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In 5,5-dimethyl-1,3-cyclohexadiene; for 96h;Inert atmosphere; Schlenk technique; Heating; |
Compound 3. A flame-dried 25 mL pressure tube was charged with 2 (640 mg, 1.0 mmol), S4 (2.0 g, 3.0 mmol), and xylenes (6 mL). The reaction mixture was degassed by bubbling argon through for 20 minutes while stirring. The reaction vessel was then placed in an oil bath at 80° C. After stirring for 20 minutes, the reaction mixture was homogenized with a high-sheer mixer for 20 seconds. The reaction vessel was then sealed and heated to 135° C. The color of the reaction changed gradually from deep blue to yellow over 4 days, at which point the reaction was allowed to cool to room temperature. Solvent and excess S4 was removed via distillation. The crude product was recrystallized in dichloromethane to give the anti isomer (217 mg, 11percent). The mother liquor was concentrated and was purified by column chromatography (silica gel, 100percent hexanes) to give the syn isomer, which was further purified by recrystallization in acetone to give 3 (1.14 g, 58percent) as rod-like crystals. Anti: M.p.>300° C. 1H NMR (300 MHz, CDCl3): delta 1.28 (s, 42H), 5.97 (s, 4H), 7.11 (dd, J=5.4 and 3.3 Hz, 4H), 7.36 (dd. J=5.4 and 3.3 Hz, 4H). 19F NMR (282 MHz, CDCl3): delta -126.73 (4F), -123.41 (4F), -122.33 (4F), -119.58 (4F), -109.62 (4F), -81.33 (6F). HR-MS (EI): calcd for C76H38F52Si2 1994.1676. found 1994.1624. Syn (3): M.p.>300° C. 1H NMR (300 MHz, CDCl3): delta 1.28 (s, 42H), 5.97 (s, 4H), 7.03 (dd, J=5.4 and 3.3 Hz, 4H), 7.27 (dd. J=5.4 and 3.3 Hz, 4H). 19F NMR (282 MHz, CDCl3): delta -126.77 (4F), -123.47 (4F), -122.50 (4F), -119.83 (4F), -109.50 (2F), -108.30 (2F), -81.47 (6F). HR-MS (EI): calcd for C76H38F52Si2 1994.1676. found 1994.1624. |