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.3.8. Synthesis of Hybrid Manganese(III)-porphyrin Magnetic Catalyst (6)
MNP@SiO -NH (1 g) and cesium carbonate (340 mg; 1.0 mmol) were added to a round-flask
2
2
containing a solution of (
mixture was put under stirring at 85 C for 24 h. Then, the magnetic material was collected using
5
) (250 mg; 0.29 mmol) in dry 1,2-dimethoxyformide (40 mL). The reaction
◦
an external magnetic field and washed (3
×
) using acetonitrile, ethyl acetate, and dichloromethane.
) was dried under reduced pressure for 48 h, at room
Finally, the MNP@SiO -NH-TDFPP-Mn(III) (
6
2
◦
temperature (25 C), and characterized by UV-Vis, TG-DSC, FT-IR, and FAAS.
3
.4. General Procedure for Catalytic Epoxidation of (−)-Isopulegol Benzyl with O and Scale-Up
2
An autoclave was charged with the (
hybrid manganese(III)-porphyrin magnetic catalyst (
isobutyraldehyde (0.25 mL; 2.5 mmol), and chlorobenzene (22 mg; 1.95
−
)-isopulegol benzyl ether (152 mg; 0.62 mmol) and
−
5
6) (4.7
×
10 mmol), butyronitrile (2 mL),
−
1
×
10 mmol) as the inert
internal standard. The autoclave was pressurised with O (5 bar) and the mixture reaction was
2
◦
conducted under stirring, at room temperature, 25 C, for 6 h. The crude mixture was washed with
sodium bicarbonate saturated solution (50 mL) and water. The ( )-isopulegol benzyl ether epoxide
−
was then isolated from the organic phase by simple distillation. Conversion and selectivity were
determined by GC, based on peak areas, using chlorobenzene as internal standard. Diastereoisomers
of ( )-isopulegol benzyl ether epoxide were purified using a silica gel column chromatography,
−
with a mixture of ethyl acetate:n-hexane (1:4) as the eluent, yielding 79% of isolated product with
diastereosiomers A and B in 51% (66 mg; 0.26 mmol) and 45% (59 mg; 0.23 mmol), respectively.
The scale-up experiment was performed using (
−
)-isopulegol benzyl ether (1) (0.982 g, 4.02 mmol),
isobutyraldehyde (1.168 g, 16.2 mmol), hybrid manganese(III)-porphyrin magnetic catalyst (
6
)
−
4
(
3.04 × 10 mmol), and butyronitrile (15 mL) as the solvent. Finally, a sodium bicarbonate saturated
solution (50 mL) was added to the crude mixture, leading to the formation of two phases. The target
epoxide was then isolated in 76% yield (3.05 mmol) from the organic phase by simple distillation.
The catalyst (6) was steadily separated from the reaction mixture, using an external magnetic stirrer
bar, followed by decantation of the liquid. Then, the solid material was washed with CH CN (15 mL),
3
◦
dried under vacuum at 60 C for 12 h, and the solid was kept under the vacuum and inert atmosphere
for reuse.
1
(
(
−
)-Isopulegol benzyl ether epoxide–diastereoisomer
A
: H-NMR (CDCl , 400 MHz)
δ
H (ppm): 7.36–7.25
3
m, 5H, HAr), 4.68 (d, J = 12.0 Hz, 1H, H11), 4.40 (d, J = 12.0 Hz, 1H, H11), 3.26 (ddd, J1 = 4.0 Hz,
J2 = 4.0 Hz, J3 = 4.0 Hz, 1H, H2), 2.76 (d, J = 8.0 Hz, 1H, H9), 2.68 (d, J = 4.0 Hz, 1H, H9), 2.24–2.19 (m,
1
1
H, H3), 1.90–1.86 (m, 1H, H6), 1.71–1.66 (m, 1H, H5), 1.43–1.39 (m, 1H, H6), 1.31–1.24 (m, 1H, H4),
.13 (s, 3H, CH -7), 1.11–1.08 (m, 1H, H1), 0.95 (d, J = 8.0 Hz, 3H, CH -10), 0.92–0.86 (m, 2H, H3,
3
3
H5); 13C-NMR (101 MHz, CDCl3)
δ
C (ppm): 16.7 (C-7), 22.3 (C-10), 26.4 (C-6), 31.5 (C-4), 33.9 (C-5),
3
9.9 (C-3), 50.8 (C-1), 56.8 (C-9), 57.9 (C-8), 70.2 (C-11), 78.8 (C-2), 127.6 (C-Ar), 128.4 (C-Ar), 139.0 (C-Ar).
+
HRMS (ESI-FIA-TOF): Calcd for C H O [M + Na ] 283.1673; Found m/z = 283.1669.
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2
1
(
(
−
)-Isopulegol benzyl ether epoxide–diastereoisomer
B: H-NMR (CDCl , 400 MHz) δ H (ppm): 7.42–7.40
3
m, 2H, HAr), 7.35–7.31 (m, 2H, HAr), 7.26–7.23 (m, 1H, HAr), 4.72 (d, J = 12.0 Hz, 1H, H11), 4.44 (d,
J = 12.0 Hz, 1H, H11), 3.32–3.26 (m, 1H, H2), 2.51–2.48 (m, 2H, H9), 2.23–2.20 (m, 1H, H3), 1.75–1.70 (m,
H, H6), 1.69–1.64 (m, 1H, H5), 1.45–1.35 (m, 1H, H4), 1.34–1.30 (m, 1H, H1), 1.25 (s, 3H, H7), 1.21–1.11
m, 1H, H6), 0.95 (d, J = 6Hz, 3H, H10), 0.92–0.85 (m, 2H, H3 and H5). 13C-NMR (101 MHz, CDCl3)
ppm): 18.9 (C-7), 22.2 (C-10), 27.8 (C-4), 31.3 (C-6), 34.2 (C-5), 39.6 (C-3), 49.2 (C-1), 52.0 (C-9), 58.3 (C-8),
1
(
(
δ C
6
9.7 (C-11), 78.3 (C-2), 127.4 (C-Ar), 127.7 (C-Ar), 128.3 (C-Ar), 138.9 (C-Ar). HRMS (ESI-FIA-TOF):
+
Calcd for C H O [M+Na ] 283.1673; Found m/z = 283.1669.
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