Columnar Mesomorphism in Heptazine Discotics
4.5 Synthesis and characterization
General procedure for the synthesis of 1a, 1b, 1c, 1d, 1e.
In a round bottom flask, 1,2- dihydroxy benzene (pyro catechol) (1eq) was dissolved in ethanol / DMF, K2CO3 (6eq) was added to it and stirred for 15 minutes. 1-Bromo alkane (2.2 eq) was added to it and the mixture was refluxed overnight. Then it was cooled to room temperature, and ethanol/DMF was evaporated. The reaction mixture was extracted with CHCl3 organic layer was dried over anhydrous Na2SO4 and the solvent was evaporated. The crude product was purified by column chromatography using petroleum ether and dichloromethane as eluent and dried under high vacuum to get the desired product.
Compound 1a: 1,2- dihydroxy benzene (10g, 90.82 mmol, 1eq), ethanol 500 mL, K2CO3 (75.31g, 544.95mmol, 6eq), 1-Bromo hexane (29.98g, 199.81 mmol, 2.2eq) Yield: 83%
; M.P. 39 ºC; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6.91 (s, 4H), 4.01 (t, J = 6.25 Hz, 4H ), 1.83 (t, J = 6.50 Hz, 4H ), 1.49 (s, 4H), 1.36 (s, 8H), 0.92 (s, 6H); 13C NMR (125 MHz, CDCl3):
δ ppm = 149.30, 121.03, 114.20, 69.32, 31.64, 29.35, 25.74, 22.;
Compound 1b: 1,2- dihydroxy benzene (10g, 90.82 mmol, 1eq), ethanol 500 mL, K2CO3 (75.31g, 544.95mmol, 6eq), 1-Bromo octane (38.58g, 199.81 mmol, 2.2eq) Yield: 85%
; M.P. 39 ºC; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6.90 (s, 4H), 4.01 (t, J = 6.25 Hz, 4H ), 1.83 (t, J = 6.50 Hz, 4H ), 1.49 – 1.47 (m, 4H), 1.34 – 1.30 (m, 16H), 0.91 (s, 6H); 13C NMR
Page | 171 (125 MHz, CDCl3): δ ppm = 149.31, 121.03, 114.23, 69.33, 31.85, 29.41, 29.38, 29.30, 26.07, 22.68, 14.09;
Compound 1c: 1,2- dihydroxy benzene (10g, 90.82 mmol, 1eq), acetone 500 mL, K2CO3 (75.31g, 544.95mmol, 6eq), 1-Bromo decane (44.19g, 199.81 mmol, 2.2eq) Yield: 83%
; M.P. 39 ºC; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6.91 (s, 4H), 4.01 (t, J = 6.50 Hz, 4H), 1.80 – 1.86 (m, 4H), 1.45 – 1.51 (m, 4H), 1.29 – 1.38 (m, 24H), 0.90 (t, J = 7.0 Hz, 6H); 13C NMR (125 MHz, CDCl3): δ ppm =149.27, 121.01, 114.13, 69.29, 31.95, 29.68, 29.63, 29.48, 29.39, 26.09, 22.72, 14.14
Compound 1d: 1,2- dihydroxy benzene (10g, 90.82mmol, 1eq), ethanol 500 mL, K2CO3 (75.31g, 544.95mmol, 6eq), 1-Bromo dodecane (49.30g, 199.81mmol, 2.2eq) Yield:
90% ; M.P. 45 ºC; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6.88 (s, 4H), 3.98 (t, J = 6.5 Hz, 4H), 1.78 – 1.83 (m, 4H), 1.43 – 1.49 (m, 4H), 1.26 – 1.34 (m, 16H), 0.88 (t, J = 7.0 Hz, 6H),
13C NMR (125 MHz, CDCl3): δ ppm = 149.27, 121.01, 114.17, 69.31, 31.94, 29.72, 29.65, 29.46, 29.38, 26.07, 22.71, 14.12;
Compound 1e: 1,2- dihydroxy benzene (10g, 90.82mmol, 1eq), ethanol 500 mL, K2CO3 (75.31g, 544.95mmol, 6eq), 1-Bromo hexadecane (61.00g, 199.81mmol, 2.2eq) Yield:
87% ; M.P. 61 ºC; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6.91 (s, 4H), 4.01 (t, J = 6.50 Hz, 4H), 1.80 – 1.86 (m, 4H), 1.46 – 1.51 (m, 4H), 1.28 – 1.38 (m, 48H), 0.90 (t, J = 6.50 Hz 6H);
13C NMR (125 MHz, CDCl3): δ ppm = 149.26, 121.01, 114.13, 69.29, 31.96, 29.74, 29.69, 29.67, 29.47, 29.39, 29.37, 26.08, 22.72, 14.14;
General procedure for the synthesis of 2a, 2b, 2c, 2d, 2e.
In a round bottom flask 1 (1 eq) was dissolved in dichloromethane, added NaNO2 (0.14 eq) and stirred. To this well-stirred suspension HNO3 (3eq in dichloromethane) was added dropwise.
This mixture was stirred at room temperature for 3h. The reaction mixture was poured into water and extracted with dichloromethane. Organic layer was washed with 5% NaHCO3
solution, water and brine. Organic layer was dried over anhydrous Na2SO4 and the solvent was removed under reduced pressure. The crude product was purified by column chromatography on silica gel (100-200 mesh) using petroleum ether and dichloromethane (10%
Page | 172 dichloromethane 90% pet ether) as eluent and dried under high vacuum to get the desired product. The yield of these nitro compounds was in the range of 60-70%.
Compound 2a: 1a (5g, 17.95 mmol, 1eq), dichloromethane 20 ml, NaNO2 (0.172g, 2.514 mmol, 0.14 eq), HNO3 (3.39g, 53.87 mmol, 3eq) Yield: 65%; 1H NMR (500 MHz, CDCl3): δ (ppm) = 7.89 (d, J = 8.50 Hz, 1H), 7.74 (s, 1H), 6.89 (d, J = 9.0 Hz, 1H) 4.09 (p, J = 6.50 Hz, 4H) 1.88 – 1.87 (m, 4H), 1.50 (bs, 4H), 1.37 (bs, 8H), 0.93 (s, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 154.72, 148.69, 141.19, 117.64, 111.07, 108.09, 69.48, 69.42, 31.49, 31.47, 28.92, 28.89, 25.61, 25.57, 22.56, 22.54, 13.95;
Compound 2b: 1b (7g, 20.92 mmol, 1eq), dichloromethane 20 ml, NaNO2 (0.200g, 2.92 mmol, 0.14 eq), HNO3 (3.95g, 62.77 mmol, 3eq) Yield: 70%;1H NMR (500 MHz, CDCl3): δ (ppm) = 7.88 (d, J = 9.00 Hz, 1H), 7.74 (s, 1H), 6.89 (d, J = 9.0 Hz, 1H) 4.08 (p, J = 6.50 Hz, 4H) 1.87 (bs, 4H), 1.50 – 1.49 (m, 4H), 1.38 – 1.31 (m, 16H), 0.90 – 0.89 (m, J = 6.50 Hz, 6H):
13C NMR (125 MHz, CDCl3): δ ppm = 154.72, 148.69, 141.20, 117.63, 111.09, 108.12, 69.49, 69.43, 31.79, 31.78. 29.29, 29.27, 29.23, 29.21, 28.97, 28.94, 25.95, 25.91, 22.65, 14.05;
Compound 2c: 1c (2.5g, 6.39 mmol, 1eq), dichloromethane 20 ml, NaNO2 (0.061g, 0.89 mmol, 0.14 eq), HNO3 (1.20g, 19.19 mmol, 3eq Yield: 65%; 1H NMR (500 MHz, CDCl3): δ (ppm) = 7.89 (d, J = 8.50 Hz, 1H), 7.74 (s, 1H), 6.89 (d, J = 9.0 Hz, 1H) 4.09 (p, J = 6.50 Hz, 4H) 1.87 (bs, 4H), 1.50 – 1.48 (m, 4H), 1.38 – 1.29 (m, 25H), 0.90 (t, J = 6.50 Hz, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 154.72, 148.70, 141.21, 117.65, 111.10, 108.13, 69.50, 69.44, 31.90, 29.59, 29.57, 29.55, 29.54, 29.32, 28.96, 28.93, 25.95, 25.91, 22.67, 14.08;
Compound 2d: (25 g, 55.96 mmol, 1eq), dichloromethane 100 ml, NaNO2 (0.537g, 7.83 mmol, 0.14 eq), HNO3 (10.57g, 167.89 mmol, 3eq Yield: 56%; M.P. 39 ºC; 1H NMR (500 MHz, CDCl3): δ (ppm) = 7.89 (d, J = 8.50 Hz, 1H), 7.74 (s, 1H), 6.89 (d, J = 9.0 Hz, 1H) 4.09 (p, J = 6.50 Hz, 4H) 1.87 (bs, 4H), 1.50 – 1.48 (m, 4H), 1.38 – 1.28 (m, 32H), 0.90 (t, J = 6.50 Hz, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 154.72, 148.70, 141.22, 117.66, 111.10, 108.14, 69.51, 69.45, 31.92, 29.68, 29.65, 29.59, 29.35, 29.32, 28.96, 28.93, 25.95, 25.91, 22.68, 14.09;
Compound 2e: (7 g, 12.52 mmol, 1eq), dichloromethane 100 ml, NaNO2 (0.120g, 1.75 mmol, 0.14 eq), HNO3 (2..36g, 37.56 mmol, 3eq) Yield: 80%; 1H NMR (500 MHz, CDCl3): δ (ppm)
= 7.89 (d, J = 8.50 Hz, 1H), 7.74 (s, 1H), 6.89 (d, J = 9.0 Hz, 1H) 4.09 (p, J = 6.50 Hz, 4H)
Page | 173 1.87 (bs, 4H), 1.50 – 1.48 (m, 4H), 1.38 – 1.28 (m, 48H), 0.90 (t, J = 6.50 Hz, 6H): C NMR (125 MHz, CDCl3): δ ppm = 154.72, 148.70, 141.22, 117.65, 111.10, 108.14, 69.50, 69.44, 31.93, 29.71, 29.67, 29.60, 29.58, 29.36, 29.33, 28.97, 28.94, 25.96, 25.91, 22.69, 14.09;
General procedure for the synthesis of 3a, 3b, 3c, 3d, 3e.
In a round bottom flask, 2 (1 eq) was dissolved in dry THF, added 10% Pd-C (0.4eq) This mixture was stirred under hydrogen atmosphere (balloon) at room temperature for 24h. The reaction mixture was filtered through celite bed. THF was evaporated under reduced pressure the product was precipitated by using methanol.
Compound 3a: (4 g, 12.37 mmol, 1eq), dry THF 50 ml, Pd-C 10% (0.526g, 4.95 mmol, 0.4 eq), 89%;1H NMR (500 MHz, CDCl3): δ (ppm) = 6.75 (d, J = 8.00 Hz, 1H), 6.32 (s, 1H), 6.22 (d, J = 8.50 Hz, 1H) 3.93 (m, 4H), 3.28 (bs, 2H), 1.84 – 1.74 (m, 4H), 1.48 – 1.46 (m, 4H), 1.35 (m, 8H), 0.92 (bs, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 150.65, 141.95, 141.32, 117.41, 106.88, 102.71, 71.00, 68.97, 31.69, 31.62, 29.62, 29.33, 25.76, 22.64, 22.63, 14.03, 14.02;
Compound 3b: (9.07 g, 23.91 mmol, 1eq), dry THF 100 ml, Pd-C 10% (1.01g, 9.56 mmol, 0.4 eq), 80%;1H NMR (500 MHz, CDCl3): δ (ppm) = 6. 65 (d, J = 8.00 Hz, 1H), 6.23 (s, 1H), 6.13(d, J = 8.00 Hz, 1H) 3.84 (m, 4H), 2.85 (bs, 2H), 1.73 – 1.65 (m, 4H), 1.38 – 1.36 (m, 4H), 1.23 – 1.20 (m, 18H), 0.81 – 0.79 (m, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 150.65, 142.04, 141.16, 117.40, 106.93, 102.77, 71.01, 69.02, 31.84, 29.64, 29.45, 29.39, 29.35, 29.31, 29.29, 26.08, 22.67, 14.09;
Compound 3c: (2.12 g, 4.86 mmol, 1eq), dry THF 20 ml, Pd-C 10% (1.20g, 1.94 mmol, 0.4 eq), 80%; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6. 75 (d, J = 8.50 Hz, 1H), 6.32 (s, 1H), 6.23 (d, J = 8.50 Hz, 1H) 3.93 (m, 4H), 3.50 – 3.48 (bs, 2H), 1.83 – 1.75 (m, 4H), 1.47 – 1.44 (m, 4H), 1.29 (m, 26H), 0.91 – 0.89 (m, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 150.66, 142.05, 141.17, 117.42, 106.91, 102.76, 71.01, 69.01, 31.93, 29.65, 29.61, 29.50, 29.45, 29.36, 26.09, 22.69, 14.11;
Page | 174 Compound 3d: (6g, 12.20 mmol, 1eq), dry THF 20 ml, Pd-C 10% (0.51g, 4.800 mmol, 0.4 eq), 90%;1H NMR (500 MHz, CDCl3): δ (ppm) = 6. 75 (d, J = 8.00 Hz, 1H), 6.32 (s, 1H), 6.22 (d, J = 8.00 Hz, 1H) 3.96 – 3.90 (m, 4H), 3.45 (bs, 2H), 1.83 – 1.74 (m, 4H), 1.47 – 1.44 (m, 4H), 1.28 (m, 32H), 0.91 – 0.89 (m, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 150.66, 142.06, 141.17, 117.43, 106.90, 102.76, 71.02, 69.03, 31.93, 29.70, 29.66, 29.65, 29.50, 29.44, 29.36, 26.08, 22.69, 14.10;
Compound 3e: (1.50g, 2.49 mmol, 1eq), dry THF 20 ml, Pd-C 10% (0.10g, 0.99 mmol, 0.4 eq), 82%; 1H NMR (500 MHz, CDCl3): δ (ppm) = 6. 75 (d, J = 8.50 Hz, 1H), 6.32 (s, 1H), 6.22 (d, J = 8.50 Hz, 1H) 3.96 – 3.90 (m, 4H), 3.44 (bs, 2H), 1.82 – 1.73 (m, 4H), 1.47 – 1.44 (m, 4H), 1.28 (m, 52H), 0.91 – 0.89 (m, 6H): 13C NMR (125 MHz, CDCl3): δ ppm = 150.66, 142.06, 141.17, 117.42, 106.90, 102.77, 71.02, 69.03, 31.93, 29.72, 29.67, 29.65, 29.50, 29.44, 29.36, 26.08, 22.69, 14.10;
General procedure for the synthesis of 5a, 5b, 5c, 5d, 5e.
A solution of 4 (1eq) and 3 (3.5 eq) in dry toluene (40ml) was refluxed for 24h under nitrogen.
After 24h. The mixture was filtered to remove the suspended particles and the filtrate was concentrated under reduced pressure. The crude product was purified by column chromatography using petroleum ether: ethyl acetate (9:1) as eluent to get the desired product which was precipitated by using cold methanol and dried under the high vacuum.
Compound 5a: 4 (0.100g, 0.361mmol, 1eq), 3a (0.360g, 1.26mmol, 3.5eq), toluene 20ml, yield: 52%, 1H NMR (500 MHz, CDCl3): δ (ppm) = 8.11 – 8.0 (bd, 1H), 7.66 (bs 2H), 7.22 – 7.02 (m, 6H), 6.82 (s, 3H), 3.97 (bs, 12H), 1.80 (bs, 16H), 1.47 (bs, 12H), 1.35 (bs, 24H), 0.92 (bs, 18H); 13C NMR (125 MHz, CDCl3): δ ppm = 162.44, 162.34, 162.17, 156.14, 155.48, 154.81, 149.28, 148.96, 146.78, 146.68, 146.60, 130.56, 130.50, 130.44, 130.21, 115.70, 115.17, 114.68, 114.32, 114.18, 113.95, 110.05, 109.72, 108.74, 108.46, 69.66, 69.60, 69.52, 69.42, 69.32, 31.65, 31.63, 29.36, 29.29, 25.78, 25.72, 25.70, 22.62, 14.02; MALDI-TOF MS for C97H126 N10O2: 1047.44 (calcd.); 1046.95 (experiment).
Compound 5b: 4 (0.300g, 1.085mmol, 1eq), 3b (1.327g, 3.79mmol, 3.5eq), toluene 20ml, yield: 60%, 1H NMR (500 MHz, CDCl3): δ (ppm) = 7.98 – 7.89 (bd, 1H), 7.50 (bs 2H), 7.13 – 6.92 (m, 6H), 6.73 (s, 3H), 3.89 – 3.88 (m, 12H), 1.71 – 1.65 (m, 18H), 1.37 (bs, 12H), 1.21
Page | 175 (bs, 49H), 0.81 – 0.80 (m, 18H); C NMR (125 MHz, CDCl3): δ ppm162.50, 162.35, 162.22, 156.19, 155.62, 155.52, 154.87, 149.39, 149.31, 149.05, 146.86, 146.68, 130.40, 130.10, 115.70, 115.08, 114.82, 114.45, 114.27, 114.03, 109.98, 109.57, 108.86, 108.51, 69.75, 69.70, 69.60, 69.54, 69.44, 69.37, 31.86, 29.45, 29.42, 29.32, 26.13, 26.05, 22.68, 14.09; MALDI- TOF MS for C97H126 N10O2: 1215.77 (calcd.); 1215.42 (experiment).
Compound 5c: 4 (0.200g, 0.72mmol, 1e q), 3c (1.027g, 2.53mmol, 3.5eq), toluene 20ml, yield: 60%, 1H NMR (500 MHz, CDCl3): δ (ppm) = 8.03 – 7.92 (bd, 1H), 7.50 (bs 2H), 7.13 – 6.92 (m, 6H), 6.73 (s, 3H), 3.89 – 3.88 (m, 12H), 1.71 (bs, 16H), 1.37 (bs, 13H), 1.21 (bs, 78H), 0.81 – 0.80 (m, 18H); 13C NMR (125 MHz, CDCl3): δ ppm = 162.50, 162.34, 162.21, 156.18, 155.61, 155.51, 154.87, 149.38, 149.32, 149.01, 146.85, 146.70, 146.65, 130.46, 130.39, 130.14, 115.75, 115.08, 114.79, 114.46, 114.26, 114.15, 114.00, 110.09, 109.64, 108.83, 108.46, 69.75, 69.70, 69.61, 69.55, 69.44, 69.36, 31.94, 29.69, 29.66, 29.62, 29.54, 29.49, 29.38, 26.15, 26.11, 26.07, 22.69, 14.10; MALDI-TOF MS for C97H126 N10O2: 1384.09 (calcd.); 1385.27 (experiment).
Compound 5d: 4 (0.200g, 0.72mmol, 1eq), 3d (1.168g, 2.53mmol, 3.5eq), toluene 20ml, yield: 521H NMR (500 MHz, CDCl3): δ (ppm) = 7.77 – 7.65 (m, 3H), 7.11 – 7.05 (m, 4H), 6.97 – 6.95 (m, 2H), 6.77 – 6.73 (m, 3H), 3.92 – 3.88 (m, 12H), 1.73 – 1.72 (m, 12H), 1.51 (bs, 8H), 1.38 (bs, 12H), 1.19 (m, 102H) 0.80 – 0.79 (m, 18H); 13C NMR (125 MHz, CDCl3): δ ppm = 162.29, 162.14, 156.08, 155.50, 154.91, 149.45, 149.34, 149.15, 146.84, 130.47, 130.22, 115.28, 114.60, 114.50, 114.31, 114.15, 108.73, 108.49, 69.78, 69.52,69.41, 31.94, 29.69, 29.53, 29.38, 26.14, 26.07, 22.69, 14.10 ; MALDI-TOF MS for C97H126 N10O2: 1552. 42 (calcd.); 1552.57 (experiment).
Compound 5e: 4 (0.300g, 1.085mmol, 1eq), 3f (2.058g, 3.79mmol, 3.5eq), toluene 20ml, yield: 70%, 1H NMR (500 MHz, CDCl3): δ (ppm) = 7.87 – 7.81 (bd, 1H), 7.44 (bs, 2H), 7.10 – 6.91 (m, 6H), 6.75 – 6.73 (m, 3H), 3.89 – 3.88 (m, 12H), 1.71 – 1.64 (m, 12H), 1.51 (bs, 14H), 1.18 (bs, 163H), 0.80 (bs, 18H); 13C NMR (125 MHz, CDCl3): δ ppm = 162.52, 156.26, 155.69, 149.45, 149.36, 149.20, 146.96, 146.74, 130.04, 114.90, 114.53, 114.31, 114.18, 109.35, 108.93, 108.5269.78, 69.46, 31.93, 29.74, 29.68, 29.54, 29.51, 29.37, 26.10, 26.07, 22.69, 14.10; MALDI-TOF MS for C97H126N10O2: 1889.06 (calcd.); 1888.96 (experiment).
Page | 176 4.6 NMR Spectra:
Figure 4.22: 1H (top) and 13C-NMR (bottom) spectra of 1a
Page | 177 Figure 4.23: 1H (top) and 13C-NMR (bottom) spectra of 2a
Page | 178 Figure 4.24: 1H (top) and 13C-NMR (bottom) spectra of 3a
Page | 179 Figure 4.25: 1H (top) and 13C-NMR (bottom) spectra of 5a