Polyethylene glycolꢀsupported BINOL phosphate
Russ.Chem.Bull., Int.Ed., Vol. 60, No. 11, November, 2011 2373
7.97 (s, 1 H). 13C NMR (CDCl3), δ: 77.50, 84.00, 110.18, 111.25,
117.78, 118.28, 118.93, 123.99, 124.19, 126.11, 127.66, 128.49,
129.47, 130.36, 130.44, 130.58, 130.69, 131.70, 132.01, 133.27,
152.72, 153.00. Found (%): C, 85.37; H, 4.58. C22H14O2. Calcuꢀ
lated (%): C, 85.14; H, 4.55.
It is known that (R)ꢀBINOLꢀderived phosphoric diester
provide high enantioselectivity if they are 3,3´ꢀdisubstiꢀ
tuted, for example, 3,5ꢀbis(trifluoromethyl)phenyl derivꢀ
ative.11,12 As a continuation of the present studies, we are
planning this type of immobilization for such Brønsted
acids. However, their synthesis is complicated by the neꢀ
cessity not only to introduce substituents at orthoꢀposition
to the acid catalytic center, but also to carry out brominaꢀ
tion at position 6 for their further addition to a polymeric
support.
( )ꢀ6ꢀAzidoꢀ1,1´ꢀbinaphthaleneꢀ2,2´ꢀdiol (3b). A mixture of
6ꢀbromoꢀ1,1´ꢀbinaphthaleneꢀ2,2´ꢀdiol (2) (1 mmol), NaN3
(2 mmol), CuI (0.1 mmol), N,N´ꢀdimethylethylenediamine
(0.15 mmol), and EtOH—H2O (7 : 3) (2 mL) was subjected to
the microwave irradiation (110 °C, 400 W) in a 2ꢀmL sealed
reactor with stirring over 2 h until compound 2 was completely
consumed (HPLC monitoring). After cooling to room temperaꢀ
ture, the product was extracted with AcOEt and washed with
brine. The organic phase was dried with Na2SO4, the solvent
was evaporated in vacuo. The product was purified by column
chromatography, using cyclohexane—AcOEt (9 : 1) as an eluꢀ
ent. Product 3b was obtained as amorphous light yellow comꢀ
pound in 89% yield, Rf = 0.28 (cyclohexane—AcOEt, 10 : 1).
1H NMR (CDCl3), δ: 4.91 (s, 2 H); 6.92 (d, 1 H, J = 8.8 Hz);
7.10 (m, 2 H); 7.33 (m, 4 H); 7.46 (d, 1 H, J = 2.2 Hz); 7.85
(t, 2 H, J = 8.9 Hz); 7.91 (d, 1 H, J = 8.2 Hz). 13C NMR
(CDCl3), δ: 110.18, 111.25, 117.78, 118.93, 123.99, 124.19,
126.11, 127.66, 128.49, 129.47, 130.36, 130.44, 130.58, 130.69,
131.70, 132.01, 133.27, 137.37, 152.72, 153.00. IR (CHCl3),
ν/cm–1: 2110 (N3). Found (%): C, 73.15; H, 4.18; N, 13.01.
C20H13N3O2. Calculated (%): C, 73.38; H, 4.00; N, 12.84.
4ꢀ(2,2´ꢀDihydroxyꢀ1,1´ꢀbinaphthalenꢀ6ꢀyl)ꢀ1Hꢀ1,2,3ꢀtriꢀ
azole attached to PEG5000 monomethyl ether at position 1 (5a).
A mixture of 6ꢀethynylꢀ1,1´ꢀbinaphthaleneꢀ2,2´ꢀdiol (3a)
(1 mmol), CuI (0.05 mmol), triethylamine (0.1 mL), and azidoꢀ
PEG5000 4a (1 mmol) in CH2Cl2 (5 mL) was subjected to the
microwave irradiation (90 °C, 400 W) in a 10ꢀmL sealed reactor
with stirring over 1.5 h until compound 3a was completely conꢀ
sumed (HPLC monitoring). After cooling to room temperature,
the reaction mixture was treated with Et2O, a polymer 5a that
formed was separated by filtration, washed with Et2O, and dried
in vacuo. The yield was 95%. 1H NMR (CDCl3), δ: 4.59 (s, 2 H,
CH2N); 7.12—7.95 (m, 11 H, Ar); 8.13 (s, 1 H, H(5)).
Experimental
31
1
P, H, and 13C NMR spectra were recorded on a Bruker
Avanceꢀ400 spectrometer (161.98 (31P), 400.13 (1H), and 100.61
(13C) MHz) in CDCl3 and DMSOꢀd6 using signals of the solꢀ
vents as references: CHCl3 (δH 7.24, δC 76.90), DMSO (δH 2.50,
δ
39.50). IR spectra were recorded on a URꢀ20 spectrometer
C
(690—3600 cm–1). Elemental analysis was performed on a Carlo
Erba CHNꢀanalyzer (the 1106 model, Italy). Experiments using
microwave irradiation were carried out in a Biotage Initiator 60
EXP microwave oven. Reaction progress was monitored by TLC
on Silufol UVꢀ254 plates and by HPLC on a Waters Millenium
717 chromatograph with a multiwave detector on a diode matrix
using Chromolith RP18 columns (50—4.6 mm). Samples of
catalysts 6a and 6b were studied by scanning electron microꢀ
scopy on a JEOL JSM 6490 LV instrument. Preparative column
chromatography was performed using Merck 60 silica gel
(0.040—0.063 mm). Polyethylene glycol monomethyl ether with
the mass 5000 Da (Fluka) was modified to 4a and 4b according
to the known procedures.24,25 The 1H NMR spectrum (CDCl3)
of PEG5000 has persistent signals in the region δ 3.37 (MeO) and
3.43—3.83 (CH2CH2). All the reactions were carried out in anꢀ
hydrous solvents under dry nitrogen.
( )ꢀ6ꢀBromoꢀ1,1´ꢀbinaphthaleneꢀ2,2´ꢀdiol (2) was obtained
according to the known procedure15,16 and its physicochemical
constants agreed with the literature data.
1ꢀ(2,2´ꢀDihydroxyꢀ1,1´ꢀbinaphthalenꢀ6ꢀyl)ꢀ1Hꢀ1,2,3ꢀtriazꢀ
ole attached to PEG5000 monomethyl ether at position 4 (5b) was
( )ꢀ6ꢀEthynylꢀ1,1´ꢀbinaphthaleneꢀ2,2´ꢀdiol (3a). A mixture
of 6ꢀbromoꢀ1,1´ꢀbinaphthaleneꢀ2,2´ꢀdiol (2) (1 mmol), triꢀ
methylsilylacetylene (1.5 mmol), CuI (0.02 mmol), Pd(PPh3)2Cl2
(0.04 mmol) and triethylamine (3 mL) was subjected to the microꢀ
wave irradiation (110 °C, 400 W) in a 5ꢀmL sealed reactor with
stirring over 2 h until compound 2 was completely consumed
(HPLC monitoring). After cooling to room temperature, the
reaction mixture was filtered through celite, the product was
extracted with AcOEt and washed with brine. The organic phase
was dried with Na2SO4, the solvent was evaporated in vacuo.
The residue was dissolved in methanol (1 mL), followed by addiꢀ
tion of 1.5 M aqueous KOH (3 mL), and the mixture was stirred
at room temperature for 4 h. Then, methanol was evaporated,
1 M aq. HCl was added to the residue to pH 4—5. The product
was extracted with AcOEt, the organic phase was washed with
brine, dried with Na2SO4, the solvent was evaporated in vacuo.
The product was purified by column chromatography, using
cyclohexane—AcOEt (9 : 1) as an eluent. Product 3a was obꢀ
tained as white amorphous compound in 85% yield, Rf = 0.26
(cyclohexane—AcOEt, 10 : 1). 1H NMR (CDCl3), δ: 3.09 (s, 1 H);
5.22 (s, 2 H); 7.06 (m, 3 H); 7.23 (d, 1 H, J = 6.6 Hz); 7.25
(d, 1 H, J = 6.6 Hz); 7.80 (t, 3 H, J = 6.6 Hz); 7.85 (d, 2 H, J = 9 Hz);
1
obtained similarly. The yield was 95%. H NMR (CDCl3), δ:
3.83 (s, 2 H); 4.77 (s, 2 H, CH2N); 7.08—7.99 (m, 11 H, Ar);
8.22 (s, 1 H, H(5)).
4ꢀ(4ꢀHydroxyꢀ4ꢀoxodinaphtho[1,2ꢀf:2´,1´ꢀd][1,3,2]dioxaꢀ
phosphepinꢀ9ꢀyl)ꢀ1Hꢀ1,2,3ꢀtriazole attached to PEG5000 monoꢀ
methyl ether at position 1 (6a). Phosphorus oxychloride
(1.5 mmol) was added to a solution of compound 5a (1 mmol)
and triethylamine (0.3 mL) in CH2Cl2 (5 mL) with stirring. The
reaction mixture was refluxed for 1 h, followed by addition of
water (0.1 mL) and stirring at 20 °C for 12 h. Then, the mixture
was treated with Et2O. A polymer 6a that formed was filtered off,
washed with Et2O, and dried in vacuo. The yield was 95%.
1H NMR (CDCl3), δ: 4.59 (s, 2 H, CH2N); 7.12—7.95 (m, 11 H,
Ar); 8.13 (s, 1 H, H(5)). 31P NMR (DMSOꢀd6), δ: 3.5.
1ꢀ(4ꢀHydroxyꢀ4ꢀoxodinaphtho[1,2ꢀf:2´,1´ꢀd][1,3,2]dioxaꢀ
phosphepinꢀ9ꢀyl)ꢀ1Hꢀ1,2,3ꢀtriazole attached to PEG5000 monoꢀ
methyl ether at position 4 (6b) was obtained similarly. The yield
1
was 97%. H NMR (CDCl3), δ: 4.91 (s, 2 H); 6.92 (d, 1 H,
J = 8.8 Hz); 7.10 (m, 2 H); 7.33 (m, 4 H); 7.46 (d, 1 H, J = 2.2 Hz);
7.85 (t, 2 H, J = 8.9 Hz); 7.91 (d, 1 H, J = 8.2 Hz); 8.22 (s, 1 H,
H(5)). 31P NMR (DMSOꢀd6), δ: 3.7.