A cooled (−78° C.) yellow solution of commercially available 3-bromo-2,4-dimethoxypyridine (1.490 g; 6.83 mmol) in anh. THF (42 ml), under nitrogen, was treated dropwise with a solution of 1.6 M n-BuLi in hexanes (4.3 ml; 6.88 mmol). The resulting orange solution was further stirred at −78° C. for 10 min. A yellow solution of methyl 5-((tert-butylsulfinyl)imino)pentanoate (1.450 g; 6.21 mmol) in anh. THF (5 ml) was then added to the cooled reaction mixture, and stirring at −78° C. was continued for 65 min. The resulting orange reaction mixture was treated successively with aq. sat. NH4Cl (22 ml), Et2O (75 ml) and water (20 ml). The separated orange organic layer was then washed with brine (30 ml), dried over anh. MgSO4, filtered, and concentrated to dryness under reduced pressure. Purification by FC (DCM/MeOH=30/1) afforded methyl 5-(2,4-dimethoxypyridin-3-yl)-5-(1,1-dimethylethylsulfinamido)pentanoate as a yellow oil. LC-MS (conditions B): tR=0.75 min.; [M+H]+: 372.82 g/mol.
