Chromatographic analysis was performed on a Shimadzu GC-9A instrument using a 2000×2 mm column, the SE-30 (5 %) stationary phase on Сhromaton N-AW-HMDS (0.125-0.160 mm), helium carrier gas (30 mL/min), temperature programming from 50 to 300 Propane-1,1-diyldibenzene (2a); Typical Procedure. In a 50-mL reaction flask, TaCl 5 (179 mg, 0.5 mmol) was placed under an argon atmosphere. To the salt, benzene (10 mL) was added at room temperature. Magnesium powder (60 mg, 2.5 mmol) was added to the stirring pale yellow solution of TaCl 5 and the resulting mixture was stirred at room temperature for 30 min. To the mixture, propionaldehyde (58 mg, 1.0 mmol) was added at room temperature and the whole mixture was stirred at 40 °C for 0.5 h. After 0.5 h at 40 o C, the reaction mixture was cooled to room temperature and diluted with petroleum ether (20 mL). Then H 2 O (15 mL) was added dropwise while the reaction flask was cooled in an ice bath. The organic layer separated, and the aqueous layer extracted with ethyl acetate (3 x 15 mL). The combined organics were dried over MgSO 4 . The reaction mixture was filtered through a filter paper and concentrated in vacuo to give crude product as a yellow oil. The residue was distilled through a micro column at 4 mmHg to give 2a (176 mg, 90%) as a colourless oil. b.p. (E)-2-Hexyldec-2-enal (3). In a 50-mL reaction flask, FeCl 3 (81 mg, 0,5 mmol) was placed under an argon atmosphere. To the salt, benzene (10 mL) was added at room temperature and the resulting mixture was stirred at room temperature for 10 min. To the mixture, octanal (128 mg, 1 mmol) was added at room temperature and the whole mixture was stirred at 21 °C 18 h. After 18 h at 21 o C, the reaction mixture was diluted with petroleum ether (20 mL), and H 2 O (15 mL) was added dropwise while the reaction flask was cooled in an ice bath. The organic layer separated, and the aqueous layer extracted with ethyl acetate (3 x 15 mL). The combined organics were dried over MgSO 4 . The reaction mixture was filtered through a filter paper and concentrated in vacuo to give crude product that was purified by column chromatography (petroleum ether : ethyl acetate = 6 : 1) to afford 7 (157 mg, 66%) as colorless oil. 1 H NMR (500 MHz, CDCl 3 ): δ= 0.88 -0.95 (q, J = 7.3 Hz, 6H, C(10,16)H), 1.28 -1.35 (m, 16 H, C(6,7,8,9,12,13,14,15)H 2 ), 1.49 -1.55 (m, 2H, C(5)H 2 ), 2.25 (t, J =7.1 Hz, 2H, C(11)H 2 ), 2.35 -2.39 (q, J = 7.5 Hz, 2H, C(4)H 2 ), 6.46 (t, J =7.5 Hz, 1H, C(3)H), 9.38 (s, 1H, C(1)H); Triphenylmethane . In a 50-mL reaction flask, TaCl 5 (2148 mg, 6 mmol) was placed under an argon atmosphere. To the salt, benzene (10 mL) was added at room temperature. Magnesium powder (432 mg, 18 mmol) was added to the stirring pale yellow solution of TaCl 5 and the resulting mixture was stirred at room temperature for 30 min. To the mixture, 4-methoxybenzaldehyde (243 mg, 2.0 mmol) was added at room temperature and the whole mixture was stirred at 80 °C 6 h. After 6 h at 80 o C, the reaction mixture was cooled to room temperature and diluted with petroleum ether . Then H 2 O (15 mL) was added dropwise while the reaction flask was cooled in an ice bath. The organic layer separated, and the aqueous layer extracted with ethyl acetate (3 x 15 mL). The combined organics were dried over MgSO 4 . The reaction mixture was filtered through a filter paper and concentrated in vacuo to give crude product that was purified by column chromatography (hexane : ethyl acetate = 6 : 1) to afford 4 (434 mg, 89%) as colorless solid: mp, 91-93 4,4'-Bipyridine . In a 50-mL reaction flask, TaCl 5 (716 mg, 2 mmol) was placed under an argon atmosphere. To the salt, pyridine (5 mL) was added at room temperature. Magnesium powder (144 mg, 6 mmol) was added to the stirring pale yellow solution of TaCl 5 and the resulting mixture was stirred at room temperature for 30 min. To the mixture, heptanal (70 mg, 0.5 mmol) was added at room temperature and the whole mixture was stirred at 115 °C for 2 h. After 2 h at 115 o C, the reaction mixture was cooled to room temperature and diluted with petroleum ether (20 mL). Then H 2 O (15 mL) was added dropwise while the reaction flask was cooled in an ice bath. The organic layer separated, and the aqueous layer extracted with ethyl acetate (3 x 15 mL). The combined organics were dried over MgSO 4 . The reaction mixture was filtered through a filter paper and concentrated in vacuo to give crude product that was purified by column chromatography (petroleum ether : ethyl acetate , 128 , 116 , 103 , 102 , 76 , 75 , 63 , 51 (30).