Easy Access to Aryl‐ and Heteroaryl‐Annulated[a]carbazoles by the Indium‐Catalyzed Reaction of 2‐Arylindoles with Propargyl Ethers

Abstract

Indoles and indium: An indium salt catalyzes the assembly of 2‐arylindoles and propargyl ethers into diverse aryl‐ and heteroaryl‐annulated[a]carbazoles in a highly regioselective manner, in which two different modes of carbon–carbon bond‐forming reactions are successfully incorporated in one step (see scheme).

Indium-Catalyzed Annulation of o-Acylanilines with Alkoxyheteroarenes: Synthesis of Heteroaryl[b]quinolines and Subsequent Transformation to Cryptolepine Derivatives

“…MeOH was stored over molecular sieves 3Å (MS 3Å) under argon. The following indium salts and substrates were synthesized according to the respective literature methods: In(NTf 2 ) 3 [ 83 , 84 ], In(ONf) 3 [ 56 , 85 ], 1-(2-aminophenyl)-2-methyl-1-propanone ( 2e ) [ 86 ], 1-(2-aminophenyl)-2,2,2-trifluoroethanone ( 2f ) [ 87 ], (2-aminophenyl)(4-methoxyphenyl)methanone ( 2j ) [ 88 ], (2-aminophenyl)(2-methylphenyl)methanone ( 2l ) [ 88 ], 3-methoxybenzo[ b ]thiophene ( 3a ) [ 89 ], 2-methoxybenzo[ b ]thiophene ( 3b ) [ 54 ], 2-methoxy-5-methylthiophene ( 3d ) [ 54 ], 2-methoxybenzo[ b ]furan ( 3f ) [ 54 ], 2-methoxy-5-phenylfuran ( 3g ) [ 54 ], 2-methoxy-1-phenyl-1 H -pyrrole ( 3h ) [ 54 ]. Unless otherwise noted, other substrates and reagents were commercially available, and used as received without further purification.…”

Direct synthesis of benzo[a]carbazoles by palladium-catalyzed domino reactions: synthesis and photophysical properties of diverse benzo[a]carbazoles

“…Therefore, development of straightforward synthetic methods for other aryl-and heteroarylannulated carbazoles like benzo[a]carbazoles surely opens up a further opportunity to utilize benzo[a]carbazoles as material sources. Unsurprisingly, many efforts have been made to develop methodologies, ranging from thermal and photochemical cyclization, palladium-catalyzed cross-coupling reactions, Fischer indolization, Diels-Alder reactions, gold-catalyzed intramolecular cyclization reactions, and irradiation of a benzotriazole derivative, for the synthesis of benzo[a]carbazole derivatives [1,[28][29][30][31][32][33][34]. In 1993, Hill et al reported the synthesis of the benzo[a]carbazole derivatives using a palladium-mediated oxidative cyclization as the key step.…”

Triggering the Directional Selectivity of a Ring‐Closure Reaction Leads to Pyridoazacarbazoles with Anticancer Properties

“…Various different methods, most of them multistep with well-known synthetic transformations like, for example, Fischer indole cyclisation, metal-catalyzed CÀC bond formation or Diels-Alder reaction, to mention only a few, are used to establish the four-membered heterocyclic compounds being differently substituted at diverse ring positions. [12,13,[15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] For some of the known heterocyclic classes described previously and especially for the substituted derivatives thereof interesting and diverse biological activities were reported. The antiproliferative properties of a wide range of differently substituted analogous structures with distinct heterocyclic scaffolds were of particular interest.…”