10.1002/ejoc.201901365
European Journal of Organic Chemistry
FULL PAPER
study are shown in the Supporting Information (Tables 6) and in the
publication (Figure 2).
1.33-1.18 (m, 5H). The 1H-NMR spectrum is in accordance to the
literature.[35]
Optimization of the PIPO-catalyzed oxidation reaction of n-octan-1,8-diol.
NaHSO4 H2O (0.5 - 1 mmol, 69.04 - 138 mg, 5 - 10 mol%) was suspended
Benzaldehyde 14. Yield: 95% (1.51 g, 14.23 mmol). 14 was obtained from
benzyl alcohol 13 (1.62 g, 15 mmol) as colorless oil using sodium
hypochlorite pentahydrate (2.96 g, 18.0 mmol, 1.2 eq.) as oxidation agent.
1H NMR (500 MHz; (CD3)2SO): 10.02 (s, 1H), 7.92 (dd, J = 1.4, 8.2 Hz,
2H), 7.71 (m, 1H), 7.61 (t, J = 7.6 Hz, 2H). The 1H-NMR spectrum is in
accordance to the literature.[35]
.
in n-butyronitrile (16 - 20 mL) and cooled to 0 °C. Sodium hypochlorite
pentahydrate (22 – 35 mmol, 3.62 – 5.73 g, 2.2 – 3.5 eq) and PIPO
(0.025 - 0.1 mmol, 75 - 300 mg, 0.25 - 1 mol%) were added. The
n-octan-1,8-diol (32) (10 - 20 mmol, 1.46 -2.92 g, 0.5 – 1 M) was dissolved
in THF (0 - 4 mL, 0 - 27% v/v) by gentle warming and added to the reaction
mixture. The reaction mixture was stirred at 0 °C until a color change from
red to colorless occurred. The reaction was quenched by addition of
aqueous HCl solution (50 mL of a 1 M solution), the phases were
separated and the organic phase was dried over MgSO4. The organic
phase was analysed by GC chromatography. Further work-up and
isolation of the product(s) was not performed. For n-octan-1,8-diol (32) an
optimization study was carried out. The results of the optimization study
are shown in the Supporting Information (Table 7).
Cinnamaldehyde (16). Yield: 75% (1.49 g, 11.25 mmol). The oxidation of
cinnamyl alcohol 16 (2.01 g, 15 mmol) was performed using sodium
hypochlorite pentahydrate (2.96 g, 18.0 mmol, 1.2 eq.) as oxidation agent.
Cinnamaldehyde 17 (1.49 g, 11.25 mmol, 75 %) was obtained as
yellowish oil after automated column chromatography using cyclohexane
and ethyl acetate as solvent (gradient from 10 to 40 % ethyl acetate in
cyclohexane), a flow of 75 mL/min on a Biotage® SNAP Ultra 50 g column.
1H NMR (500 MHz; (CD3)2SO): 9.69 (d, J = 7.6 Hz, 1H), 7.75 (m, 4H), 7.47
(m, 2H), 6.87 (dd, 1H J = 7.8, 16.0 Hz). The 1H-NMR spectrum is in
accordance to the literature.[35]
General protocol for PIPO-oxidation of primary alcohols to aldehydes.
.
NaHSO4 H2O (0.75 mmol, 103.6 mg, 5 mol%) was suspended in
n-butyronitrile (15 mL) and cooled to 0 °C. Sodium hypochlorite
pentahydrate (16.5 – 22.5 mmol, 2.71 – 3.70 g, 1.1 – 1.5 eq) and PIPO
(0.0375 mmol, 112.5 mg, 0.25 mol%) were added. The primary alcohol
(15 mmol) was added under vigorous stirring and the reaction mixture was
stirred at 0 °C until completion (GC-control). The reaction was quenched
by addition of aqueous HCl solution (15 mL of a 2 M solution), the phases
were separated and the aqueous phase extracted with n-butyronitrile (2x
5 mL). Organic phases were combined, dried over MgSO4 and the solvent
removed in vacuo. The product was analysed using 1H-NMR spectroscopy
in DMSO-d6.
4-Nitrobenzaldehyde 20. Yield: 94% (2.12 g, 14.00 mmol). 20 was
obtained from 4-nitrobenzyl alcohol 19 (2.30 g, 15 mmol) as a slightly
yellowish solid using sodium hypochlorite pentahydrate as oxidation agent
(2.96 g, 18.0 mmol, 1.2 eq.). 1H NMR (500 MHz; (CD3)2SO): 10.17 (s, 1H),
8.42 (d, J = 8.5 Hz, 2H), 8.17 (d, J = 8.5 Hz, 2H). The H-NMR spectrum
is in accordance to the literature.[35]
1
3-Nitrobenzaldehyde 23. Yield: 92% (2.09 g, 13.8 mmol) 23 was obtained
from 3-nitrobenzyl alcohol 22 (2.30 g, 15 mmol) as yellowish solid using
sodium hypochlorite pentahydrate (2.96 g, 18.0 mmol, 1.2 eq) as oxidation
agent. 1H NMR (500 MHz; (CD3)2SO): 10.14 (s,1H), 8.67 (m, 1H), 8.52
(ddd, J = 1.1, 2.4, 8.3 Hz 1H), 8.33 (d, J = 7.7 Hz, 1H), 7.89 (t, J = 7.9 Hz,
1H). The 1H-NMR spectrum is in accordance to the literature.[35]
n-Octanal (2). Yield: 90% (1.728 g, 13.5 mmol). (2) was obtained from
n-octan-1-ol (1) (2.35 mL, 15 mmol) as colorless oil using sodium
hypochlorite pentahydrate (2.70 g, 16.42 mmol, 1 eq.) as oxidation agent.
1H NMR (500 MHz; (CD3)2SO): 9.66 (t, J = 1.6 Hz, 1 H), 2.41 (td, J = 1.6,
7.3 , 7.3), 1.51 (p, J = 7.2 Hz, 2 H), 1.25 (m, 6 H), 0.86 (t, J = 6.9 Hz,
3 H).The 1H-NMR spectrum is in accordance to the literature.[35]
4-Methoxybenzaldehyde 26. Yield: 88% (1.79 g, 13.15 mmol). 26 was
obtained from 4-methoxybenzyl alcohol 25 (2.07 g, 15 mmol) as slightly
yellowish liquid using sodium hypochlorite pentahydrate as oxidation agent
(2.96 g, 18.0 mmol, 1.2 eq.) at room temperature instead of 0 °C. 1H NMR
(500 MHz; (CD3)2SO): 9.87 (s, 1H), 7.86 (d, J = 8.8 Hz, 2H), 7.11 (d,
n-Decanal (5). Yield: 89% (2.09 g, 13.4 mmol). (5) was obtained from
n-decan-1-ol (4) (2.86 mL, 15 mmol) as colorless oil using sodium
hypochlorite pentahydrate (2.70 g, 16.42 mmol, 1.1 eq.) as oxidation
agent. 1H NMR (500 MHz; (CD3)2SO): 9.66 (t, J = 1.5 Hz, 1H), 2.41 (td,
J = 1.5, 7.3 Hz, 2H), 1.51 (p, J = 7.1 Hz, 2H), 1.25 (m, 6 H), 0.86 (t,
J = 6.9 Hz, 3H). The 1H-NMR spectrum is in accordance to the literature.[35]
1
J = 8.7 Hz, 2H), 3.33 (s, 3H). The H-NMR spectrum is in accordance to
the literature.[35]
3-Methoxybenzaldehyde 29. Yield: 88% (1.79 g, 13.2 mmol). 29 was
obtained from 3-methoxybenzyl alcohol 28 (2.07 g, 15 mmol) as slightly
yellowish liquid using sodium hypochlorite pentahydrate (2.96 g,
18.0 mmol, 1.2 eq.) as oxidation agent at room temperature instead of
0 °C. 1H NMR (500 MHz; (CD3)2SO): 9.98 (s, 1H), 7.52 (m, 2H), 7.42 (m,
1H), 7.28 (m, 1H), 3.83 (s, 3H). The 1H-NMR spectrum is in accordance to
the literature.[35]
n-Hexanal (8). Yield: 85% (1.275 g, 12.75 mmol). Synthesis of n-
hexanal (8) from n-hexan-1-ol (7) (1.88 mL, 15 mmol) was performed in
n-octanenitrile as solvent instead of n-butyronitrile using sodium
hypochlorite pentahydrate as oxidation agent (2.70 g, 16.42 mmol, 1.1 eq.).
1
n-Hexanal (8) (, 85 %) was obtained as colorless oil. H NMR (500 MHz;
(CD3)2SO): 9.66 (t, J = 1.6 Hz, 1H), 2.41 (td, J = 1.6, 2.4 Hz, 2H), 1.52 (p,
J = 7.3 Hz, 2H), 1.26 (m, 4H), 0.86 (t, J = 7.1 Hz, 3H). The 1H-NMR
spectrum is in accordance to the literature.[35]
General protocol for PIPO-oxidation of dialcohols to dialdehydes.
NaHSO4 H2O (0.5 mmol, 51.8 mg, 5 mol%) was suspended in
.
n-butyronitrile (11 mL) and cooled to 0 °C. Sodium hypochlorite
pentahydrate (17.3 mmol, 2.84 g, 2.3 eq) and PIPO (0.38 mmol, 225 mg,
1 mol%) were added. The primary dialcohol (7.5 mmol, 1 M) was dissolved
in THF (4 mL, 27% v/v) by gentle warming and added to the reaction
mixture after cooling to RT. The reaction mixture was stirred at 0 °C until
a color change from red to colorless occurred. The reaction was quenched
by addition of aqueous HCl-solution (50 mL of a 1 M solution), the phases
were separated and the aqueous phase extracted with ethyl acetate (3x
30 mL). Organic phases were combined, dried over MgSO4 and the
solvent removed in vacuo. The crude product was analysed using GC
Cyclohexancarbaldehyde (11).Yield: 58% (0.98 g, 8.7 mmol). Synthesis of
cyclohexancarbaldehyde 11 from cyclohexanemethanol 10 (1.84 mL,
15 mmol) was performed in n-decanenitrile as solvent instead of
n-butyronitrile using sodium hypochlorite pentahydrate as oxidation agent
(2.70 g, 16.42 mmol, 1.1 eq.). Cyclohexancarbaldehyde 11 (0.98 g,
8.7 mmol, 58 %) was obtained as colorless oil. 1H NMR (500 MHz;
(CD3)2SO): 9.55 (s, 1H), 2.27 (m, 1H), 1.81 (m, 2H), 1.65-1.55 (m, 3H),
This article is protected by copyright. All rights reserved.