO. The
residual proton signals of solvents were used as inter-
nal references [CHCl3 δH 7.25 ppm, (CD3)(CD2H)CO
δH 2.05 ppm]. Mass spectra were recorded on an instru-
ment MKh-1321, ionizing energy 70 eV, direct sample
admission into the ion source at 100–120°C. GC-MS
analysis was carried out on a mass spectrometer Hewlett
Packard 5995, ionizing energy 70 eV, temperature of
the separator 240°C, of the ion source, 250°C. Capillary
quartz column 25 m × 0.32 mm, stationary phase Ultra-2
(95% of methylsilicone, 5% of phenylmethylsilicone)
0.53 μm. Oven temperature: starting 100°C, final 240°C,
heating rate 5 deg min–1. Carrier gas helium, flow rate
1 ml min–1. The sample of 3–5% solution 2 μL. ESR spec-
tra of cation-radicals were recorded on ESR spectrometers
Varian E-109 and Bruker, the g-factor value was measured
with respect to diphenylpicrylhydrazyl. The ESR spectra
were simulated using the program WINEPR Sim-Fonia.
The experiments of voltammetry were performed on
an instrument BAS-100 Electrochemical Analyzer.
The properties of compounds V, IX, XII, XV are
published in [2], of compounds VIa–VIc, in [3].
2-(4-Methylphenyl)-1,3,4-triphenylbut-2-ene-1,4-
dione (III) and 1-(4-methylphenyl)-2,3,4-triphen-
ylbut-2-ene-1,4-dione (IV) were obtained alongside
compounds V (yield 10%) and compounds VIa–VIc
(yield 21%) as a result of oxidation of a mixture of dia-
rylacetylenes I and II. The mixture of reaction products
was analyzed by GC-MS.
Compound III. Yield 8%. Mass spectrum, m/z (IOтH.
,
%): 402 (11) [M]+, 297 (23) [M – PhCO]+, 105 (100)
[PhCO]+, 77 (42) [Ph]+.
Compound IV. Yield 7%. Mass spectrum, m/z (Irel,
%): 402 (12) [M]+, 297 (17) [M – PhCO]+, 283 (19) [M –
4-MeC6H4CO]+, 119 (100) [4-MeC6H4CO]+, 105 (92)
[PhCO]+, 91 (67) [4-MeC6H4]+, 77 (50) [Ph]+.
Diarylacetylenes were prepared by methods [2, 3].
The properties of compounds I, VII, X, XIII, XVI, XVII,
XXIII, XXIV, XXVI, XXVII are published in [2], of
compound II, in [3], of compound XXVIII, in [7].
1,2-Bis(4-methylphenyl)-3,4-diphenylbut-2-ene-
1,4-dione (VIII) was obtained alongside compounds V
(yield 20%) and IX (yield 9%) by oxidation of a mixture of
diarylacetylenes I and VII. The mixture of reaction prod-
ucts was analyzed by GC-MS. Yield 5%. Mass spectrum,
m/z (Irel, %): 416 (14) [M]+, 311 (20) [M – PhCO]+, 297
(24) [M – 4-MeC6H4CO]+, 119 (100) [4-MeC6H4CO]+,
105 (95) [PhCO]+, 91 (70) [4-MeC6H4]+, 77 (58) [Ph]+.
Bis(pentamethylphenyl)acetylene (XX), mp 251–
253°C. 1H NMR spectrum (CDCl3), δ, ppm: 2.24 s (12H,
4Me), 2.25 s (6H, 2Me), 2.55 s (12H, 4Me). Found, %:
C 90.92; H 9.60. C24H30. %: C 90.51; H 9.49.
Bis(2,3,5,6-tetramethylphenyl)acetylene (XXI), mp
235–237°C. 1H NMR spectrum (CDCl3), δ, ppm: 2.25 s
(12H, 4Me), 2.48 s (12H, 4Me), 6.92 s (2Harom). Found,
%: C 91.02; H 9.00. C22H26. Calculated, %: C 90.98;
H 9.02.
1,2-Diphenyl-3,4-bis(4-fluorophenyl)but-2-ene-1,4-
dione (XI) was obtained alongside compounds V (yield
23%) and XII (yield 5%) by oxidation of a mixture of
diarylacetylenes I and X. The mixture of reaction prod-
ucts was analyzed by GC-MS. Yield 7%. Mass spectrum,
m/z (Irel, %): 424 (10) [M]+, 319 (18) [M – PhCO]+, 301
(17) [M – 4-FC6H4CO]+, 123 (100) [4-FC6H4CO]+, 105
(87) [PhCO]+, 95 (60) [4-FC6H4]+, 77 (71) [Ph]+.
Bis(2,4,6-trimethylphenyl)acetylene (XXII), mp
128–130°C. 1H NMR spectrum (CDCl3), δ, ppm: 2.31 s
(6H, 2Me), 2.50 s (12H, 4Me), 6.92 s (4Harom). Found, %:
C 91.67; H 8.31. C20H22. Calculated, %: C 91.55; H 8.45.
Bis(4-methyl-2,5-dimethoxyphenyl)acetylene
1
(XXV), mp 143–145°C. H NMR spectrum (CDCl3),
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010

OXIDATION OF AROMATIC COMPOUNDS: XVII.
1289
Bubnov, M.P., and Cherkasov, V.K., Zh. Org. Khim., 2008,
vol. 44, p. 802.
1,2-Bis(4-tert-butylphenyl)-3,4-bis(4-methyl-
phenyl)but-2-ene-1,4-dione (XIV) was obtained
alongside compounds IX (yield 7%) and XV (yield
10%) by oxidation of a mixture of diarylacetylenes VII
and XIII. After performing the reaction the mixture of
products was subjected to column chromatography on
silica gel. Compound XIV. Yield 5%, mp 209–211°C.
1H NMR spectrum [(CD3)2CO], δ, ppm: 1.23 s (9H,
t-Bu), 1.26 s (9H, t-Bu), 2.23 s (3H, Me), 2.29 s (3H,
Me), 7.04 s (4Harom), 7.13 d (2Harom, J 8.4 Hz), 7.15 d
(2Harom, J 8.2 Hz), 7.29 d (2Harom, J 8.4 Hz), 7.41 d
(2Harom, J 8.3 Hz), 7.71 d (2Harom, J 8.2 Hz), 7.81 d
(2Harom, J 8.3 Hz). Mass spectrum, m/z (Irel, %): 528 (21)
[M]+, 443 (8), 409 (10) [M – 4-MeC6H4CO]+, 367 (11)
[M – 4-t-BuC6H4CO]+, 161 (88) [4-t-BuC6H4CO]+, 119
(100) [4-MeC6H4CO]+, 91 (25) [4-MeC6H4]+. Found,
%: C 86.30; H 7.70. C38H40O2. Calculated, %: C 86.32;
H 7.63. M 528.30.
2. Rudenko, A.P. and Vasil’ev, A.V., Zh. Org. Khim., 1995,
vol. 31, p. 1502.
3. Vasil’ev, A.V. and Rudenko, A.P., Zh. Org. Khim., 1997,
vol. 33, 1639.
4. Vasil’ev,A.V., Rudenko,A.P., and Fundamenskii, V.S., Zh.
Org. Khim., 2001, vol. 37, p. 558.
5. Shchukin, A.O., Vasil’ev, A.V., Fukin, G.K., and Ruden-
ko, A.P., Zh. Org. Khim., 2007, vol. 43, p. 1455.
6. Shchukin, A.O., Vasil’ev, A.V., and Fukin, G.K., Zh. Org.
Khim., 2008, vol. 44, p. 318.
7. Vasilyev, A.V., Shchukin, A.O., Walspurger, S., and Som-
mer, J., Eur. J. Org. Chem., 2008, p. 4632.
8. Cariou, M., Tetrahedron, 1991, vol. 47, p. 799.
9. Bosch, E., Hubig, S.M., and Kochi, J.K., J. Am. Chem.
Soc., 1998, vol. 120, p. 386.
10. Ishizu, K., Ohuchi, M., Nemoto, F., and Suga, M., Bull.
Chem. Soc. Jpn., 1973, vol. 46, p. 2932.
REFERENCES
11. Davies, A.G. and Ng, K., Aust. J. Chem., 1995, vol. 48,
p. 167.
1. Vasil’ev,A.V.,Aristov, S.A., Fukin, G.K., Kozhanov, K.A.,
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 46 No. 9 2010