Benz indole

Intramolecular acylation of l-benzyl-2-(2-carboxybenzoyl)pyrrole under Friedel-Crafts conditions yields l//-benz[/]indole-4,9-dione (79KGS1564). When the 1-position is unsubstituted, cyclization occurs to that position (B-77MI30502). 

This methodology has since been applied to constructing [6]-an-nelated carbazoles, and benz[/]indole, and the tetracyclic skeleton of the benzophenanthridine alkaloids. Arynes used in this type of reaction include 3,4-didehydropyridine in the synthesis of ellipticine 8 and isoellipticine 9," 3,4-(methylenedioxy)benzyne, and 2,3-naphthalyne. ... 

Lin and colleagues expanded the Nenitzescu indole synthesis to include a wide variety of 1,3-diazaheterocycle-fused [l,2-fl]indoles (Scheme 13, equation 1 and 55-57) [51], Parr and Reiss employed the Nenitzescu indole synthesis to prepare several benz[ ]indoles and 1,2-annulated indoles (equations 2, 3) [52]. 

Suginome and coworkers discovered the novel [3+2] regioselective photoaddilion of 2-amino-1,4-naphthoquinones with electron-rich alkenes to afford lH-benz[/] indole-4,9-diones (Schane 16, equation 1) [112]. Likewise, amino-1,4-benzoquinones with alkenes gave lH-indole-4,7-diones (equation 2). If the initial photoproducts could not indolize by loss of alcohoL then the corresponding dihydro compounds were isolated. Parker and Mindt found that qui-none monoimides were smoothly photocyclized to the respective 5-hydroxyindoles (equation 3) [113]. 

The thermal chemistry of a number of related aryl-substituted 2/f-azirines were also studied. The 2-naphthyl-substituted azirines 299 were found to rearrange to benz[g]indole 300. The selectivity encountered here was attributed to the higher energy content of the intermediate leading to the alternative benz[/]indole system 302. Heteroaromatic systems were also found to undergo thermal rearrangement via highly selective reaction paths ... 

SCHEME 2.38 N-Vinylation of benz[ ]indole with acetylene. 

The condensed indole, benz[ ]indole, under the same conditions, is coupled with benzoylbromoacetylene to furnish a mixture of 3- and 2-benzoylethynylindoles in a 45% overall yield (Scheme 2.59, Table 2.6). In this case, 2-(2-benzoyl-l-bromovinyll) benz[ ]indole, stabilized by strong intramolecular hydrogen bonding between the NH and C=0 groups (5 NH 14.59 ppm), is also detected ( H NMR) [523]. 

Miao L, Haque 1, Manzoni MR, Tham WS, Chemler Sr., Diastereo- and enantioselective copper-catalyzed intramolecular carboamination of alkenes for the synthesis of hexahydro-l/f-benz[/]indoles. Org. Lett. 2010 12(21) 4739-4741. 

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