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. 2020 Jun 17;16:1320–1334. doi: 10.3762/bjoc.16.113

Table 4.

Synthesis of tetrahydropyrrolo[3,4-e]indole-1,3-diones 21a–g by aromatization of 9e–f, 9h–k and 9m.a

graphic file with name Beilstein_J_Org_Chem-16-1320-i002.jpg
entry 9 R1 R2 R3 R4 oxidant solvent T (°C) t (h) 21 (%)b
1 9e Ph CO2Et H H MnO2 CH2Cl2 25 24 (c)
2 9e Ph CO2Et H H MnO2 PhMe 100 24 (c)
3 9e Ph CO2Et H H DDQ CH2Cl2 25 48 21a (88)
4 9f Ph CN H H DDQ CH2Cl2 25 48 21b (94)
5 9h Ph CO2Me Br H MnO2 PhMe 140 24 21c (69)
6 9h Ph CO2Me Br H DDQ CH2Cl2 25 48 21c (90)
7 9i Me CO2Et Br H DDQ CH2Cl2 25 48 21d (86)
8 9j Ph CO2Et Br H DDQ CH2Cl2 25 48 21e (89)
9 9k Ph CO2Et H OMe DDQ CH2Cl2 25 48 21f (90)
10 9m Ph COMe Br H DDQ CH2Cl2 25 48 21g (90)

aReagents: 9 (1.0 mol equiv), MnO2 (4.0 mol equiv) and DDQ (2.5 mol equiv). bFollowing purification by column chromatography. cSubstrate 9e was recovered.