Oxidation of alkylphenylacetylenes and dialkylacetylenes on palladium catalysts in DMSO

Article abstract of DOI:10.1023/A:1011308811448

Alkylphenyl-and dialkylacetylenes are oxidized by the DMSO-PdCl₂ or DMSO-Pd/C system to give the corresponding 1,2-diketones. Oxidation of these compounds, unlike that of diarylacetylenes, is less selective and is accompanied by the partial cle

Full text of DOI:10.1023/A:1011308811448

Russian Chemical Bulletin, International Edition, Vol. 50, No. 4, pp. 649—653, April, 2001
649
Oxidation of alkylphenylacetylenes and dialkylacetylenes
on palladium catalysts in DMSO
M. S. Yusubov,a« V. D. Filimonov,b and Ki-Whan Chic
àSiberian State Medical University,
2 Moskovskii trakt, 634050 Tomsk, Russian Federation.
bTomsk Polytechnical University,
30 prosp. Lenina, 634004 Tomsk, Russian Federation.
Fax: +7 (382 2) 41 5235. E-mail: filim@org.chtd.tpu.edu.ru
cUlsan University, 680749 Ulsan, Korea
Alkylphenyl- and dialkylacetylenes are oxidized by the DMSO—PdCl2 or DMSO—Pd/C
system to give the corresponding 1,2-diketones. Oxidation of these compounds, unlike that of
diarylacetylenes, is less selective and is accompanied by the partial cleavage of triple bonds and
formation of ketones, 1,3-diketones, and aromatic compounds as secondary condensation
products.
Key word: alkylphenylacetylenes, alkylacetylenes, diketones, dimethyl sulfoxide, palladium
chloride.
Previously,1—3 we have carried out successful oxida-
tion of different diarylacetylenes and 1-phenylprop-1-
yne (1à) under the action of DMSO in the presence of
catalytic amounts of Pd/C or PdCl2 to form 1,2-di-
ketones. In these reactions, DMSO, which was con-
verted into dimethyl sulfide, served as the true oxidant
and oxidation proceded, apparently, through the conju-
gate addition of palladium and DMSO at the triple
bonds.4,5 In the present work, we studied oxidation
of alkylaryl- and dialkylacetylenes 1à—d by the
DMSO—PdCl2 or DMSO—Pd/C systems.
ning of the reaction, the conversion of the initial alkyne
1a also being low. The reaction was accelerated in the
presence of CuCl2, the initial alkyne disappeared after
5 h (GLC), and the yield of diketone 2a was 67%. In the
absence of Pd/C, copper salts in DMSO are inactive in
these oxidation reactions.
Scheme 1
O
R
DMSO—PdCl2
R
80—125 °C
Results and Discussion
O
1a,b
2a,b
Oxidation of alkyne 1a by DMSO—PdCl2 was inves-
tigated in the temperature range of 80—125 °C
(Scheme 1). In all cases, 1-phenylpropane-1,2-dione
(2a) was obtained as the major product in 55—77%
yields (Table 1), i.e., oxidation of alkyne 1a proceeded
analogously to oxidation of tolan3 but more rapidly.
Apparently, insignificant resinification of the reaction
mixture is associated with the fact that product 2a
contains the active ketomethylene fragment, which can
be involved in different condensation reactions. As in
the case of diarylalkynes, oxidation of alkyne 1 did not
afford carboxylic acids (GLC and GLC/MS) and conse-
quently, the triple bond was not cleaved. 1-Phenyl-
propan-2-one (3), which was the formal hydration prod-
uct of alkyne 1a, was isolated from the reaction mixture
in a yield smaller than 1%; this was identified by
GLC/MS. Oxidation in the presence of Pd/C instead of
PdCl2 proceeded much more slowly and diketone 2a was
obtained only in 10% yield within 25 h after the begin-
R = Me (a), Pr (b)
Oxidation of 1-phenylpent-1-yne (1b) differs from
that of 1-phenylprop-1-yne (1a). In the former case,
PdCl2 is reduced to Pd0 and the oxidation is retarded.
Thus Pd precipitated as a black powder at 115 °C after
5 min. GLC analysis of the reaction mixture demon-
strated that the content of diketone 2b was 31 and 59%
after 1 and 2 h, respectively. Further oxidation pro-
ceeded very slowly due apparently to the low concentra-
tion of PdCl2, which is more active in the oxidation than
Pd. Oxidation of alkyne 1b at 90 °C was accompanied by
the smallest resinification without reduction of PdCl2
and the yield of diketone 2b was 76% (see Table 1).
Reduction of PdCl2 depends on its concentration
and the reaction temperature. At the concentrations of
PdCl2 of 10 and 25%, reduction started at 100 and
85 °C, respectively. The reduction can be accounted for
by the involvement of PdCl2 in redox reactions of,
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 623—627, April, 2001.
1066-5285/01/5004-649 $25.00 © 2001 Plenum Publishing Corporation

650
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 4, April, 2001
Yusubov et al.
Table 1. Oxidation of alkynes 1a,b with the DMSO—PdCl2 and
DMSO—Pd/C—CuCl2•2H2O systems
reaction proceeded much more slowly and the target
diketones 2a,b were obtained in yields of no higher
than 77%.
Oxidation of dialkylacetylenes, viz., of oct-4-yne 1c
and tetradec-7-yne 1d, differs from that of 1a. The
conversions of the former compounds into 1,2-diketones
were not the major reaction pathways.
Oxidation of oct-4-yne 1c with the DMSO—PdCl2
system (Scheme 2) was carried out in the temperature
range of 55—90 °C. In this case, the formation of
metallic palladium and substantial resinification of the
reaction mixture were also observed. Dilution of DMSO
with benzene or methanol did not eliminate resinification
of the reaction mixture. Oxidation of oct-4-yne at 60 °C
afforded a mixture of four major products identified by
GLC/MS as acid 5 (17%), octan-4-one (7) (9%),
octane-4,5-dione (2c) (20%), and octane-3,5-dione
(8) (52%).
Reagent
Substrate
T
/°Ñ
t
/h
Pro-
duct
Yield
(%)
DMSO—PdCl2
DMSO—PdCl2
DMSO—PdCl2
DMSO—PdCl2
DMSO—PdCl2
DMSO—Pd/C
DMSO—Pd/C—
—CuCl2•2H2O
DMSO—PdCl2
DMSO—PdCl2
DMSO—PdCl2
DMSO—Pd/C—
—CuCl2•2H2O
1a
1a
1a
1a
1a
1a
1a
80
90
19
12
3
3
3
2a
2a
2a
2a
2a
2a
2a
76
77
68a
67
100
115
125
105
115
59
25
5
10b
67
1b
1b
1b
1b
90
15
1.5
1.5
27
2b
2b
2b
4
76
100
115
105
55a
59c
86
a Under an atmosphere of N2.
b The presence of the initial alkyne 1a (56%) was established
by GLC.
Scheme 2
c The formation of Pd as a black powder was observed and the
initial alkyne 2b was isolated in 12% yield (GLC).
DMSO—PdCl2
Pr
Pr
Pr—CO—CO—Pr +
apparently, the methylene groups of the propyl fragment
rather than of the triple bond. A similar reduction
process of PdCl2 has been observed previously3 in the
oxidation of 2,7-bis(phenylethynyl)fluorene giving rise
to 2,7-bis(phenyldioxoethyl)fluorenone instead of the
expected 2,7-bis(phenyldioxoethyl)fluorene. We believe
that the oxidation of the methylene group follows the
appearance of the carbonyl groups, because the reduc-
tion of palladium was observed only after the formation
of diketone 2b. The reaction of diketone 2b with the
DMSO—PdCl2 system at 105 °C also afforded Pd0 as
well as benzoic acid (4) (8.5% after 1.5 h).
Under the action of the DMSO—Pd/C—
CuCl2•2H2O system on alkyne 1b, only acid 4 (86%)
was obtained instead of the expected diketone 2b. In the
absence of CuCl2•2H2O, oxidation proceeded very
slowly and diketone 2b was obtained in low yield (10%)
after 25 h, the degree of conversion of the initial alkyne
being also low. Thus, the presence of CuCl2•2H2O
favors apparently the oxidation of alkyne 1b to tetraketone
PhCOCOCOCOCH3, which is unstable and is converted
into benzoic acid, as in the case of oxidation of
diphenylbutadiyne.2 The reaction afforded butyric acid
(5) along with benzoic acid. The former was identified
by GLC/MS. This fact suggests also the cleavage of the
C—C bond between the adjacent carbonyl groups in
diketone 2b.
60 °C
1c
2c
+ Pr—COOH + Pr—CO—Bu + Et— CO—CH2 —CO—Pr
5
7
8
Oxidation of alkyne 1c with PdCl2 in a 3 : 1
DMSO—MeOH mixture at 60 °C or with
PdCl2—CuCl2•2H2O in a 3 : 1 C6H6—DMSO mixture
at 80 °C are even more complicated processes. In the
former case, acid 5 and octan-4-one 7 along with a
mixture of at least six isomeric compounds with the
molecular mass of 344 were detected in the reaction
mixture by GLC/MS. The data from mass spectrometry
for two of these compounds are in favor of structures 9
and 10 (Scheme 3, Table 2). The probable structural
formula of the remaining four compounds (11—14) were
suggested based on the mass spectra (Scheme 4, see
Table 2). As would be expected for alkyl aryl ketones,6,7
the mass spectra of compounds 9 and 11—14 have the
most intense peaks of the molecular ions [ArC≡O]+.
Further fragmentation of these ions occurred as the loss
of both the CO molecule (the necessary stage of frag-
mentation of the majority of mononuclear aromatic
ketones)6,7 and the C2H4 molecule. These results suggest
that the reaction of oct-4-yne with PdCl2 in the
DMSO—MeOH mixture involved trimerization of two
oct-4-yne molecules and one molecule of diketone 2c or
8. Trimerization of two molecules of octan-4-one 7 with
one molecule of diketone 2ñ or 8 (see Scheme 4) is also
not ruled out.
As in the case of phenylpropyne 1a, an admixture of
the product of formal hydration of the triple bond, viz.,
1-phenylpentan-2-one (6), was detected in the reaction
mixture by GLC/MS.
Oxidation of alkynes 1a and 1b under an atmosphere
of N2 did not lead to an increase in the yields of
diketones 2a and 2b and also did not preclude partial
resinification of the reaction mixture. Below 80 °C, the
Six major reaction products were detected by
GLC/MS when the reaction was carried out in benzene
instead of MeOH. Two of these products were 1,2-di-
ketone 2c and trimerization product 10. The 13C NMR

Oxidation of alkylacetylenes by PdCl2 in DMSO
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 4, April, 2001
651
Scheme 3
m/z 99
(100%)
m/z 71
m/z 57
(43%)
m/z 29
(35%)
(5%)
Me
CH2
CH2
C
O
CH2
C
O
CH2
Me
m/z
m/z
43
85
(20%)
(7%)
m/z 71
m/z 113
(35%)
(87%)
8
Pr
Pr
Pr
Pr
Pr
Pr
Et
Pr
Et
Pr
Pr
Et
CH2
CH2
–CH2=CH2
C
O
Pr
C
CH2
C Me
+•
Pr
Pr
OH
+•
O
+•
CH2
H
m/z 316 (16%)
9
•
–Me
•
–Pr
Pr
Pr
Pr
Pr
Et
Pr
Pr
Et
C
Pr
Pr
Et
H
–CO
–C2H4
+
O+
+
Pr
H
Pr
CH2
H2C
CH2
CH2
m/z 301 (100%)
m/z 245 (89%)
m/z 273 (66%)
–C2H4
+
Pr
CH2
Me
+
CH2
H
H
Me
Pr
Et
Et
+
Me
Pr
Me
Pr
•
–C2H4
–CH2
C
C
C
O
O
O
Pr
Pr
Pr
m/z 273 (66%)
m/z 245 (89%)
m/z 231 (16%)
Pr
Pr
Pr
Pr
Pr
Me
Pr
Pr
Me
+O
+
C
CH2 CH2 Me
+
CH2
CH2
C
CH2 CH2 Me
m/z 71 (46%)
Pr
O
+•
m/z 273 (86%)
10
–CH2=CH2
Pr
Pr
Pr
Pr
Pr
Pr
Pr
Me
Pr
Pr
Me
Pr
Pr
Me
•
–Me
+
O+
CH2
C
Me
CH2
C
Pr
O
+•
m/z 259 (38%)
m/z 316 (31%)
m/z 301 (100%)

652
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 4, April, 2001
Yusubov et al.
Table 2. Characteristics of mass spectra of compounds 2a—c, 3,
6, and 8—14
Scheme 4
O
Pr + Pr
or
Et + Bu
Com-
pound
MS (EI, 70 eV), m/z (Irel (%))
O
Et + Pr
2a
2b
148 [M]+ (5), 105 [PhCO]+ (100), 77 [Ph]+ (48),
51 [C4H3]+ (16)
176 [M]+ (4), 147 [M – Et]+ (2),
105 [PhCO]+ (100), 77 [Ph]+ (52), 51 [C4H3]+ (19),
43 [Pr]+ (12)
O
O
Pr + Pr
or
Et + Bu
Et/Pr
Pr/Et
O
2c
142 [M]+ (8), 113 [M – Et]+ (2),
71 [C4H7O]+ (100), 55 [C3H3O]+ (10),
43 [C2H3O]+ (71), 27 [C2H3]+ (14)
134 [M]+ (57), 91 [M – C2H3O]+ (100),
Et, Pr, Bu
3
6
8
65 [C5H5]+ (16),
43 [C2H3O]+ (91)
162 [M]+ (19), 91 [M – C4H7O]+ (43),
71 [C4H7O]+ (100), 65 [C5H5]+ (14), 43 [Pr]+ (40)
142[M]+ (36), 114 [M – C2H4]+ (15%),
113 [M – Et]+ (87), 99 [M – Pr]+ (100),
85 [M – C3H5O]+ (7), 71 [C4H7O]+ (35),
57 [C3H5O]+ (43), 43 [Pr]+ (20)
11—14
Pr + Pr
or
Et + Bu
Et
O
Pr
O
O
O
9
344 [M]+ (44), 316 (16), 301 (100), 273 (66),
245 (89), 231 (16), 215 (21), 203 (6), 189 (11),
161 (5), 147 (5), 133 (4), 131 (7), 119 (7),
71 (31), 43 (13)
344 [M]+ (36), 316 (31), 301 (100), 273 (86),
259 (38), 245 (24), 231 (36), 203 (11), 201 (12),
189 (10), 185 (10), 161 (7), 159 (10), 147 (10),
71 (46), 43 (6)
344 [M]+ (24), 316 (5), 301 (14), 273 (100),
245 (11), 231 (11), 217 (11), 203 (6), 189 (7),
161 (4), 147 (4), 133 (4), 131 (5), 71 (29), 43 (10)
344 [M]+ (25), 316 (5), 301 (23), 273 (100),
245 (13), 231 (20), 217 (5), 203 (6), 189 (5),
133 (4), 71 (7), 43 (4)
344 [M]+ (24), 316 (6), 301 (20), 273 (100),
245 (11), 231 (21), 217 (7), 203 (6), 189 (4),
161 (4), 133 (4), 43 (3)
Pr + Pr
or
Et + Bu
10
with the corresponding 1,6- and 1,7-diketones were
obtained, but oct-1-yne and dec-5-yne remained intact.8
Thus, hydration and oxidation of alkylphenyl-
acetylenes and dialkylacetylenes with DMSO—PdCl2 to
1,2-diketones are accompanied by the previously un-
known reactions giving rise to 1,3-diketones and alkyl
aryl ketones.
11
12
13
14
Experimental
344 [M]+ (44), 316 (5), 301 (26), 273 (100),
245 (14), 231 (11), 201 (12), 189 (7), 147 (4),
71 (10), 43 (4)
The IR spectra were recorded on a Mattson 5000 spectro-
photometer in thin films or in KBr pellets. The 1H and 13C NMR
spectra were measured on a Bruker AC-300 spectrometer
(300 MHz) with Me4Si as the internal standard using CDCl3 as
the solvent. The GLC-mass spectra were obtained on a Hewlett
Packard 5890/II gas chromatograph equipped with a quadru-
pole mass spectrometer (HP MSD 5971) as the detector (EI,
70 eV) and a 30-m½0.25-mm HP-5 quartz column with a
copolymer of diphenyl- (5%) and dimethylsiloxane (95%) as the
stationary phase (0.25 µm). Melting points were determined on
an Electrothermal-9100 instrument. GLC was carried out on a
Young Model 680A chromatograph equipped with a flame
ionization detector and a 6FT10#OV-101 WHP 100/120 col-
umn with nitrogen as the carrier gas. Column chromatography
was performed on Silica gel 60 G (Merck). TLC was carried out
on Silica gel 60 F254 plates (Merck) using hexane or a 5 : 1
hexane—benzene mixture as the eluent. Alkynes 1a—c were
purchased from Aldrich. Dimethyl sulfoxide and PdCl2 of the
"chemically pure" grade were used without additional purifica-
tion; Pd/C was a commercial catalyst containing 0.8% of
palladium.
spectrum of the mixture following its chromatographic
purification on silica gel had at least 6 signals in the
region of δ 196.6—211.01, 29 signals in the region of
aromatic and unsaturated C atoms (δ 115.07—160.73),
and more than 45 signals in the region of aliphatic C
atoms (δ 14.06—62.95).
Oxidation of tetradec-7-yne 1d in DMSO containing
PdCl2—CuCl2•2H2O at 70 °C also gave rise to a com-
plex mixture of reaction products. Hexanoic acid (6%),
heptanoic acid (2%), tetradecan-7-one (41%), and
tetradecane-7,8-dione (2d) (32%) were identified in the
reaction mixture by GLC/MS. The absence of β-diketone
and the high yield of α-diketone 2d indicate that hydra-
tion and oxidation of alkyne 1d were the major processes
in this reaction.
1-Phenylpropane-1,2-dione (2a). Palladium chloride (36 mg,
0.2 mmol) was added to a solution of 1-phenylprop-1-yne (1à)
(232 mg, 2 mmol) in DMSO (5 mL). The reaction mixture was
stirred at 90 °C for 12 h, diluted with water (30 mL), and
extracted with ether (3½30 mL). The ethereal layer was washed
Previously,8 hydration of acetylenic ketones in a
10 : 1 acetonitrile—water mixture containing PdCl2(CN)2
with sonication was examined. In the case of dec-7-yn-
2-one, a trimerization product of the initial alkyne along

Oxidation of alkylacetylenes by PdCl2 in DMSO
Russ.Chem.Bull., Int.Ed., Vol. 50, No. 4, April, 2001
653
with water (20 mL) and a saturated NaCl solution (20 mL) and
then dried with Na2SO4. The solvent was distilled off in vacuo
and the residue was chromatographed on silica gel (hex-
ane—benzene, 5 : 1). 1-Phenylpropan-2-one (3) and diketone
2a were obtained in yields of 3.0 mg (1%) and 228 mg (77%),
respectively. Diketone 2a was obtained as a yellow viscous liquid,
nD17 1.5350; bis-4-nitrophenylhydrazone, m.p. 254—256 °C (cf.
lit. data:9 m.p. 254—255 °C). IR of 2à (oil), ν/cm–1: 1674, 1712
(C=O). 1H NMR (CCl4), δ: 2.45 (s, 3 H, CH3); 7.20—7.50 (m,
3 H, H arom.); 7.95 (dd, 2 H, H arom., J = 2.0 and 8.0 Hz).
1-Phenylpentane-1,2-dione (2b). Palladium chloride (36 mg,
0.2 mmol) was added to a solution of 1-phenylpent-1-yne (1b)
(288 mg, 2 mmol) in DMSO (5 mL) and the reaction mixture
was stirred at 90 °C for 15 h. Subsequent workup was carried
out as described above. Diketone 2b was obtained as a yellow
viscous liquid in a yield of 268 mg (76%). IR of 2b (oil),
ν/cm–1: 1672, 1712 (C=O). 1H NMR (CCl4), δ: 1.07 (t, 3 H,
CH3, J = 7.0 Hz); 1.73 (m, 2 H, C(4)H2); 2.83 (t, 2 H, C(3)H2,
J = 7.0 Hz); 7.46 (m, 3 H, H arom.); 8.00 (dd, 2 H, H arom.,
J = 2.0 and 8.0 Hz). Found (%): C, 75.04; H, 6.79. C11H12O2.
Calculated (%): C, 74.97; H, 6.87.
Oxidation of 1-phenylpent-1-yne (1b) with the
DMSO—Pd/C—CuCl2•2H2O system. Pd/C (100 mg) and
CuCl2•2H2O (34 mg, 0.2 mmol) were added to a solution of
1-phenylpent-1-yne (1b) (144 mg, 1 mmol) in DMSO (5 mL)
and the reaction mixture was stirred at 105 °C for 27 h. After
cooling, propan-2-ol (5 mL) was added and the catalysts was
filtered off. The filtrate was diluted with a saturated solution of
NaCl (20 mL) and extracted with ether (2½30 mL). The
ethereal layer was washed with water (20 mL) and a saturated
solution of NaCl (20 mL) and then dried with Na2SO4. The
solvent was distilled off in vacuo and benzoic acid (4) was
obtained in a yield of 105 mg (86%), m.p. 123—125 °C (cf. lit.
data:10 m.p. 122.5 °C).
CuCl2•2H2O (53 mg, 0.2 mmol) were added to a solution of
oct-4-yne (1ñ) (173 mg, 1.57 mmol) in benzene (6.0 mL) and
DMSO (2.0 mL). The reaction mixture was stirred at 80 °C for
35 h, diluted with water (30 mL), and extracted with ether
(3½30 mL). The ethereal layer was washed with water (20 mL)
and a saturated solution of NaCl (20 mL) and then dried with
Na2SO4. The solvent was distilled off in vacuo and a dark resin
was obtained in a yield of 200 mg. This was chromatographed
on silica gel (hexane) and an oily pale-yellow liquid was ob-
tained in a yield of 97 mg. According to the GLC data, the
mixture contained 14% of diketone 2ñ. Analysis by GLC/MS in
the linear temperature programming mode from 60 to 240 °C
(8 °C min–1) demonstrated that the reaction mixture contained
butyric acid (5) (3%, TR 15.87 min), octan-4-one (7) (5%,
TR 23.26 min), diketone 2ñ (27%, TR 29.95 min), and a
mixture of compounds 9—14 (the total yield was 46%,
TR 62.87—70.08 min).
Oxidation
of
tetradec-7-yne
(1d)
with
the
DMSO—PdCl2—CuCl2•2H2O system. Palladium chloride
(18 mg, 0.1 mmol) and CuCl2•2H2O (34 mg, 0.2 mmol) were
added to a solution of tetradec-7-yne (1d) (194 mg, 1 mmol) in
DMSO (5 mL). The reaction mixture was stirred at 70 °C for
9 h and worked up in a manner analogous to that described for
the oxidation of 1c. An oily pale-yellow liquid was obtained in a
yield of 187 mg. Analysis by GLC/MS in the linear temperature
programming mode from 80 to 240 °C (10 °C min–1) demon-
strated that the reaction mixture contained hexanoic acid (6%,
TR 8.63 min), heptanoic acid (2%, TR 13.04 min), tetradecan-
7-one (41%, TR 35.54 min), and tetradecane-7,8-dione (32%,
TR 38.19 min).
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 00-03-
32812a).
Oxidation of oct-4-yne (1ñ) with the DMSO—PdCl2 sys-
tem. Palladium chloride (18 mg, 0.1 mmol) was added to a
solution of oct-4-yne (1ñ) (110 mg, 1 mmol) in DMSO (5 mL).
The reaction mixture was stirred at 60 °C for 32 h, diluted with
water (30 mL), and extracted with ether (3½30 mL). The
ethereal layer was washed with water (20 mL) and a saturated
solution of NaCl (20 mL) and then dried with Na2SO4. The
solvent was distilled off in vacuo. The residue was dissolved in
hexane and passed through a layer of silica gel (h = 2 cm). The
hexane was distilled off in vacuo and an oily pale-yellow liquid
was obtained in a yield of 95 mg. The product was analyzed by
GLC-mass spectrometry in the linear temperature programming
mode from 60 to 240 °C (8 °C min–1). The mixture contained
butyric acid (5) (17%, TR 15.94 min), octan-4-one (7) (9%,
TR 22.86 min), octane-3,5-dione (8) (52%, TR 28.98 min), and
octane-4,5-dione (2ñ) (20%, TR 30.18 min).
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Oxidation
of
oct-4-yne
(1ñ)
with
the
DMSO—PdCl2—MeOH system. Palladium chloride (18 mg,
0.1 mmol) and CuCl2•2H2O (34 mg, 0.2 mmol) were added to
a solution of oct-4-yne (110 mg, 1 mmol) (1ñ) in MeOH
(5 mL) and DMSO (2.5 mL) and the reaction mixture was
stirred at 60 °C for 10 h. Subsequent workup was carried out as
described above. An oily product that crystallized was obtained
in a yield of 106 mg. Analysis by GLC/MS performed in the
linear temperature programming mode from 100 to 240 °C
(10 °C min–1) revealed the presence of octan-4-one (7) (6%,
TR 8.50 min) and a mixture of compounds 9—14 (the total yield
was 92%, TR 13.49, 14.20, 15.90, 23.34, 24.39, and 24.99 min,
respectively).
Oxidation of oct-4-yne (1ñ) with the DMSO—PdCl2—C6H6
system. Palladium chloride (28 mg, 0.157 mmol) and
Received March 27, 2000;
in revised form November 20, 2000