2′‐Hydroxy‐4′′‐dimethylaminochalcone

The title compound, 3‐[4‐(di­methyl­amino)­phenyl]‐1‐(2‐hydroxy­phenyl)­prop‐2‐en‐1‐one, C₁₇H₁₇NO₂, is a chalcone derivative substituted by 2′‐hydroxyl and 4′′‐di­methyl­amino groups. The crystal structure indicates that the aniline and hydroxy­phenyl groups are nearly coplanar, with a dihedral angle of 10.32 (16)° between their phenyl rings. The molecular planarity of this substituted chalcone is strongly affected by the 2′‐hydroxyl group.     

The 5‐Methylisocytosine β‐D‐Ribopyranosyl (4′ → 2′)‐Oligonucleotide

In the context of Eschenmoser's work on pyranosyl‐RNA (‘p‐RNA’), we investigated the synthesis and base‐pairing properties of the 5‐methylisocytidine derivative. The previously determined clear‐cut restrictions of base‐pairing modes of p‐RNA had led to the expectation that a 5‐methylisocytosine β‐D ‐ribopyranosyl (= D ‐pr(^MeisoC)) based (4′ → 2′)‐oligonucleotide would pair inter alia with D ‐pr(isoG) and L ‐pr(G) based oligonucleotides (D ‐pr and L ‐pr = pyranose form of D ‐ and L ‐ribose, resp.). Remarkably, we could not observe pairing with the D ‐pr(isoG) oligonucleotide but only with the L ‐pr(G) oligonucleotide. Our interpretation concludes that this – at first hand surprising – observation is caused by a change in the nucleosidic torsion angle specific for isoC.     

Synthesis of 3′‐1,2,4‐triazolo‐ and 3′‐1,3,4‐thiadiazoliminothymidines

New 5′‐acetyl‐3′‐1,3,4‐thiadiazoliminothymidines 11, 14 were prepared, via spontaneous rearrangments, by cycloaddition of 5′‐acetyl‐3′‐deoxy‐3′‐isothiocyanatothymidine 9 with 1‐aza‐2‐azoniaallene hexachloantimonates. Similary, 3′‐cyano analogue 19 was reacted with the same cumulenes to furnish 3′‐1,2,4‐triazolo‐thymidines 22, 24 , and 26 . Deblocking of the acylated products afforded the free nucleosides. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:298–303, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10146     

Substituted 2,2′‐Bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyl Complexes of Zinc

The condensation reaction of 2,2′‐diamino‐4,4′‐dimethyl‐6,6'‐dibromo‐1,1′‐biphenyl with 2‐hydroxybenzaldehyde as well as 5‐methoxy‐, 4‐methoxy‐, and 3‐methoxy‐2‐hydroxybenzaldehyde yields 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyl ( 1a ) as well as the 5‐, 4‐, and 3‐methoxy‐substituted derivatives 1b , 1c , and 1d , respectively. Deprotonation of substituted 2,2′‐bis(salicylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls with diethylzinc yields the corresponding substituted zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐1,1′‐biphenyls ( 2 ) or zinc 2,2′‐bis(2‐oxidobenzylideneamino)‐4,4′‐dimethyl‐6,6′‐dibromo‐1,1′‐biphenyls ( 3 ). Recrystallization from a mixture of CH₂Cl₂ and methanol can lead to the formation of methanol adducts. The methanol ligands can either bind as Lewis base to the central zinc atom or as Lewis acid via a weak O–H ··· O hydrogen bridge to a phenoxide moiety. Methanol‐free complexes precipitate as dimers with central Zn₂O₂ rings.     

4,4′′′′‐Azobis[2,2′: 6′,2″‐terpyridine] and its Metal Complexes

By two different routes, 4,4′′′′‐azobis[2,2′: 6′,2″‐terpyridine] was synthesized. Its ruthenium complexes show interesting metal‐to‐ligand charge transfer (MLCT) absorption maxima in the electronic spectra. They represent the first ruthenium complexes of terpyridine units to give blue solutions.     

Synthesis and Solid‐state Reaction of 1‐[3′‐(Benzotriazol‐2″‐yl)‐4′ ‐hydroxybenzoyl]‐3‐methyl‐5‐pyrazolones

A new kind of UV stabilizers, 1‐(3′‐(benzotriazol‐2″‐yl)‐4′‐hydroxy‐benzoyl)‐3‐methyl‐5‐pyrazolones (1a‐d), was synthesized with the aim to bind them chemically to certain polymers. The reaction of 1d with substituted benzaldehydes 4 in the molten state at 150°C and in the solid state at room temperature produced the condensation products l‐(3′‐(5″‐chlorobenzotriazol‐2″‐yl)‐4′‐hydroxyl‐5′‐chlorobenzoyl)‐3‐methyl‐4‐arylmethylene‐5‐pyrazolones (2) and 4,4′‐arylmethylene‐bis [1‐(3′‐(5″‐chloro‐benzotriazol‐2″‐yl)‐4′‐hydroxy‐5′‐chloro‐benzoyl)‐3‐methyl‐5‐pyrazolone] s (3), respectively, as the major product. On the other hand, the reaction of 1d with 4 at 50°C in chloroform solution proceeded non‐selectively to give a mixture of 2 and 3.     

Synthesis and photophysical properties of 2,5,8,11‐tetrakis(5‐hexylthiophen‐2‐yl)tetrathieno[2,3‐a:3′,2′‐c:2′′,3′′‐f:3′′′,2′′′‐h]naphthalene

The title compound, C₅₈H₆₄S₈, has been prepared by Pd‐catalysed direct C—H arylation of tetrathienonaphthalene (TTN) with 5‐hexyl‐2‐iodothiophene and recrystallized by slow evaporation from dichloromethane. The crystal structure shows a completely planar geometry of the TTN core, crystallizing in the monoclinic space group P2₁/c. The structure consists of slipped π‐stacks and the interfacial distance between the mean planes of the TTN cores is 3.456 (5) Å, which is slightly larger than that of the comparable derivative of tetrathienoanthracene (TTA) with 2‐hexylthiophene groups. The packing in the two structures is greatly influenced by both the aromatic core of the structure and the alkyl side chains.     

4′‐Vinyl‐2,2′:6′,2′′‐ter­pyridine

The title compound, C₁₇H₁₃N₃, is a versatile precursor for polymeric ter­pyridine derivatives and their metal complexes. The mol­ecule has transoid and near‐coplanar pyridine rings. However, the vinyl group is forced out of the plane of the terpyridyl moiety by a close H?H contact.     

5′‐Allyl‐2′‐benzoyloxy‐3′‐methoxy‐4‐nitroazobenzene

The structure of the title compound, 4‐allyl‐2‐methoxy‐6‐[(4‐nitrophenyl)diazenyl]phenyl benzoate, C₂₃H₁₉N₃O₅, displays the characteristic features of azobenzene derivatives. The azobenzene moiety of the molecule has a trans configuration and in this moiety, average C—N and N=N bond lengths are 1.441 (3) and 1.241 (3) Å, respectively.     

4′‐Iodo‐2,2′:6′,2′′‐terpyridine

In the nearly planar title compound, C₁₅H₁₀IN₃, the three pyridine rings exhibit transoid conformations about the interannular C—C bonds. Very weak C—H...N and C—H...I interactions link the molecules into ribbons. Significant π–π stacking between molecules from different ribbons completes a three‐dimensional framework of intermolecular interactions. Four different packing motifs are observed among the known structures of simple 4′‐substituted terpyridines.     

4,4′‐Bis(2,2,2‐trifluoroethoxymethyl)‐2,2′‐bipyridine

As part of a homologous series of novel polyfluorinated bipyridyl (bpy) ligands, the title compound, C₁₆H₁₄F₆N₂O₂, contains the smallest fluorinated group, viz. CF₃. The molecule resides on a crystallographic inversion centre at the mid‐point of the pyridine C_ipso—C_ipso bond. Therefore, the bpy skeleton lies in an anti conformation to avoid repulsion between the two pyridyl N atoms. Weak intramolecular C—H...N and C—H...O interactions are observed, similar to those in related polyfluorinated bpy–metal complexes. A π–π interaction is observed between the bpy rings of adjacent molecules and this is probably a primary driving force in crystallization. Weak intermolecular C—H...N hydrogen bonding is present between one of the CF₃CH₂– methylene H atoms and a pyridyl N atom related by translation along the [010] direction, in addition to weak benzyl‐type C—H...F interactions to atoms of the terminal CF₃ group. It is of note that the O—CH₂CF₃ bond is almost perpendicular to the bpy plane.     

Synthesis and Characterization of Fluorinated Polyimide Derived from 3,3′‐Diisopropyl‐4,4′‐diaminodiphenyl‐3′′,4′′‐difluorophenylmethane

A novel aromatic diamine monomer, 3,3′‐diisopropyl‐4,4′‐diaminodiphenyl‐3′′,4′′‐difluorophenylmethane (PAFM), was successfully synthesized by coupling of 2‐isopropylaniline and 3,4‐difluorobenzaldehyde. The aromatic diamine was adopted to synthesize a series of fluorinated polyimides by polycondensation with various dianhydrides: pyromellitic dianhydride (PMDA), 3,3′,4,4′‐biphenyltetracarboxylic dianhydride (BPDA), 4,4′‐oxydiphthalic anhydride (ODPA) and 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA) via the conventional one‐step method. These polyimides presented excellent solubility in common organic solvents, such as N,N‐dimethylformamide (DMF), N,N‐dimethyl acetamide (DMAc), dimethyl sulfoxide (DMSO), N‐methyl‐2‐pyrrolidone (NMP), chloroform (CHCl₃), tetrahydrofuran (THF) and so on. The glass transition temperatures (T_g) of fluorinated polyimides were in the range of 260–306°C and the temperature at 10% weight loss in the range of 474–502°C. Their films showed the cut‐off wavelengths of 330–361 nm and higher than 80% transparency in a wavelength range of 385–463 nm. Moreover, polymer films exhibited low dielectric properties in the range of 2.76–2.96 at 1 MHz, as well as prominent mechanical properties with tensile strengths of 66.7–97.4 MPa, a tensile modulus of 1.7–2.1 GPa and elongation at break of 7.2%–12.9%. The polymer films also showed outstanding hydrophobicity with the contact angle in the range of 91.2°–97.9°.     

1,1′‐Nitramino‐5,5′‐bitetrazoles

1,1′‐Dinitramino‐5,5′‐bitetrazole and 1,1′‐dinitramino‐5,5′‐azobitetrazole were synthesized for the first time. The neutral compounds are extremely sensitive and powerful explosives. Selected nitrogen‐rich salts were prepared to adjust sensitivity and performance values. The compounds were characterized by low‐temperature X‐ray diffraction, IR and Raman spectroscopy, multinuclear NMR spectroscopy, elemental analysis, and DTA/DSC. Calculated energetic performances using the EXPLO5 code based on calculated (CBS‐4M) heats of formation and X‐ray densities support the high performances of the 1,1′‐dinitramino‐5,5′‐bitetrazoles as energetic materials. The sensitivities toward impact, friction, and electrostatic discharge were also explored. Most of the compounds show sensitivities in the range of primary explosives and should only be handled with great care!     

Concise Synthesis of α‐Methylene‐β‐hydroxy‐γ‐carboxy‐γ‐lactams

A concise protocol for the synthesis of α‐methylene‐β‐hydroxy‐γ‐carboxy‐γ‐lactams has been described via alkylation of amino acid derived iminoesters with α‐bromomethylmethacrylate, followed by allylic hydroxylation. All the synthesized compounds have been evaluated for their cytotoxicity on multiple myeloma cancer cell lines.     

Metal Salts of 3,3′‐Diamino‐4,4′‐dinitramino‐5,5′‐bi‐1,2,4‐triazole in Pyrotechnic Compositions

The synthesis of alkali and alkaline earth salts of 3,3′‐diamino‐4,4′‐dinitramino‐5,5′‐bi‐1,2,4‐triazole (H₂ANAT) is reported. The fast and convenient three steps reaction toward the target compounds does not require any organic solvents. In addition to an intensive characterization of all synthesized metal salts, the focus was on developing chlorine and nitrate‐free red‐light‐generating pyrotechnical formulations. Strontium 3,3′‐diamino‐4,4′‐dinitramino‐5,5′‐bitriazolate hexahydrate served as colorant and oxidizer in one molecule. The energetic properties of all developed pyrotechnical formulations assure safe handling and manufacturing.     

7‐Halogenated 7‐Deaza‐2′‐deoxyxanthine 2′‐Deoxyribonucleosides

The synthesis of the 7‐halogenated derivatives 1b (7‐bromo) and 1c (7‐iodo) of 7‐deaza‐2′‐deoxyxanthosine ( 1a ) is described. A partial Br→I exchange was observed when the demethylation of 6‐methoxy precursor compound 4b was performed with Me₃SiCl/NaI. This reaction is circumvented by the nucleophilic displacement of the MeO group under strong alkaline conditions. The halogenated 7‐deaza‐2′‐deoxyxanthosine derivatives 1b , c show a decreased S‐conformer population of the sugar moiety compared to the nonhalogenated 1a . They are expected to form stronger triplexes when they replace 1a in the 1 ?dA?dT base triplet.     

Building Functionality into 4′‐Hydrazone Derivatives of 2,2′: 6′,2″‐Terpyridine

The syntheses of the five 2,2′: 6′,2″‐terpyridine (tpy) ligands 5 – 9 functionalized in the 4′‐position with a hydrazone substituent RR′C?N? NH (R=R′=Me; R=H, R′=4‐BrC₆H₄, 4‐O₂NC₆H₄, 4‐MeOC₆H₄, or 3,5‐(MeO)₂C₆H₃) are described. Protonation of the tpy domain of the ligands is facile. Solution behaviour has been studied by NMR and electronic spectroscopies. Representative structural data are presented for neutral and monoprotonated ligands, and illustrate that H‐bonding involving the formal amine NH unit is a dominant structural motif in all cases.     

Photohydrodimerization of 6‐Methoxyflavone to 6,6″‐Dimethoxy‐2,2″‐Biflavanones

6‐Methoxyflavone ( 7 ) easily afforded two hydrodimers of rac‐6,6Prime;‐dimethoxy‐2,2″‐biflavanone ( 8a ) and meso‐6,6″‐dimethoxy‐2,2″‐biflavanone ( 8b ) and one reductive product of 6‐methoxyflavanone ( 9 ) by using photolysis with the electron‐donating amines including triethylamine, 2‐(N,N‐dimethylamino)ethanol or N,N‐dimethylaniline in solvents of acetonitrile, benzene or methylene dichloride. They were found to give higher yields of rac‐6,6″‐dimethoxy‐2,2″‐biflavanone ( 8a ) and meso‐6,6″‐dimethoxy‐2,2″‐biflavanone ( 8b ) (38.7% and 4.5%, 35.3% and 6.2%, respectively) in the reaction conditions of 1/10 molar ratio of 6‐methoxy‐flavone ( 7 ) to triethylamine in a solvent of acetonitrile with irradiation of twenty‐four hours by using 306 nm and 352 nm lamps.