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optical rotation of the catalysts was measured in dichloromethane
by using a WZZ-2A Automatic Polarimeter.
Synthesis of catalyst 1-Gn (n=1, 2, 3)
The obtained PAMAM-Gn-imidazole dendrimer (2.5 mmol) was dis-
solved in dry toluene (50 mL) in a Schlenk tube. Asymmetric chiral
salen ligand (CL) (10.1 mmol for G1; 20.1 mmol for G2; 40.1 mmol
for G3) was added to the solution at RT. The mixture was heated
Preparation of catalysts 1-Gn (n=1, 2, 3)
to reflux for 72 h under N . After the removal of the solvent, the
Synthesis of PAMAM-Gn-imidazole (n=1, 2, 3)
2
residue was dissolved in anhydrous methanol. Ti(OiPr) (10.1 mmol
4
Ethylene diamine (5.5 mmol, 0.33 g) was added to a solution of
methyl acrylate (20 mmol, 1.72 g) in methanol (20 mL). The Michael
addition was performed at 408C under an atmosphere of N2 for
for G1; 20.1 mmol for G2; 40.1 mmol for G3) was then added drop-
wise to the above methanolic solution. The mixture was stirred for
3 h at RT and concentrated under vacuum. The resulting yellow
solid was treated with water (100 mL), filtered, and washed with
water and n-hexane. The crude product was dissolved in CH Cl
5
days. After removal of excess reactants and solvent under
vacuum, the obtained amino propionate ester was further treated
2
2
with 1-(3-aminopropyl)imidazole (30 mmol, 3.79 g) at 408C for
and filtered to remove any traces of TiO . The filtrate was concen-
2
7
days under N . Through the amidation, imidazole groups were
2
trated in vacuum and further dried under vacuum overnight at
decorated on the periphery of PAMAM-G1-imidazole. After concen-
tration in vacuum, the residue was washed with n-hexane to
remove the unreacted 1-(3-aminopropyl) imidazole to give
PAMAM-G1-imidazole as a light yellow, viscous liquid. Similar Mi-
chael addition of the methyl acrylate to the corresponding
PAMAM-G1-NH2 core or PAMAM-G2-NH2 core and followed by
complete amidation with 1-(3-aminopropyl)imidazole gave the imi-
dazole-modified PAMAM dendrimers of PAMAM-G2-imidazole or
PAMAM-G3-imidazole, respectively.
4
08C to give 1-Gn (n=1, 2, 3) as yellow powders.
Catalyst 1-G1: HRMS (MALDI-TOF): m/z:
C171H238Cl Ti N O : 3177.62 [M] ; found: 3176.79; Ti content:
calcd
for
+
4
4
22 16
À1
À1
0
3
1
9
4
ꢀ
.89 mmolg (calcd 1.11 mmolg ); FTIR (KBr): g =3391, 3360,
max
134, 3068, 2945, 2881, 1734, 1652, 1626, 1555, 1463, 1440, 1397,
360, 1344, 1305, 1270, 1254, 1205, 1171, 1130, 1095, 1074, 1036,
28, 865, 848, 802, 756, 704, 658, 644, 625, 588, 562, 490, 466,
À1
D
25
À1
12 cm ; [a] =À315 (c=0.005, CH Cl ); the M of 1-G1 was
2
2
n
3610 gmol , which was measured by GPC using conventional
PAMAM-G1-imidazole: HRMS (MALDI-TOF): m/z calcd for
calibration with PS standards.
+
C H N O : 776.49 [M] ; found: 775.63; elemental analysis calcd
38
60 14
4
À1
À1
Catalyst 1-G2: Ti content: 0.87 mmolg (calcd 1.05 mmolg );
FTIR (KBr): gmax =3394, 3271, 3080, 2952, 2864, 1652, 1626, 1555,
(
%) for C H N O (Mol. Wt.: 776.97): C 58.74, H 7.78, N 25.24;
38 60 14 4
found: C 57.31, H 8.12, N 25.76; FTIR (KBr): gmax =3274, 3111, 2951,
1
463, 1439, 1390, 1360, 1344, 1301, 1272, 1254, 1206, 1173, 1092,
2
1
844, 1732, 1662, 1649, 1568, 1555, 1542, 1510, 1451, 1438, 1362,
À1
1028, 920, 866, 847, 802, 773, 758, 704, 663, 647, 625, 585, 555,
280, 1259, 1230, 1111, 1081, 1035, 915, 827, 745, 665, 625 cm
;
À1
D
25
1
492, 412 cm ; [a] =À290 (c=0.005, CH Cl ); the M of 1-G2 was
H NMR (CDCl , 500 MHz) d=2.28 (br t, 4H, NCH CH N, core), 2.73
2
2
n
3
2
2
À1
ꢀ
7590 gmol , which was measured by GPC using conventional
(
br t, 8H, NCH CH C=O, branches), 2.48 (br m, 8H, NCH CH C=O,
2 2 2 2
calibration with PS standards.
branches), 3.17 (br t, 8H, O=CNHCH CH CH N, branches), 2.62 (br
2
2
2
m, 8H, O=CNHCH CH CH N, branches), 3.98 (br t, 8H,
À1
À1
2
2
2
Catalyst 1-G3: Ti content: 0.83 mmolg (calcd 1.03 mmolg );
FTIR (KBr): gmax =3394, 3271, 3081, 2952, 2864, 1652, 1626, 1555,
1
O=CNHCH CH CH N, branches), 6.85 (d, 4H, NCH=NCH=CHN, imi-
2
2
2
dazole), 6.94 (d, 4H, NCH=NCH=CHN, imidazole), 7.41 ppm (s, 4H,
NCH=NCH=CHN, imidazole).
463, 1439, 1391, 1360, 1344, 1302, 1271, 1254, 1206, 1174, 1092,
028, 921, 866, 847, 802, 772, 758,704, 663, 648, 625, 586, 555, 492,
1
4
ꢀ
À1
D
25
65, 413 cm ; [a] =À295 (c=0.005, CH Cl ); the M of 1-G3 was
PAMAM-G2-imidazole: Elemental analysis calcd (%) for
2
2
n
À1
15550 gmol , which was measured by GPC using conventional
C H N O (Mol. Wt.: 1949.23): C 57.88, H 7.86, N 24.42; found: C
94
152 34 12
calibration with PS standards.
5
2
1
8.05, H 8.16, N 24.71; FTIR (KBr): gmax =3270, 3104, 3063, 2935,
833, 1728, 1662, 1553, 1546, 1516, 1452, 1360, 1283, 1232, 1110,
À1
1
082, 1032, 914, 820, 745, 665, 625 cm ; H NMR (CDCl , 500 MHz)
3
d=2.32 (br t, 4H, NCH CH N, core), 2.77 (br t, 24H, NCH CH C=O,
2
2
2
2
branches), 2.33 (br m, 24H, NCH CH C=O, branches), 3.24 (br t, 8H,
Preparation of catalyst 2-G3
2
2
O=CNHCH CH N, branches), 2.61 (br m, 8H, O=CNHCH CH N,
2
2
2
2
CL (40.1 mmol, 21.62 g) was added to a solution of PAMAM-G3-NH2
branches), 3.21 (br t, 16H, O=CNHCH CH CH N, branches), 2.68 (br
2
2
2
(
2.5 mmol, 8.14 g) in dry toluene (50 mL). The resulting mixture
m, 16H, O=CNHCH CH CH N, branches), 4.06 (br t, 16H,
2
2
2
was heated to reflux for 72 h under N . After the removal of sol-
2
O=CNHCH CH CH N, branches), 6.87 (d, 8H, NCH=NCH=CHN, imi-
2
2
2
vent, the residue was treated with Ti(OiPr) (40.1 mmol, 11.40 g) in
4
dazole), 6.98 (d, 8H, NCH=NCH=CHN, imidazole), 7.43 ppm (s, 8H,
NCH=NCH=CHN, imidazole).
anhydrous methanol (50 mL) for 3 h at RT. The solvent was re-
moved under reduced pressure. Water (100 mL) was added, and
the resulting yellow solid was collected by filtration, washed with
water and n-hexane, and further dissolved in CH Cl . The solution
PAMAM-G3-imidazole: Elemental analysis calcd (%) for
C206H336N O (Mol. Wt.: 4294.7): C 57.58, H 7.88, N 24.12%; found:
74
28
2
2
C 56.91, H 8.12, N 24.76; FTIR (KBr): gmax =3270, 3104, 3064, 2949,
of CH Cl was filtered to remove any traces of TiO . Concentration
2 2 2
2
1
828, 1732, 1660, 1556, 1541, 1513, 1455, 1361, 1282, 1231, 1109,
and drying of the filtrate give yellow powders of 2-G3 (in which
the generation number of PAMAM is 3). Elemental analysis calcd
À1
1
081, 1032, 914, 820, 743, 665, 625 cm ; H NMR (CDCl , 500 MHz)
3
d=2.31 (br t, 4H, NCH CH N, core), 2.75 (br t, 56H, NCH CH C=O,
(%) for C766H1216Ti N O (Mol. Wt.: 13924.27): C 66.06, H 8.82, N
2
2
2
2
16 90 92
À1
branches), 2.36 (br m, 56H, NCH CH C=O, branches), 3.25 (br t,
9.05; found: C 66.54, H 9.07, N 9.32; Ti content: 0.87 mmolg
2
2
À1
2
4H, O=CNHCH CH N, branches), 2.63 (br m, 24H,
(calcd 1.23 mmolg ); FTIR (KBr): gmax =3363, 3272, 3072, 2953,
2
2
O=CNHCH CH N, branches), 3.23 (br t, 32H, O=CNHCH CH CH N,
2864, 1650, 1626, 1556, 1464, 1439, 1391, 1361, 1344, 1303, 1271,
1253, 1207, 1174, 1096, 1028, 919, 866, 847, 802, 773, 757,704, 667,
2
2
2
2
2
branches), 2.66 (br m, 32H, O=CNHCH CH CH N, branches), 4.01
2
2
2
À1
D
(
br t, 32H, O=CNHCH CH CH N, branches), 6.83 (d, 16H, NCH=
645, 625, 584, 555, 492, 471, 412 cm ; [a] =À280 (c=0.005,
2
2
2
25
À1
NCH=CHN, imidazole), 6.72 (d, 16H, NCH=NCH=CHN, imidazole),
.4 ppm (s, 16H, NCH=NCH=CHN, imidazole).
CH Cl ); the M of 2-G3 was ꢀ13950 gmol , which was measured
2
2
n
7
by GPC using conventional calibration with PS standards.
ChemCatChem 2015, 7, 4066 – 4075
4073
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim