Selenadiazole Ring Research Articles

Molecular Recognition by Chalcogen Bond: Selective Charge‐Transfer Crystal Formation of Dimethylnaphthalene with Selenadiazolotetracyanonaphthoquinodimethane

AbstractThe title nonplanar electron acceptor (1) fused with a selenadiazole ring selectively forms a crystalline charge‐transfer complex (CT crystal) with 2,6‐dimethylnaphthalene (2,6‐DMN). On the other hand, the sulfur analogue (2) has less recognition ability and forms CT crystals with both 2,6‐ and 2,7‐DMN. X‐ray analyses of 1, 2, and their CT crystals revealed that the Se⋅⋅⋅N chalcogen bond (ChB) in 1 is strong enough to determine the crystal packing with the formation of a cavity suitable for 2,6‐DMN. On the contrary, ChB through S⋅⋅⋅N contact in 2 competes with other weak interactions such as a C−H⋅⋅⋅N hydrogen bond. The stronger ChB involving Se is the key for 1 to separate 2,6‐DMN (>97 wt %) from a complex isomer mixture containing ca. 10 wt % each of 2,6‐ and 2,7‐DMN by a simple, efficient and straightforward mixing‐filtration‐heating process.

Synthesis of the Derivatives of 4-(1,2,3-Selenadiazol-4-yl)-5-methyl-2-furoate Functionalyzed at the Methyl Group

By treating ethyl 4-acetyl-5-methyl-2-furoate with selenium dioxide ethyl 4-(1,2,3-selenadiazol-4-yl)-5-methyl-2-furoate was synthesized. It was established, that when treated with N-bromosuccinimide this compound decomposes. That is why for preparing its derivatives functionalized at the methyl group the substituent desired must be introduced before the formation of selenadiazole ring. By this way corresponding phosphonate and a series of phenyl ethers were syhthesized.

Rac-12-Selena-13,14-di-aza-tri-cyclo-[9.3.0.02,4]tetra-deca-11,13-diene.

The centrosymmetric crystal structure of the title compound, C11H16N2Se, is built up from alternating strands of (R,R)- and (S,S)-enanti-omers. These strands, which propagate along the c-axis direction, are composed of homochiral mol-ecules related to each other by twofold screw axes. The shape of the mol-ecule is an almost planar unit around the selena-diazole ring with a hexa-methyl-ene chain as an arched handle.

Synthesis of 4-(2-Fluoro-4-hydroxyphenyl)-1,2,3-thia- and -Selenadiazoles and Glycosides on Their Base

Basing on 2-fluoro-4-methoxyacetophenone 2-fluoro-4-hydroxyphenyl-1,2,3-thiadiazole was synthesized by means of the Hurd-Mori reaction. Under the conditions of phase transfer catalysis in water-chloroform system it was glycosylated with 1-α-bromo-2,3,4-tri-O-acetyl-D-xylopyranose. 2-Fluoro-4-hydroxy-1,2,3-selenadiazole can be prepared by oxidation of 2-fluoro-4-hydroxyacetophenone with selenium dioxide in acetic acid. Glycosylation of 2-fluoro-4-hydroxy-1,2,3-selenadiazole with 1-α-bromo-2,3,4,6-tetra-O-acetyl-D-galactopyranose leads to formation of corresponding glycoside. Alternative pathway for preparing of 1-β-[3-fluoro-4-(1,2,3-selenadiazol-4-yl)-phenyl]-2,3,4-tri-O-acetyl-D-xylopyranose including synthesis of 2-fluoro-4-hydroxyacetophenone xyloside and subsequent formation of selenadiazole ring was developed.

Dearomatization of oxa- or selenadiazolopyridines with neutral nucleophiles as an efficient approach to pharmacologically relevant nitrogen compounds

Highly electrophilic 6-nitro-4-azabenzofuroxan and 6-nitro-4-azabenzo[1,2,5]selenadiazole add π-excessive (het)arenes and other neutral nucleophiles at 7-position to give C–C and N–C-bonded adducts, 1,4-dihydropyridines fused with furoxan or selenadiazole ring.

5-[1-(4-Methyl-phen-yl)-2-nitro-but-yl]-4-phenyl-1,2,3-selenadiazole.

In the title compound, C19H19N3O2Se, the selenadiazole ring is roughly planar [maximum deviation 0.033 (6) Å]. The attached phenyl ring is twisted away at an angle of 47.5 (1)°. The butyl group is in an extended conformation [C—C—C—C torsion angle = 174.7 (2)°]. In the crystal, C—H⋯O inter­actions form C(10) chains running aling the c-axis direction.

Phenyl substituted Mg porphyrazines: The effect of annulation of a chalcogen-containing heterocycle on the spectral-luminescent properties

We have performed complex experimental and theoretical investigations of the spectral-luminescent properties and electronic structure of new phthalocyanine analogs, Mg octaphenylporphyrazine and its derivatives with an annulated thiadiazole or selenadiazole ring instead of two phenyl groups. Fluorescence characteristics have been determined at 293 and 77 K: emission, excitation, and fluorescence polarization spectra; fluorescence quantum yield φF, and lifetime τF. Annulation of a five-membered chalcogen-containing heterocycle leads to splitting of the long-wavelength absorption band Q(0-0) and to the bathochromic shift of its longest wavelength component Qx(0-0), which increase upon passage from S to Se. At the same time, the fluorescence quantum yield φF and lifetime τF decrease, which is related to the intramolecular heavy-atom effect. The geometric structure of the ground state of the Mg porphyrazine molecules has been determined based on the density functional theory (DFT), and excited electronic states have been calculated with modified parametrization of the INDO/S method, INDO/Sm. Semiquantitatively, the calculated level positions of the lowest Q states and spectral shifts of Mg octaphenylporphyrazine and S-derivative agree with experimental data. For the range of the Soret band, calculated transition energies and their intensity distributions substantially depend on the dihedral angle γ between a phenyl ring and porphyrazine macrocycle. We show that, based on calculations at the angle γ = 60°, bands in the observed absorption spectra can be assigned with an accuracy of ∼2000 cm−1.

Ethyl 3-(4-meth-oxy-phen-yl)-2-phenyl-3-(4-phenyl-1,2,3-selenadiazol-5-yl)propano-ate.

In the title compound, C26H24N2O3Se, the selenadiazole ring is planar [maximum deviation = 0.002 (2) Å]. The dihedral angle between the selenadiazole ring and the attached phenyl ring is 49.00 (13)°. The crystal structure is stabilized by inter­molecular C—H⋯N and C—H⋯π inter­actions.

5-[1-(4-Meth-oxy-phen-yl)-2-nitro-but-yl]-4-phenyl-1,2,3-selenadiazole.

In the title compound, C19H19N3O3Se, the selenadiazole ring is essentially planar (r.m.s. deviation = 0.001 Å). The heterocyclic ring makes dihedral angles of 50.2 (2) and 76.3 (9)°, respectively, with the meth­oxy­phenyl and phenyl rings.

5-(2-Nitro-1-phenyl-but-yl)-4-phenyl-1,2,3-selenadiazole.

In the title compound, C18H17N3O2Se, the selenadiazole ring is planar [maximum deviation = 0.012 (2) Å for the ring C atom bearing the phenyl substituent]. The dihedral angle between the selenadiazole ring and the attached benzene ring is 46.5 (1)°. There is one short intra­molecular C—H⋯Se contact.

Ethyl 2-phenyl-3-(4-phenyl-1,2,3-selenadiazol-5-yl)-3-p-tolyl-propano-ate.

In the title compound, C26H24N2O2Se, the selenadiazole ring is essentially planar [maximum deviation = 0.004 (3) Å]. The dihedral angle between the selenadiazole ring and the attached benzene ring is 50.17 (1)°. The crystal packing is stabilized by inter­molecular C—H⋯N inter­actions.

Photoinduced decarboxylation of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid

Photoinduced reactions of 9‐oxo‐6,9‐dihydro[1,2,5]selenadiazolo[3,4‐f]quinoline‐8‐carboxylic acid (SeQCA) were investigated in alkaline media (aqueous NaOH solutions) by electron paramagnetic resonance (EPR) spectroscopy, following the in situ formation of paramagnetic species. According to UV–Vis and nuclear magnetic resonance investigations, protonation (pH ≈ 11) and deprotonation (pH ≈ 13) of the imino hydrogen of the 4‐pyridone moiety has to be considered, reflected also in the different EPR spectra observed upon irradiation. Photoinduced generation of radicals was found only for carboxylate substituted SeQCA; other studied selenadiazoloquinolone derivatives, together with those substituted at the C(8) position (R = H, COOCH2CH3, COOCH3, COCH3 or CN), did not generate paramagnetic species during exposure. Consequently, photodecarboxylation was suggested as the decisive step, accompanied by the decomposition of the selenadiazole ring, resulting in the formation of ortho‐hydroxylate anions. EPR parameters elucidated from experimental EPR spectra obtained at pH ≈ 11 and pH ≈ 13 indicate the formation of oxygen‐centered radicals at the decarboxylated 4‐pyridone ring. EPR spin trapping experiments with nitromethane confirmed a very effective photoinduced electron transfer from all the selenadiazoloquinolones investigated. Copyright © 2011 John Wiley & Sons, Ltd.

4-{(4-Chloro-phen-yl)[4-(4-methyl-phen-yl)-1,2,3-selenadiazol-5-yl]meth-yl}-4,5,6,7-tetra-hydro-1,2,3-benzoselenadiazole.

In the title compound, C22H19ClN4Se2, the mean plane of the non-fused selenadiazole ring forms dihedral angles of 54.20 (16)° and 70.48 (11)°, respectively, with the essentially planar [maximum deviations of 0.025 (5) and 0.009 (2) Å, respectively] methyl­phenyl and chloro­phenyl substituents. The tetra­hydro-1,2,3-benzoselenadiazole group is disordered over two sets of sites with a refined occupancy ratio of 0.802 (5):0.198 (5). In the crystal, weak inter­molecular C—H⋯N inter­actions are observed.

Anodic oxidation of selenadiazoloquinolones in alkaline media

Newly synthesized derivatives of 6-oxo-6,9-dihydro[1,2,5]selenadiazolo[3,4-h]quinoline variously substituted at position 7 (R = H, COOH, COCH(3), CN, COOC(2)H(5) and COOCH(3)) are established in strongly alkaline aqueous solutions (0.1 M NaOH; pH ∼ 13) as N(9)-deprotonated structures, but in less alkaline solutions (0.001 M NaOH; pH ∼ 11) the N(9)-protonated oxo tautomeric forms dominate. Upon their anodic oxidation in alkaline solutions, the selenadiazole ring is replaced, forming instead the paramagnetic species analogous to the ortho semiquinone radical anions as monitored by in situ EPR spectroscopy. The quantum chemical calculations for two representative selenadiazoloquinolones (R = H and COOH) and their anodic oxidation products presented are in agreement with experiments.

4-(4-Chlorophenyl)-5-[1-(4-chlorophenyl)-2-methyl-2-nitropropyl]-1,2,3-selenadiazole

In the title compound, C18H15Cl2N3O2Se, the selenadiazole ring makes dihedral angles of 49.87 (3) and 55.70 (3)° with the two benzene rings. The dihedral angle between the two benzene rings is 11.90 (5)°. In the crystal structure, intra­molecular C—H⋯O and C—H⋯Se inter­actions and inter­molecular C—H⋯O, C—H⋯Cl and C—H⋯N inter­actions are observed.

5-(2-Methyl-2-nitro-1-phenylpropyl)-4-phenyl-1,2,3-selenadiazole

In the title compound, C18H17N3O2Se, the selenadiazole ring makes dihedral angles of 37.71 (8) and 66.79 (6)° with the adjacent phenyl ring and the aromatic ring of the phenyl­propyl group, respectively. The mol­ecular structure is stabilized by weak intra­molecular C—H⋯Se inter­actions and the crystal packing is stabilized by a weak C—H⋯π inter­action.

4-( ortho-hydroxyphenyl)-1,2,3-selenadiazole as a source of 2-benzofuranselenolate

The novel 4-( ortho-hydroxyphenyl)-1,2,3-selenadiazole smoothly transforms into 2-benzo-furanselenolate through potassium carbonate catalyzed selenadiazole ring cleavage. The presence of alkyneselenolate is proved by the formation of methyl( ortho-methoxy-phenylethynyl)selenide in the presence of methyl iodide. Alkylation and oxidation reactions of 2-benzofuranselenolate are described.

The crystal structure of a cyclodecabis[1,2,3]selenadiazole

4,5,6,10,11,12-hexahydrocyclodeca[1,2-d∶6,7-d′]bis[1,2,3]selenadiazole, C10H12N4Se2, crystallizes in triclinic space group P\(\bar 1\) witha=5.4625(3),b=7.2091(4),c=8.3122(6) A, α=65.313(5), β=77.476(5), γ=77.442(5)°,V=287.35(4) A3,Z=1. The structure was refined toR=0.031 andRw=0.030 for 2018 observed reflections. The molecule lies on an inversion center. The cyclodecadiene ring adopts an elongated chair conformation. The near-zero torsion angle of the elongated chair lies at the ring-fusion bonds, with a magnitude of 2.9(3)°. The five atoms of the selenadiazole ring exhibit maximum deviation 0.005(2) A from planarity, with the adjacent carbon atoms lying respectively 0.020(2) and 0.059(2) A to the same side of this plane. The torsion angles about the bonds comprising the sides of the elongated chair vary in magnitude from 61.0(2)° to 55.7(2)°. The cyclodecadiene C=C bond lengths are 1.368(2) A. The selenium-carbon bond length is 1.850(2) A. The Se−N distance is quite long, 1.888(2) A.

1,2,5‐Selenadiazoles. Synthesis and properties

Abstract4‐Amino‐1, 2, 5‐selenadiazole‐3‐carboxylic acid and 4‐amino‐1, 2, 5‐selenadiazole‐3‐carboxamides have been prepared by ring‐cleavage of [1, 2, 5]selenadiazolo[3, 4‐d]pyrimidin‐7(6H)‐one by basic reagents. The primary amide (III), as well as an N‐alkyl amide, may be produced by the action of a primary amine. Hydrazine reductively cleaves the selenadiazole ring. The preparation of similar 4‐ureido derivatives by ring‐cleavage of [1,2,5]selenadiazolo[3, 4‐d]pyrimidine‐5, 7(4 H, 6H)‐dione has been demonstrated with two examples.N‐Butyl‐4‐ureido‐1, 2, 5‐selenadiazole‐3‐carboxamide is easily hydrolyzed in aqueous base to the corresponding acid, and it has been shown that this reaction proceeds by way of [1, 2, 5]selenadiazolo[3,4‐d]pyrimidine‐5, 7 (4H, 6H)‐dione.The 4‐amino‐1, 2, 5‐selenadiazole‐3‐carboxylic acid derivatives have marked cytotoxic, antibacterial, and antifungal activity.