[Cl:1][C:2]1[CH:7]=[C:6]([CH:8]=[CH2:9])[N:5]=[C:4]([CH3:10])[N:3]=1.[N+](=[CH:13][C:14]([O:16][CH2:17][CH3:18])=[O:15])=[N-]>C1(C)C=CC=CC=1>[Cl:1][C:2]1[N:3]=[C:4]([CH3:10])[N:5]=[C:6]([CH:8]2[CH2:9][CH:13]2[C:14]([O:16][CH2:17][CH3:18])=[O:15])[CH:7]=1To a solution of 6-2 (15.0 g, 97 mmol) in toluene (300 mL) heating at 100° C. under a nitrogen atmosphere was added a solution of ethyl diazoacetate (30.2 mL, 291 mmol) in toluene (100 mL) over 1.5 h. Heating was continued for 2 h after which the reaction mixture was cooled to room temperature and concentrated to dryness. The residue was partitioned between saturated sodium bicarbonate solution (1 L) and ethyl acetate (1 L). The organic layer was separated, dried over sodium sulfate, filtered and concentrated under reduced pressure. The crude residue was purified by silica gel chromatography (0-100% EtOAc/hexanes) to give 6-3 (trans isomer) as a colorless oil. MS: m/z=241.1 (M+H).
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