Job/Unit: O20147
/KAP1
Date: 23-04-12 15:50:10
Pages: 10
M. Tanasova, B. Borhan
FULL PAPER
raphy was performed using SiliCycle silica gel (230–400 mesh).
1H NMR spectra were obtained with a Varian Inova 300 MHz or
500 MHz instrument and are reported in parts per million (ppm)
relative to the solvent resonances (δ), with coupling constants (J)
in Hertz (Hz). UV/Vis spectra were recorded with a Perkin–Elmer
Lambda 40 spectrophotometer and are reported as λmax [nm]. CD
spectra were recorded with a JASCO J-810 spectropolarimeter,
equipped with a temperature controller (Neslab 111) for low tem-
perature studies. The CD spectra were measured as molecular elipl-
icity (millidegrees), and normalized for the concentration of the
porphyrin to yield Molecular CD [m–1 cm–1]. All the CD spectra
were recorded with 1 μm solution of porphyrin tweezer in hexanes
(for chiral diamines) or methylcyclohexane (for carrier derivatized
carboxylic acids) using a 10 mm UV quartz cell at 0 °C and are
reported at 20 equiv. of the chiral substrate. ZnTPP-C5 and ZnTPP-
C3 were obtained following previously published procedures.[7c]
ZnTPP-Ac was synthesized according to Scheme 1, following the
procedures described below.
(5 mL) was added tetrabutylammonium fluoride (1 m in THF,
0.4 mL, 0.4 mmol, 3 equiv.) and the mixture was stirred at room
temperature for 24 h. The reaction mixture was then partitioned
between water (10 mL) and CH2Cl2 (20 mL), the organic layer was
separated, dried with anhydrous Na2SO4, and the solvent was re-
moved under reduced pressure. After column chromatography pu-
rification (silica gel; CH2Cl2/hexane, 10%), 5-(3-ethynylphenyl)-
10,15,20-triphenylporphyrin (77 mg, 98%) was obtained. MS
(DCI): calcd. for C46H30N4 638.5 [M]+; found 639.4 [M + H]+,
319.2 [M]+2. IR (film): ν = 3374, 3076, 2967, 2926, 2956, 2161,
˜
1686, 1653, 1558, 1541, 1340, 1250, 1001, 796 cm–1. 1H NMR
(300 MHz, CDCl3): δ = –2.8 (s, 2 H), 3.2 (s, 1 H), 7.8 (m, 9 H), 7.9
(dd, J1 = 1.8, J2 = 1.0 Hz, 2 H), 8.2 (m, 7 H), 8.4 (s, 1 H), 8.9 (m,
8 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 83.9, 101,119.3,
120.8, 126.4, 128.2, 131.2, 131.8, 131.9, 134.6, 135.6, 137.7, 140.5,
143.2, 150.1 ppm.
5-(3-Ethynylphenyl)-10,15,20-triphenylporphyrin
(18 mg,
0.028 mmol, 1 equiv.) was then zincated with Zn(OAc)2·2H2O
(93 mg, 0.42 mmol, 15 equiv.) in CH2Cl2 (10 mL) at room tempera-
ture overnight. The color of the solution changed from dark-purple
to reddish-purple during the course of the reaction. The reaction
mixture was purified by column chromatography (silica gel,
CH2Cl2) and the purple band was collected. The solvent was re-
moved under reduced pressure to yield zincated porphyrin 3 as a
purple solid (16.6 mg, 77%). MS (DCI): calcd. for C46H28N4Zn
3-[2-(Trimethylsilanyl)ethynyl]benzaldehyde (1): (Trimethylsilyl)-
acetylene (3.8 g, 38.7 mmol, 1.8 equiv.), 3-bromobenzaldehyde
(4.0 g, 21.6 mmol, 1 equiv.), Pd(OAc)2 (56 mg, 0.25 mmol,
0.01 equiv.), triphenylphosphane (112 mg, 0.43 mmol, 0.02 equiv.),
and anhydrous deoxygenated triethylamine (21 mL) were combined
in a round-bottomed flask and brought to quick reflux under argon
by placing the flask in an oil bath preheated to 100 °C. The solution
was heated to reflux for 10 h and cooled to room temperature. The
reaction mixture was filtered and the filtrate was extracted with
saturated NaHCO3 (2ϫ15 mL) and CH2Cl2 (2ϫ20 mL). The or-
ganic layers were combined and the solvent was removed under
reduced pressure to give the crude aldehyde as a brown oil. The oil
was purified by column chromatography (silica gel; EtOAc/hexanes,
5%) to give 3-(1-trimethylsilylethyne)benzaldehyde (3.34 g, 77%).
1H NMR (CDCl3, 300 MHz): δ = 0.07 (s, 9 H), 7.72 (d, J = 7.4 Hz,
1 H), 7.81 (d, J = 7.4 Hz, 1 H), 7.97 (dd, J1 = 1.6, J2 = 1.2 Hz, 1
H), 9.87 (s, 1 H) ppm. 13C NMR (CDCl3, 75 MHz): δ = 3.4, 98.9,
103.2, 124.4, 128.6, 128.9, 133.2, 136.3, 136.8, 191.6 ppm. MS
(DCI): m/z = 202.2 [C12H14OSi].
700.1 [M]+; found 701.8 [M + H]+, 350.0 [M]+2. IR (film): ν =
˜
2973, 2929, 2866, 2165, 1682, 1606, 1558, 1340, 1250, 1003, 843,
1
798, 700 cm–1. H NMR (300 MHz, CDCl3): δ = 3.2 (s, 1 H), 7.8
(m, 9 H), 7.9 (dd, J1 = 1.6, J2 = 1.2 Hz, 2 H), 8.2 (m, 7 H), 8.4 (s,
1 H), 8.9 (m, 8 H) ppm. 13C NMR (CDCl3, 125 MHz): δ = 74.8,
78.1, 104.1, 110.5, 115.2, 115.4, 120.7, 121.6, 122.6, 124.5, 124.7,
126.5, 127.9, 128.3, 128.8, 132.3, 132.8, 134.3, 134.6, 135.2, 140.0,
142.3, 142.5, 148.2, 149.9 ppm.
Bis[5-(3-ethynylphenyl)-10,15,20-triphenylporphyrinatozinc]
(ZnTPP-Ac Tweezer): Porphyrinatozinc complex
3 (90 mg,
0.14 mmol, 1 equiv.) was combined with Cu(OAc)2·H2O (235 mg,
1.17 mmol, 8.4 equiv.) and pyridine (12 mL). The solution was
stirred at 40 °C under an oxygen atmosphere for 24 h, during which
the color of the reaction mixture changed from purple to blue-
green. The reaction mixture was then cooled to room temperature
and extracted with H2O (10 mL) and NaHCO3 (20 mL) until the
aqueous layer was clear. The organic layer was dried with anhy-
drous Na2SO4, filtered, and concentrated under reduced pressure
to give a crude purple-blue film, which was purified by flash
chromatography (silica gel; hexane) to yield the ZnTPP-Ac tweezer
(79 mg, 82%). MS (FAB+): calcd. for C92H54N8Zn2 1402.28; found
10,15,20-Triphenyl-5-{3-[2-(trimethylsilanyl)ethynyl]phenyl}-
porphyrin (2): Aldehyde 1 (200 mg, 1 mmol, 1 equiv.), pyrrole
(260 mg, 4 mmol, 4 equiv.), and benzaldehyde (318 mg, 3 mmol,
3 equiv.) were combined in a flask with CH2Cl2 (150 mL) and the
solution was purged with N2 for 15 min. BF3·OEt2 (50 μL,
0.4 mmol, 0.1 equiv.) was added, the reaction vessel was shielded
from light, and the reaction mixture was stirred at room tempera-
ture overnight. p-Chloranil (980 mg, 4 mmol, 4 equiv.) was then
added in one portion and the flask was placed in a preheated oil
bath at 45 °C. The solution was heated to reflux for 2 h, then co-
oled to room temperature and the solvent volume was reduced un-
der reduced pressure. The reaction mixture was submitted to flash
chromatography (silica gel; CH2Cl2/hexane, 50%) affording a mix-
ture of porphyrins. A second round of purification by column
chromatography (silica gel; CH2Cl2/hexane, 5%) gave 2 (256 mg,
1424.2 [M + Na]+. IR (film): ν = 2983, 2916, 2883, 1684, 1587,
˜
1
1476, 1361, 1250, 1003, 798 cm–1. H NMR (300 MHz, CDCl3): δ
= 7.7 (m, 18 H), 7.95 (dd, J1 = 1.8, J2 = 1.1 Hz, 4 H), 8.2 (m, 14
H), 8.4 (s, 2 H), 8.9 (m, 8 H) ppm. 13C NMR (CDCl3, 125 MHz):
δ = 72.8, 76.7, 102.9, 110.1, 114.9, 115.0, 119.1, 119.6, 120.1, 123.0,
124.1, 124.3, 125.7, 127.0, 127.3, 127.9, 134.3, 134.8, 136.4, 136.9,
137.2, 140.0, 141.9, 142.1, 146.7, 150.3 ppm.
37%). MS (DCI): m/z = 710.7 [C H N Si]. IR (film): ν = 3292,
˜
49 38
4
Supporting Information (see footnote on the first page of this arti-
cle): Synthetic procedures and characterization data for all com-
pounds, binding constant determination, ECCD data obtained for
chiral amides with sterically encumbered porphyrin tweezers, and
molecular modeling data.
3055, 2961, 1597, 1523, 1487, 1441, 1338, 1205, 1070, 1001, 996,
908, 798, 752, 731, 702 cm–1. 1H NMR (300 MHz, CDCl3): δ =
–2.7 (s, 2 H), 0.92 (s, 9 H), 7.8 (m, 9 H), 7.9 (dd, J1 = 1.8, J2
=
1.0 Hz, 2 H), 8.2 (m, 7 H), 8.4 (s, 1 H), 8.9 (m, 8 H) ppm. 13C
NMR (CDCl3, 125 MHz): δ = 2.3, 53.6, 85.6, 116.2, 121.9, 122.7,
126.5, 127.5, 127.9, 129.2, 129.7, 130.3, 130.9, 132.4, 134.6, 142.7,
150.2 ppm.
Acknowledgments
5-(3-Ethynylphenyl)-10,15,20-triphenylporphyrinatozinc (3): To
solution of 2 (88.5 mg, 0.14 mmol, 1 equiv.) in anhydrous THF
a
Generous support was provided by a National Science Foundation,
USA (NSF CAREER, grant number CHE-0094131). The authors
8
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