Naphtho 2,3-/ indole-5,10-dione

The demethylation of 4-methoxy- and 4,lTdimethoxy-derivatives 1396 was carried out by the action of dimethyl sulfide/BCls complex in dichloromethane under reflux to give 4-hydroxy- and 4,lTdihydroxy-l//-naphtho[2,3-/]-indole-5,10-diones 1397 (Equation 295) <2001CHE944>. 

Naphtho[2,3/]indole-5,10-dione 21 reacted with excess chlorosulfonic acid in dioxan containing sodium sulfate to give the sulfonyl chloride 22 in 63% yield. ° In this indole derivative sulfonation again occurs in the expected 3-position. 

There are four parent isomeric indoloquinones the 4,5-dione (2), 5,6-dione (3), 6,7-dione (4), and 4,7-dione (5). In the isoindole series there are two isomers isoindole-4,5-dione (6) and -4,7-dione (7). There are many benzo, naphtho, and other extended analogs and they will be treated later. In the indole series, there are only a few representatives of systems 2-4 and the same holds for the isoindole series. However, there are many examples of 5. 

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