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Can. J. Chem. Vol. 91, 2013
Fig. 1. Probable structure of the catalyst.
2-Nitro-1-(4-nitrophenyl)-3-[(tetrahydro-2H-pyran-2-yl)oxy]
propan-1-ol (p)
Diastereomeric mixture, colourless semisolid. IR (KBr, cm–1) :
1
3456, 3018, 2932, 1533, 1440, 1361, 1215, 1036. H NMR (400 MHz,
CDCl3) ␦: 1.52–1.75 (m, 6H), 3.45–3.56 (m, 3H), 3.95–4.11 (m, 2H),
4.53–4.57 (m, 1H), 4.87–4.92 (m, 1H), 5.40–5.45 (m, 1H), 7.60–7.63
(m, 2H), 8.25–8.28 (m, 2H). 13C NMR (100 MHz, CDCl3) ␦: 18.76,
19.06, 19.15, 19.38, 25.03, 29.72, 29.96, 30.18, 30.23, 62.16, 62.62,
62.70, 63.17, 64.19, 64.38, 64.80, 65.17, 71.32, 71.35, 71.62, 72.33,
90.52, 90.89, 91.26, 91.33, 98.68, 99.42, 99.92, 124.04, 124.15, 127.11,
127.41, 127.55, 127.71, 145.12, 145.34, 148.23. ESI-MS (m/z): 326.0 (M+).
Anal. calcd. for C14H18N2O7: C 51.53, H 5.56, N 8.59; found: C 51.66,
H 5.62, N 8.41.
Table 1. Study of the solvent effect.
2-Nitro-tetradecan-3-ol (u)
Diastereomeric mixture, colourless liquid. IR (KBr, cm–1) : 3431,
3018, 2925, 2866, 1553, 1440, 1215. 1H NMR (400 MHz, CDCl3) ␦: 0.88
(t, J = 6.4 Hz, 6H), 1.25 (bs, 32H), 1.35–1.52 (m, 4H), 1.56 (dd, J = 6.8,
3.2 Hz, 6H), 2.28 (s, 1H), 2.37 (s, 1H), 3.90 (m, 1H), 4.18 (m, 1H), 4.51
(m, 2H). 13C NMR (100 MHz, CDCl3) ␦: 12.3, 14.1, 16.2, 22.69, 25.14,
25.73, 29.3, 29.4, 29.5, 29.6, 31.9, 33.0, 72.0, 72.8, 86.3, 87.7. ESI-MS
(m/z): 259.10 (M+). Anal. calcd. for C14H29NO3: C 64.83, H 11.27,
N 5.40; found: C 64.49, H 11.00, N 5.55.
Entry
Solventa
Time (h)
Yield (%)b
1
DMSO
DMF
CHCl3
CH2Cl2
THF
12
12
4
4
12
4
38
56
93
89
62
90
92
2
3
4
5
6
7
EtOH
No solvent
2
2-Methyl-2-nitrotetradecan-3-ol (v)
Note: Aldehyde (1 mmol)/nitromethane/PDPP/ethyl acrylate = 1:2:0.1:0.1.
a0.5 mL of solvent.
bIsolated yields.
Racemic mixture, colourless liquid. IR (KBr, cm–1) : 3343, 3018,
1
2932, 2859, 1540, 1460. H NMR (400 MHz, CDCl3) ␦: 0.88 (t, J =
6.4 Hz, 3H), 1.28–1.69 (m, 16H), 1.55 (s, 3H), 1.56 (s, 3H), 1.85–1.89 (m,
1H), 2.01–2.07 (m, 1H), 2.25–2.30 (m, 1H), 3.89 (m, 1H), 4.00 (m, 1H).
13C NMR (100 MHz, CDCl3) ␦: 10.22, 14.15, 20.19, 22.70, 23.79, 23.90,
25.26, 26.40, 29.36, 29.46, 29.54, 29.61, 31.44, 31.91, 33.54, 71.82,
92.22, 94.32. ESI-MS (m/z): 274.2 (M+ + 1). Anal. calcd. for C15H31NO3:
C 65.89, H 11.43, N 5.12; found: C 65.65, H 11.09, N 5.32.
mixture of preformed PDPP–EA complex (0.05 mmol),
p-chlorobenzaldehyde (0.5 mmol), and nitromethane (1.0 mmol)
was stirred without solvent with continuous monitoring by thin-
layer chromatography (TLC) after every 0.5 h. The reaction was
found to be complete within 2 h and the formation of only one
polar product was observed, which was confirmed to be the de-
sired product after characterization by spectroscopic methods.
Additionally, we observed that the reaction behaved exactly the
same way, even after mixing 10 mol% of both the catalysts with
reactants in no particular order, to give the desired -nitroalcohol
exclusively under similar reaction conditions. Since swelling of
the resin often governs the activity of polymer-bound catalysts,
we wanted to study the effect of the solvent on the overall effi-
ciency of the protocol. It was observed that the reaction works
well in ethanol, chloroform, and dichloromethane and takes al-
most 4 h for completion. But the reactions in dimethyl sulfoxide
vations led us to conclude that the reaction indeed works better
under SolFC than in solvent media.
To explore the role of nitroalkane as a solvent, we stirred an
equimolar mixture of p-chlorobenzaldehyde and nitromethane in
the presence of 1 equiv. of ethyl acrylate conjugated polystyryl-
time (7 h) for complete conversion. As the reaction was compara-
tively much slower under this reaction condition, the role of ni-
tromethane was subjected to further investigations. It was
observed that the addition of 3 and 4 equiv. nitromethane to that
observations suggested that nitromethane did not play the same
role as that of other solvents, which is the swelling of the polysty-
ryl resin. Therefore, it was concluded that the better reaction rate
in pure nitromethane (2 equiv.) may be the result of a concentra-
tion effect under SolFC rather than a solvent effect.
5,9-Dimethyl-2-nitrodec-8-en-3-ol (w)
Diastereomeric mixture, colourless liquid. IR (KBr, cm–1) :
1
3540, 3025, 2925, 1620, 1553, 1454, 1381, 1215. H NMR (400 MHz,
CDCl3) ␦: 0.93 (d, J = 6.8 Hz, 3H), 0.96 (dd, J = 6.4, 3.2 Hz, 3H),
1.06–1.49 (m, 8H), 1.54 (t, J = 6.4, 6H), 1.60 (s, 6H), 1.68 (s, 6H),
1.55–1.73 (m, 2H), 1.95–2.02 (m, 4H), 2.35–2.39 (m, 1H), 2.40–2.46
(m, 1H), 3.94–4.03 (m, 1H), 4.25–4.34 (m, 1H), 4.45–4.55 (m, 2H),
5.06–5.10 (m, 2H). 13C NMR (100 MHz, CDCl3) ␦: 10.1, 10.2, 17.6, 18.6,
18.7, 20.0, 20.3, 25.14, 25.19, 25.3, 25.7, 28.4, 28.6, 28.8, 29.1, 35.7,
36.1, 37.6, 37.8, 40.0, 40.1, 40.4, 69.8, 70.1, 70.8, 71.1, 86.3, 86.8, 87.9,
88.4, 124.3, 131.5, 131.6. ESI-MS (m/z): 219 (M+). Anal. calcd. for
g,6 i,6 j,6 m,6 n,10 o,69 q,70 r,6 s,71 and t10 (for IR, NMR, and MS data,
see the Supplementary data) were confirmed by comparing their
analytical data with the literature values.
Results and discussion
Synthesis of the catalyst
The polystyryl-diphenylphosphine–ethyl acrylate (PDPP–EA)
complex prepared by mixing an equimolar ratio of PDPP
(0.5 mmol) and ethyl acrylate (0.5 mmol) was analyzed by IR spec-
troscopy. In the PDPP–EA complex, 1 (Fig. 1), it was observed that
the IR peak at 1719 cm–1 for C=O stretching (str.) of the ester moiety
in ethyl acrylate was absent. This might be due to the fact that the
anion formed in complex 1 as a result of the addition of triphen-
ylphosphine to ethyl acrylate might be predominant as oxygen
centered rather than carbon centered and hence the peak for C=O
str. was absent after complexation.
Optimization of reaction conditions
We chose the reaction of p-chlorobenzaldehyde with nitrometh-
ane as the pilot reaction to optimize the reaction conditions. As
our stated aim was to accomplish the reaction under SolFC, a
Correlation of catalyst loading and reaction time
The catalyst requirement for optimum efficiency of the proto-
col was also studied to find that 10 mol% of the catalyst (in situ
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