[C:1](Cl)(Cl)=[O:2].[NH2:5][C:6]1[CH:11]=[CH:10][CH:9]=[C:8]([CH3:12])[N:7]=1.C(N(CC)C(C)C)(C)C.[C:22]([OH:26])([CH3:25])([CH3:24])[CH3:23].[OH-].[Na+]>O.C(OCC)(=O)C>[C:22]([O:26][C:1](=[O:2])[NH:5][C:6]1[CH:11]=[CH:10][CH:9]=[C:8]([CH3:12])[N:7]=1)([CH3:25])([CH3:24])[CH3:23]462 ml of ethyl acetate were added to a reaction system and cooled to −15° C. followed by blowing in 114.4 g (1.16 moles) of phosgene over the course of 1.8 hours. A mixed solution containing 50.2 g (0.462 moles) a of 2-amino-6-picoline, 131.8 g (1.02 moles) of N,N-diisopropylethylamine, 85.7 g (1.16 moles) of t-butanol and 231 mL of ethyl acetate was then dropped into this phosgene solution over the course of 2.8 hours while holding the internal temperature at −15° C. to 0° C. Following completion of dropping, the solution was stirred for 1.7 hours. Next, 300 mL of water and 200 mL of 28% sodium hydroxide were sequentially added while holding the internal temperature at 0° C. or lower. The aqueous phase was extracted with 300 mL of ethyl acetate. The organic phases were combined and mixed and then concentrated under reduced pressure. A mixed solution of methanol and water was added to the resulting crude product. The precipitated crystals were then subjected to suction filtration and dried under reduced pressure to obtain 93.4 g of the target (6-methyl-pyridin-2-yl)-carbamic acid tert-butyl ester (yield: 94%). The yield of 1,3-bis-(6-methyl-pyridin-2-yl)-urea (urea compound) was 3%.
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