CAPÍTULO I. LA LOGOTERAPIA
1.4. El Problema del Significado
2-Bromo-5-styrylfuran (5). To a solution of 4 (4.47 g, 11.4 mmol) in THF (100 mL) at 0 °C, nBuLi (1.6 M in hexane, 10.7 mL, 11.4 mmol) was added
dropwise, followed by stirring for 10 min, after which time a solution of 3 (1.94 g, 11.4 mmol) in THF (40 mL) was added. The reaction mixture was allowed to warm to room temperature and stirred for 24 h. The reaction was quenched with water (10 mL) and the resulting mixture was extracted with diethyl ether (3×70 mL). The combined organic layers were washed with brine and dried over Na2SO4. After filtration, the solvent was evaporated and
the crude mixture was purified by column chromatography with pentane as the eluent to give the product (1.66 g, 58%) as a mixture of cis- and trans-5 as a yellow oil. In the 1H and 13C
NMR spectra, it was possible to assign the signals for each isomer separately. cis-5: 1H NMR
(400 MHz, CDCl3, ppm) δ 7.44–7.39 (m, J = 7.7 Hz, 2H, CArH), 7.36–7.30 (m, 2H, CArH), 7.29–7.23 (m, 1H, CArH), 6.47 (d, J = 12.6 Hz, 1H, CH=CH), 6.28 (d, J = 12.4 Hz, 1H, CH=CH), 6.19 (d, J = 3.4 Hz, 1H, CArH), 6.14 (d, J = 3.3 Hz, 1H, CArH). 13C NMR (75 MHz, CDCl3, ppm) δ 154.1, 137.0, 128.7, 128.5, 128.2, 127.6, 120.9, 117.3, 112.9, 111.9. trans-5: 1H NMR (400 MHz, CDCl 3, ppm) δ 7.47–7.41 (m, 2H, CArH), 7.35–7.29 (m, 2H, CArH), 7.26–7.20 (m, 1H, CArH), 7.01 (d, J = 16.3 Hz, 1H, CH=CH), 6.76 (d, J = 16.2 Hz, 1H, CH=CH), 6.31 (d, J = 3.4 Hz, 1H, CArH), 6.26 (d, J = 3.3 Hz, 1H, CArH). 13C NMR (75 MHz, CDCl3, ppm) δ 155.2, 136.7, 128.7, 127.8, 127.7, 126.4, 121.7, 115.5, 113.4, 110.7. IR (neat, cm–1) ῦ max 3144, 3062, 3027, 1597, 158, 1480, 1446, 1187, 1126, 1014, 953, 923, 780, 690.
5-Styrylfuran-2-carbaldehyde (6). To a solution of 5 (1.5 g, 6.06 mmol) in THF (100 mL) at –78 °C, nBuLi (4.5 mL, 7.27 mmol, 1.6M in hexane) was
added dropwise. The reaction mixture was stirred for 15 min before DMF (0.93 mL, 12.12 mmol) was added. The reaction mixture was allowed to warm to room temperature and stirring was continued for 1 h. The reaction mixture was poured into an ice-cooled aqueous solution of HCl (200 mL, 2M) and the aqueous layer was extracted with diethyl ether (3×100 mL). The combined organic layers were washed with brine and dried over Na2SO4. After filtration, the solvent was evaporated and the crude mixture was
purified by column chromatography with pentane/CH2Cl2 (4/1) as the eluent to afford cis-6
(420 mg, 35%) as a mixture with the trans isomer (cis/trans 95/5, according to 1H NMR
spectroscopy) as a yellow oil, and pure trans-7 (439 mg, 37%) as orange crystals. cis-6: 1H
NMR (400 MHz, CDCl3, ppm) δ 9.54 (s, 1H, COH), 7.44–7.41 (m, 2H, CArH), 7.41–7.35 (m, 2H, CArH), 7.35–7.30 (m, 1H, CArH), 7.11 (d, J = 3.8, 1H, CArH), 6.83 (d, J = 12.5 Hz, 1H, CH=CH), 6.48 (d, J = 12.5 Hz, 1H, CH=CH), 6.31 (d, J = 3.7 Hz, 1H, CArH). trans-6: 1H NMR (400 MHz, CDCl 3, ppm) 9.59 (s, 1H, COH), 7.53–7.48 (m, 2H, CArH), 7.42–7.34 (m, 3H, CArH, CH=CH), 7.34–7.28 (m, 1H, CArH), 7.25 (d, J = 3.7 Hz, 1H, CArH), 6.93 (d, J
= 16.3 Hz, 1H, CH=CH), 6.53 (d, J = 3.7 Hz, 1H, CArH). The NMR spectroscopic data were
in agreement with values reported in the literature.[25] O
Br
O O
Towards processive catalysis
177 (Z)-2-Styryl-4H-furo[3,2-b]pyrrole-5-carboxylic acid ethyl ester (cis-7). See General procedure 5.1 (p.153): Aldehyde cis-6 (0.44 g, 2.2 mmol), ethyl azidoacetate (0.64 g, 4.9 mmol), absolute ethanol (25 mL), sodium ethoxide (1.7 g, 4.9 mmol, 20 wt % in ethanol), 0 °C, 4 h, toluene (40 mL), reflux, 2 h. Column chromatography on silica gel with pentane/ethyl acetate (4/1) as the eluent afforded the product (0.23 g, 36%) as an orange oil, which contained the trans isomer (cis/trans 97/3, according to 1H NMR spectroscopy). 1H NMR (300 MHz,
CDCl3, ppm) δ 9.21 (s, 1H, NH), 7.56–7.47 (m, 2H, CArH), 7.43–7.34 (m, 2H, CArH), 7.34– 7.27 (m, 1H, CArH), 6.73 (dd, J = 1.6, 0.9 Hz, 1H, CArH), 6.57 (d, J = 12.6 Hz, 1H, CH=CH), 6.40 (d, J = 12.7 Hz, 1H, CH=CH), 6.26 (s, 1H, CArH), 4.35 (q, J = 7.1 Hz, 2H, CH2CH3), 1.38 (t, J = 7.1 Hz, 3H, CH2CH3). 13C NMR (75 MHz, CDCl3, ppm) δ 162.1, 158.0, 147.3, 137.2, 130.2, 129.4, 128.6, 128.1, 127.5, 124.5, 118.6, 98.0, 96.5, 60.5, 14.4. IR (neat, cm–1) ῦmax 3296, 2975, 2068, 1666, 1519, 1433, 1281, 1200, 1018, 884, 798, 754, 698. MALDI-
ToF MS (dithranol) m/z calcd C17H15NO3: 281.11; found: 280.91.
(E)-2-Styryl-4H-furo[3,2-b]pyrrole-5-carboxylic acid ethyl ester (trans-7). See General procedure 5.1 (p.153): Aldehyde trans-6 (0.52 g, 2.6 mmol), ethyl azidoacetate (0.68 g, 5.3 mmol), absolute ethanol (25 mL), sodium ethoxide (1.8 g, 5.3 mmol, 20 wt % in ethanol), 0 °C, 3 h, toluene (50 mL), reflux, 2 h. Column chromatography on silica gel with pentane/ethyl acetate (4/1) as the eluent afforded the pure product (0.35 g, 47%) as a yellow solid. 1H NMR
(300 MHz, CDCl3, ppm) δ 8.68 (s, 1H), 7.52–7.44 (m, 2H, CArH), 7.41–7.30 (m, 2H, CArH), 7.29–7.22 (m, 1H, CArH), 7.18 (d, J = 16.2 Hz, 1H, CH=CH), 6.89 (d, J = 16.2 Hz, 1H, CH=CH), 6.81–6.73 (m, 1H, CArH), 6.36 (s, 1H, CArH), 4.35 (d, J = 7.1 Hz, 2H, CH2CH3), 1.38 (t, J = 7.1 Hz, 3H, CH2CH3). 13C NMR (75 MHz, CDCl3, ppm) δ 161.8, 159.3, 148.0, 136.7, 130.1, 128.7, 128.5, 128.4, 126.5, 124.4, 116.9, 97.0, 96.5, 60.5, 14.5. IR (neat, cm–1) ῦmax 3286, 2967, 2928, 1671, 1432, 1286, 1208, 1100, 1027, 953, 750, 685. MALDI-ToF MS
(dithranol) m/z calcd for C17H15NO3: 281.11; found: 280.95.
(Z)-2-Styryl-4H-furo[3,2-b]pyrrole-5-carboxylic acid (cis-8). See General procedure 5.2 (p.154): NaOH (0.33 g, 8.2 mmol), water (5 mL), cis-7 (0.15 g, 0.54 mmol), ethanol (10 mL), reflux, 40 min. The product (0.13 g, 95 %) was obtained without further purification as a green solid. 1H NMR
(300 MHz, DMSO-d6, ppm) δ 12.63–12.19 (brs, 1H, COOH), 11.46 (s, 1H, NH), 7.55–7.43 (m, 2H, CArH), 7.43–7.24 (m, 3H, CArH), 6.60 (s, 1H, CArH), 6.54 (d, J = 12.8 Hz, 1H, CH=CH), 6.49–6.39 (m, 2H). 1H NMR (300 MHz, Acetone-d 6, ppm) δ 10.47 (s, 1H, NH), 7.56–7.49 (m, 2H, CArH), 7.42–7.34 (m, 2H, CArH), 7.34–7.27 (m, 1H, CArH), 6.68 (dd, J = 1.7, 0.9 Hz, 1H, CArH), 6.59 (d, J = 12.7 Hz, 1H, CH=CH), 6.46 (d, J = 12.9 Hz, 1H, CH=CH), 6.42 (s, 1H, CArH). 13C NMR (75 MHz, DMSO-d6, ppm) δ 162.4, 156.9, 146.8, 137.0, 129.7, 128.6, 128.23, 128.20, 127.6, 125.4, 118.3, 99.4, 95.4. 13C NMR (75 MHz, acetone-d6, ppm) δ 163.0, 158.9, 148.5, 138.6, 131.5, 130.1, 129.9, 129.3, 128.6, 126.2, 119.6, 99.8, 96.9. IR (neat, cm–1) ῦ max 3417, 3378, 2967, 2902, 2557, 1640, 1541, 1437, 1260, O N H EtOOC O N H EtOOC O N H HOOC
Chapter 6
178
1079, 914, 750, 690. MALDI-ToF MS (dithranol) m/z calcd for C15H11NO3: 253.07; found:
252.87.
(E)-2-Styryl-4H-furo[3,2-b]pyrrole-5-carboxylic acid (trans-8). See General procedure 5.2 (p.154): NaOH (0.71 g, 18 mmol), water (5 mL), trans- 7 (0.34 g, 1.2 mmol), ethanol (15 mL), reflux, 1 h. The product (0.30 g, 98 %) was obtained without further purification as a green solid. 1H
NMR (300 MHz, DMSO-d6, ppm) δ 12.51–12.32 (brs, 1H, COOH), 11.55 (s, 1H, NH), 7.67–7.51 (m, 2H, CArH), 7.44–7.22 (m, 3H, CArH), 7.22–7.05 (m, 2H, CH=CH), 6.69 (s, 1H, CArH), 6.63 (s, 1H, CArH). 13C NMR (75 MHz, DMSO-d6, ppm) δ 162.4, 158.2, 147.2, 136.5, 130.2, 128.8, 127.8, 127.0, 126.4, 125.1, 117.4, 98.3, 95.4. IR (neat, cm–1) ῦ max 3373, 2928, 2552, 1662, 1442, 1273, 1217, 940, 754, 685, 607. MALDI-ToF MS (dithranol) m/z calcd for C15H11NO3 – H+: 252.07; found: 252.11.
Compound trans-10. Compound trans-8 (63 mg, 0.25 mmol) was dissolved in TFA (2 mL) and stirred at 50 °C. After 7 min, carbaldehyde 9 (53 mg, 0.25 mmol) was added, followed by POCl3 (1.5 mL, 16.2
mmol). After 7 min, the reaction mixture was allowed to cool to room temperature and was poured into a saturated solution of NaHCO3. The precipitate was
collected and dried in vacuo. The resulting compound was dissolved in chloroform (50 mL) and triethylamine (TEA; 0.17 mL, 1 mmol) was added followed by BF3·OEt2 (0.12 mL, 1
mmol). The reaction mixture was heated at reflux for 30 min. After cooling to room temperature, the reaction mixture was diluted with chloroform, washed with a saturated aqueous solution of sodium bicarbonate and brine, and dried over Na2SO4. After filtration, the
solvent was evaporated and the crude mixture was purified by column chromatography with chloroform as the eluent to give the product (70 mg, 61%) as metallic blue–grey crystals. 1H
NMR (400 MHz, CDCl3, ppm) δ 7.85–7.81 (m, 2H, CArH), 7.57–7.53 (m, 2H, CArH), 7.50–
7.44 (m, 2H, CArH), 7.44–7.39 (m, 3H, CArH), 7.39–7.34 (m, 2H, CArH), 7.08 (s, 1H), 6.98
(d, J = 15.9 Hz, 1H), 6.95–6.94 (m, 1H), 6.59 (s, 1H), 6.51 (s, 1H), 6.46–6.44 (m, 1H). IR (neat, cm–1) ῦ
max 3135, 2928, 2846, 1597, 1567, 1411, 1329, 1308, 1243, 1057, 949, 888, 750,
629. UV–vis (CH2Cl2) λabs = 675 nm. MALDI-ToF MS (dithranol) m/z calcd for
C29H19BF2N2O2: 450.24; found: 450.89.
Compound cis-10. Compound cis-8 (43 mg, 0.17 mmol) was dissolved in TFA (2 mL) and stirred at 50 °C. After 7 min, carbaldehyde 9 (36 mg, 0.17 mmol) was added followed by POCl3 (1.5 mL, 16.2 mmol). After 7
min, the reaction mixture was allowed to cool to room temperature and was poured into a saturated solution of NaHCO3. The precipitate
was collected and dried in vacuo. The resulting compound was dissolved in chloroform (10 mL) and BF3·OEt2 (0.08 mL, 0.68 mmol) was added followed by TEA (0.11 mL, 0.68 mmol). The
reaction mixture was heated at reflux for 30 min. After cooling to room temperature, the reaction mixture was diluted with chloroform, washed with a saturated aqueous solution of sodium bicarbonate and brine, and dried over Na2SO4. After filtration, the solvent was
O N H HOOC N B N F F O O N B N F F O O
Towards processive catalysis
179 evaporated and the crude mixture was purified by column chromatography with chloroform as the eluent to give the product (18 mg, 23%) as metallic dark-green crystals. 1H NMR (400
MHz, CDCl3, ppm) δ 7.86–7.81 (m, 2H), 7.57–7.53 (m, 2H), 7.49–7.33 (m, 7H), 7.08 (s,
1H), 6.99–6.94 (m, 2H), 6.59 (s, 1H), 6.50 (s, 1H), 6.45 (s, 1H). 6.5.2 Synthesis of BODIPY dimer
Ethyl 2-(4-vinylphenyl)-4H-furo[3,2-b]pyrrole-5-carboxylate (15). See General procedure 5.1 (p.153): Aldehyde 14 (1.8 g, 8.8 mmol), ethyl azidoacetate (2.3 g, 17.9 mmol), absolute ethanol (100 mL), sodium ethoxide (5.7 g, 17.9 mmol, 20 wt % in ethanol), 0 °C, 3 h, toluene (30 mL), reflux, 2 h. Column chromatography on silica gel with pentane/ethyl acetate (4/1) as the eluent afforded the pure product (1.2 g, 48%) as a orange solid. 1H NMR (300 MHz, CDCl 3, ppm) δ 8.69 (s, 1H, NH), 7.69 (d, J = 8.4 Hz, 2H, CArH), 7.44 (d, J = 8.3 Hz, 2H, CArH), 6.83–6.79 (m, 1H, CArH), 6.72 (dd, J = 17.6, 10.8 Hz, 1H, CH=CH), 6.71 (s, 1H, CArH), 5.78 (d, J = 17.6 Hz, 1H, CH=CH), 5.28 (d, J = 10.8 Hz, 1H, CH=CH), 4.35 (q, J = 7.1 Hz, 2H, CH2CH3), 1.38 (t, J = 7.1 Hz, 3H, CH2CH3). 13C NMR (75 MHz, CDCl3, ppm) δ 162.0, 159.7, 147.9, 137.2, 136.3, 130.40, 130.36, 126.6, 124.13, 124.11, 114.2, 96.8, 93.6, 60.5, 14.5. IR (neat, cm–1) ῦ max 3416, 3299, 2980, 2250, 2120,
1688, 1437, 1286, 1208, 914. HRMS (EI) m/z calcd for C17H15NO3 + H+: 282.1086; found:
282.1090 (|Δ| = 1.4 ppm).
2-(4-Vinylphenyl)-4H-furo[3,2-b]pyrrole-5-carboxylic acid (11). See General procedure 5.2 (p.154): NaOH (2.4 g, 60 mmol), water (5 mL), 15 (1.12 g, 4.0 mmol), ethanol (10 mL), reflux, 35 min. The product (0.91 g, 90 %) was obtained without further purification as a green
solid. 1H NMR (300 MHz, DMSO-d 6, ppm) δ 11.34 (brs, 1H), 7.74 (d, J = 7.6 Hz, 2H, CArH), 7.51 (d, J = 7.1 Hz, 2H, CArH), 7.08 (s, 1H, CArH), 6.74 (dd, J = 17.2, 10.6 Hz, 1H, CH=CH), 6.58 (s, 1H, CArH), 5.86 (d, J = 18.3 Hz, 1H, CH=CH), 5.27 (d, J = 11.3 Hz, 1H, CH=CH). 13C NMR (75 MHz, DMSO-d 6, ppm) δ 162.5, 158.1, 147.0,
136.4, 136.1, 130.4, 130.3, 126.7, 124.8, 123.8, 114.5, 95.6, 95.1. HRMS (EI) m/z calcd for C15H11NO3 – H+: 252.0660; found: 252.0665 (|Δ| = 1.98 ppm).
2-(4-Vinylphenyl)-4H-furo[3,2-b]pyrrole-5-carbaldehyde (12). Acid 11 (0.51 g, 2.0 mmol) and N,O-dimethylhydroxylamine hydrochloride (0.43 g, 4.4 mmol) were combined in a Schlenk flask equipped with a septum and a stirrer and flushed with argon 3 times. A mixture of THF/CH2Cl2
(5/1, 24 mL) was then added, followed by iPr
2NEt (0.83 mg, 6.4 mmol),
and the mixture was cooled to 0 °C and stirred for 15 min, after which time the Deoxo-Flour reagent (50%, v/v in THF 2 mL, 4.4 mmol) was added. The mixture was then allowed to warm to room temperature and stirred for 2 h, after which time the reaction was quenched with NH4Cl and extracted with diethyl ether. The combined organic layers were washed with water
and dried over Na2SO4. After filtration, the solvent was evaporated and the formed Weinreb O N H COOEt O N H COOH O N H O
Chapter 6
180
amide 16 (0.24 g, 0.8 mmol) was dissolved in THF (5 mL) and added dropwise to a solution of LiAlH4 (38 mg, 0.8 mmol) in THF (5 mL) at –78 °C. The reaction mixture was then stirred
at 0 °C for 90 min, and allowed to warm to room temperature. After 30 min, the reaction was quenched with an aqueous solution of KHCO3 (1M) and extracted with ethyl acetate. The
combined organic layers were washed with water and dried over Na2SO4. After filtration, the
solvent was evaporated and the residue was purified by column chromatography with ethyl acetate/pentane (1/2) as the eluent to afford the pure product (57 mg, 30 %) as a yellow solid.
1H NMR (300 MHz, CDCl 3, ppm) δ 9.47 (s, 1H, COH), 8.90 (brs, 1H, NH), 7.73 (d, J = 8.4 Hz, 1H, CArH), 7.47 (d, J = 8.1 Hz, 2H, CArH), 6.83–6.64 (m, 3H), 5.81 (d, J = 17.7 Hz, 1H, CH=CH), 5.31 (d, J = 10.8 Hz, 1H, CH=CH). 13C NMR (75 MHz, CDCl 3, ppm) δ 161.9, 159.3, 148.8, 137.0, 136.2, 130.5, 129.0, 126.6, 124.9, 124.0, 114.0, 96.7; 93.6. MALDI- ToF MS (dithranol) m/z calcd for C15H11NO2 + Na+: 260.06; found: 260.15.
BODIPY 17. To a stirred solution of aldehyde 12 (50 mg, 0.21 mmol) in CH2Cl2 (10
mL) under an argon atmosphere, 2,4-dimethylpyrrole (22 mg, 0.23 mmol) was added. The mixture was cooled to 5 °C and POCl3 (37 mg,
0.23 mmol) was added. After stirring at 5 °C for another 30 min, the mixture was allowed to warm to room temperature and stirred overnight, followed by the addition of iPr
2NEt (0.11 g, 0.84 mmol) and after 15 min by
BF3·OEt2 (0.12 g, 0.84 mmol). After 15 min, the reaction mixture was diluted with chloroform,
washed with a saturated aqueous solution of sodium bicarbonate and brine, and dried over Na2SO4. After filtration, the solvent was evaporated and the crude mixture was purified by
column chromatography with chloroform/pentane (2/1) as the eluent to give the pure product (40 mg, 53%) as metallic dark-red crystals. 1H NMR (300 MHz, CDCl
3, ppm) δ 7.75 (d, J = 8.4 Hz, 2H, CArH), 7.48 (d, J = 8.5 Hz, 2H, CArH), 7.08 (s, 1H, CArH), 6.91 (s, 1H, CArH), 6.74 (dd, J = 17.6, 10.9 Hz, 1H, CH=CH2), 6.50 (s, 1H, CArH), 6.10 (s, 1H, CArH), 5.83 (d, J = 17.6 Hz, 1H, CH=CH2), 5.34 (d, J = 11.0 Hz, 1H, CH=CH2), 2.59 (s, 3H, CH3), 2.25 (s, 3H, CH3). 13C NMR (75 MHz, CDCl3, ppm) δ (2C overlapped) 166.7, 159.2, 148.5, 142.4, 139.0, 137.2, 136.1, 129.2, 126.8, 125.4, 123.4, 119.9, 115.3, 102.3, 95.3, 29.7, 15.0, 11.4. IR (neat, cm–1) ῦ max 3127, 2920, 2850, 1731, 1597, 1463, 1368, 1234, 1161, 1096, 1070, 953,
802, 664. UV–vis (CH2Cl2) λabs = 586 nm. MALDI-ToF MS (dithranol) m/z calcd for
C21H17BF2N2O: 362.14; found: 362.09; calcd for dimer + Na+: 747.28; found: 746.90.
BODIPY 18. Compound 17 (31mg, 86 µmol) and [1,3-bis(2,4,6-trimethylphenyl)- 2-imidazolidinylidene]dichloro (phenylmethylene)(tricyclohexylphosphine) ruthenium (second-generation Grubbs catalyst, 4 mg, 4 µmol) were combined in a Schlenk finger equipped with a stirrer and a septum and flushed with argon 3 times. Chloroform (3 mL) was added and the mixture was stirred at 40 °C for 12 h. Subsequently, the solvent was evaporated and the crude mixture was purified by column chromatography with chloroform/MeOH (99/1) as the eluent to give the pure product (10 mg, 34%) as metallic
N BN F F O O O N N N B B N F F F F
Towards processive catalysis
181 dark-purple crystals. The low solubility of the product in the available deuterated solvents (e.g., CDCl3, THF-d8, toluene-d6) prevented interpretation of the NMR spectra. UV–vis (CH2Cl2)
λabs = 626 nm. MALDI-ToF MS (dithranol) m/z calcd for C40H30B2F4N4O2: 696.249; found:
696.208; calcd for C40H30B2F4N4O2 – F–: 677.25; found: 677.17.
6.5.3 Synthesis of BODIPY polymers
BODIPY 22. Boronic acid 13 (0.5 g, 3.4 mmol), BODIPY 21 (0.77 g, 1.5 mmol), and [1,1’-bis(diphenylphosphino)ferrocene] palladium(II) dichloride dichloromethane complex (1:1; 50 mg, 52 µmol) were combined in a Schlenk finger equipped with a stirrer and a septum and washed with argon 3 times. A degassed mixture of toluene (20 mL), ethanol (4 mL), and an aqueous solution of Na2CO3 (2 M, 4 mL) was added, and the mixture was stirred
at 70 °C for 12 h. Subsequently, the mixture was cooled to room temperature and the organic phase was washed with water (50 mL), dried over Na2SO4, and evaporated. After filtration, the
solvent was evaporated and the crude mixture was purified by column chromatography with chloroform/pentane (2/1) as the eluent to give the pure product (0.40 g, 58%) as metallic dark- red crystals. 1H NMR (400 MHz, CDCl 3, ppm) δ 7.49 (d, J = 8.0 Hz, 4H, CArH), 7.24 (d, J = 8.2 Hz, 4H, CArH), 7.18 (s, 1H, CArH), 6.77 (dd, J = 17.6, 10.9 Hz, 2H, CH=CH2), 5.81 (dd, J = 17.6, 0.8 Hz, 2H, CH=CH2), 5.30 (dd, J = 10.9, 0.8 Hz, 2H, CH=CH2), 2.56 (s, 6H, CH3), 2.25 (s, 6H, CH3). 13C NMR (75 MHz, CDCl3, ppm) δ 155.4, 137.3, 136.43, 136.36, 133.0, 131.8, 129.8, 126.3, 120.3, 114.0, 30.9, 13.5, 10.3. UV–vis (CH2Cl2) λabs = 546 nm.
MALDI-ToF MS (dithranol) m/z calcd for C29H27BF2N2 – F–: 433.22; found: 433.45.
BODIPY polymer 23. Compound 22 (0.14 g, 0.30 mmol) and second-generation Grubbs catalyst (13 mg, 15 µmol) were combined in a Schlenk finger equipped with a stirrer and a septum and washed with argon 3 times. EtCl2 (6 mL) was added and the
mixture was stirred at 55 °C for 1 day. After evaporation of the solvent, the residue was dissolved in a minimal amount of CH2Cl2 and precipitated into an excess of MeOH to give the
pure product (0.11 g, 83%) as a dark-purple solid. The low solubility of the product in the available deuterated solvents (e.g., CDCl3, THF-d8, toluene-d6) prevented interpretation of the
NMR spectra. UV–vis (CH2Cl2) λabs = 553 nm. MALDI-ToF MS (dithranol) m/z calcd for
C56H50B2F4N4 (dimer): 876.42; found: 876.65; calcd for C56H50B2F4N4 – F–: 857.42; found:
857.64.
BODIPY copolymer 27. Compound 22 (157 mg, 0.35 mmol), 24 (83 mg, 0.42 mmol) and second-generation Grubbs catalyst (30 mg, 35 µmol) were combined in a Schlenk finger equipped with a stirrer and a septum and washed with argon 3 times. CHCl2 (6 mL) was
added and the mixture was stirred at 50 °C for 1 day. After evaporation of the solvent, the residue was dissolved in a minimal amount of chloroform and precipitated into an excess of
N B N F F N B N F F n O 4O m N B N F F n
Chapter 6
182
MeOH to give the product (0.11 g, 89%) as a dark-purple powder. The low solubility of the product in the available deuterated solvents (e.g., CDCl3, THF-d8, toluene-d6) prevented
interpretation of the NMR spectra. UV–vis (CH2Cl2) λabs = 550 nm.
BODIPY copolymer 28. Compound 22 (100 mg, 0.22 mmol), cyclooctene (31 mg, 0.27 mmol), and second-generation Grubbs catalyst (19 mg, 22 µmol) were combined in a Schlenk finger equipped with a stirrer and a septum and washed with argon 3 times. CHCl2 (6 mL) was added and the mixture was stirred at 50 °C for 20 h. After
evaporation of the solvent, the residue was dissolved in a minimal amount of chloroformand precipitated into an excess of MeOH to give the product (0.11 g, 89%) as a dark-brown powder. The low solubility of the product in the available deuterated solvents (e.g., CDCl3, THF-d8,
toluene-d6) prevented interpretation of the NMR spectra. UV–vis (CH2Cl2) λabs = 551 nm.
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185
Summary
For a synthetic reaction to be useful and find broader applications beyond a simple proof of concept, it needs to be selective and provide high yields. These and other requirements were postulated by Sharpless when he laid the foundations of click chemistry at the beginning of this millennium. Soon thereafter, the beneficial effect of copper(I) ions on the regioselectivity and rate of the azide–alkyne cycloaddition reaction were discovered and this reaction became the most prominent member of the click reaction family. Because the starting compounds for this simple, selective and orthogonal reaction are readily available, click chemistry has found applications in organic chemistry, polymer and biochemistry fields. The formed 1H-1,2,3- triazole linker has become the key structural element of many novel biohybrid materials. Owing to the intrinsic structure of the triazole with three heteroatoms and a polarised C–H bond, studies that took advantage of the metal-binding and hydrogen-donating and -accepting properties have also emerged. In these cases, the triazole has served as the key functional element of supramolecular structures, sensors, ligands and recently also catalytic systems.
Catalytic systems, in particular, very often consist of N-heterocyclic moieties. Porphyrins, comprising four pyrrole moieties, are one example of such systems. Due to the ease of functionalisation and a variety of metals that can be coordinated by the porphyrin moiety, these molecules have found wide applications in various metal-catalysed reactions. The natural occurrence of porphyrins in living cells also makes them very interesting for studies that mimic processes found in nature. Recently, systems were described that mimicked the behaviour of processive catalytic systems, such as DNA polymerase and λ-exonuclease. However, a complete understanding of the ongoing processes in these model catalytic systems is still of great