2.2. Synthesis of Oxetane Derivatives

3,3-Di[3-iodocarbazol-9-ylmethyl]oxetane (3) was synthesized and characterized according to the procedure described in the literature [15].

3,3-Di[3-(1-naphthyl)carbazol-9-ylmethyl]oxetane (4). 0.4 g (0.6 mmol) of 3,3-di[3-iodocarbazol-9-yl]methyloxetane (3), 0.26 g (1.5 mmol) of naphthalene-1-boronic acid, 0.02 g (0.03 mmol) of PdCl₂(PPh₃)₂ and 0.17 g (3.0 mmol) of powdered KOH were stirred in 8 mL of THF containing degassed water (1 mL) at 80 °C under nitrogen for 1.5 h. After TLC control the reaction mixture was cooled and quenched by the addition of ice water. The product was extracted with chloroform. The combined extract was dried over anhydrous Na₂SO₄. The crude product was purified by silica gel column chromatography using the mixture of ethyl acetate and hexane (vol. ratio 1:7) as an eluent. Yield: 0.3 g of white crystals (75%). DSC: T_m = 250 °C. MS (APCI⁺, 20 V): 669.49 ([M+H], 100%). ¹H NMR (400 MHz, CDCl₃, δ:ppm): 8.21–8.04 (m, 4H, Ar), 7.93–7.79 (m, 6H, Ar), 7.56–7.28 (m, 16H, Ar), 7.26–7.20 (m, 2H, Ar), 4.75 (s, 4H, 2×OCH₂), 4.72 (s, 4H, 2×NCH₂). ¹³C NMR (100 MHz, CDCl₃, δ:ppm): 141.90, 140.85, 140.65, 133.90, 132.52, 132.15, 128.38, 128.30, 127.41, 126.38, 126.28, 126.04, 125.76, 125.45, 123.46, 123.41, 122.09, 120.79, 119.98, 108.876, 108.44, 76.12, 50.79, 47.64. FT-IR (KBr), cm⁻¹: 3051, 2954, 2923, 2853, 1941, 1733, 1623, 1600, 1572, 1535, 1490, 1465, 1394, 1330, 1290, 1264, 1226, 1156, 986, 968, 800, 776, 745.

3,3-Di[3-(9-ethylcarbazol-3-yl)carbazol-9-ylmethyl]oxetane (5). 0.4 g (0.6 mmol) of 3,3-di[3-iodocarbazol-9-yl]methyloxetane (3), 0.48 g (1.5 mmol) of 9-ethyl-9H-carbazole-3-boronic acid pinacol ester, 0.02 g (0.03 mmol) of PdCl₂(PPh₃)₂ and 0.17 g (3.0 mmol) of powdered KOH were stirred in 8 mL of THF containing degassed water (1 mL) at 80 °C under nitrogen for 2 h. After TLC control the reaction mixture was cooled and quenched by the addition of ice water. The product was extracted with chloroform. The combined extract was dried over anhydrous Na₂SO₄. The crude product was purified by silica gel column chromatography using the mixture of ethyl acetate and hexane (vol. ratio 1:5) as an eluent. Yield: 0.25 g of white amorphous product (52%). MS (APCI⁺, 20 V): 803.58 ([M+H], 100%). ¹H NMR (400 MHz, CDCl₃, δ:ppm): 8.31–8.09 (m, 6H, Ar), 7.47–7.34 (m, 10H, Ar), 7.31–7.12 (m, 10H, Ar), 4.65 (s, 4H, 2×OCH₂), 4.64 (s, 4H, 2×NCH₂), 4.37–4.26 (m, 4H, 2×NCH₂CH₃), 1.38 (t, 6H, J = 6.8 Hz, 2×CH₃). ¹³C NMR (100 MHz, CDCl₃, δ:ppm): 141.90, 140.50, 140.44, 139.16, 134.44, 132.97, 126.24, 126.04, 125.78, 125.53, 123.95, 123.59, 123.57, 123.15, 120.77, 120.57, 119.80, 119.20, 119.09, 118.87, 108.99, 108.86, 108.73, 108.60, 76.07, 50.825, 47.52, 37.68, 13.90. FT-IR (KBr), cm⁻¹: 3048, 2967, 2928, 2870, 1877, 1731, 1627, 1600, 1472, 1456, 1380, 1330, 1231, 1154, 1124, 1088, 1065, 1024, 969, 878, 798, 781, 745, 727.

3,3-Di[3-(4-(diphenylamino)phenyl)carbazol-9-ylmethyl]oxetane (6). 0.4 g (0.6 mmol) of 3,3-di[3-iodocarbazol-9-yl]methyloxetane (3), 0.43 g (1.5 mmol) of 4-(diphenylamino)phenylboronic acid, 0.02 g (0.03 mmol) of PdCl₂(PPh₃)₂ and 0.17 g (3.0 mmol) of powdered KOH were stirred in 8 mL of THF containing degassed water (1 mL) at 80 °C under nitrogen for 1.5 h. After TLC control the reaction mixture was cooled and quenched by the addition of ice water. The product was extracted with chloroform. The combined extract was dried over anhydrous Na₂SO₄. The crude product was purified by silica gel column chromatography using the mixture of ethyl acetate and hexane (vol. ratio 1:7) as an eluent. Yield: 0.3 g of white amorphous product (56%). MS (APCI⁺, 20 V): 903.56 ([M+H], 100%). ¹H NMR (400 MHz, CDCl₃, δ:ppm): 8.24–8.06 (m, 6H, Ar), 7.63–7.55 (m, 2H, Ar), 7.51–7.33 (m, 7H, Ar), 7.29–7.19 (m, 12H, Ar), 7.14–7.03 (m, 12H, Ar), 6.99–6.90 (m, 5H, Ar), 4.65 (s, 4H, 2×OCH₂), 4.61 (s, 4H, 2×NCH₂). ¹³C NMR (100 MHz, CDCl₃, δ:ppm): 147.82, 146.65, 141.86, 140.66, 135.95, 132.89, 129.30, 127.95, 126.32, 125.33, 124.41, 124.28, 123.87, 123.48, 122.807, 120.71, 119.90, 118.66, 108.96, 108.85, 75.99, 50.77, 47.49. FT-IR (KBr), cm⁻¹: 3055, 3031, 2954, 2923, 2866, 1965, 1625, 1589, 1515, 1488, 1451, 1384, 1331, 1275, 1230, 1178, 1155, 1073, 1028, 969, 889, 803, 748, 696.