Pd(0)-Catalyzed Intramolecular Heck reaction of 2/3-Aryl(amino)methyl-3/2-bromoindoles: Syntheses of 3,4-Benzo[c]-ß-carbolines, Benzo[4,5]isothiazolo[2,3-a]indole 5,5-Dioxides, and 1,2-Benzo[a]-γ-carbolines.

One-pot synthesis of 3,4-benzo[c]-ß-carbolines was achieved from 2-aryl(tosylamino)methyl-3-bromoindoles via 10 mol % Pd(OAc)2/PPh3-mediated intramolecular Heck coupling using K2CO3 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-2-bromoindoles 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 γ-carboline framework, 3-tosyl-6,9-dihydro-1,2-benzo[a]-γ-carbolines, could be achieved from 3-aryl(tosylamino)methyl-2-bromoindoles containing a mesitylene sulfonyl unit as a protecting group on the indole nitrogen.

Crystal structures of 1-benzene-sulfon-yl-2-methyl-3-(4-nitro-benzoyl)-2,3-di-hydro-1H-indole and 1-benzene-sulfon-yl-2-methyl-3-[(thio-phen-2-yl)carbon-yl]-2,3-di-hydro-1H-indole.

In the title indole derivatives, C22H16N2O5S, (I) and C20H15NO3S2, (II), the sulfonyl-bound phenyl rings are almost orthogonal to the indole ring system, subtending dihedral angles of 88.33 (10) and 87.58 (16)°, respectively. In both compounds, the sulfonyl S atom has a distorted tetra-hedral geometry [O-S-O = 119.98 (9) and N-S-C = 104.01 (8)° for compound (I) and O-S-O = 120.08 (18) and N-S-C = 104.91 (14)° for compound (II)] and the sum of the bond angles at N indicates sp2 hybridization. The mol-ecules of both (I) and (II) feature intra-molecular C-H⋯O hydrogen bonds that generate S(6) ring motifs with the sulfone O atom. In the crystals, mol-ecules of (I) are linked by C-H-O hydrogen bonds, forming R44(18) ring motifs while mol-ecules of (II) are linked by C-H-O and C-H-S hydrogen bonds, forming R22(12) ring motifs. Compound (II) was refined as an inversion twin.

Crystal structures of two new carbazole derivatives: 12-(4-nitro-phen-yl)-7-phenyl-sulfonyl-7H-benzofuro[2,3-b]carbazole and 2-methyl-4-(4-nitro-phen-yl)-9-phenyl-sulfonyl-9H-thieno[2,3-b]carbazole.

The title compounds, C30H18N2O5S, (I), and C27H18N2O4S2, (II), are carbazole derivatives with a phenyl-sulfonyl group and a nitro-phenyl group attached to the carbazole moiety in identical positions in both mol-ecules. A benzo-furan ring system in (I) and a methyl-thio-phene ring in (II) are fused with the respective carbazole moieties on the same sides. The mean plane of the carbazole ring system makes a dihedral angle of 3.17 (7)° with the benzo-furan ring system in (I) and a dihedral angle of 3.39 (11)° with the methyl-thio-phene ring in (II), implying that both fused units are essentially planar. The mean planes of the carbazole ring systems in both the compounds are almost orthogonal to the respective nitro-substituted phenyl rings, making dihedral angles of 75.64 (10) and 77.63 (12)° in compounds (I) and (II), respectively. In (I), the phenyl-sulfonyl ring system is positionally disordered with a refined occupancy ratio of 0.63 (2):0.37 (2). In both compounds, the mol-ecular structures are stabilized by intra-molecular C-H⋯O hydrogen bonds, generating S(6) ring motifs with the sulfone group O atoms. In the crystal of compound (I), mol-ecules are linked by pairs of C-H⋯O hydrogen bonds, which generate R22(18) inversion dimers, and inter-connected by C(14) chains running along the c-axis direction, whereas in compound (II), the C-H⋯O hydrogen bonds generate R43(37) ring motifs. In the crystals of both compounds, C-H⋯O hydrogen-bonded sheets are formed lying parallel to (10-1). In addition, C-H⋯π and offset π-π inter-actions [inter-centroid distance = 3.7158 (14) Šin (I) and 3.9040 (15) Šin (II)] are also present in the crystals of both compounds.

Crystal structures of three carbazole derivatives: 12-ethyl-7-phenyl-sulfonyl-7H-benzofuro[2,3-b]carbazole, (1), 2-(4,5-dimeth-oxy-2-nitro-phen-yl)-4-hy-droxy-9-phenyl-sulfonyl-9H-carbazole-3-carbaldehyde, (2), and 12-phenyl-7-phenyl-sulfonyl-7H-benzofuro[2,3-b]carbazole, (3).

The three title compounds, C26H19NO3S, (1), C27H20N2O8S, (2), and C30H19NO3S, (3), are carbazole derivatives, where (1) and (3) are heterocycle-containing carbazoles with a benzo-furan moiety fused to a carbazole unit. In (2), a di-meth-oxy-nitro-phenyl ring is attached to the carbazole moiety. In the three derivatives, a phenyl-sulfonyl group is attached to the N atom of the carbazole unit. Compound (1) crystallizes with two independent mol-ecules in the asymmetric unit (A and B). The carbazole skeleton in the three compounds is essentially planar. In compound (1), the benzene ring of the phenyl-sulfonyl moiety is almost orthogonal to the carbazole moiety, with dihedral angles of 85.42 (9) and 84.52 (9)° in mol-ecules A and B, respectively. The benzene ring of the phenyl-sulfonyl group in compounds (2) and (3) are inclined to the carbazole moiety, making dihedral angles of 70.73 (13) and 81.73 (12)°, respectively. The S atom has a distorted tetra-hedral configuration in all three compounds. In the crystals, C-H⋯O hydrogen bonds give rise to R22(12) inversion dimers for compound (1), and to R22(24) inversion dimers and R44(40) ring motifs for compound (2). The crystal packing in (1) also features C-H⋯π and π-π inter-actions [shortest inter-centroid distance = 3.684 (1) Å], leading to supra-molecular three-dimensional aggregation. In the crystal of compound (2), the combination of the various C-H⋯O hydrogen bonds leads to the formation of a three-dimensional network. In the crystal of compound (3), mol-ecules are linked by C-H⋯O hydrogen bonds, forming chains running parallel to the a axis, and the chains are linked by C-H⋯π inter-actions, forming corrugated sheets parallel to the ab plane.

Synthesis of Cyclo[b]fused Carbazoles via SnCl4-Mediated Domino Reaction of 2-Indolylmethylpivalates with Arenes and Heteroarenes.

A straightforward synthesis of aryl and heteroaryl-annulated cyclo[b]carbazoles has been developed via SnCl4-mediated one-pot arylation, cyclization and aromatization reaction sequence from 3-acetyl/aroyl-2-pivaloyloxymethylindoles. The starting material is easily accessible from commercially available 2-methylindole via Friedel-Crafts acylation, bromination and pivaloylation. Remarkably, electron withdrawing/donating aroyl units including heterocyclic systems are well tolerated in the present domino reaction protocol. Furthermore, this methodology could be extended to the synthesis of dibenzofurocarbazole via bis-annulation of 2,5-bis(2-pivaloyloxymethyl)pyrrole.

3-Bromo-methyl-4-meth-oxy-2-(2-nitro-phen-yl)-9-phenyl-sulfonyl-9H-carbazole.

In the title compound, C26H19BrN2O5S, the carbazole tricycle is essentially planar, with the largest deviation being 0.126 (3) Šfor the C atom connected to the nitro-phenyl group. The carbazole moiety is almost orthogonal to the benzene rings of the adjacent phenyl-sulfonyl and nitro-phenyl groups, making dihedral angles of 85.43 (15) and 88.62 (12)°, respectively. The mol-ecular conformation is stabilized by two C-H⋯O hydrogen bonds involving the sulfone group, which form similar six-membered rings. In the crystal, mol-ecules symmetrically related by a glide plane are linked in C(6) chains parallel to [001] by C-H⋯O hydrogen bonds formed with the participation of the nitro group. The chains are reinforced by additional C-H⋯π inter-actions.

2-(4,5-Dimeth-oxy-2-nitro-phen-yl)-4-meth-oxy-9-phenyl-sulfonyl-9H-carbazole-3-carbaldehyde.

In the title compound, C28H22N2O8S, the carbazole ring system is roughly planar, with a maximum deviation of 0.084 (3) Šfor the C atom connected to the 4,5-dimeth-oxy-2-nitro-phenyl ring. The dihedral angle between the carbazole system and the dimeth-oxy-substituted nitro-phenyl ring is 57.05 (10)°. The aldehyde C atom deviates by 0.164 (5) Šfrom its attached carbazole ring system. The mol-ecular structure is stabilized by C-H⋯O inter-actions which generate two S(6) and one S(7) ring motif. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming R 3 (3)(15) ring motifs, which are further crosslinked by R 3 (2)(19) ring motifs, resulting in (002) layers. The crystal packing also features C-H⋯π inter-actions.

2-(4,5-Di-chloro-2-nitro-phen-yl)-4-meth-oxy-3-methyl-9-phenyl-sulfon-yl-9H-carbazole.

In the title compound, C26H18Cl2N2O5S, the carbazole ring system is essentially planar with a maximum deviation of 0.0498 (16) Šfor the N atom. The carbazole ring system is almost orthogonal to the phenyl-sulfonyl and di-chloro-substituted nitro-phenyl rings, making dihedral angles of 84.23 (7) and 85.46 (12)°, respectively. The mol-ecular structure features intra-molecular C-H⋯O inter-actions, which generate two S(6) ring motifs. In the crystal, mol-ecules are linked by C-Cl⋯O halogen bonds [3.016 (3) Å, 166.63 (5)°], which generate infinite C(8) chains running parallel to [010].

2-(4-Chloro-2-nitro-phen-yl)-4-meth-oxy-9-phenyl-sulfonyl-9H-carbazole-3-carbaldehyde.

In the sterically hindered title compound, C26H17ClN2O6S, the carbazole ring has a maximum deviation from planarity of 0.067 (4) Šfor the C atom connected to the aldehyde group. The carbazole moiety forms a dihedral angle of 72.8 (1)° with the nitro-substituted benzene ring. The O atom of the meth-oxy group deviates by 0.186 (1) Šfrom the adjacent carbazole moiety. The phenyl-sulfonyl group forms intra-molecular C-H⋯O bonds between sulfone O atoms and the carbazole moiety, resulting in two S(6) rings. In the crystal, the nitrated benzene rings are linked via C-H⋯O inter-actions forming infinite C(7) chains along [100]. The crystal packing is also characterized by C-H⋯π inter-actions, which result in inversion dimers.

2-(4-Fluoro-2-nitro-phen-yl)-4-hy-droxy-9-phenyl-sulfonyl-9H-carbazole-3-carbaldehyde.

In the title compound, C25H15FN2O6S, the carbazole ring system is essentially planar, with a maximum deviation of 0.1534 (16) Šfor the C atom connected to the 4-fluoro-2-nitro-phenyl ring. It is almost orthogonal to the phenyl-sulfonyl and nitro-phenyl rings, making dihedral angles of 88.45 (8) and 79.26 (7)°, respectively. The mol-ecular structure is stabilized by O-H⋯O and C-H⋯O hydrogen bonds, which generate three S(6) ring motifs. In the crystal, mol-ecules are linked by two C-H⋯O hydrogen bonds, which generate C(6) and C(9) chains running in the [100] and [010] directions, respectively, so forming a two-dimensional network lying parallel to (001). There are also supra-molecular R 4 (3)(28) graph-set ring motifs enclosed within these networks.

2-(4,5-Dimeth-oxy-2-nitro-phen-yl)-4-meth-oxy-3-methyl-9-phenyl-sulfonyl-9H-carbazole.

In the title compound, C28H24N2O7S, the carbazole system is essentially planar, with a maximum deviation of 0.0644 (19) Šfor the C atom connected to the 4,5-dimeth-oxy-2-nitro-phenyl group. The dihedral angle between the carbazole moiety and the dimethoxy-substituted nitrophenyl ring is 58.55 (7)°. The sulfonyl group forms two intra-molecular C-H⋯O bonds with the adjacent carbazole system, forming two cyclic S(6) motifs. In the crystal, mol-ecules are linked along the a axis in bands consisting of cyclic R 3 (3)(15) motifs through two further C-H⋯O hydrogen bonds.

Synthesis of calothrixins and its analogs using FeCl3-mediated domino reaction protocol.

A novel one pot synthesis of calothrixin B and its analogs is achieved involving an FeCl3-mediated domino reaction of enamines in dry DMF at reflux. Alternatively, the enamines upon interaction with CuBr2 in DMF at reflux led to the formation of 1-phenylsulfony-2-(2'-nitroaryl)-4-hydroxycarbazole-3-carbaldehydes in excellent yields.

1-{2-[(E)-2-(2-Nitro-phen-yl)ethen-yl]-1-phenyl-sulfonyl-1H-indol-3-yl}ethanone.

In the title compound, C24H18N2O5S, the S atom has a distorted tetra-hedral configuration, with bond angles varying from 105.11 (7) to 119.98 (8)°. As a result of the electron-withdrawing character of the phenyl-sulfonyl group, the N-Csp (2) bond lengths [1.414 (2) and 1.413 (2) Å] are slightly longer than the reported value of 1.355 (14) Šfor N atoms with a planar configuration. The indole moiety is essentially planar, with a maximum deviation of 0.0177 (14) Šfor the N atom. The phenyl ring of the sulfonyl substituent makes a dihedral angle of 85.70 (7)° with the mean plane of the indole moiety. The mol-ecular structure features intra-molecular C-H⋯O hydrogen bonds, which generate S(6) and S(12) ring motifs. In the crystal, adjacent mol-ecules are linked via C-H⋯O hydrogen bonds, forming infinite C(7) chains running along the a-axis direction. The crystal packing also features C-H⋯π inter-actions, which form a three-dimensional structure.

3-Iodo-2-methyl-1-phenyl-sulfonyl-1H-indole.

In the title compound, C(15)H(12)INO(2)S, the sulfonyl-bound phenyl ring forms a dihedral angle 82.84 (9)° with the indole ring system. The mol-ecular structure is stabilized by a weak intra-molecular C-H⋯O hydrogen bond. The crystal structure exhibits weak inter-molecular C-H⋯π inter-actions and π-π inter-actions between the indole groups [centroid-centroid distance between the five-membered and six-membered rings of the indole group = 3.7617 (18) Å].