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General procedure: Titanium tetrachloride (1.90 g, 10 mmol) was slowly added to100 mL of anhydrous THF at 0 C, followed by addition of 5 mmol of the aldehyde (1) and stirred for 10 min, then ethyl 2-(3-bromopyridin-2-yl)acetate (2) (1.47 g, 6 mmol) was added. Subsequently, a solution of pyridine (3.16 g, 40 mmol) in 25 mL of anhydrous THF was added dropwise during a period of 30-60 min at 0 C. The reaction mixture was then stirred for 1 h at room temperature and refluxed for 24 h. After that the mixture was poured on to crashed ice and extracted with ethyl acetate (4 30 mL). The combined extracts were successively washed with brine, saturated sodium hydrogen carbonate and brine, and then dried over anhydrous MgSO4. The organic phase was filtrated and the solvent was removed in vacuo, the residue was purified by column chromatography (silica gel) using PE/EA (5:1) / DCM/MeOH (50:1) to provide 3.
General procedure: Titanium tetrachloride (1.90 g, 10 mmol) was slowly added to100 mL of anhydrous THF at 0 C, followed by addition of 5 mmol of the aldehyde (1) and stirred for 10 min, then ethyl 2-(3-bromopyridin-2-yl)acetate (2) (1.47 g, 6 mmol) was added. Subsequently, a solution of pyridine (3.16 g, 40 mmol) in 25 mL of anhydrous THF was added dropwise during a period of 30-60 min at 0 C. The reaction mixture was then stirred for 1 h at room temperature and refluxed for 24 h. After that the mixture was poured on to crashed ice and extracted with ethyl acetate (4 30 mL). The combined extracts were successively washed with brine, saturated sodium hydrogen carbonate and brine, and then dried over anhydrous MgSO4. The organic phase was filtrated and the solvent was removed in vacuo, the residue was purified by column chromatography (silica gel) using PE/EA (5:1) / DCM/MeOH (50:1) to provide 3.