Iodine → 2-Tert-butyl-3-bromo-4-iodo-6-trimethylsilylpyridine

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Reaction Conditions

Reaction Steps

Procedure analogous to P. N. W. Baxter, Chem. Eur. J. 2003, 9, 2531: 65.6 ml (105 mmol) of n-BuLi, 1.6 M in hexane, are added dropwise over the course of 15 min. to a vigorously stirred mixture, cooled to −78° C., of 14.0 ml (100 mmol) of diisopropylamine and 500 ml of THF. The reaction mixture is stirred at −78° C. for 45 min. and then cooled to −90° C. A solution, pre-cooled to −90° C., of 30.1 g (105 mmol) of 2-tert-butyl-3-bromo-6-trimethylsilylpyridine in 100 ml of THF is added dropwise at such a rate that the temperature does not exceed −80° C. After stirring at −90° C. for a further 1 h, the reaction mixture is warmed to −75° C., stirred at −75° C. for a further 15 min. and then re-cooled to −90° C. A solution of 30.5 g (120 mmol) of iodine in 80 ml of THF is then added dropwise at such a rate that the temperature does not exceed −75° C., the reaction mixture is stirred at −75° C. for a further 4 h and allowed to warm to room temperature. After addition of 10 ml of water and removal of the THF in vacuo, 1000 ml of tert-butyl methyl ether are added, and 100 ml of saturated sodium sulfite solution are added dropwise to the mixture in order to reduce excess iodine. The org. phase is separated off, washed three times with 300 ml of water each time, dried over sodium sulfate, the solvent is removed in vacuo, and the residue is recrystallised once from cyclohexane. Yield: 14.8 g (36 mmol), 34%. Purity: >95% according to 1H-NMR.

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