Cl[C:2]1([CH:10]=[N:11][OH:12])[CH:7]=[CH:6][CH:5]=[C:4]([O:8][CH3:9])[CH2:3]1.[CH2:13]([O:15][C:16]([CH:18]1[CH2:23][CH2:22][C:21](=[CH2:24])[CH2:20][CH2:19]1)=[O:17])[CH3:14].C(N(CC)CC)C>C(Cl)Cl.O>[CH2:13]([O:15][C:16]([CH:18]1[CH2:19][CH2:20][C:21]2([O:12][N:11]=[C:10]([C:2]3[CH:7]=[CH:6][CH:5]=[C:4]([O:8][CH3:9])[CH:3]=3)[CH2:24]2)[CH2:22][CH2:23]1)=[O:17])[CH3:14]A solution of 1-chloro-1-hydroxyiminomethyl-3-methoxybenzene (31 g, 167 mmol) in DCM (50 ml) was slowly added dropwise to a solution of 4-methylenecyclohexanecarboxylic acid ethyl ester (28 g, 167 mmol) in DCM (950 ml) at 0° C. Subsequently, a solution of triethylamine (50 ml) in DCM (50 ml) was slowly added dropwise at 0° C. and the resulting mixture was stirred overnight at RT. The reaction mixture was diluted with water (500 ml). The combined organic phases were washed with 10% aq. citric acid solution (800 ml) and sat. aq. NaCl solution (500 ml), dried over sodium sulphate and the solvent was removed under vacuum. The desired product 3-(3-methoxyphenyl)-1-oxa-2-azaspiro[4.5]dec-2-ene-8-carboxylic acid ethyl ester (51 g) was reacted without further purification.
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