New route to the synthesis of the indolo[7,6-g]indole ("bis(pyrrolo)naphthalene") system starting from 1,5-dihydroxynaphthalene

A short and convenient route for the synthesis of indolo[7,6-g]indole deriv atives starting from dihydroxynaphthalene is described. 1,9-Dihydroxynaphth alene (I) after alkylation, nitration and reduction gave 4,8-diamino-1,5-di butoxynaphthalene (4). After reaction with iodine, 4,8-diamino-1,5-disubsti tuted naphthalene gave the corresponding 3,7-diodonaphthalene (5) in nearly quantitative yields. Palladium-catalyzed reaction of this diiodonaphthalen e derivative with (trimethylsilyl)acetylene (TMSA), followed by efficient C uI-mediated cyclization with simultaneous elimination of the TMS substituen t, allowed an efficient preparation of 5,10-dibutoxyindolo[7,6-g]indole (8) . (C) 1999 Elsevier Science Ltd. All rights reserved.