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N.Ch. Maity et al. / Journal of Molecular Catalysis A: Chemical 366 (2013) 380–389
reaction mixture was heated at 60 ◦C for 2 h and then cooled to
room temperature. The white solid which was precipitated out
was separated by centrifugation. The white solid was taken in
ethyl acetate (50 mL) and treated with saturated NaHCO3 solu-
tion (5 mL). The organic layer was repeatedly washed sequentially
with water (5 × 20 mL) and brine (2 × 50 mL), dried over anhydrous
MgSO4 and the solvent was removed completely under reduced
pressure to get a light brown viscous liquid. Yield: 3.80 g, 90%;
FT-IR (KBr) ꢀmax/cm−1: 3436, 2924, 1647, 1517, 1459, 1023, 670,
464; 1H NMR (CDCl3, 200 MHz) ı, ppm: 11.70 (s, 2H), 9.85 (s, 2H),
7.51 (d, J = 1.8 Hz, 2H), 7.35 (d, J = 1.4 Hz, 2H), 3.62 (s, 4H), 2.74 (t,
J = 5.8 Hz, 4H), 2.67 (s, 4H), 1.88–1.76 (m, 2H), 1.42 (s, 18H); 13C
(CDCl3, 125 MHz), ı, ppm: 196.67, 159.73, 137.53, 134.41, 131.08,
129.68, 119.82, 61.29, 54.55, 53.58, 34.33, 28.79, 27.25; TOFMAS
(ES+) (m/z): 481.54 (M+H); Anal. Calcd. for C29H40N2O4: C, 72.47;
H, 8.39; N, 5.83. Found: C, 72.24; H, 8.25; N, 5.92.
residue was extracted in ethyl acetate (EtOAc). The organic layer
was washed successively with water, brine and dried over anhy-
drous Na2SO4. The solvent was removed under reduced pressure
to get dark brown residue that was used directly as catalyst without
further purification.
3; Yield: 0.33 g, 94%; m.p.: >240 ◦C; FT-IR (KBr) ꢀmax/cm−1: 3422,
2930, 2860, 1613, 1540, 1432, 1388, 1339, 1309, 1236, 1202, 1165,
1027, 826, 567; Cl-TOFMAS (ES+) m/z: 611.65 (92%), 1257.31 (8%);
[˛]D24 = +1015 (c = 0.02, CHCl3); Anal. Calcd. for C35H48ClMnN4O2:
C, 64.96; H, 7.48; N, 8.66. Found: C, 64.84; H, 7.32; N, 8.53.
4; Yield: 0.31 g, 92%; m.p.: >250 ◦C; FT-IR (KBr) ꢀmax/cm−1
:
3426, 2927, 1610, 1538, 1454, 1307, 1161, 1027, 697, 568, 466;
[˛]D24 = −173 (c = 0.02, CHCl3); Cl-TOFMAS (ES+) m/z: 710.38 (53%);
1453.69 (47%); Anal. Calcd. for C86H100Cl2Mn2N8O4: C, 69.30; H,
6.76; N, 7.52. Found: C, 69.21; H, 6.6; N, 7.41.
2.6. General epoxidation reaction procedure
2.3. Synthesis of ligand 3ꢀ
2.6.1. UHP oxidant system
Catalyst 1/2/3/4 (5 mol%) was dissolved in (1:1) DMC:MeOH
(1 mL) to which pyridine N-oxide (PyNO) (11.5 mg, 0.12 mmol)
and n-dodecane (7.5 mg as an internal standard) were added. The
resulting solution was stirred for 10–15 min at room temperature.
The desired olefin (0.625 mmol) was added to the above mixture
and the reaction temperature was brought to 5 ◦C. UHP (144.8 mg,
1.5 mmol, in four equal portions) was added to the above mixture
under stirring. The progress of the reaction was monitored on gas
chromatography (GC). After the completion of the reaction, cat-
alyst was separated from the product epoxides by precipitation
with hexane (2 mL) and was used as such for further catalytic runs.
Epoxides were purified by flash chromatography through neutral
alumina using ethyl acetate and hexane (9:1) as eluent.
Dialdehyde 7 (0.55 g, 1.1 mmol) was taken in dry THF (0.5 mL)
to which (1S,2S)-(+)-diamino cyclohexane (0.125 g, 1.1 mmol) dis-
solved in dry THF (1 mL) was added and the reaction mixture was
stirred for 2–3 h at room temperature. THF was removed from the
resulting pale yellow solution under reduced pressure. The residue
was washed with methanol and then dried in vacuum to get bright
yellow product. Yield: 0.59 g, 93%; m.p.: 122–124 ◦C; FT-IR (KBr)
ꢀmax/cm−1: 3427, 2934, 2862, 1628, 1443, 1360, 1265, 1206, 1158,
1097, 1029, 874, 801, 703, 420; 1H (CDCl3, 500 MHz) ı, ppm: 13.78
(s, 2H), 8.27 (s, 2H), 7.19 (s, 2H), 6.97 (s, 2H), 3.48 (s, 4H), 3.31
(t, J = 3 Hz, 2H), 2.64 (s, 4H), 2.6 (s, 4H), 1.95–1.71 (m, 10H), 1.38
(s, 18H); 13C (CDCl3, 125 MHz) ı, ppm: 165.53, 159.20, 136.73,
130.02, 129.85, 128.35, 118.23, 72.35, 62.06, 54.99, 53.91, 34.74,
33.18, 29.48, 27.53, 24.31; [˛]D24 = +97 (c = 0.8, CHCl3); TOFMAS
(ES+) (m/z): 559.64 (M+H, 90%); 1118.3 (M+H, 10%); Anal. Calcd. for
2.6.2. NaOCl oxidant system
Catalyst 1 (5 mol%) was dissolved in DMC (1 mL) to which pyri-
dine N-oxide (PyNO) (11.5 mg, 0.12 mmol) and n-dodecane (7.5 mg
as an internal standard) and the resulting solution was stirred for
10–15 min at room temperature. The desired olefin (0.625 mmol)
was added to the above mixture and reaction temperature was
brought to 5 ◦C. To the above mixture, buffered NaOCl (pH 11.3;
1.5 mmol) was added in drop wise manner over 1 h and the reaction
was monitored by GC. After the reaction, the organic layer was sep-
arated, washed with water, brine and finally dried over anhydrous
Na2SO4. The catalyst was separated from the product epoxide by
precipitation with hexane (2 mL) and used as such for further cat-
alytic runs. The evaporation of the solvent under reduced pressure
yielded the crude epoxide which was purified by flash chromatog-
raphy through neutral alumina using ethyl acetate and hexane (9:1)
as eluent.
C
35H50N4O2: C, 75.23; H, 9.02; N, 10.03. Found: C, 75.02; H, 8.89;
N, 9.83.
2.4. Synthesis of ligand 4ꢀ
Solution of dialdehyde 7 (0.55 g, 1.1 mmol) in dry THF (0.5 mL)
and (1R,2R)-(+)-1,2-diphenylethylene diamine (0.230 g, 1.1 mmol)
in dry THF (1 mL) were mixed and the resultant solution was stirred
for 6–7 h at room temperature. THF was removed from the resulting
solution under reduced pressure. The yellow residue thus obtained
was washed with methanol and then dried under vacuum to get
bright yellow residue. Yield: 0.600 g, 80%; m.p.: 190–194 ◦C; FT-
IR (KBr) ꢀmax/cm−1: 3426, 2949, 1625, 1445, 1265, 1158, 1029,
767, 699, 573; 1H NMR (CDCl3, 500 MHz) ı, ppm: 13.63 (s, 2H),
8.31 (s, 2H), 7.18 (s, br, 12H), 6.92 (s, 2H), 4.69 (s, 2H), 3.43 (s,
4H), 2.58 (s, 4H), 2.54 (s, 4H), 1.50 (s, 2H), 1.38 (s, 18H); 13C NMR
(CDCl3, 125 MHz) ı, ppm: 166.95, 159.12, 139.63, 136.78, 130.37,
130.08, 128.58, 128.31, 128.05, 127.49, 118.19, 80.12, 62.06, 55.11,
53.91, 34.78, 29.44, 27.59; [˛]D24 = −28 (c = 0.8, CHCl3); TOFMAS
(ES+) m/z: 673.54 (M+OH, 55%), 1330.08 (M+OH, 45%); Anal. Calcd.
For C86H104N8O4: C, 78.62; H, 7.98; N, 8.53. Found: C, 78.52; H, 7.81;
N, 8.40.
3. Results and discussion
Solvents play an important role in a chemical transformation.
It determine the interactions between reaction partners; conse-
quently have direct bearing on mode and stability of the transition
states and intermediates, which is reflected in reaction outcome,
i.e. conversion and selectivity [23]. Due to this reason exploring
newer solvent systems for new and even well-known reactions has
become an important area of research. Since, solvents often consti-
tute major volume of reactions; their selection should therefore be
based on parameters, e.g., easy recovery, reuse, safety, and more
importantly acceptability to the environment health. Among the
new generation of solvents ionic liquids and organic carbonates are
vigorously promoted for carrying out various organic transforma-
tions, as most of them fall under the category of “green” solvents.
In the present study our focus was on utilizing these solvents for
2.5. Synthesis of complexes 3 and 4
Ligand 3ꢀ/4ꢀ (0.54 mmol) was dissolved in DCM:MeOH (6 mL,
1:1) in a three necked round bottom flask under nitrogen to which
Mn(CH3COO)2·4H2O (0.140 g, 0.55 mmol) was added and the reac-
tion mixture was stirred for 6 h at 60 ◦C. After bringing the reaction
mixture at RT, LiCl (0.057 g, 1.37 mmol) was added and was fur-
ther stirred for 4 h under aerobic condition. The solvent from the
reaction mixture was removed under reduced pressure and the