Synlett 2003(15): 2329-2332  
DOI: 10.1055/s-2003-42119
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of Donor-Acceptor Substituted Molecular Caltrops: Strategic Use of an AB3 Synthon Based on a Tetraphenylmethane Core

Saumitra Sengupta*, Subir Kumar Sadhukhan, Sanjukta Muhuri
Department of Chemistry, Jadavpur University, Kolkata 700 032, India
Fax: +91(33)24146266; e-Mail: jusaumitra@yahoo.co.uk;
Further Information

Publication History

Received 29 July 2003
Publication Date:
21 November 2003 (online)

Abstract

Using a tetraphenylmethane based AB3 tecton, a facile synthetic route to donor-acceptor substituted unsymmetrical mole­cular caltrops is described. The former compound was readily prepared in two steps from the cheap commercial dye New Fuchsin.

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Compound 5: mp 206-207 °C (MeOH). IR (KBr): 3400, 1605, 1500, 1460, 1370 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 2.33 (s, 9 H), 6.65 (dd, J = 8.4, 2.1 Hz, 3 H), 6.70 (d, J = 6.6 Hz, 2 H), 6.99 (d, J = 6.6 Hz, 2 H), 7.02 (d, J = 2.1 Hz, 3 H), 7.65 (d, J = 8.4 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 28.2, 63.3, 98.7, 114.5, 130.1, 131.9, 138.0, 140.5, 146.5, 153.6.

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Representative Procedure for Three-fold Sonogashira Couplings on 5: PdCl2(PPh3)2 (5 mg) was added to a degassed solution of 5 (0.10 g, 0.13 mmol), phenyl acetylene (0.08 g, 0.8 mmol) and CuI (4 mg) in a mixture of DMF (3 mL) and Et3N (2 mL). The reaction mixture was stirred at r.t. for 16 h. It was then concentratedd under reduced pressure, diluted with water and extracted with CH2Cl2. The organic layer was dried and the solvent removed under reduced pressure. The residue was purified by silica gel chromatography (10% EtOAc in light petroleum) to give 6 (0.057 g, 66%) as a white solid; mp 126-127 °C (CHCl3-MeOH). IR (KBr): 3410, 1600, 1520, 1465, 1360 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 2.43 (s, 9 H), 6.73 (d, J = 8.6 Hz, 2 H), 6.90-7.16 (m, 8 H), 7.29-7.48 (m, 12 H), 7.49-7.62 (m, 6 H). 13C NMR (75 MHz, CDCl3): δ = 21.0, 64.5, 88.5, 93.8, 114.5, 121.2, 123.9, 125.6, 128.3, 128.7, 128.9, 130.1, 131.9, 132.2, 138.0, 139.5, 147.0, 156.5. 8: mp 105-106 °C (MeOH). IR (KBr): 3290, 3000, 2910, 2090, 1595, 1480 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 2.35 (s, 9 H), 3.26 (s, 3 H), 6.71 (d, J = 8.7 Hz, 2 H), 6.93 (d, J = 8 Hz, 3 H), 7.00 (d, J = 8.7 Hz, 2 H), 7.01 (s, 3 H), 7.33 (d, J = 8 Hz, 3 H). 13C NMR (75 MHz, CDCl3): δ = 20.9, 64.0, 80.9, 82.3, 114.5, 119.6, 128.3, 131.7, 132.1, 138.0, 139.9, 147.0, 153.7.

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Compound 9: mp 130-132 °C (MeOH). IR (KBr): 2916, 1596, 1521, 1500, 1442, 1344 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 2.36 (s, 9 H), 5.08 (s, 2 H), 6.78 (d, J = 9 Hz, 2 H), 6.92 (dd, J = 8.1, 2 Hz, 3 H), 7.01 (d, J = 2 Hz, 3 H), 7.06 (d, J = 9 Hz, 2 H), 7.25-7.33 (m, 11 H), 7.42-7.46 (m, 6 H), 7.54 (d, J = 8.1 Hz, 3 H), 8.18 (d, J = 9 Hz, 2 H). 13C NMR (75 MHz, CDCl3): δ = 21.4, 64.5, 69.1, 88.5, 93.8, 114.2, 121.2, 123.9, 124.2, 128.0, 128.5, 128.7, 128.9, 131.3, 131.4, 131.9, 132.2, 132.6, 139.5, 139.8, 144.8, 147.0, 156.7.
Compound 10: mp 132-135 °C (MeOH). IR (KBr): 2900, 2100, 1590, 1518, 1487, 1350 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 2.36 (s, 9 H), 3.24 (s, 3 H), 5.09 (s, 2 H), 6.73 (d, J = 9 Hz, 2 H), 6.91 (dd, J = 8, 1.8 Hz, 3 H), 7.00 (d, J = 1.8 Hz, 3 H), 7.06 (d, J = 9 Hz, 2 H), 7.30-7.36 (m, 5 H), 8.08 (d, J = 8.7 Hz, 2 H). Compound 13: mp 203-205 °C. IR (KBr): 2902, 1604, 1521, 1508, 1456, 1344, 1242 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 1.33 (s, 27 H), 2.36 (s, 9 H), 5.16 (s, 2 H), 6.87 (d, J = 9 Hz, 2 H), 7.00 (d, J = 16.2 Hz, 3 H), 7.05-7.12 (m, 6 H), 7.24 (d, J = 9 Hz, 2 H), 7.28 (d, J = 16.2 Hz, 3 H), 7.35-7.53 (m, 14 H), 7.62 (d, J = 9 Hz, 3 H), 8.25 (d, J = 9 Hz, 2 H). 13C NMR (75 MHz, CDCl3): δ = 20.7, 31.7, 35.0, 64.1, 69.0, 114.0, 124.2, 124.4, 124.8, 125.8, 126.0, 126.6, 128.0, 129.5, 129.9, 130.3, 132.6, 133.1, 134.4, 135.1, 135.4, 140.5, 145.0, 146.4, 156.5.

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Compound 11: mp 201-202 °C. IR (KBr): 3290, 1595, 1500, 1445, 1260 cm-1. 1H NMR (300 MHz, CDCl3/TMS): δ = 2.35 (s, 9 H), 6.73 (d, J = 8.7 Hz, 2 H), 7.00 (d, J = 16.2 Hz, 3 H), 7.05-7.11 (m, 6 H), 7.14 (d, J = 8.7 Hz, 2 H), 7.20-7.31 (m, 6 H), 7.34 (d, J = 5.4 Hz, 3 H), 7.35 (d, J = 16.2 Hz, 3 H), 7.45-7.54 (m, 9 H). 13C NMR (75 MHz, CDCl3): δ = 20.2, 63.7, 114.3, 124.4, 126.1, 126.5, 127.4, 128.6, 129.1, 129.7, 132.2, 132.7, 133.7, 134.7, 137.8, 139.2, 146.3, 153.4. Compound 12: mp 220-224 °C (CHCl3-MeOH). IR (KBr): 3300, 1600, 1510, 1440, 1280 cm-1. 1H NMR (300 MHz, CDCl3): δ = 1.33 (s, 27 H), 2.34 (s, 9 H), 4.67 (br s, 1 H), 6.72 (d, J = 8.5 Hz, 2 H), 6.98 (d, J = 16 Hz, 3 H), 7.04-7.11 (m, 6 H), 7.14 (d, J = 8.3 Hz, 2 H), 7.26 (d, J = 16 Hz, 3 H), 7.37 (d, J = 8.2 Hz, 6 H), 7.45 (d, J = 8.8 Hz, 6 H), 7.48 (d, J = 9.2 Hz, 3 H).