[CH2:1]([C:3]1[CH:8]=[CH:7][CH:6]=[CH:5][C:4]=1[CH2:9][CH2:10][C:11](Cl)=[O:12])[CH3:2].[N+:14](=[CH2:16])=[N-:15]>C(Cl)Cl.CCOCC>[N+:14](=[CH:16][C:11](=[O:12])[CH2:10][CH2:9][C:4]1[CH:5]=[CH:6][CH:7]=[CH:8][C:3]=1[CH2:1][CH3:2])=[N-:15]A solution of 3-(2-ethylphenyl)propanoyl chloride (crude, 23.8 mmole) in methylene chloride was slowly added to a solution of diazomethane (generated from 15.6 g of 1-methyl-3-nitro-1-nitrosoguanidine) in ether (100 ml) cooled in an ice bath. The mixture was then warmed up to room temperature and stirred overnight. The mixture was concentrated in vacuo and purified by column chromatography (10→20% ethyl acetate/hexanes) to give 1-diazo-4-(2-ethylphenyl)butan-2-one (3.47 g, 72% over 2 steps). 1H NMR (CDCl3) δ 7.1-7.25 (4H, m, phenyl), 5.21 (1H, broad s, diazo), 2.97 (2H, m, CH2 of ethyl), 1.20 (3H, t, CH3). Step 3:
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