Volume 78, Issue 5

An environmentally friendly strategy for the photo-catalyzed three-component reaction between quinoxalin-2(1 H )-ones, vinylarenes, with inexpensive and easily accessible ethyl bromodifluoroacetate/sodium difluoromethanesulfinate is described. This protocol exhibits mild conditions, high efficiency, and excellent functional group tolerance, providing a highly efficient approach for the synthesis of difluorobenzylated quinoxalin-2(1 H )-ones by the formation of two carbon-carbon bonds. A radical mechanism is responsible for this three-component transformation.

A new series of indeno[1,2- b ]indol-5(4b H )-ylbenzimidamide derivatives 3a – 3j has been synthesized as potential casein kinase II (CK2) inhibitors. A convenient and straightforward synthesis protocol was used via a reaction of β -enaminones 1a – 1j with ninhydrin 2 . This transformation proceeds under mild conditions (boiling ethanol, 0.5 h) in absence of catalyst in good to excellent yields (66–86%). The new compounds have been characterized by NMR, HRMS and IR spectra.

Three chloridocuprate complexes with methylene blue counterions of the chemical compositions [MB] + 2 [CuCl 4 ] 2− · H 2 O ( 1 ), [MB] + 2 [CuCl 4 ] 2− ( 2 ) and [(MB) + (CuCl 2 ) − ] 3 ( 3 ) (where [MB] +  – methylthioninium cation; methylene blue cation) have been prepared by solvent-assisted mechanochemical synthesis. The reactions were carried out by mixing the copper(II) chloride dihydrate, CuCl 2 ⋅2H 2 O, and methylene blue pentahydrate, [MB] + Cl − · 5H 2 O by grinding in an agate mortar with the addition of DMF as a solvent. The crystal structures of the compounds have been determined by single-crystal X-ray diffraction. The content of an asymmetric unit of the crystals consists of: ( 1 ) a tetrahedral [CuCl 4 ] 2− anion, two [MB] + cations and one water molecule of crystallization; ( 2 ) a tetrahedral [CuCl 4 ] 2− anion and two [MB] + cations; ( 3 ) trimeric [(MB) + (CuCl 2 ) − ] 3 molecules with the Cu atoms coordinated by a nitrogen atom of the phenothiazine ring and two chlorine ions in a trigonal planar geometry with the copper atom in the oxidation state of +1.

The crystal structure of a curcumin-BF 2 complex has been successfully refined from single-crystal X-ray diffraction data of crystals with one molecule of co-crystallized dichloromethane. The complex has a nearly coplanar structure. The molecules form a mesh structure by intermolecular multiple hydrogen bonds, as well as weak hydrogen bonds with CH 2 Cl 2 molecules. An investigation of the photo-physical properties has indicated that the curcumin-BF 2 complex possesses a wide absorption band and an intense red emission in the solid state due to a strong electron-withdrawing effect of the BF 2 groups. DFT calculations of a single molecule verify the relationships between the photo-physical properties and its intrinsic electronic features, but neglect the role of hydrogen bonding.

The synthesis and the crystal structure of the double cluster compound [Nb 6 Cl 14 (MeCN) 4 ][Nb 6 Cl 14 (pyz) 4 ]·6CH 3 CN are described. The synthesis is based on a partial ligand exchange reaction, which proceeds upon dissolving [Nb 6 Cl 14 (pyz) 4 ]·2CH 2 Cl 2 in acetonitrile. The compound is built up of two discrete neutral cluster units, which consist of octahedra of Nb 6 atoms coordinated by 12 edge-bridging chlorido and two terminal chlorido ligands, and four acetonitrile ligands on one and four pyrazine ligands on the other cluster unit. Co-crystallized acetonitrile molecules are also present. The single-crystal structure determination has revealed a cluster arrangement in which the [Nb 6 Cl 14 (pyz) 4 ] units are connected by (halogen) lone-pair–(pyrazine) π interactions. These lead to chains of [Nb 6 Cl 14 (pyz) 4 ] clusters. These chains are further connected to cluster layers by (nitrile-halogen) dipole–dipole interactions, in which the [Nb 6 Cl 14 (MeCN) 4 ] and co-crystallized MeCN molecules are also involved. These cluster layers are arranged parallel to the crystallographic {011} plane.

The high-pressure/high-temperature synthesis of  β -MgB 4 O 7 at 9 GPa and 1200 °C is presented. The determination of its crystal structure by single-crystal X-ray diffraction has shown that the compound is isotypic to the transition metal borates with the structure type of β - M B 4 O 7 ( M  = Mn–Zn). β -MgB 4 O 7 crystallizes in the orthorhombic space group Cmcm with the lattice parameters a  = 10.848(2), b  = 6.513(2), and c  = 5.144(1) Å. The structural relation between the normal-pressure phase α -MgB 4 O 7 to the here presented high-pressure phase β -MgB 4 O 7 and to other reference compounds is discussed.

The silicide Eu 2 Ru 3 Si 5 was synthesized from the elements in a sealed tantalum tube in a high-frequency furnace, while the gallide Eu 2 Ir 3 Ga 5 was obtained by arc-melting. Both structures were refined from single-crystal X-ray diffractometer data: P 4/ mnc , a = 1072.69(8), c = 569.55(5) pm, wR = 0.0453, 617 F 2 values, 31 variables for Eu 2 Ru 3 Si 5 and a = 1122.18(7), c = 583.17(4) pm, wR = 0.0546, 729 F 2 values, 31 variables for Eu 2 Ir 3 Ga 4.95(1) . The gallide shows small defects on one 8 h site. The transition metal atoms in Eu 2 Ru 3 Si 5 and Eu 2 Ir 3 Ga 5 have octahedral p element coordination. These Ru@Si 6 respectively Ir@Ga 6 polyhedra are condensed to three-dimensional [Ru 3 Si 5 ] 6− respectively [Ir 3 Ga 5 ] 4− polyanionic networks. The ground states of Eu(III) in Eu 2 Ru 3 Si 5 and Eu(II) in Eu 2 Ir 3 Ga 5 were determined by 151 Eu Mössbauer spectroscopy.

The Ca 2 Pd 2 Ge-type stannides Sr 2 Pd 2 Sn and Eu 2 Pd 2 Sn were synthesized by reaction of the elements in sealed tantalum ampoules in a high-frequency furnace and characterized by powder X-ray diffraction. The structure of Sr 2 Pd 2 Sn ( Fdd 2, a = 1063.95(5), b = 1623.22(9), c = 594.63(14) pm, w R 2 = 0.0472, 972 F 2 values and 26 variables) was refined from single-crystal X-ray diffractometer data. The striking structural motif features equidistant chains formed by the palladium atoms (304.7 pm Pd–Pd), which are interlinked by the tin atoms (266.9 and 268.7 pm Pd–Sn). Together, the palladium and tin atoms form a three-dimensional [Pd 2 Sn] δ – polyanionic network in which the strontium atoms reside in larger cavities. The divalent character of europium in Eu 2 Pd 2 Sn was manifested by 151 Eu Mössbauer spectroscopy. The isomer shift is δ = −9.48(1) mm s −1 at room temperature. The results of 119 Sn Mössbauer-spectroscopic experiments have confirmed the tin site determined by the single-crystal study, the isomer shifts being δ = 1.71(1) mm s −1 for Eu 2 Pd 2 Sn and δ = 1.73(1) mm s −1 for Sr 2 Pd 2 Sn. Sr 2 Pd 2 Sn is a Pauli paramagnet with a susceptibility of 2.2(1) × 10 −5 emu mol −1 at room temperature. Eu 2 Pd 2 Sn shows Curie-Weiss paramagnetism with an experimental magnetic moment of 7.85(1) µ B per Eu atom, confirming divalent europium. The europium magnetic moments order antiferromagnetically at T N = 14 K.

The reaction of keten-O,N-acetals, which can exist in tautomeric forms, with orthoamides of alkine carboxylic acids 4 affords pyridine carboxylic acid esters or -nitriles. Analogous reactions of the orthoamides 4 with imidazole-2-yliden-acetic acid ester or -acetonitrile deliver imidazo[1,2- a ]pyridines. From N -alkyl-3,3-diamino-acrylic acid derivatives and orthoamides of propiolic acid 4-aza-heptatriencarbonitriles can be prepared, whereas orthoamides of phenylpropiolic acid deliver directly 2 H -pyrimidine-2-ylidene-cyanacetic acid derivatives. 4-Amino-cumarine reacts with orthoamides 4 to give isomeric 5-oxo-[1]-benzopyrano[4,3- b ]pyridines. The orthoamides 4 transform 1,3-diimino-isoindolin into 2-cyanphenylpyrimidines. 2-(Pyrazol-1-yl)-benzamides can be prepared from 3-indazolinon and orthoamides 4 . The reaction of orthoamides 4 with 6-amino-1,3-dimethyl-uracil proceeds in a complex manner and gives primary products which are very likely imidazo-diazepines. By thermolysis of one of these products a fluorescent pyrolo-imidazolidindione is obtained, which was alkylated with triethyloxonium tetrafluoroborate to give a quaternary ammonium tetrafluoroborate.