R. Kannappan et al. / Journal of Molecular Catalysis A: Chemical 339 (2011) 72–78
73
1155, 1H-NMR (CD CN, ıppm): 8.43 (s, 1H), 7.78 (d, J = 8.1 Hz, 2H),
2
. Experimental
3
7
.73 (d, J = 7.5 Hz, 2H), 7.60–7.54 (m, 4H), 7.51–7.34 (m, 4H), 7.20
2.1. Materials and general methods
(d, J = 7.5 Hz, 2H), 3.60 (s, 3H), 3.45 (m, 1H), 2.93 (m, 1H), 2.44 (s,
3
H), 1.98–1.96 (m, 4H), 1.41–1.13 (m, 4H).
Commercially available reagents were used as received. (Rac)-
-phenylethanol picolinic acid ester (PEP), (S)-1-phenylethanol
(2d) ESI-HRMS (CH OH) found: m/z = 548.1153, calcd for
3
64
+
1
C26H31N O S ZnCl = 548.1117; IR (KBr): 3257, 2859, 1612, 1331,
3 2
1
pyridinephosphonic acid ester [16] (PEPP = TSA), and 8-isopropyl-
-quinolinecarboxaldehyde [17] were prepared according to
1155; H-NMR (CD OD, ıppm): 8.34 (s, 1H), 8.15 (d, J = 8.4 Hz, 1H),
3
2
7.76–7.74 (m, 1H), 7.70–7.65 (m, 2H), 7.57 (d, J = 7.5 Hz, 1H), 7.47
(d, J = 8.1 Hz, 2H), 6.76 (d, J = 7.5 Hz, 2H), 4.35 (septet, J = 6.6 Hz, 1H),
3.40 (m, 1H), 3.20 (m, 1H), 1.88 (s, 3H), 1.74 (d, J = 6.0 Hz, 6H),
2.07–1.33 (m, 8H).
the literature procedures. (1R,2R)-N-(N,N-dimethylsulfamoyl)-1,2-
diaminocyclohexane (1c) was prepared and purified as previously
−
1
[
18]. Infrared spectra (4000–500 cm ) were recorded using KBr
1
13
pellets. H (300 MHz) and C (60 MHz) NMR spectra were obtained
and referenced to TMS as an internal standard. The low- and
high-resolution mass spectra were acquired on samples dissolved
in methanol or dichloromethane solution by the ESI ionization
method.
(2e) ESI-HRMS (CH OH) found: m/z = 626.1293, calcd for
3
C28H31N O S ZnF3+ = 626.1279; IR (KBr): 3277, 2863, 1701, 1450,
6
4
3
4
1
1331, 1194; H-NMR (CD CN, ıppm): 8.43 (d, J = 8.1 Hz, 1H), 8.01 (s,
3
1H), 7.87–7.69 (m, 3H), 7.55 (d, J = 8.4 Hz, 1H), 7.40 (d, J = 8.1 Hz, 2H),
6.93 (d, J = 6.9 Hz, 2H), 5.56 (b, 1H), 4.50 (septet, J = 6.6 Hz, 1H), 3.45
(
m, 1H), 3.0 (m, 1H), 2.26 (s, 3H), 1.97 (d, J = 5.4 Hz, 6H), 2.01–1.74
(m, 4H), 1.74–1.44 (m, 4H).
2f) ESI-HRMS (CH OH) found: m/z = 662.0933, calcd for
2
2
.2. Synthetic procedures
(
3
C27H31N O S ZnF + = 662.0949; IR (KBr): 3227, 2870, 1612,
1330, 1159; H-NMR (CD CN, ıppm): 8.43 (s, 1H), 7.8 (d, J = 8.1 Hz,
64
.2.1. Preparation of
3
5
2
1
3
N-(2-amino-cyclohexyl)-4-methyl-benzenesulfonamide (1a) and
3
N-(2-amino-cyclohexyl)-2,4,6-trimethyl-benzenesulfonamide
1H), 7.86 (m, 1H), 7.82 (m, 1H), 7.75 (m, 1H), 7.74 (d, J = 7.5 Hz,
1H), 7.75 (d, J = 8.7 Hz, 2H), 7.40 (d, J = 8.4 Hz, 2H), 6.70 (br 1H), 4.45
(septet, J = 6.9 Hz, 1H), 3.07 (m, 2H), 2.42 (s, 3H), 1.70–1.40 (m, 4H),
1.39 (d, J = 6.9 Hz, 6H), 1.30–1.20 (m, 4H).
(
1b)
The sulfonamides 1a and 1b were prepared from trans-(R,R)-
,2-diaminocyclohexane directly rather than as its l-tartrate
salt as previously reported [19]. To a stirred solution of (R,R)-
,2-diaminocyclohexane (3.00 g, 11.4 mmol) in aqueous NaOH
1
(2g) ESI-HRMS (CH OH) found: m/z = 506.0682, calcd for
3
64
+
1
C23H25N O S ZnCl = 506.0647; IR (KBr): 3245, 2853, 1643, 1323,
1155; H-NMR (CD CN, ıppm): 8.80 (d, J = 8.7 Hz, 1H), 8.52 (s, 1H),
3 2
1
(
2 N, 15 mL) was added triethylamine (2.1 mL, 15.2 mmol) and
3
◦
dichloromethane (100 mL). The mixture was cooled to 0 C and a
solution of p-toluene- or 2,4,6-trimethylphenyl (mesityl) sulfonyl
chloride (7.6 mmol) in dichloromethane (50 mL) was added drop-
wise over 30 min. After the addition was complete, the mixture
was allowed to warm to rt and stirred for 12 h. The resulting mix-
ture was washed with aqueous HCl (2 N, 3 × 50 mL) and the organic
phase was removed. The aqueous phase was adjusted to pH 9 by
addition of NaOH pellets and the basic aqueous solution was then
extracted with dichloromethane (3 × 30 mL). The dichloromethane
8.28 (d, J = 8.7 Hz, 1H), 8.23 (d, J = 8.1 Hz, 1H), 8.11 (m, 1H), 7.91 (m,
1H), 7.84 (d, J = 8.4 Hz, 1H), 7.59 (d, J = 8.0 Hz, 2H), 6.72 (d, J = 8.4 Hz,
2H), 4.91 (s, 1H), 3.65 (m, 1H), 3.50 (m, 1H), 2.20 (s, 3H), 2.35–1.80
(m, 4H), 1.60–1.28 (m, 4H).
(2h) ESI-HRMS (CH OH) found: m/z = 654.1624, calcd for
3
C30H35N O S ZnF3+ = 654.1592; IR (KBr): 3223, 2859, 1601, 1319,
6
4
3
4
1
1194; H-NMR (CD OD, ıppm): 8.29 (s, 1H), 8.05 (d, J = 8.7 Hz, 1H),
3
7.70 (d, J = 8.4 Hz, 1H), 7.64 (d, J = 6.6 Hz, 1H), 7.54 (m, 1H), 7.48 (d,
J = 8.4 Hz, 1H), 6.30 (s, 2H), 5.17 (s, 1H), 4.36 (septet, J = 6.8 Hz, 1H),
3.32 (m, 1H), 3.12 (m, 1H), 2.60 (s, 3H), 2.42 (s, 6H), 3.20–2.8 (m,
4H), 1.66 (d, J = 6.3 Hz, 6H), 1.80–1.20 (m, 4H).
layers were combined, dried over anhydrous MgSO , filtered, and
4
the solvent was removed under reduced pressure to obtain 1a and
1
b as yellow solids. The NMR spectra for 1a–c agreed with the
(2i) ESI-HRMS (CH OH) found: m/z = 564.1211, calcd for
3
64
+
earlier reports [18,19].
C25H31N O S ZnCl = 564.1178; IR (KBr): 3227, 2942, 1618, 1331,
5
2
1
147; 1H-NMR (CD CN, ıppm): 8.80 (s, 1H), 7.58–7.56 (m, 4H),
3
2
.2.2. Preparation of Zn complexes
The synthesis of 2a is described below and the compounds
b–2i were prepared using the same procedure. Monosulfonamide
7.74–7.25 (m, 6H), 3.76 (s, 3H), 3.45 (m, 1H), 3.25 (m, 1H), 2.80
(s, 3H), 2.67 (s, 3H), 2.30–1.70 (m, 4H), 1.60–1.30 (m, 4H).
2
derivative 1a was dissolved in methanol (0.50 mmol, 50 mL). To
this solution a methanolic solution of 2-pyridinecarboxaldehyde
2.3. Kinetics for methanolysis of 1-phenylethyl picolinate (PEP)
catalyzed by Zn–imine complexes
(
0.50 mmol, 25 mL) was added, followed by the appropriate zinc
salt dissolved in methanol (0.50 mmol, 25 mL). The resulting mix-
ture was refluxed overnight, then the solvent was evaporated and
the residual solid was triturated with small portions of diethyl ether
to obtain the spectroscopically pure product 2a.
The methanolysis of rac-1-phenylethyl picolinate (PEP) was car-
ried out three times consecutively at the same substrate/catalyst
concentration; the listed rate constant (Table 1) is the average
from the three runs. A 100 mM stock solution was prepared by
dissolving 22.7 mg of rac–PEP in 1 mL of CD OD/CD Cl (1:1). A
(
2a) ESI-HRMS (CH OH) found: m/z = 456.0504, calcd for
3
+
C19H23N O SZnCl = 456.0491; IR (KBr): 3241, 2863, 1643, 1331,
159; H-NMR (CD CN, ıppm): 8.69 (d, J = 4.8 Hz, 1H), 8.34 (s, 1H),
3
2
3
2
2
1
1
8
1
2
20 mM solution of the Zn-complex was prepared in 1.0 mL of 1:1
CD OD/CD Cl . A 1.0 mM stock solution of the complex (Cat-1) was
3
.21 (m, 1H), 7.83 (m, 1H), 7.75 (d, J = 7.5 Hz, 1H), 7.63 (d, J = 8.4 Hz,
H), 7.0 (d, J = 8.1 Hz, 2H), 5.35 (s, 1H), 3.20 (m, 1H), 3.30 (m, 1H)
.19 (s, 3H), 1.73–1.97 (m, 4H), 1.32–1.17 (m, 4H).
3
2
2
prepared by diluting 50 L of the 20 mM solution to 1 mL with
CD OD/CD Cl (1:1); A 10 mM stock solution of the complex (Cat-
3
2
2
(
2b) ESI-HRMS (CH OH) found: m/z = 459.0526, calcd for
2) was prepared by diluting 500 L of the 20 mM solution to 1 mL
3
6
4
+
C18H24N O S ZnCl = 459.0600; IR (KBr): 3245, 2863, 1626, 1327,
151; H-NMR (CD CN, ıppm): 8.26 (s, 1H), 7.72 (d, J = 8.1 Hz, 2H),
with CD OD/CD Cl (1:1). Samples for NMR reaction monitoring
4
2
3
2
2
1
1
were prepared by pipetting 100 L of 100 mM substrate stock solu-
3
7
.31 (d, J = 1.2 Hz, 1H), 7.21 (br, 1H), 7.07 (d, J = 8.1 Hz, 2H), 5.45
tion into an NMR tube and diluting it to 1 mL with CD OD/CD Cl
3
2
2
(
1
s, 1H), 3.66 (s, 3H), 3.42 (m, 2H), 2.29 (s, 3H), 1.98–1.96 (m, 4H),
.32–1.17 (m, 4H).
2c) ESI-HRMS (CH OH) found: m/z = 611.1237, calcd for
(1:1); then 100 L of the catalyst solution (Cat-1 or Cat-2) was
added. NMR spectra were recorded at 2-min intervals (T = 292 K)
while monitoring the disappearance of the substrate methyl sig-
nal at 1.95 ppm and the emergence of the product alcohol methyl
(
3
6
4
+
C30H32N O S ZnCl = 611.1226; IR (KBr): 3245, 2863, 1618, 1327,
4
2