One-pot synthesis of 3,4-benzo[c]-β-carbolines was achieved from 2-aryl(tosylamino)methyl-3-bromoindoles via 10 mol % Pd(OAc) 2 /PPh 3 -mediated intramolecular Heck coupling using K 2 CO 3 as a base in DMF at 110 °C with concomitant aromatization through an elimination of tosylsulfinic acid. Under identical conditions, the isomeric 3-aryl(tosylamino)methyl-2bromoindoles upon intramolecular Heck reaction furnished benzo [4,5]isothiazolo[2,3-a]indole 5,5-dioxides instead of the expected γ-carbolines. However, synthesis of the expected γcarboline framework, 3-tosyl-6,9-dihydro-1,2-benzo[a]-γ-carbolines, could be achieved from 3-aryl(tosylamino)methyl-2bromoindoles containing a mesitylene sulfonyl unit as a protecting group on the indole nitrogen.

The title compounds, C28H21FN2O7S (I) and C25H16N2O2S (II), are carbazole derivatives with a benzenesulfonyl group attached to the carbazole moiety at the N atom on both molecules. A fluoro-substituted nitrophenyl ring system in I and a fused isoquinoline ring in II are attached to the respective carbazole moieties. In both compounds, the carbazole ring systems are essentially planar, with maximum deviations of 0.028 (2) and 0.026 (2) Å for carbon atoms in compounds I and II, respectively. The carbazole ring system is almost orthogonal to the benzene ring attached to sulfonyl group, with dihedral angles of 79.7 (2) in I and 88.2 (2)° in II, respectively. The mean planes of the carbazole ring systems make dihedral angles of 66.1 (2) and 1.3 (2)°, respectively, with the nitrophenyl ring in I and the planar isoquinoline moiety [maximum deviation of 0.009 (3) Å for a carbon atom in II, indicating that the ring system in II is essentially planar]. The benzenesulfonyl ring is almost normal to the isoquinoline ring, with a dihedral angle of 87.9 (2)° in II and the nitrophenyl ring forms a dihedral angle of 17.8 (2)° in I. In both compounds, intramolecular C—H...O hydrogen bonds generate S(6) ring motifs with the sulfone group O atoms. In crystals of compound I, the molecules are linked by C—H...O intermolecular weak hydrogen bonds, which generate C(7) and C(10) chains running parallel to [010] and [100], respectively.

In both of the title compounds, C26H19NO2S2, (I), and C25H19NO2S2, (II), the benzothiophene rings are essentially planar with maximum deviations of 0.026 (1) and −0.016 (1) Å for the carbon and sulfur atoms in compounds (I) and (II), respectively. In (I), the thiophene ring system is almost orthogonal to the phenyl ring attached to the sulfonyl group, subtending a dihedral angle of 88.1 (1)°, and the dihydropyridine ring adopts a screw–boat conformation. In both compounds, the molecular structure is consolidated by weak C—H...O intramolecular interactions formed by the sulfone oxygen atoms, which generate S(5) ring motifs. In the crystal of II, molecules are linked via C—H...O hydrogen bonds, generating C(7) chains running along the [100] direction. No significant intermolecular interactions are observed in I.

Heteroarylmethylenephosphorus ylides underwent Michael addition with alkynediones and alkynediesters, followed by intramolecular cyclization and elimination of triphenylphosphine oxide to afford 1,2-diaroylbenzenes and 1,2-alkoxy­carbonylcarbo- and heterocycles. The analogous (4 + 2) cycloaddition led to the formation of 2,3-diaroylquinolines.