[CH:1]([C:4]([CH3:22])([N:7]1[C:11](=[O:12])[CH:10]2[CH2:13][CH2:14][C:15]3[N:16]([CH3:20])[CH:17]=[CH:18][C:19]=3[CH:9]2[C:8]1=[O:21])[C:5]#[N:6])([CH3:3])[CH3:2]>ClC1C=CC=CC=1.[O-2].[O-2].[Mn+4]>[CH:1]([C:4]([CH3:22])([N:7]1[C:11](=[O:12])[C:10]2[CH:13]=[CH:14][C:15]3[N:16]([CH3:20])[CH:17]=[CH:18][C:19]=3[C:9]=2[C:8]1=[O:21])[C:5]#[N:6])([CH3:3])[CH3:2]Activated manganese dioxide (27.0 g, 0.310 mol) is added to a solution of 3,3a,4,5,6,8b-hexahydro-α-isopropyl-α,6-dimethyl-1,3-dioxobenzo[1,2-b:3,4-c']dipyrrole-2(1H)-acetonitrile (51.3 g, 0.167 mol) in chlorobenzene. The reaction mixture is stirred overnight at reflux temperature, cooled and filtered twice through diatomaceous earth with methylene chloride. The filtrate is concentrated in vacuo to a black oil which is flash chromatographed twice with methylene chloride then hexanes:methylene chloride to afford a yellow solid (5.50 g, 11.6%). Recrystallization from hexanes:methylene chloride afforded the title product, mp 123°-128° C.
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