[CH3:1][C:2]([CH3:24])=[CH:3][C:4]([N:6]1[C:12]2[CH:13]=[CH:14][CH:15]=[CH:16][C:11]=2[CH2:10][N:9]([C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])[CH2:8][CH2:7]1)=[O:5]>[Hg]>[CH3:1][C:2]1([CH3:24])[C:13]2[C:12]3=[C:11]([CH2:10][N:9]([C:17]([O:19][C:20]([CH3:23])([CH3:22])[CH3:21])=[O:18])[CH2:8][CH2:7][N:6]3[C:4](=[O:5])[CH2:3]1)[CH:16]=[CH:15][CH:14]=2A solution of 0.33 g (1.0 mmol) of tert-butyl 1-(3-methylbut-2-enoyl)-2,3-dihydro-1H-benzo[e][1,4]diazepine-4(5H)-carboxylate of step 1.1 was irradiated with a 150 W mercury lamp in a immersion well reactor with a pyrex filter in 20 mL of acetone until completion of the reaction monitored by liquid chromatography. The solution was concentrated in vacuo and the residue was purified by column chromatography on silica (eluent: 10-30% ethyl acetate in heptane) to yield 202 mg of the title compound as a beige solid.
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