Switchable Columnar Metallomesogens
J. Am. Chem. Soc., Vol. 120, No. 12, 1998 2917
16.94 (0.073 mol) of silver(I) oxide. The mixture was refluxed for 24
h in the dark. The mixture was filtered through Celite, which was
washed with diethyl ether, and the solvent was removed under vacuum.
To the resulting mixture, which contained the ester (ca. 4 g as estimated
from 1H NMR spectroscopy) and byproducts such as starting material,
iododalkane, alkanol, and alkyl ether, was added 150 mL of methanol,
70 mL of water, and 6 g of LiOH, and the mixture was stirred overnight
at room temperature. After this time, 150 mL of 3.5% NaOH was
added. The organic products were extracted with diethyl ether. The
aqueous phase, which contains the salt of the chiral acid, was acidified
by the addition of HCl. The acid was extracted with diethyl ether and
dried over MgSO4, and the solvent evaporated. The colorless product
was purified by flash chromatography using a hexane/ethyl acetate [9:1]
mixture as eluent.
Preparation of 1-(3,4-dibenzyloxyphenyl)-3-(3,4,5-tribenzylox-
yphenyl)-1,3-propanedione (pBdK). To a solution of 4.5 g (0.01 mol)
of methyl 3,4,5-tribenzyloxybenzoate and 3.3 g (0.01 mol) of 3,4-
dibenzyloxyacetophenone in dry dimethoxyethane, under an inert
atmosphere, was added 0.476 g (0.02 mol) of sodium hydride. The
reaction mixture was refluxed for 14 h, and then cooled, poured into
water. The solution was acidified with dilute HCl and the precipitate
obtained was collected by filtration. The solid was dissolved in
dichloromethane and filtered to eliminate solid impurities. The solvent
was removed under vacuum, the solid was stirred in hot ethanol to
remove any starting materials, and the yellow pure product was filtered
off. Yield: 72%. mp: 128 °C. 1H NMR (300 MHz, CDCl3): δ 5.13
(s, 2H), 5.15 (s, 4H), 5.22 (s, 2H), 5.24 (s, 2H), 6.49 (s, 1H), 6.97 (d,
J ) 8.5 Hz, 1H), 7.20-7.50 (m, 28H), 7.59 (d, J ) 2.0 Hz, 1H), 16.95
(s, 1H). 13C NMR (300 MHz, CDCl3): δ 70.9, 71.5, 71.5, 75.2, 92.3,
107.1, 113.4, 113.5, 121.7, 127.2, 127.5, 127.6, 128.0, 128.1, 128.2,
128.6, 128.6, 130.9, 136.5, 136.7, 136.8, 137.4, 142.2, 148.7 152.8,
184.1, 185.0. IR (Nujol): 1664, 1594, 1454, 1273 cm-1. Anal. Calcd.
for C50H42O7: C, 79.56; H, 5.61. Found: C, 79.31; H, 5.57.
Preparation of 1-(3,4-Dihydroxyphenyl)-3-(3,4,5-trihydroxyphe-
nyl)-1,3-propanedione (pHdK). A suspension of 3.5 g (4.6 mmol)
of the protected â-diketone and 1.75 g of 10% palladium hydroxide
on carbon in 35 mL of cyclohexene and 90 mL of absolute ethanol
was refluxed for 2 h. The mixture was cooled and filtered through
Celite to remove the catalyst. The ethanol was removed, and
dichloromethane and hexane were added. A brown precipitate formed
and was collected by filtration. Yield 91%. 1H NMR (300 MHz,
DMSO-d6): δ 6.78 (s, 1H), 6.83 (d, J ) 8.1 Hz, 1H), 7.05 (s, 2H),
7.44-7.49 (m, 2H), 9.11 (s, 1H), 9.26 (s, 2H), 9.35 (s, 1H), 9.89 (s,
1H), 17.40 (s, 1H). 13C NMR (300 MHz, DMSO-d6): δ 90.9, 106.7,
114.3, 115.6, 120.2, 125.1, 126.3, 138.5, 145.5, 145.7, 146.0, 150.4,
184.3. IR (Nujol): 1653, 1592, 1522, 1458, 1294 cm-1. Anal. Calcd.
for C15H12O7: C, 59.22; H, 3.98. Found: C, 59.13; H, 3.88.
(2S)-2-Hexyloxypropanoic Acid (“6”). Yield: 42%. [R]D25: -22°.
1H NMR (300 MHz, CDCl3): δ 0.86 (t, 3H), 1.20-1.40 (m, 6H), 1.42
(d, J ) 6.9 Hz, 3H), 1.50-1.60 (m, 2H), 3.42 (dt, J ) 9.0, 6.6 Hz,
1H), 3.55 (dt, J ) 9.0, 6.6 Hz, 1H), 3.96 (c, J ) 6.9 Hz, 1H), 10.00 (s,
1H). 13C NMR (300 MHz, CDCl3): δ 14.0, 18.2, 22.5, 25.6, 29.6,
31.6, 70.6, 74.5, 178.2. IR (neat): 3700-2500, 1719, 1458, 1127 cm-1
.
MS (FAB+) m/z (%): 175 [M + H]+.
25
(2S)-2-Heptyloxypropanoic Acid (“7”). Yield: 55%. [R]D
:
-20°. 1H NMR (300 MHz, CDCl3): δ 0.86 (t, J ) 6.5 Hz, 3H), 1.20-
1.35 (m, 8H), 1.43 (d, J ) 6.9 Hz, 3H), 1.59 (t, J ) 6.9 Hz, 2H), 3.42
(dt, J ) 9.0, 6.7 Hz, 1H), 3.55 (dt, J ) 9.0, 6.7 Hz, 1H), 3.97 (c, J )
6.9 Hz, 1H), 7.5 (s, 1H). 13C NMR (300 MHz, CDCl3): δ 14.0, 18.1,
22.6, 25.9, 29.0, 29.6, 31.7, 70.6, 74.5, 177.3. IR (neat): 3700-2500,
1723, 1458, 1241, 1127 cm-1. MS (FAB+) m/z (%): 189 [M + H]+.
Preparation of Methyl 3,4,5-Tribenzyloxybenzoate (MtBB). A
mixture of 4 g (0.022 mol) of methyl 3,4,5-trihydroxybenzoate, 9 g
(0.065 mol) of anhydrous potassium carbonate, and 11.1 g (0.065 mol)
of benzyl bromide in 200 mL of dry acetone was refluxed for 6 h. The
mixture was poured into water, the white precipitate was extracted with
diethyl ether and dried over MgSO4, and the solvent removed under
vacuum. The product obtained was recrystallized from hexane. The
ester was obtained as a white solid in a 76% yield. mp: 98 °C. 1H
NMR (300 MHz, CDCl3): δ 3.87 (s, 3H), 5.10 (s, 2H), 5.12 (s, 4H),
7.20-7.50 (m, 17H). 13C NMR (300 MHz, CDCl3): δ 52.2, 71.2,
75.1, 109.0, 125.2, 127.6, 128.0 128.0, 128.2, 128.6 136.7, 137.5, 142.4,
General Procedure for the Preparation of the Ligands dK“6”
and dK“7”. To a solution of 0.5 g (1.64 mmol) of the pentahydroxy
â-diketone in dry dichloromethane was added 8.62 mmol of the chiral
acid with stirring under an inert atmosphere. A solution of 1.8 g (9.02
mmol) of dicyclohexylcarbodiimide in dichloromethane was added by
syringe. Finally, 180 mg (1.48 mmol) of (dimethylamino)pyridine in
dichloromethane was added. The mixture was stirred at room tem-
perature for 2 days. The precipitated dicyclohexylurea was filtered
off. The solvent was removed, and the product purified by flash
chromatography using hexane/ethyl acetate [9:1] as eluent to give the
pure product as a red liquid.
152.6, 166.6. IR (Nujol): 1716, 1587, 1427, 1336, 1215, 1111 cm-1
.
Anal. Calcd for C29H26O5: C, 76.63; H, 5.77. Found: C, 76.22; H,
5.34.
Preparation of 3,4-Dihydroxyacetophenone (dHA). A suspension
of 5 g (0.045 mol) of catechol in CH2Cl2 was slowly added to a stirred
suspension of 18.2 g (0.136 mol) of aluminum trichloride in dry CH2-
Cl2 under an inert atmosphere. Acetyl chloride (3.3 mL, 0.046 mol)
was then added by syringe. After stirring at room temperature
overnight, the mixture was poured into dilute HCl, extracted with diethyl
ether, and dried over MgSO4. The product obtained after removing
the solvent was purified by flash chromatography using hexane/ethyl
acetate [3:1] as eluent and recrystallized from hexane. Yield: 51%.
1H NMR (300 MHz, DMSO-d6): δ 2.49 (s, 3H), 6.85 (d, J ) 8.6 Hz,
1H), 7.38-7.42 (m, 2H), 9.38 (s, 1H), 9.88 (s, 1H). 13C NMR (300
MHz, DMSO-d6): δ 26.3, 115.0, 115.1, 121.8, 129.1, 145.2, 150.7,
1-{3,4-Bis[(2S)-2-hexyloxypropanoyloxy]phenyl}-3-{3,4,5-tris-
[(2S)-2-hexyloxypropanoyloxy]phenyl}-1,3-propanedione (dK“6”).
Yield: 36%. [R]D25: -65°. 1H NMR (300 MHz, CDCl3): δ 0.86 (t,
J ) 6.9 Hz, 15H), 1.20-1.40 (m, 30H), 1.50-1.70 (m, 25H), 3.40-
3.50 (m, 5H), 3.60-3.70 (m, 5H), 4.10-4.20 (m, 5H), 6.68 (s, 1H),
7.38 (d, J ) 8.7 Hz, 1H), 7.76 (s, 2H), 7.82 (d, J ) 2.1 Hz, 1H), 7.86
(dd, J ) 8.4, 2.1 Hz, 1H), 16.63 (s, 1H). 13C NMR (300 MHz,
CDCl3): δ 14.0, 18.7, 22.6, 25.7, 29.7, 31.6, 71.0, 74.7, 93.3, 119.5,
122.6, 123.7, 125.7, 133.7, 143.5, 168.9, 170.3, 170.6, 183.2, 184.0,
202.5, 206.1. IR (neat): 1783, 1608, 1576, 1467, 1260, 1116 cm-1
.
MS (FAB+) m/z (%): 1086 [M + H]+.
196.3. IR (Nujol): 3450-3000, 1663, 1591, 1524, 1456, 1375 cm-1
.
Anal. Calcd. for C8H8O3: C, 63.15; H, 5.30. Found: C, 62.98; H,
5.05.
1-{3,4-Bis[(2S)-2-heptyloxypropanoyloxy]phenyl}-3-{3,4,5-tris-
[(2S)-2-heptyloxypropanoyloxy]phenyl}-1,3-propanedione (dK“7”).
Yield: 22%. [R]D25: -64°. 1H NMR (300 MHz, CDCl3): δ 0.85 (t,
J ) 6.6 Hz, 15H), 1.20-1.35 (m, 40H), 1.54 (d, J ) 6.7 Hz, 15H),
1.50-1.65 (m, 10H), 3.35-3.50 (m, 5H), 3.60-3.75 (m, 5H), 4.05-
4.20 (m, 5H), 7.38 (d, J ) 8.4 Hz, 1H), 7.75 (s, 2H), 7.82 (d, J ) 2.0
Hz, 1H), 7.87 (dd, J ) 8.6, 2.1 Hz, 1H), 16.63 (s, 1H). 13C NMR
(300 MHz, CDCl3): δ 14.0, 18.7, 22.6, 26.0, 29.1, 29.8, 31.8, 70.9,
74.7, 93.3, 119.5, 122.6, 123.7, 125.7, 133.6, 137.5, 142.1, 143.5, 145.4,
168.9, 170.3, 170.6, 183.2, 184.0. IR (neat): 1782, 1608, 1576, 1466,
1260, 1116 cm-1. MS (FAB+) m/z (%): 1156 [M + H]+.
Preparation of Bis{1-[3,4-bis((2S)-2-hexyloxypropanoyloxy)-
phenyl]-3-[3,4,5-tris((2S)-2-hexyloxypropanoyloxy)phenyl]-1,3-
propanedionato}oxovanadium(IV) (dK“6”VO). To a solution of
206.15 mg (0.19 mmol) of the chiral â-diketone dK“6” in 8 mL of
ethanol was added 19.2 mg (0.19 mmol) of triethylamine in ethanol.
Preparation of 3,4-Dibenzyloxyacetophenone (dBA). To a solu-
tion of 2 g (0.013 mol) of 3,4-dihydroxyacetophenone and 4.5 g (0.026
mol) of benzyl bromide in dry acetone was added 3.63 g (0.026 mol)
of anhydrous K2CO3. After refluxing for 20 h the reaction mixture
was allowed to cool, and the salts were filtered off. The solvent was
removed under vacuum, and a solid was obtained which was purified
by two recrystallizations from ethanol and hexane, respectively.
Yield: 78%. mp: 84 °C. 1H NMR (300 MHz, CDCl3): δ 2.49 (s,
3H), 5.19 (s, 2H), 5.22 (s, 2H), 6.91 (d, J ) 8.2 Hz, 1H), 7.3-7.5 (m,
10H), 7.50 (dd, J ) 8.4, 1.6 Hz, 1H), 7.58 (d, J ) 1.6 Hz, 1H). 13C
NMR (300 MHz, CDCl3): δ 26.2, 70.8, 71.1, 112.9, 113.7, 123.5,
127.1, 127.4, 128.0, 128.0, 128.5, 128.6, 130.8, 136.5, 136.8, 148.6,
153.2, 196.7. IR (Nujol): 1668, 1588, 1514, 1425, 1146 cm-1. Anal.
Calcd. for C22H20O3: C, 79.50; H, 6.06. Found: C, 79.37; H, 6.87.