Facile and convenient synthesis of aryl hydrazines via copper-catalyzed C–N cross-coupling of aryl halides and hydrazine hydrate

An efficient and convenient method for the synthesis of aryl hydrazines has been developed via copper-catalyzed cross-coupling of aryl bromides and hydrazine with a readily accessible ligand and water as a solvent. The multigram scale procedure is applicable to aryl bromides bearing both moderately electron-donating and electron-withdrawing substituents in the aromatic nucleus. No column chromatography is required to obtain aryl hydrazine hydrochlorides in good yields.     

Polar Red‐Emitting Rhodamine Dyes with Reactive Groups: Synthesis,Photophysical Properties,and Two‐Color STED Nanoscopy Applications

The synthesis, reactivity, and photophysical properties of new rhodamines with intense red fluorescence, two polar residues (hydroxyls, primary phosphates, or sulfonic acid groups), and improved hydrolytic stability of the amino‐reactive sites (NHS esters or mixed N‐succinimidyl carbonates) are reported. All fluorophores contain an N‐alkyl‐1,2‐dihydro‐2,2,4‐trimethylquinoline fragment, and most of them bear a fully substituted tetrafluoro phenyl ring with a secondary carboxamide group. The absorption and emission maxima in water are in the range of 635–639 and 655–659 nm, respectively. A vastly simplified approach to red‐emitting rhodamines with two phosphate groups that are compatible with diverse functional linkers was developed. As an example, a phosphorylated dye with an azide residue was prepared and was used in a click reaction with a strained alkyne bearing an N‐hydroxysuccinimid (NHS) ester group. This method bypasses the undesired activation of phosphate groups, and gives an amphiphilic amino‐reactive dye, the solubility and distribution of which between aqueous and organic phases can be controlled by varying the pH. The presence of two hydroxyl groups and a phenyl ring with two carboxyl residues in the dyes with another substitution pattern is sufficient for providing the hydrophilic properties. Selective formation of a mono‐N‐hydroxysuccinimidyl ester from 5‐carboxy isomer of this rhodamine is reported. The fluorescence quantum yields varied from 58 to 92 % for free fluorophores, and amounted to 18–64 % for antibody conjugates in aqueous buffers. The brightness and photostability of these fluorophores facilitated two‐color stimulated emission depletion (STED) fluorescence nanoscopy of biological samples with high contrast and minimal background. Selecting a pair of fluorophores with absorption/emission bands at 579/609 and 635/655 nm enabled two‐color channels with low cross‐talk and negligible background at approximately 40 nm resolution.     

Cyclometallated Platinum(II) Complexes for Obtaining Phenyl-Containing Silicone Rubbers via Catalytic Hydrosilylation Reaction

Russian Journal of General Chemistry - C,N-Chelate deprotonated diaminecarbene platinum(II) complexes were studied as polysiloxane system hydrosilylation catalysts. Phenyl-containing silicone...     

Structure of 2-chloro-3-phenylbenzoic acid

The carbonylation reaction of 2,3-dichlorobiphenyl proceeds with a substitution of the chlorine atom in position 3 and results in the formation of 2-chloro-3-phenylbenzoic acid. The structure of this acid is revealed by single crystal XRD. It is determined by steric interactions of substituents in positions 2,4,2′, and 6′, a stable carboxyl supramolecular synthon, and weak interactions with the participation of the carbonyl oxygen atom and the chlorine atom. Original Russian Text Copyright ? 2009 by V. P. Boyarskiy, M. S. Fonari, K. Suwinska, and Yu. A. Simonov __________ Translated from Zhurnal Strukturnoi Khimii, Vol. 50, No. 3, pp. 605–607, May–June, 2009.     

Coupling of C-amino aza-substituted heterocycles with an isocyanide ligand in palladium(ii) complex

The reaction of cis-dichlorobis(2,6-xylylisocyanide)palladium(ii) with 2-aminopyrazine affords a binuclear palladium complex, in which one of the metal atoms is involved in the palladacyclic ligand. In the contrast, the coupling of isocyanide ligands in cis-dichlorobis-(2,6-xylylisocyanide)palladium(ii) with another C-amino aza-substituted heterocycle, viz.,4-acetyl-3-amino-5-methylpyrazole, gives a mononuclear cationic palladium diaminocarbene complex. Both compounds were characterized by elemental analysis, IR spectroscopy, ¹H, ¹³C{₁H}, DEPT90/DEPT135, and ¹H,¹³C-HSQC/¹H,¹³C-HMBC NMR spectroscopy, high-resolution electrospray ionization mass spectrometry, and X-ray diffraction.     

Determination of dielectric properties of ore minerals in the microwave band

We consider a method for determining the complex dielectric permittivity of ore and nonmetal minerals in the microwave band of electromagnetic radiation. The results of measuring the reflectivity and transmittivity of chalcopyrite, magnetite, sphalerite, and labradorite samples in the frequency range 77–300 GHz are presented. A method for calculation of the complex dielectric permittivity of minerals on the basis of the obtained experimental data is proposed. The approximation formulas for calculation of the complex dielectric permittivity of the studied minerals are given. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 51, No. 12, pp. 1071–1080, December 2008.     

Unusual Formation of 1,2,4-Oxadiazine Core in Reaction of Amidoximes with Maleic or Fumaric Esters

We have developed a simple and convenient method for the synthesis of 3-aryl- and 3-hetaryl-1,2,4-oxadiazin-5-ones bearing an easily functionalizable (methoxycarbonyl)methyl group at position 6 via the reaction of aryl or hetaryl amidoximes with maleates or fumarates. The conditions for this reaction were optimized. Different products can be synthesized selectively in good yields depending on the base used and the ratio of reactants: substituted (1,2,4-oxadiazin-6-yl)acetic acids, corresponding methyl esters, or hybrid 3-(aryl)-6-((3-(aryl)-1,2,4-oxadiazol-5-yl)methyl)-4H-1,2,4-oxadiazin-5(6H)-ones. The reaction is tolerant to substituents’ electronic and steric effects in amidoximes. As a result, a series of 2-(5-oxo-3-(p-tolyl)-5,6-dihydro-4H-1,2,4-oxadiazin-6-yl)acetic acids, their methyl esters, and 1,2,4-oxadiazoles based on them were prepared and characterized by HRMS, ¹H, and ¹³C NMR spectroscopy. The structures of three of them were elucidated with X-ray diffraction.     

Photostable, amino reactive and water-soluble fluorescent labels based on sulfonated rhodamine with a rigidized xanthene fragment

Highly water soluble fluorescent dyes were synthesized and transformed into new amino reactive fluorescent labels for biological microscopy. To this end, rhodamine 8 (prepared from 7-hydroxy-1,2,3,4-tetrahydroquinoline (7) and phthalic anhydride in 85 % aq. H(3)PO(4)) was sulfonated with 30 % SO(3) in H(2)SO(4) and afforded the water soluble disulfonic acid 3 a (64 %). Amidation of the carboxy group in 3 a with 2-(methylamino)ethanol in the presence of O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluroniumPF(6) (-) (HATU) led to alcohol 3 b (66 %), which was transformed into the amino reactive mixed carbonate 3 d with di(N-succinimidyl)carbonate and Et(3)N. Reaction of the carboxy group in 3 a with MeNH(CH(2))(2)CO(2)Me and N,N,N',N'-tetramethyl-O-(N-succinimidyl)-uroniumBF(4) (-) (TSTU) yielded methyl ester 13. After saponification of the aliphatic carboxy group in 13, the compound was converted into NHS-ester 3 e (using HATU and Et(3)N). Heating of 7 with trimellitic anhydride in H(3)PO(4) gave a mixture of dicarboxylic acids 14 and 15 (1:1). Regioisomer 15 was isolated, sulfonated with 30 % SO(3) in H(2)SO(4), and disulfonic acid 3 f was used for the synthesis of the mono NHS-ester 3 g, in which the sterically unhindered carboxy group was selectively activated (with N-hydroxysuccinimide, HATU, and Et(3)N). The sulfonated rhodamines 3 b, c and f are soluble in water (up to 0.1 M), have excellent photostabilities and large fluorescence quantum yields. Subdiffraction resolution images of tubulin filaments of mammalian cells stained with these dyes illustrate their applicability as labels for stimulated emission depletion microscopy and other fluorescence techniques.