Nanoscale Borromeates
repeated additions and removal of MeOH (20 mL) by rotary
evaporation under reduced pressure at 50 °C, leaving a pink
sticky residue. This residue was treated with CH2Cl2, and the
solvent was removed by rotary evaporation under reduced
pressure at 40 °C until a light pink amorphous solid remained
that is moisture sensitive. Yield of crude DAB-Hn‚nTFA: 1.32
g, 95%. 1H NMR (500 MHz, CD3OD, 25 °C): δ 4.20 (s, 4H),
7.18 (dd, J ) 3.5, 7.3 Hz, 2H), 7.33 (d, J ) 8.5 Hz, 4H), 7.64
(d, J ) 8.5 Hz, 4H), 8.06 (d, J ) 3.5 Hz, 2H), 8.66 (d, J ) 7.3
Hz, 2H). 13C NMR (125 MHz, CD3OD, 25 °C) δ 43.6, 112.8,
114.8, 117.9 (q, J ) 291 Hz, TFA), 122.6, 132.8, 133.0, 149.8,
152.2, 155.2, 162.3 (q, J ) 35.5 Hz, TFA) 170.0. HRMS (ESI):
m/z 399.1836 (100) [M - 4CF3CO2H + H]+, 819.3428 (62) [2M
- 8CF3CO2H + Na]+.
MHz, CD3SOCD3, 25 °C): δ 4.75 (bs, 24H), 6.46 (bs, 12H), 6.55
(bs, 48H), 6.61 (bd, J ) 6.6 Hz, 24H), 6.70 (bd, 24H), 7.29 (bs,
12H), 7.95 (bs, 12H), 8.38 (d, J ) 7.2 Hz, 12H), 8.43 (d, J )
7.8 Hz, 12H), 8.66 (t, J ) 7.2 Hz, 6H), 8.70 (t, J ) 7.8 Hz, 6H),
9.03 (s, 12H), 9.05, (s, 12H). 13C NMR of BR‚12TFA (150 MHz,
CD3OD, 25 °C): δ 63.1, 112.6, 113.9, 117.9 (q, J ) 296 Hz,
TFA), 122.3, 130.8, 131.2, 135.1, 145.5, 148.2, 151.7, 153.3,
162.0, 162.5 (q, J ) 34.6 Hz, TFA) 169.8. 13C NMR data for
BR‚12TFA and Zn@BR‚14TFA (125 MHz, CD3SOCD3, 25
°C): δ 60.8, 109.7, 111.4, 114.3, 116.9 (q, J ) 298 Hz, TFA),
120.6, 129.6, 130.8, 133.6, 144.2, 146.2, 146.6, 148.9, 149.9,
151.1, 153.3,158.1 (q, J ) 31.6 Hz, TFA),160.7, 163.8, 167.3.
HRMS (ESI): m/z 1465.1902 (10) [M - 3CF3CO2]3+, 1070.1398
(100) [M - 4CF3CO2]4+, 833.7088 (50) [M - 5CF3CO2]5+
.
4-(4-Acetoxymethylphenyl)-2,6-diformylpyridine (8).
4-Bromo-2,6-diformylpyridine (5) (500 mg, 2.34 mmol), 4-ac-
etoxymethylphenyl boronic acid (6) (453 mg, 2.34 mmol), and
tetrakistriphenylphosphine palladium(0) (265 mg, 0.23 mmol)
were added to a degassed PhMe (30 mL) solution containing
NaHCO3 (2.0 g) and H2O (4 mL). The reaction mixture was
then heated under an inert atmosphere of argon at 90 °C for
15 h. The solvents were removed by rotary evaporation, and
the resulting residue was purified by column chromatography
[SiO2: CH2Cl2] to yield the title compound 8 as a white solid
(610 mg). Recrystallized from CH2Cl2/hexanes (524 mg).
Yield: 79%. Mp: 139-141 °C. 1H NMR (500 MHz, CD2Cl2, 25
°C): δ 2.13 (s, 3H), 5.17 (s, 2H), 7.54 (d, J ) 8.4 Hz, 2H), 7.79
(d, J ) 8.4 Hz, 2H), 8.39 (s, 2H), 10.20 (s, 2H). 13C NMR (150
MHz, CD2Cl2, 25 °C): δ 21.1, 65.7, 123.0, 127.7, 129.2, 136.0,
139.0, 150.9, 154.1, 170.9, 192.8. HRMS (EI): m/z 283.0850.
BR(C6H4CH2OAc)6‚12TFA and Zn@BR(C6H4CH2OAc)6‚
14TFA. Compound 4 (220 mg, 0.367 mmol) was dissolved in
TFA (2 mL) and stirred at room temperature for 10 min.
Excess TFA was removed by rotary evaporation under reduced
pressure followed by subsequent additions and removals of
MeOH (3 × 5 mL), leaving a pink tar. Zn(OAc)2 (67.0 mg, 0.367
mmol) was added to a stirred i-PrOH solution (5 mL) contain-
ing the freshly deprotected DAB-Hn‚nTFA, followed by 8 (104
mg, 0.367 mmol) dissolved in CH2Cl2 (1 mL). The reaction
mixture was first heated to remove CH2Cl2 solvents and then
at 70 °C for 24 h, producing an off-white colored precipitate
which was removed by filtration, washed with i-PrOH and
Et2O, and dried to afford the title compound as a mixture of
BR(C6H4CH2OAc)6‚12TFA and Zn@BR(C6H4CH2OAc)6‚
14TFA (86:14) as a light orange powder. Yield: 336 mg, 97%.
The product can be crystallized from a methanolic solution into
1
which Et2O was allowed to diffuse slowly. H NMR data for
4-(4-Methylthiophenyl)-2,6-diformylpyridine (9). 4-Bro-
mo-2,6-diformylpyridine (5) (500 mg, 2.34 mmol), 4-methyl-
thiophenyl boronic acid (7) (453 mg, 2.34 mmol), and tetraki-
striphenylphosphinepalladium(0) (265 mg, 0.23 mmol) were
added to a degassed 1:1 THF/H2O (20 mL) solution containing
NaHCO3 (2.0 g). The reaction mixture was then heated under
an inert atmosphere of argon at 85 °C for 15 h. The reaction
mixture was transferred to a separatory funnel containing H2O
(50 mL), and the aqueous solution was extracted with CH2Cl2
(3 × 100 mL). The combined organic layers were dried (MgSO4)
and filtered, and the solvents were removed by rotary evapora-
tion. The resulting residue was purified by column chroma-
tography [SiO2: CH2Cl2] to yield the title compound 9 as a
light yellow solid. Recrystallized from EtOAc/hexanes (502
mg). Yield: 83%. Mp: 168-170 °C. 1H NMR (500 MHz,
CD2Cl2, 25 °C): δ 2.13 (s, 3H), 5.17 (s, 2H), 7.54 (d, J ) 8.4
Hz, 2H), 7.79 (d, J ) 8.4 Hz, 2H), 8.39 (s, 2H), 10.20 (s, 2H).
13C NMR (150 MHz, CD2Cl2, 25 °C): δ 21.1, 65.7, 123.0, 127.7,
129.2, 136.0, 139.0, 150.9, 154.1, 170.9, 192.8. HRMS (EI): m/z
257.0512.
BR(C6H4CH2OAc)6‚12TFA (600 MHz, CD3OD, 25 °C): δ 2.12
(s, 18H), 4.86 (s, 24H), 5.23 (s, 12H), 6.52 (bs, 12 H), 6.71 (d,
J ) 7.8 Hz, 24H), 6.76 (d, J ) 7.8 Hz, 24H), 7.65 (d, J ) 8.4
Hz, 12H), 8.00 (d, J ) 4.2 Hz, 12H), 8.03 (d, J ) 8.4 Hz, 12H),
8.63 (s, 12H), 8.93 (s, 12H). 1H NMR data for Zn@BR-
(C6H4CH2OAc)6‚14TFA (600 MHz, CD3OD, 25 °C): δ 2.14 (s,
18H), 4.76 (d, J ) 14 Hz, 12H), 4.81 (d, J ) 14 Hz, 12H), 5.25
(s, 12H), 6.58 (d, J ) 8.6 Hz, 24H), 6.63 (d, J ) 8.6 Hz, 24H),
7.31 (bs, 12H), 7.67 (d, J ) 8.6 Hz, 12H), 8.06 (d, J ) 8.6 Hz,
12H), 8.16 (bs, 12H), 8.23 (d, J ) 2.1 Hz, 12H), 8.65 (s, 12H),
8.94 (s, 12H). 1H NMR data for BR(C6H4CH2OAc)6‚12TFA
and Zn@BR(C6H4CH2OAc)6‚14TFA (600 MHz, CD3SOCD3,
25 °C): δ 2.12 (s, 12H), 2.14 (s, 12H), 4.78 (bs, 24H), 5.21 (s,
12H), 5.24 (s, 12H), 6.46 (bs, 12H), 6.56 (bs, 48H), 6.62 (bd, J
) 6.6 Hz, 24H), 6.73 (bd, J ) 6.6 Hz, 24H), 7.32 (bs, 12H),
7.67 (d, J ) 8.4 Hz, 12H), 7.70 (d, J ) 8.4 Hz, 12H), 8.07 (d,
J ) 8.4 Hz, 12H), 8.12 (d, J ) 8.4 Hz, 12H), 8.76 (s, 12H),
8.84(s,12H),9.02,(s,12H).13CNMRdataforBR(C6H4CH2OAc)6‚
12TFA and Zn@BR(C6H4CH2OAc)6‚14TFA (150 MHz, CD3-
SOCD3, 25 °C): δ 20.7, 61.0, 64.8, 109.8, 111.4, 115.5, 117.0
(q, J ) 298 Hz, TFA), 120.7, 126.6, 127.6, 128.9, 129.0, 129.6,
133.6, 134.5, 139.6, 146.9, 147.3, 149.0, 150.0, 151.2, 153.4,
153.9, 158.2 (q, J ) 32.6 Hz, TFA), 160.6, 163.8, 167.4 170.3.
HR-ESI-MS: m/z 1760.9303 (50) [M - 3CF3CO2]3+, 1292.4819
BR‚12TFA and Zn@BR‚14TFA. Compound 4 (600 mg,
1.00 mmol) was dissolved in TFA (5 mL) and stirred at room
temperature for 10 min. Excess TFA was removed by rotary
evaporation under reduced pressure followed by subsequent
additions and removals of MeOH (3 × 5 mL), leaving a pink
tar. Zn(OAc)2 (183.0 mg, 1.00 mmol) was added to a stirred
i-PrOH (10 mL) solution containing the freshly deprotected
DAB-Hn‚nTFA, followed by DFP (135 mg, 1.00 mmol), and
the reaction mixture was heated at 70 °C for 24 h, producing
an off-white precipitate which was removed by filtration,
washed with i-PrOH and Et2O, and dried to afford the title
compound as a mixture of BR‚12TFA and Zn@BR‚14TFA (86:
14) as an off-white powder. Yield: 754 mg, 95%. 1H NMR data
for BR‚12TFA (600 MHz, CD3OD, 25 °C): δ 4.84 (s, 24H), 6.50
(bs, 12H), 6.69 (d, J ) 8.5 Hz, 24H), 6.73 (d, J ) 8.5 Hz, 24H),
7.97 (d, J ) 2.4 Hz, 12H), 8.31 (d, J ) 7.8 Hz, 12H), 8.61 (t, J
) 7.8 Hz, 6H), 8.89 (s, 12H). 1H NMR data for Zn@BR‚14TFA
(600 MHz, CD3OD, 25 °C): δ 4.74 (d, J ) 14 Hz, 12H), 4.80
(d, J ) 14 Hz, 12H), 6.57 (d, J ) 8.4 Hz, 24H), 6.61 (d, J ) 8.4
Hz, 24H), 7.30 (d, J ) 5.4 Hz, 12H), 8.20 (d, J ) 2.4 Hz, 12H),
8.34 (d, J ) 7.8 Hz, 12H), 8.63 (t, J ) 7.8 Hz, 6H), 8.92 (s,
(100) [M - 4CF3CO2]4+, 1011.3981 (20) [M - 5CF3CO2]5+
.
BR(C6H4SMe)6‚12TFA and Zn@BR(C6H4SMe)6‚14TFA.
Compound 4 (209 mg, 0.350 mmol) was dissolved in TFA (2
mL) and stirred at room temperature for 10 min. Excess TFA
was removed by rotary evaporation under reduced pressure,
followed by subsequent additions and removals of MeOH (3 ×
5 mL), leaving a pink tar. Zn(OAc)2 (64.0 mg, 0.350 mmol) was
added to a stirred i-PrOH solution (5 mL) containing the
freshly deprotected DAB-Hn‚nTFA, followed by 9 (90 mg, 0.350
mmol) dissolved in CH2Cl2 (1 mL). The reaction mixture was
first heated to remove CH2Cl2 solvents and then at 70 °C for
24 h producing a yellow precipitate which was removed by
filtration, washed with washed with i-PrOH and Et2O, and
dried to afford the title compound as a mixture of BR-
(C6H4SMe)6‚12TFA and Zn@BR(C6H4SMe)6‚14TFA (74:26)
as a yellow solid. Yield: 282 mg, 89%. 1H NMR (600 MHz,
CD3OD, 25 °C): δ 2.59 (s, 18H), 4.86 (s, 24H), 5.23 (s, 12H),
1
12H). H NMR data for BR‚12TFA and Zn@BR‚14TFA (600
J. Org. Chem, Vol. 70, No. 20, 2005 7961