10.1002/chem.201606048
Chemistry - A European Journal
FULL PAPER
added to the reaction mixture at 120 °C under a N2 atmosphere. After 18
h, the mixture in both tubes was separately worked up. For Tube A, the
mixture was passed through a membrane filter (Millipore Corp., Billerica,
MA; Millex-LH, 0.45 μm) to remove the insoluble catalyst, and the filtered
residue was washed with EtOAc (30 mL). The combined filtrate was
washed with H2O (3 × 20 mL), dried (MgSO4), filtered, and concentrated
in vacuo. The residue was purified by silica gel column chromatography
(hexane/EtOAc, 20:1) or preparative TLC (hexane) to afford the
corresponding stilbenes. For Tube B, the mixture was treated as
described for Tube A to afford the corresponding phthalide or phthalimide.
Conclusions
In conclusion, we have demonstrated that terephthalaldehyde is
a readily available, easy to handle, inexpensive, and quite
practical CO-carrier. Furthermore, we have developed a Pd/C-
catalyzed simultaneously-proceeding efficient Mizoroki–Heck
and carbonylation reaction protocol using the in situ generated
styrene derivatives and CO derived from the corresponding
cinnamaldehyde derivatives through a virtual one-pot three
reactions system (decarbonylation, carbonylation, and Mizoroki–
Heck reactions).
Reuse test of 10% Pd/C for the simultaneous synthesis of 4-
methoxystilbene and phthalide in a virtual one-pot manner
10% Pd/C (59.9 mg, 37.5 μmol), 4-methoxycinnamaldehyde (60.8 mg,
375 μmol), Na2CO3 (79.5 mg, 750 μmol), and iPrOH (1 mL) were placed
in Tube A of H-shaped pressure tight glass sealed tubes, and 10% Pd/C
(26.6 mg, 25.0 μmol), 2-iodobenzylalcohol (58.5 mg, 250 μmol), PPh3
(26.2 mg, 100 μmol), and iPrOH/NMP (0.5 mL/0.5 mL) were placed in
Tube B of the H-shaped tubes. Each tube was sealed with a screwcap
fitted with a Teflon® seal. Both tubes were heated under N2 atmosphere
at 120 °C for 6 h. A solution of the iodobenzene (153 mg, 750 μmol) and
tetrabutylammonium iodide (139 mg, 375 μmol) in NMP (1 mL) was
added to the Tube A at 120 °C under N2 atmosphere. Each reaction
mixture was stirred for further 18 h, and then the reaction mixture in Tube
A was filtered using a Kiriyama funnel (1 µm filter paper). The catalyst on
the filter paper was sequentially washed with EtOAc (20 mL), H2O (20
mL), and MeOH (20 mL), and the filtrate and wash EtOAc were
combined and concentrated in vacuo to give 4-methoxystilbene (57.5 mg,
0.274 mmol, 73%). The recovered catalyst was dried at room
temperature under reduced pressure for 24 h, then weighed [66.5 mg,
111%, 66.5 ÷ 59.9 × 100]. The reaction mixture in Tube B was worked up
in the same manner. Phthalide was obtained in 81% yield (27.2 mg,
0.203 mmol), and the catalyst (28.7 mg) was recovered [108%, 28.7 ÷
26.6 × 100]. The reaction for the second run was carried out using
recovered catalyst in the same manner as the first run. 4-
Methoxystilbene was not obtained, and the catalyst (57.5 mg) was
recovered [96%, 57.5 ÷ 59.9 × 100]. The formation of only a trace
amount of phthalide in Tube B was observed, and the catalyst (26.1 mg)
was recovered [98%, 26.1 ÷ 26.6 × 100].
Experimental Section
General procedure for ester synthesis (Table 3)
A mixture of 10% Pd/C (26.6 mg, 25.0 μmol), terephthalaldehyde (33.5
mg, 250 μmol), Na2CO3 (53.0 mg, 500 μmol) in iPrOH (1 mL) in a 17-mL
test tube was stirred using
a
personal organic synthesizer
ChemistationTM (EYELA, Tokyo) or ChemistPlazaTM (Shibata Scientific
Technology, Ltd., Tokyo) at 120 °C under an N2 atmosphere. After 24 h,
a solution of iodoarene (250 μmol), PPh3 (26.2 mg, 100 μmol) in N-
methylpyrrolidone (NMP, 1 mL) was added to the reaction mixture at
100 °C under a N2 atmosphere. After 24 h, the mixture was passed
through a membrane filter (Millipore Corp., Billerica, MA; Millex-LH, 0.45
μm) to remove the insoluble catalyst, and the filtered residue was
washed with EtOAc (30 mL). The combined filtrate was washed with H2O
(3 × 20 mL), dried (MgSO4), filtered, and concentrated in vacuo. The
residue was purified by silica gel column chromatography (hexane/EtOAc,
20:1) or preparative TLC (hexane) to afford the corresponding ester.
General procedure for the decarbonylative Mizoroki–Heck
reaction (Table 4)
A mixture of 10% Pd/C (26.6 mg, 25.0 μmol), 4-methoxycinnamaldehyde
(40.5 mg, 250 μmol), Na2CO3 (53.0 mg, 500 μmol) in iPrOH (1 mL) in a
17-mL test tube was stirred using
ChemistationTM (EYELA, Tokyo, Japan) or ChemistPlazaTM (Shibata
Scientific Technology, Ltd., Tokyo, Japan) at 120 °C under N2
a personal organic synthesizer
a
atmosphere. After 24 h, a solution of iodobenzene (51.0 mg, 250 μmol)
the additive (500 μmol) in NMP (1 mL) was added to the reaction mixture
at 120 °C under a N2 atmosphere. After 24 h, the mixture was passed
through a membrane filter (Millipore Corp., Billerica, MA; Millex-LH, 0.45
μm) to remove the insoluble catalyst, and the filtered residue was
washed with EtOAc (30 mL). The combined filtrate was washed with H2O
(3 × 20 mL), dried (MgSO4), filtered, and concentrated in vacuo. The
residue was purified by silica gel column chromatography (hexane/EtOAc,
20:1) or preparative TLC (hexane) to afford the 4-methoxystilbene.
Acknowledgements
This work was partly supported by a Research Fellowship for
Young Scientists of the Japan Society for the Promotion of
Science (Grant number 15J11072). We thank the N.E. Chemcat
Corporation for kindly providing 10% Pd/C.
Keywords: Carbonylation • Cleavage reactions • Heck reaction •
Heterogeneous catalysis • Palladium
General procedure for simultaneous synthesis of
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diarylethene and ester in a virtual one-pot manner (Table 5)
10% Pd/C (59.9 mg, 37.5 μmol), the cinnamaldehyde derivative (375
μmol), Na2CO3 (79.5 mg, 750 μmol), and iPrOH (1 mL) were placed in
Tube A of the H-shaped pressure tight glass sealed tube, while 10%
Pd/C (26.6 mg, 25.0 μmol), 2-iodobenzylalcohol or 2-iodobenzamide
(250 μmol), PPh3 (26.2 mg, 100 μmol), and iPrOH/NMP (0.5 mL/0.5 mL)
were in Tube B of the H-shaped tube. Both tubes were sealed with a
screwcap fitted with a Teflon® seal. The both tubes were heated at
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6 h, a solution of the iodoarene (750 μmol), and
tetrabutylammonium iodide (139 mg, 375 μmol) in NMP (1 mL) was
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