[C:1]([O:5]/[CH:6]=[CH:7]\[C:8]1[CH:13]=[CH:12][C:11]([CH3:14])=[CH:10][N:9]=1)([CH3:4])([CH3:3])[CH3:2].[N+](=[CH:17][C:18]([O:20][CH2:21][CH3:22])=[O:19])=[N-]>C1(C)C=CC=CC=1.S([O-])([O-])(=O)=O.[Cu+2]>[C:1]([O:5][CH:6]1[CH:7]([C:8]2[CH:13]=[CH:12][C:11]([CH3:14])=[CH:10][N:9]=2)[CH:17]1[C:18]([O:20][CH2:21][CH3:22])=[O:19])([CH3:4])([CH3:3])[CH3:2]The solution of (Z)-2-(2-tert-butoxyvinyl)-5-methylpyridine (12-3) (1.20 g, 6.27 mmol) in toluene (20 mL) and anhydrous copper sulfate (100 mg, 0.63 mmol) was heated to 75° C. Then the solution of ethyl diazoacetate (2.17 g, 18.8 mmol) in toluene (10 mL) was added dropwise over 2 h. It was heated for another 2 h after the addition was completed. The mixture was restored to room temperature for overnight. The solvent was removed under reduced pressure and the residue was purified by silca gel chromatography with gradient eluent (PE/EA=40/1; 20/1; 10/1). The product was obtained as a yellow oil (500 mg, 34%). LRMS (ES) calculated M+H for C16H24NO3: 278.3. Found: 278.2.
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