Luscombe et al.
[M+, 3%], 889 (34), 888 (100), 887 (9), 886 (24). Anal. Calcd for
C27H22F20O3; C, 36.5; H, 2.5. Found: C, 36.9; H, 2.4.
in conventional organic solvents. We believe that the dendron-
based SAMs provide a new and interesting route to structurally
different monolayers.
3,5-Bis[3,5-bis(1H,1H,2H,2H,3H,3H,4H,4H-perfluorodecan-
l-yloxy)benzyloxy]benzyl Alcohol (22b). Diisopropyl azodicar-
boxylate (0.67 mL, 3.3 mmol) was slowly added to a stirred solution
of alcohol 19b (2.94 g, 3.3 mmol), 3,5-dihydroxy ester 9b (0.28 g,
1.7 mmol), and PPh3 (0.87 g, 3.3 mmol) in THF (6.6 mL) at room
temperature. After being stirred overnight at room temperature the
reaction mixture was purified directly by flash chromatography
(10:1 hexane/EtOAc) to give ester 33 (2.83 g, 89%) as a white
solid. To a magnetically stirred slurry of LiAlH4 (0.15 g, 3.4 mmol)
in anhydrous THF (2 mL) was added ester 24 (3.2 g, 1.68 mmol)
dissolved in anhydrous THF (5 mL) dropwise at 0 °C under a
nitrogen atmosphere. After 4 h of stirring at room temperature, the
reaction was quenched by dropwise addition of water (0.35 mL),
0.5 N NaOH (0.35 mL), and water (1 mL) to give a white
precipitate. The reaction mixture was filtered trough celite and
washed with diethyl ether and then the filtrate was concentrated
under reduced pressure. The residue was extracted with diethyl ether
(3 × 50 mL) and the organic phase was dried over MgSO4 and
concentrated under reduced pressure. The crude product was
purified by flash chromatography (3:1 hexane:EtOAc) to give
alcohol 22b (2.25 g, 71%) as a white solid: Rf 0.14 (5:1 hexane:
EtOAc); 1H NMR (400 MHz, CDCl3) δ 6.62 (s, 2H), 6.56 (s, 4H),
6.52 (s, 1H), 6.39 (s, 2H), 4.96 (s, 4H), 4.64 (s, 2H), 3.98 (t, J )
6.0 Hz, 8H), 2.11 (m, 8H), 1.95-1.84 (m, 16H); 13C NMR (125
MHz, CDCl3) δ 160.2, 160.1, 143.4, 139.2, 120.4, 118.3, 116.0,
113.2, 110.7, 108.6, 105.7, 105.1, 101.3, 100.6, 70.0, 67.2, 65.3,
30.7, 28.6, 17.2; 19F NMR (376 MHz, CDCl3) δ -81.1 (m, 12F),
-114.7 (m, 8F), -122.2 (m, 8F), -123.1 (m, 8F), -124.2 (m, 8F),
-126.4 (m, 8F); Vrnax(film) 3442, 1636, 1456 cm-1; m/z (FAB) 1904
[M + Na+, 60%], 1881 (60), 1741 (75), 1157 (95), 1048 (100),
871 (l00), 218 (l00).
3,4,5-Tris(prop-2-en-1-yloxy)benzyl Alcohol (10a). To a flame-
dried 100-mL three-necked flask equipped with a pressure equalized
dropping funnel under N2 was added THF (20 mL) and LiAlH4
(1.3 g, 34 mmol). Methyl 3,4,5-tris(prop-2-en-l-yloxy)benzoate 9a
(5.2 g, 17 mmol) was dissolved in THF (20 mL) and added
dropwise to the LiAlH4 slurry. The reaction mixture was stirred
for 3 h. The reaction was quenched by the dropwise addition of
water (1 mL), followed by sodium hydroxide solution (15%
aqueous; 1 mL) and water (3 mL) to give a white precipitate. The
reaction mixture was filtered and the mixture was concentrated
under reduced pressure. The residue was extracted with ether (20
mL) and the organic phases were dried (MgSO4). Purification by
flash chromatography (3:1 hexane:EtOAc) furnished the alcohol
10a (4.63 g, 98%) as a yellow oil: Rf 0.21 (1:1 hexane:EtOAc);
1H NMR (250 MHz, CDCl3) δ 6.50 (s, 2H), 5.97 (m, 3H), 5.11
(m, 6H), 4.49 (d, J ) 6.0 Hz, 6H), 4.40 (s, 2H), 2.90 (s, 1H); 13C
NMR (63 MHz, CDCl3) δ 152.5, 136.8, 134.6, 133.4, 117.5, 117.2,
105.9, 74.1, 69.8, 65.0; Vmax (film) 3392, 2871, 1649, 1594, 1505
cm-1; m/z (ES) 294.1704 [(M + NH4)+‚C16H24NO4 requires M
294.1704], 294 [(M + NH4)+, 100%], 277 (66), 259 (98), 235 (15),
and 58 (14).
Experimental Section
A typical procedure for the large-scale synthesis of a thiol-
terminated perfluorinated dendron is as follows:
5,5,6,6,7,7,8,8,9,9,10,10,10-Tridecafluoro-3-iodo-decan-1-ol (7).
To a Schlenk tube were added perfluorohexyl iodide 1a (20 g, 45
mmol), 3-buten-1-ol 6 (3.9 g, 54 mmol), and AIBN (0.37 g, 2.2
mmol). The reaction mixture was degassed by the freeze-pump-
thaw method (repeated 3 times) and heated to 80 °C under nitrogen
atmosphere. After being stirred for 2 h, it was cooled to room
temperature, another portion of AIBN (0.37 g, 2.2 mmol) was
added, and the solution was heated again to 80 °C. After being
stirred for 3 h the reaction mixture was poured directly into warm
n-hexane (100 mL) and crystallized overnight in the fridge. The
precipitated white solid was collected, washed with small portions
of n-hexane, and dried under reduced pressure to give the alcohol
(20 g, 87%) as white crystals: mp 45-48 °C (from n-hexane); 1H
NMR (500 MHz, CDCl3) δ 1.6 (br s, 1H), 1.99-2.11 (m, 2H),
2.83-3.06 (m, 2H), 3.78-3.93 (m, 2H); NMR spectra agreed with
values quoted in the literature.41
1H,1H,2H,2H,2H,3H,4H,4H-Perfluorodecan-1-ol (4a). To a
magnetically stirred solution of sodium bis(2-methoxyethoxy)-
aluminum hydride (70 wt % solution in toluene, 36 g, 123 mmol)
in anhydrous diethyl ether (500 mL) was added alcohol 7 (34 g,
65 mmol) dissolved in anhydrous diethyl ether (100 mL) dropwise
at room temperature under a nitrogen atmosphere. After 3 h of
stirring at room temperature, 2 M HCl aqueous solution (300 mL)
was added dropwise. The organic layer was then separated, washed
with brine (150 mL), dried with MgSO4, and concentrated under
reduced pressure. The crude product was purified by flash chro-
matography (1:1 hexane:EtOAc) to give alcohol 4a (23 g, 91%) as
a colorless viscous liquid: 1H NMR (400 MHz; CDCl3) δ 1.43 (br
s, 1H), 1.62-1.76 (m, 4H), 2.04-2.18 (m, 2H), 3.70 (t, J ) 6.0
Hz, 2H); NMR spectra agreed with values quoted in the literature.34
3,5-Bis(1H,1H,2H,2H,3H,3H,4H,4H-perfluorodecan-1-yloxy)-
benzyl Alcohol (19b). To a magnetically stirred solution of
perfluorinated alcohol 4a (23 g, 58 mmol) and pyridine (11 mL,
79 mmol) in DCM (250 mL) was added p-toluenesulfonyl chloride
(15 g, 79 mmol) in an ice/water bath under a nitrogen atmosphere.
The reaction mixture was then stirred for 1 h in an ice/water bath
and overnight at room temperature. After completion of the reaction,
the DCM solution was concentrated under reduced pressure and
the resulting slurry was purified by flash chromatography (5:1
hexane:EtOAc) to give tosylate 8 (26 g, 81%) as a white solid.
To a magnetically stirred clear solution of tosylate 8 (5.46 g, 10
mmol) and 3,5-dihydroxy benzoate 9b (0.78 g, 4.6 mmol) in dry
DMF (18 mL) was added K2CO3 (1.8 g, 13 mmol) and the mixture
was heated to 65 °C for 8 h. The solution was then cooled to room
temperature and ether (100 mL) and water (100 mL) were added.
The aqueous phase was extracted with ether (3 × 100 mL) and the
collected organic phase was washed with brine (3 × 50 mL), dried
with MgSO4, and concentrated under reduced pressure. The residue
was purified by flash chromatography (1:10 ethyl acetate:hexane
v/v) to give the ester (4.05 g, 96%) as a white solid: Rf 0.44 (3:1
hexane:EtOAc); mp 70-71 °C; 1H NMR (400 MHz, CDCl3) δ 6.51
(s, 2H), 6.36 (s, 1H), 4.63 (s, 2H), 3.99 (t, J ) 8.0 Hz, 4H), 2.16
(m, 4H), 1.89-1.80 (m, 8H); 13C NMR (125 MHz, CDCl3) δ 160.1,
143.4, 120.4, 118.3, 116.0, 113.1, 111.0, 108.6, 105.0, 100.5, 67.2,
65.3, 30.6, 29.2, 17.2; 19F NMR (376 MHz, CDCl3) δ -81.1 (m,
6F), -114.7 (m, 4F), -122.1 (m, 4F), -123.1 (m, 4F), -123.8
3,5-Bis(prop-2-en-l-yloxy)benzyl Alcohol (10b). To a flame-
dried 100-mL three-necked flask equipped with a pressure equalized
dropping funnel under N2 was added THF (60 mL) and LiAlH4
(1.86 g, 49.0 mmol). The ester 9b (6.08 g, 24.5 mmol) was dissolved
in THF (60 mL) and added dropwise to the LiAlH4 slurry. The
reaction mixture was stirred for 3 h. The reaction was quenched
by the dropwise addition of water (1 mL), followed by sodium
hydroxide solution (15% aqueous; 1 mL) and water (3 mL) to give
a white precipitate. The reaction mixture was filtered and the
mixture was concentrated under reduced pressure. The residue was
extracted with ether (20 mL) and the organic phases were dried
(MgSO4). Purification by flash chromatography (1:1 hexane:EtOAc)
furnished the alcohol 10b (5.34 g, 99%) as a yellow oil: Rf 0.38
(m, 4F), -126.4 (m, 4F); Vmax (CHCl3) 3458, 1636, 1472 cm-1
;
m/z (EI) 888.1155 [M+‚C27H22F26O3 requires M 888.1154], 890
1
(1:1 hexane:EtOAc); H NMR (250 MHz, CDCl3) δ 6.52 (s, 2H),
(41) Cheng, X.; Das, M. K.; Diele, S.; Tschierske, C. Langmuir 2002,
18, 6521.
6.42 (s, 1H), 6.03 (m, 2H), 5.34 (dd, J ) 6.0 and 12.0 Hz, 4H),
5512 J. Org. Chem., Vol. 72, No. 15, 2007