10.1002/cctc.201801164
ChemCatChem
FULL PAPER
7.43 (s, 8 H), 6.95-7.03 (m, 40 H), 6.46 (s, 16 H), 4.55 (bs, 16 H), 4.13
(bs, 16 H), 3.86 (bs, 16 H), 3.54 (bs, 16 H), 3.24 (bs, 16 H), 1.79-1.88 (m,
48H), 1.53-1.69 (m, 48 H), 1.36-1.38 (m, 144 H), 1.20 (s, 72 H). 13C{1H}
NMR (100 MHz, CDCl3): δ=166.0, 165.3, 160.7, 158.0, 154.9, 149.0,
147.6, 140.1, 137.9, 136.9, 136.5, 134.9, 128.4, 127.8, 127.6, 127.1,
127.0, 126.1, 120.7, 119.0, 118.8, 117.9, 115.2, 72.9, 72.6, 71.9, 69.9,
50.1, 35.1, 35.0, 34.1, 33.2, 33.1, 31.5, 30.3, 29.5, 29.4, 27.3, 27.2, 24.3.
MALDI (DCTB matrix): calcd (m/z) for C416H520N40O32Cs [M+Cs]+ 6723.9.
Found 6724. Elemental analysis. Calcd for C416H520N40O32.2 CH2Cl2. C,
74.24; H, 7.81; N, 8.28; O, 7.57. Found: C, 74.46; H, 7.95; N, 8.34; O,
7.95. IR (KBr, cm-1) 3135, 2950, 2862, 2094, 1628, 1599, 1462, 1439,
1389, 1361, 1306, 1272, 1202, 1172, 1045, 1027, 980, 876, 860, 827,
802, 772, 731, 696. UV-Vis (DMF) max 334 nm, ε 10430 L.mol-1.cm-1.
[]20 + 105.34 (c 0.002 CHCl3).
recorded with this multisite catalyst than with its homogeneous
monomer analogue in all the cases studied. The location of the
various cobalt sites, connected to the conformationally floppy
support by a flexible link, is clearly favorable for their optimal
arrangement to achieve a bimetallic cooperativity. Furthermore,
and due to its insolubility in the reaction conditions, the catalyst
was easily recovered by simple filtration and successfully
recycled in subsequent catalytic runs, proving the stability of the
cobalt sites in these conditions. We also demonstrated that the
targeted enantioenriched products were recovered almost rid of
any cobalt traces, without requiring a prior purification by flash
column chromatography. This characteristic, which is due to the
particular structure of our support, is of major importance for the
development of new catalytic processes dedicated to the
preparation of enantioenriched synthons towards biological
applications. The functionalization of these calix[8]arene by
ligands of various structures can also be envisioned by
generalizing our simple Click reaction approach. It should make
it possible to easily perform a large range of asymmetric
catalysis reactions with these insoluble catalysts, notably those
for which the notion of cooperativity is essential.
Complex Cat-1. In a Schlenk flask equipped with a magnetic stirring
bar and flushed with argon, compound 4 (0.5 g, 0.075 mmol) was
dissolved in dry CH2Cl2 (10 mL). Solution of Co(OAc)2.3H2O (0.187 g,
0.75 mmol) in dry methanol (6 mL) was added to the resulting CH2Cl2
solution under argon. The reaction mixture was stirred at r.t. for 4 hours.
The mixture was cooled at 0°C, p-toluenesolfonic acid monohydrate
(0.143 g, 0.75 mmol) in CH2Cl2 (5 mL) was added under air; the mixture
was further stirred under 1 atm of oxygen for 16 hours. The mixture was
then evaporated under reduced pressure and the solid was washed with
methanol, affording a green solid after drying under vacuum (0.534 g,
84 %). 1H NMR (400 MHz, DMSO-d6): δ=8.37 (s, 8 H), 8.03 (s, 8 H), 7.91
(s, 8 H), 7.81-7.83 (m, 16 H), 7.46-7.48 (m, 32 H), 7.03-7.08 (m, 56 H),
6.54 (bs, 16 H), 4.64 (bs, 16 H), 4.32 (bs, 16 H), 3.92 (bs, 8 H), 3.61 (s,
24 H), 3.05 (s, 16H), 2.25 (s, 24 H), 1.56-1.96 (m, 24 H), 1.30 (s, 72 H).
13C{1H} NMR (100 MHz, DMSO-d6): δ=164.8, 164.3, 164.2, 161.9, 154.1,
148.5, 146.7, 142.9, 141.8, 137.5, 136.8, 136.2, 134.8, 130.4, 129.3,
129.0, 128.6, 128.0, 127.4, 125.5, 119.6, 119.3, 118.5, 117.3, 114.5,
72.6, 69.4, 69.0, 49.3, 35.8, 35.7, 33.6, 31.5, 30.5, 30.2, 29.6, 29.4, 26.8,
24.3, 20.8. Elemental analysis. Calcd for C472H560N40O56S8Co8.5 CH2Cl2.
C, 64.79; H, 6.50; N, 6.34; S, 2.90. Found: C, 64.34; H, 6.57; N, 6.67; S,
2.40. IR (KBr, cm-1) 2946, 2864, 2094, 1623, 1529, 1467, 1435, 1385,
1320, 1254, 1201, 1168, 1121, 1033, 1010, 813, 782, 743, 681, 567. UV-
Vis (DMF) max 400 nm, ε 7263 L.mol-1.cm-1. []20 + 1020.4 (c 8.10-6
DMF). XPS quantification calcd for. C472N40O56S8Co8. C, 80.8; N, 6.8; O,
9.6; S, 1.4; Co, 1.4. Found: C, 81.3; N, 5.7; O, 10.7; S, 1.3; Co, 1.
Experimental Section
General. Complete synthetic procedures, description of catalytic tests,
characterization details and copy of NMR, IR, UV and XPS spectra and
GC chromatograms are given in the supporting information. All reactions
were carried out under argon atmosphere and all glassware was flamed
before use. Dichloromethane (CH2Cl2) was distilled over CaH2 and
Methanol (MeOH) was distilled over magnesium. Extra dry
Dimethyformamide (DMF) and Toluene were purchased from ACROS
and Alfa Aesar. Sodium hydride (NaH) was purchased from Aldrich. All
commercially available reagents were used as received. 5-Ethynyl-2-
hydroxybenzaldehyde and (1S, 2S)-diaminocyclohexane mono-
(hydrogen chloride) were prepared by previously reported procedures. 1H
NMR and 13C NMR spectra were recorded on either a Bruker DPX 250,
Brucker 300 MHz, Bruker Avance 360 MHz, Bruker 400 (400 MHz) or
Bruker DRX 400 (400 MHz) instrument and data are reported in ppm with
the solvent signal as reference. The HRMS analyses were performed
Compound 9. In a Schlenk flask equipped with a magnetic stirring
bar and flushed with argon, (1S, 2S)-diaminocyclohexane mono-
with
a MicroTOFq (quadrupole coupled with TOF analyzer). Gas
(hydrogen chloride)
C (0.081 g, 0.54 mmol), 3,5-di-tert-butyl-2-
chromatography (GC) analyses were performed on a Varian 430-GC gas
chromatograph. Elemental analyses and MALDI were performed by the
microanalysis service and Mass Spectrometry group of the Institut de
Chimie des Substances Naturelles in Gif-Sur-Yvette (France). ICP-MS
analyses were performed by IRAMIS (CEA-Saclay).
hydroxybenzaldehyde (0.126 g, 0.54 mmol) and 4 Å molecular sieves
(1g) were introduced and dry and degassed methanol (5 mL) was added
under argon. The reaction mixture was stirred at r.t. under argon for 4
hours. Dry Et3N (0.205 mL, 1.47 mmol) was added under argon, and
compound 8, dissolved in CH2Cl2 (6 mL), was then added to the
methanol mixture. The reaction was stirred overnight at r.t. under argon.
The mixture was filtered on Celite, the filtrate was evaporated under
reduced pressure. The solid residue was purified by silica gel column
chromatography with pentane/AcOEt (7/3) as eluent, to afford a yellow
solid (0.241 g, 61 %). 1H NMR (400 MHz, CDCl3): δ=14.09 (s, 1 H), 13.62
(s, 1 H), 8.32 (s, 1 H), 8.29 (s, 1 H), 7.72 (d, J = 1.6Hz, 1 H), 7.59 (s, 1 H),
7.28-7.43 (m, 7 H), 6.96 (d, J = 6.9 Hz, 1 H), 6.89 (d, J = 9.0 Hz, 2 H),
6.80 (d, J = 9.0 Hz, 2 H), 5.00 (s, 2 H), 4.45 (t, J = 6.9 Hz, 2 H), 3.94 (t, J
= 5.8 Hz, 2 H), 3.29-3.38 (m, 2 H), 2.14 (quint, J = 7.2 Hz, 2 H), 1.74-2.04
(m, 10H), 1.45 (s, 9 H), 1.39 (m, 9 H), 1.21 (s, 9 H). 13C{1H} NMR (100
MHz, CDCl3): δ=166.1, 165.4, 160.8, 158.1, 153.2, 148.0, 140.1, 137.9,
137.4, 136.5, 128.7, 128.0, 127.6, 127.2, 127.1, 126.9, 126.1, 120.6,
118.8, 118.5, 116.0, 115.5, 72.5, 72.4, 70.8, 67.6, 50.1, 35.1, 35.0, 34.1,
33.2, 33.1, 31.5, 30.3, 29.6, 29.5, 27.4, 26.4, 24.4. HRMS (ESI, positive
mode): calcd (m/z) for C51H65N5NaO4 [M+Na]+ 834.4929. Found
834.4905. Elemental analysis. Calcd for C51H65N5O4. C, 75.43; H, 8.07;
N, 8.62; O, 7.88. Found: C, 75.00; H, 8.28; N, 8.19; O, 7.70. IR (KBr, cm-
Compound 4. In a Schlenk flask equipped with a magnetic stirring
bar and flushed with argon, (1S, 2S)-diaminocyclohexane mono-
(hydrogen chloride) (0.336 g, 2.43 mmol), 3,5-di-tert-butyl-2-
hydroxybenzaldehyde (0.569 g, 2.43 mmol) and 4 Å molecular sieves
(1g) were introduced and dry and degassed methanol (20 mL) was
added under argon. The reaction mixture was stirred at r.t. under argon
for 4 hours. Dry Et3N (0.965 mL, 7.02 mmol) was added under argon,
and the compound 3 was dissolved in CH2Cl2 (30 mL) and added to the
methanol mixture. The reaction was stirred over night at r.t. under argon.
The mixture was filtered on Celite, the filtrate was evaporated under
reduced pressure. The solid residue was washed with methanol (30 mL)
and ethanol (30 mL). The yellow solid was dissolved in Et2O, precipitated
with ethanol and filtered, affording a yellow solid after drying under
vacuum (1.4 g, 79 %). 1H NMR (400 MHz, CDCl3): δ=14.12 (s, 8 H),
13.58 (s, 8 H), 8.28 (s, 8 H), 8.19 (s, 8 H), 7.68 (s, 8 H), 7.61 (s, 8 H),
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