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Russ.Chem.Bull., Int.Ed., Vol. 53, No. 3, March, 2004
Ananikov and Beletskaya
Table 2. Catalytic addition of Ph S to alkynes using the regenerated catalyst
2
2
Cycle
Alkyne
Yield
of product (%)
Regenerated
catalyst (%)
Regenerated
PPh3b (%)
а
b
1
2
98
92
70
96
97
87
90
50
55
3
a
Measured by NMR spectroscopy after the end of the reaction.
Calculated per the initial amount.
b
PPh3 (1.5•10–4 mol), and a catalyst (Pd(OAc)2, Pd(PPh3)4, or
lyst and 50—70% triphenylphosphine can be regenerated
by a simple procedure of flash chromatography (Table 2).
Triphenylphosphine cannot be regenerated completely beꢀ
cause of its partial oxidation to triphenylphosphine oxide.
The regeneration procedure repeated triply did not noꢀ
ticeably decrease the catalytic activity of the isolated palꢀ
ladium complexes (see Table 2). In particular, after the
addition of Ph S to hexꢀ1ꢀyne (cycle 1, see Table 2), the
–
6
PdCl ) (1.0•10 mol) was heated at 140 °C until complete
2
melting and shaken to form a homogeneous dark black melt
(
1—3 min). The melt was cooled to ~20 °C until solidification,
–
3
alkyne (1.5•10 mol) was added, and the tube was sealed (or
hermetically closed). The reaction mixture was kept for 10 min
at 140 °C in a thermostat. Heating resulted in the formation of a
homogeneous dark brown melt, whose color changed during the
reaction to light brown or yellow.
2
2
regenerated catalyst was repeatedly used for the addition
Isolation and purification of products. After completing the
reaction, unreacted alkyne was removed in vacuo, and the prodꢀ
of Ph S to butꢀ3ꢀynꢀ1ꢀol (cycle 2, see Table 2). After the
2
2
2
5
uct was purified by flash chromatography. Gradient elution
was carried out with a mixture of light petroleum and ethyl
acetate (0—10%). After chromatography, the solvent was evapoꢀ
rated in vacuo, and the resulting products were dried in vacuo.
The structures of the reaction products were confirmed by
repeated isolation of the catalyst, it was also used in the
reaction with N,Nꢀdimethylpropargylamine (cycle 3, see
Table 2). In all cases, high yields (96—98%) and selectiviꢀ
ties of the reactions were observed. The 3 Р{ H} NMR
spectrum of the regenerated catalyst in deuterated benꢀ
zene exhibited signals at 29.4 and 30.8 ppm correspondꢀ
1
1
1Н, 13С, and 77Se NMR spectroscopy (comparing with the pubꢀ
14—18
lished spectral data
) and by mass spectrometry. The addiꢀ
ing to the binuclear cisꢀ/transꢀ[Pd (SPh) (PPh ) ] comꢀ
tion products of Ph S and Ph Se to N,Nꢀdimethylpropargylꢀ
2
4
3 2
2 2 2 2
plexes.1
7,18
Thus, in the presence of an excess of triꢀ
amine were isolated in the form of oxalate as described previꢀ
ously. Their structures were established by Xꢀray diffraction
phenylphosphine, the catalytically active palladium comꢀ
plexes are highly stable and do not decompose after reꢀ
generation.
1
7,18
analysis.
Regeneration of the catalyst and triphenylphosphine after the
reaction (general procedure). After completing the reaction
–
3
–4
in melt (1.0•10 mole of Ar E , 1.5•10 mole of PPh3,
3
2
2
Experimental
–
5
–3
.0•10 mole of the catalyst, and 1.0•10 mole of an alkyne),
the reaction mixture was adsorbed on silica gel, and chromatoꢀ
graphic purification was performed as described above. Triꢀ
phenylphosphine was eluted in the first fractions (light petroꢀ
leum), and the product was isolated by gradient elution (ethyl
acetate 0—10%). The palladium complexes were eluted in the
last fractions with a light petroleum—ethyl acetate (1 : 1) mixꢀ
ture. After the solvent was removed and the residue was dried in
vacuo, triphenylphosphine and palladium complexes were obꢀ
tained as white crystals and brown oil, respectively (identified by
Diaryl dichalcogenides and alkynes were commercially availꢀ
able and used after spectral monitoring of purity ( Н and
С NMR). Solvents were purified according to standard proceꢀ
dures. All syntheses were carried out in an argon atmosphere.
Reaction mixtures were heated in a temperatureꢀcontrolled
oil bath.
1
1
3
NMR spectra were recorded on a Bruker DRX500 specꢀ
trometer with working frequencies of 500, 125, and 95 MHz for
1
13
77
the Н, С, and Se nuclei, respectively. For recording
1
31
14,18
Н and Р NMR spectroscopy).
1
Н NMR spectra, signals of residual protons of solvents were
used as standards. External standards Ph Se /CDCl (463.0 ppm)
2
2
3
This work was financially supported by the President
7
7
31
and Н PO /H O (0 ppm) were used for Se and P NMR
3
4
2
of the Russian Federation (Grant for Young Scientists
MDꢀ2384.2004.3), the Russian Foundation for Basic Reꢀ
search (Project No. 04ꢀ03ꢀ32501), and the Division of
Chemistry and Materials Sciences (program "Theoretical
and Experimental Investigation of the Nature of Chemiꢀ
cal Bond and Mechanisms of the Most Important Chemiꢀ
cal Reactions and Processes").
7
7
spectra, respectively. Se NMR spectra were recorded using the
1
77
24
H— Se HMQC inverse procedure. NOESY spectra were
recorded as described previously.18 All measurements were perꢀ
formed at room temperature.
Solventꢀfree addition of diaryl dichalcogenides to alkynes (genꢀ
eral procedure). The reaction was carried out in a sealed or
–
3
hermetically closed tube. A mixture of Ar E (1.0•10 mol),
2
2