Indole Ring System Research Articles

3-(2-Acetamido-eth-yl)-1H-indol-5-yl 4-nitro-phenyl carbonate.

In the title mol­ecule, C19H17N3O6, the indole ring system is essentially planar (r.m.s. deviation = 0.009 Å) and forms a dihedral angle of 31.96 (9)° with the nitro-substituted benzene ring. In the crystal, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, forming inversion dimers which are connected by further N—H⋯O hydrogen bonds into a two-dimensional network parallel to (102).

Diethyl 3,3'-(phenyl-methyl-ene)bis-(1H-indole-2-carboxyl-ate).

In the title compound, C29H26N2O4, the benzene ring is twisted by 73.5 (5) and 84.9 (3)° with respect to the mean planes of the two indole ring systems; the mean planes of the indole ring systems are oriented at a dihedral angle of 82.0 (5)°. In the crystal, mol­ecules are linked by pairs of N—H⋯O hydrogen bonds into chains.

3-(1H-Indol-3-yl)-2-(2-nitrobenzenesulfonamido)propanoic acid including an unknown solvate

In the title compound, C17H15N3O6S, which crystallized with highly disordered methanol and/or water solvent mol­ecules, the dihedral angle between the the indole and benzene ring systems is 5.3 (2)°, which allows for the formation of intra­molecular π–π stacking inter­actions [centroid–centroid separations = 3.641 (3) and 3.694 (3) Å] and an approximate overall U-shape for the mol­ecule. In the crystal, dimers linked by pairs of Ns—H⋯Oc (s = sulfonamide and c = carboxyl­ate) hydrogen bonds generate R 2 2(10) loops, whereas Ni—H⋯π (i = indole) inter­actions lead to chains propagating in [100] or [010]. Together, these lead to a three-dimensional network in which the solvent voids are present as inter­secting (two-dimensional) systems of [100] and [010] channels. The title compound was found to contain a heavily disordered solvent mol­ecule, which could be methanol or water or a mixture of the two. Due to its uncertain nature and the unresolvable disorder, the data were processed with the SQUEEZE option in PLATON [Spek (2009 ▶). Acta Cryst. D65, 148–155], which revealed 877.8 Å3 of solvent-accessible volume per unit cell and 126 electron-units of scattering density or 109.7 Å3 (16 electron units) per organic mol­ecule.. This was not included in the calculations of overall formula weight, density and absorption coefficient.

3-(1H-Indol-3-yl)-4-(morpholin-4-yl)cyclobut-3-ene-1,2-dione

3-(1H-Indol-3-yl)-4-(morpholin-4-yl)cyclobut-3-ene-1,2-dione was obtained in good yields (72–82%) by nucleophilic substitution of 3-chloro-4-(1H-indol-3-yl)cyclobut-3-ene-1,2-dione with morpholine.

Tryptophan oxygenation: mechanistic considerations

From a protein structural viewpoint, tryptophan is often considered an inert structural amino acid, playing a role as a hydrophobic anchor in membrane proteins or as part of the hydrophobic core of soluble proteins. However, tryptophan is the only polyaromatic amino acid and, from a chemical viewpoint, possesses unique reactivity owing to the electron-richness of the indole system. This reactivity is seen in the area of natural products and metabolites which have exquisite modifications of the indole ring system. Enzymes have evolved multiple strategies to break or modify the indole ring; one particular class is the IDO/TDO (indoleamine/tryptophan dioxygenase) superfamily. A new member of this family, PrnB, on the surface catalyses a very different reaction, but actually shares much of the early chemistry with the tryptophan dioxygenases. Studies on PrnB have contributed to our understanding of the wider superfamily. In the present mini-review, recent developments in our understanding of how the TDO class of enzymes use activated molecular oxygen to break the indole ring are discussed.

Gold(I)‐Catalyzed Rearrangement of 3‐Silyloxy‐1,5‐enynes: An Efficient Synthesis of Benzo[b]thiophenes, Dibenzothiophenes, Dibenzofurans, and Indole Derivatives

With the IPr ligand (IPr=1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) on gold(I) excellent yields in the benzanellation of 2-substituted thiophenes, benzothiophenes, pyrroles, benzofurans, and indoles were achieved. The 1-siloxybut-3-ynyl side chains, incorporated in the anellation, are easily accessible by the addition of a propargyl metal reagent to a formyl group and silylation of the alcohol. This conveniently allows an anellation at the position of the formyl group under mild conditions. All reactions involve a 2,3-shift of the side chain in the anellation step and thus, provide an easy access to specific substitution patterns. Only in the case of 2-substituted indoles with their highly nucleophilic 3-position a direct hydroarylation without shift is observed. On the other hand, 3-substituted indoles give the same products as 2-substituted indoles. Then, a 3,2-shift in the indole ring system has to be involved.

Synthesis of a novel series of chalcones and pyrazolines, possessing indole with 4-(2,2,2-trifluroethoxy) pyridine moiety

A new method for the construction of novel fluorine-containing indole ring system has been reported. These indoles were converted into a new series of fluorine-containing indolyl chalcones (1a-g) and pyrazolines (2a-g). All the newly synthesized compounds were characterized with the help of IR, MS and NMR spectroscopic data.

5-Meth-oxy-1-[(5-meth-oxy-1H-indol-2-yl)meth-yl]-1H-indole.

In the title compound, C19H18N2O2, the two indole ring systems are essentially planar [maximum deviation = 0.015 (2) Å in both indole ring systems] and make a dihedral angle of 72.17 (7)° with each other. In the crystal, the mol­ecules are linked into a zigzag chain along the a axis via N—H⋯O hydrogen bonds.

(Z)-3-(1H-Indol-3-yl)-2-(3,4,5-tri-methoxy-phen-yl)acrylonitrile.

In the title compound, C20H18N2O3, the C=C bond of the acrylonitrile group that links the indole and the 3,4,5-trimeth­oxy­phenyl rings has Z geometry, with dihedral angles between the plane of the acrylonitrile unit and the planes of the benzene and indole ring systems of 21.96 (5) and 38.94 (7)°, respectively. The acrylonitrile group is planar (r.m.s. deviation from planarity = 0.037 Å). Mol­ecules are linked into head-to-tail chains that propagate along the b-axis direction by bifurcated N—H⋯O inter­molecular hydrogen bonds, which form an R 1 2(5) motif between the indole NH group and the two meth­oxy O atoms furthest from the nitrile group.

2-(4-Bromo-1H-indol-3-yl)acetonitrile

In the title compound, C10H7BrN2, the non-H atoms, except the N atom of the acetonitrile group and the C atom bonded to it, lie in the least-squares plane defined by the atoms of the indole ring system (r.m.s deviation = 0.019 Å), with the N and C atom of the cyano group displaced by 2.278 (1) and 1.289 (1) Å, respectively, out of that plane. In the crystal, N—H⋯N hydrogen bonds link the mol­ecules into a C(7) chain along [100].

Methyl 4-(5-methoxy-1H-indol-3-yl)benzoate

In the title compound, C17H15NO3, the dihedral angle between the benzene ring and the indole ring system is 22.5 (3)°. In the crystal, mol­ecules are linked by N—H⋯π and C—H⋯O inter­actions.

2-(6-Chloro-1H-indol-3-yl)acetonitrile

In the title compound, C10H7ClN2, the carbonitrile group is twisted away from the plane of the indole ring system [Ccy—Cme—Car—Car = −44.7 (8)°; cy = cyanide, me = methyl­ene and ar = aromatic]. In the crystal, N—H⋯N hydrogen bonds link the mol­ecules into C(7) chains propagating in [010]. Aromatic π–π stacking inter­actions [minimum centroid–centroid separation = 3.663 (3) Å] are also observed.

SYNTHESIS OF 1-BENZYL-3-[4-(ARYL-1-PIPERAZINYL) CARBONYL]-1H-INDOLES: NOVEL LIGANDS WITH POTENTIAL D4 DOPAMINERGIC ACTIVITY

ABSTRACT The synthesis of a series of functionalized 1-Benzyl-3-[4-Aryl-1-piperazingl]carbonyl-1 H -Indoles 6(a-f), as a potential new class of bioactive ligands at D 4 receptors is reported. The synthetic strategy took place through a five steps sequence to provide indole amides 6(a-f) in 75-92% yield. Keywords : Indole, Arylpiperazines, dopaminergic activity. e-mail: hpessoa@ciq.uchile.cl INTRODUCTION The indole ring system is present in many biologically active medicinal agents and natural products 1-3 . The first synthesis of substituted indoles was conducted by Fischer and Jourdan as early as 1883, and since then the bicyclic heteroaromatic core has been the target of many synthetic approaches and reactivity studies. 4-7 Indoles are also prominent structural elements in the neurotransmitter serotonin, the antiinflammatory drug indomethacin and other molecules showing promise in the treatment of cardiovascular disease, erectile dysfunction, cancer and neurological conditions such as the Alzheimer’s disease

2-Methyl-1-phenyl-1H-indole-3-carbonitrile

In the title compound, C16H12N2, the dihedral angle between the indole ring system and the pendant phenyl ring is 64.92 (5)°. The crystal packing features aromatic π–π stacking [centroid–centroid separation = 3.9504 (9) Å] and C—H⋯π inter­actions.

6-Methoxy-2-methyl-1-phenyl-1H-indole-3-carbonitrile

In the title compound, C17H14N2O, the dihedral angle between the indole ring system and the phenyl ring is 64.48 (7)°. The crystal packing features weak C—H⋯π inter­actions.

ChemInform Abstract: Reactions of Indole with Nucleophiles

AbstractReview: 43 refs.

2-Methyl-1-phenylsulfonyl-1H-indole-3-carbaldehyde

In the title compound, C16H13NO3S, the sulfonyl-bound phenyl ring forms a dihedral angle of 84.17 (6)° with the indole ring system. An intra­molecular C—H⋯O hydrogen bond generates an S(6) ring motif. The crystal structure exhibits weak inter­molecular C—H⋯O hydrogen bonds and π–π inter­actions between the five- and six-membered rings of the indole group [centroid–centroid distance = 3.6871 (9) Å].

Spiro[cyclopropane-1,3′-indolin]-2′-one

In the title mol­ecule, C10H9NO, the dihedral angle between the mean plane of the cyclo­propane ring and the essentially planar [maximum deviation = 0.032 (2) Å] indole ring system is 87.65 (17)°. In the crystal, inter­molecular N—H⋯O hydrogen bonds link mol­ecules into one-dimensional chains along [100].

1-(4-Bromophenyl)-2-methyl-1H-indole-3-carbonitrile

In the title compound, C16H11BrN2, the dihedral angle between the indole ring system and the phenyl ring is 58.85 (11)°.

1-(4-Methoxyphenyl)-2-methyl-1H-indole-3-carbonitrile

In the title compound, C17H14N2O, the dihedral angle between the indole ring system and the benzene ring is 58.41 (4)°. The crystal packing features π–π stacking [shortest centroid–centroid separation = 3.8040 (9) Å] and C—H⋯π inter­actions.