C([Li])CCC.CN(C)CCNC.[CH3:13][O:14][C:15]1[N:20]=[CH:19][C:18]([CH:21]=[O:22])=[CH:17][CH:16]=1.[I:23]I.[Cl-].[Na+]>C1COCC1>[I:23][C:17]1[CH:16]=[C:15]([O:14][CH3:13])[N:20]=[CH:19][C:18]=1[CH:21]=[O:22]At −78° C., 25.1 ml (40.1 mmol, 1.1 eq.) of n-butyllithium were added to a solution of 5.7 ml (43.8 mmol, 1.2 eq.) of N,N,N′-trimethylethylenediamine in 135 ml of THF, the mixture was stirred for 45 min and 5.0 g (36.5 mmol) of 6-methoxypyridine-3-carbaldehyde were added. After 45 min at −78° C., a further 45.6 ml (72.9 mmol, 2.0 eq.) of n-butyllithium were added, the reaction mixture was stirred for 1 h, allowing the temperature to rise to −40° C., the mixture was stirred at −40° C. for a further 1 h and then cooled back to −78° C., and a solution of 18.5 g (72.9 mmol) of iodine in 90 ml of THF was added over a period of 50 min. The temperature was maintained at −78° C. for a further 4 h and then slowly allowed to rise to RT overnight. The reaction mixture was poured into 300 ml of saturated aqueous sodium chloride solution and, after phase separation, the aqueous phase was extracted twice with ethyl acetate. The combined organic phases were dried (sodium sulphate), filtered and concentrated under reduced pressure. The residue was stirred with acetonitrile and filtered off, and the precipitate was dried under HV. Yield: 647 mg (purity 91%, 6% of theory)
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