Direct catalytic synthesis of ß-(C3)-substituted pyrroles: a complementary addition to the Paal-Knorr reaction.

The synthesis of ß-(C3)-functionalized pyrroles is a challenging task and requires a multistep protocol. An operationally simple direct catalytic synthesis of ß-substituted pyrroles has been developed. This one-pot multicomponent method combined aqueous succinaldehyde as 1,4-dicarbonyl, primary amines, and isatins to access hydroxyl-oxindole ß-tethered pyrroles. Direct synthesis of the ß-substituted free NH-pyrrole is the central intensity of this work. DFT-calculations and preliminary mechanism investigation support the possible reaction pathway.

Crystal structure of 15,16-ep-oxy-7ß,9α-di-hydroxy-labdane-13(16),14-dien-6-one.

In the title mol-ecule, C20H30O4, both cyclo-hexane rings adopt chair conformations. In the crystal, mol-ecules are connected by O-H⋯O hydrogen bonds forming chains along [100]. In addtion, an intra-molecular O-H⋯O hydrogen bond forms an S(5) ring.

Crystal structure of N-[(2-hy-droxy-naphthalen-1-yl)(4-methyl-phen-yl)meth-yl]acetamide.

In the title mol-ecule, C20H19NO2, the naphthalene ring system subtends a dihedral angle of 82.50 (7)° with the benzene ring and an intra-molecular N-H⋯O hydrogen bond closes an S(6) ring. In the crystal, mol-ecules are linked by O-H⋯O hydrogen bonds, which generate C(8) chains propagating in the [010] direction. The crystal structure also features weak π-π inter-actions [centroid-centroid separation = 3.7246 (10) Å].

Crystal structure of bis-(3-bromo-pyridine-κN)bis-(O-ethyl di-thio-carbonato-κ(2) S,S')nickel(II).

In the title mol-ecular complex, [Ni(C3H5OS2)2(C5H4BrN)2], the Ni(2+) cation is located on a centre of inversion and has a distorted octa-hedral N2S4 environment defined by two chelating xanthate ligands and two monodentate pyridine ligands. The C-S bond lengths of the thio-carboxyl-ate group are indicative of a delocalized bond and the O-Csp (2) bond is considerably shorter than the O-Csp (3) bond, consistent with a significant contribution of one resonance form of the xanthate anion that features a formal C=O+ unit and a negative charge on each of the S atoms. The packing of the mol-ecules is stabilized by C-H⋯S and C-H⋯π inter-actions. In addition, π-π inter-actions between the pyridine rings [centroid-to-centroid distance = 3.797 (3) Å] are also present. In the crystal structure, mol-ecules are arranged in rows along [100], forming layers parallel to (010) and (001).

Crystal structure of 4-[(E)-(4-chloro-benzyl-idene)amino]-3-(2-methyl-benz-yl)-1H-1,2,4-triazole-5(4H)-thione.

In the title mol-ecule, C17H15ClN4S, the benzene rings form dihedral angles of 16.6 (1) and 77.2 (1)° with the triazole ring. The dihedral angle between the benzene rings is 86.6 (1)°. In the crystal, pairs of N-H⋯S hydrogen bonds form inversion dimers with graph-set notation R 2 (2)(8). Weak C-H⋯S hydrogen bonds link these dimers into layers parallel to (100). Weak intra-molecular C-H⋯S and C-H⋯N contacts are observed.

5-((Meth-oxy-imino)-{2-[(2-methyl-phen-oxy)meth-yl]phen-yl}meth-yl)-N-phenyl-1,3,4-oxa-diazol-2-amine.

In the title mol-ecule, C24H22N4O3, the plane of the oxa-diazole ring forms a dihedral angle of 32.41 (12)° with that of the phenyl ring and dihedral angles of 74.51 (10) and 56.38 (10)° with the planes of the benzene rings. In the crystal, pairs of N-H⋯N hydrogen bonds link molecules into inversion dimers featuring R 2 (2)(8) graph-set motifs.

4-Amino-3-(3-meth-oxy-benz-yl)-1H-1,2,4-triazole-5(4H)-thione.

In the title mol-ecule, C10H12N4SO, the triazole ring forms a dihedral angle of 73.0 (5)° with the benzene ring. The meth-oxy group is approximtely coplanar with the benzene ring with a C C-O-Cmeth-yl torsion angle of 4.7 (3)°. In the crystal, N-H⋯S hydrogen bonds connect pairs of inversion-related mol-ecules, which are in turn connected by N-H⋯N hydrogen bonds into chains of rings along [010]. Weak C-H⋯O hydrogen bonds connect these chains into a two-dimensional network parallel to (-102).

Ethyl 2,6-bis-(4-chloro-phen-yl)-4-(4-fluoro-anilino)-1-(4-fluoro-phen-yl)-1,2,5,6-tetra-hydro-pyridine-3-carboxyl-ate.

In the title compound, C32H26Cl2F2N2O2, the tetra-hydro-pyridine ring adopts a distorted boat conformation. The chlorophenyl rings are inclined to one another by 55.2 (1)°, while for the fluorophenyl rings the dihedral angle is 80.7 (1)°. The amino group and carbonyl O atom are involved in an intra-molecular N-H⋯O hydrogen bond. In the crystal, weak C-H⋯O, C-H⋯F and C-H⋯Cl inter-actions link the mol-ecules into a three-dimensional network.

Methyl 4-(4-fluoro-anilino)-1,2,6-tris-(4-fluoro-phen-yl)-1,2,5,6-tetra-hydro-pyri-dine-3-carboxyl-ate.

In the title mol-ecule, C31H24F4N2O2, the tetra-hydro-pyridine ring adopts a distorted boat conformation. An intra-molecular N-H⋯O hydrogen bond is formed by the amino group and ccarboxyl C=O atom. The crystal structure features weak C-H⋯F and C-H⋯O inter-actions.

Ethyl 2,6-bis-(4-chloro-phen-yl)-4-(4-methyl-anilino)-1-(4-methyl-phen-yl)-1,2,5,6-tetra-hydro-pyridine-3-carboxyl-ate.

In the title mol-ecule, C34H32Cl2N2O2, the tetra-hydro-pyridine ring adopts a distorted boat conformation and both 4-chloro-phenyl substituents are in axial positions. An intra-molecular N-H⋯O hydrogen bond is formed by the amino group and carbonyl O atom. In the crystal, weak C-H⋯Cl inter-actions link the mol-ecules into chains along [010].

Ethyl 4-anilino-2,6-bis-(4-fluoro-phen-yl)-1-phenyl-1,2,5,6-tetra-hydro-pyridine-3-carboxyl-ate.

In the title compound, C(32)H(28)F(2)N(2)O(2), the tetra-hydro-pyridine ring adopts a distorted boat conformation. The two fluoro-phenyl groups are attached to the tetra-hydro-pyridine ring in a trans orientation. The dihedral angle between the planes of the fluoro-substituted rings is 57.0 (1)°. The amino group and carbonyl O atom are involved in intra-molecular hydrogen bonding. In the crystal, weak C-H⋯O, C-H⋯F and C-H⋯π inter-actions link the mol-ecules into columns along [010].

Ethyl 2-[4-(2-chloro-benzo-yl)-2,6-di-methyl-phen-oxy]ethano-ate.

The asymmetric unit of the title compound, C(19)H(19)ClO(4), contains two independent mol-ecules. The dihedral angles between the benzene rings are 63.41 (8) and 61.41 (9)°. Adjacent mol-ecules of different types are inter-connected in pairs through π-π inter-actions between their central benzene rings [centroid-centroid separation = 3.801 (2) Å, inter-planar spacing = 3.605 (2) Å, centroid shift = 1.204 (2) Å]. Finally, C-H⋯O hydrogen bonds link these dimers into bilayers parallel to (100).

2-Amino-7,7-dimethyl-5-oxo-4-(p-tol-yl)-5,6,7,8-tetra-hydro-4H-chromene-3-carbonitrile.

In the title mol-ecule, C(19)H(20)N(2)O(2), the cyclo-hexene ring adopts a sofa conformation, while the pyran ring adopts a flattened boat conformation. In the crystal, mol-ecules are linked by N-H⋯N and N-H⋯O hydrogen bonds, forming a two-dimensional network parallel to (010).

3-(4-Chloro-anilino)-5,5-dimethyl-cyclo-hex-2-en-1-one.

The asymmetric unit of the title compound, C(14)H(16)ClNO, contains two independent mol-ecules, both with the cyclo-hexene ring in a sofa conformation. In the crystal, N-H⋯O hydrogen bonds link the mol-ecules related by translation along the a axis into two crystallographically independent chains. Weak C-H⋯π inter-actions are also observed.

(E)-4-(4-Meth-oxy-phen-yl)but-3-en-2-one.

In the title compound, C(11)H(12)O(2), the dihedral angle between the benzene ring and the but-3-en-2-one group is 4.04 (5)°. The crystal packing features chains, parallel to [-101], composed of dimers connected by weak C-H⋯O inter-actions..

2-Methylxanthen-9-one.

In the title compound, C(14)H(10)O(2), the tricycle is not planar, being bent with a dihedral angle of 4.7 (1)° between the two benzene rings. In the crystal, π-π inter-actions between the six-membered rings of neighbouring mol-ecules [centroid-centroid distances = 3.580 (3) and 3.605 (3) Å] form stacks propagating along [101].

Trimeth-yl(triphenyl-meth-oxy)silane.

In the title mol-ecule, C(22)H(24)OSi, the Si-O-C angle is 139.79 (11)°, the O-C-C angles of the triphenyl-meth-oxy group are in the range 106.13 (13)-109.22 (14)° and the O-Si-C angles of the trimethyl-sil-yloxy group are in the range 103.08 (10)-113.53 (10)°. In the crystal, face-to-face π-π interactions are observed between the phenyl rings [centroid separation = 4.194 (1) Å, interplanar spacing = 3.474 Šand centroid shift = 2.35 Å]. The three phenyl groups of the triphenyl-methyl substituent are mutually nearly perpendicular, with dihedral angles in the range 80.49 (8)-81.53 (8)°. There are only weak inter-molecular van der Waals inter-actions in the crystal.