Enantioselective synthesis of C3-functionalized 2,1-benzothiazine 2,2-dioxides by N-heterocyclic carbene catalysis.

We present herein an approach for the enantioselective C3-functionalization of 2,1-benzothiazine 2,2-dioxides using N-heterocyclic carbene (NHC) catalysis. Our method involves a sequence of [3+3] cycloaddition and ring-opening reactions with different - and -nucleophiles, followed by silylation. Overcoming the challenge of selectivity targeting the C3 position, this protocol demonstrates a broad substrate scope and high enantioselectivity.

Enantioselective [3 + 3] Annulation-Deoxalation Strategy for Rapid Access to δ-Oxoesters via N-Heterocyclic Carbene Catalysis.

A new and unprecedented stereoselective synthetic approach to δ-oxoesters derivatives from readily available starting materials has been developed. This method, catalyzed by N-heterocyclic carbene, involves an annulation-deoxalation reaction of alkynyl aldehydes with 2,4-diketoesters and proceeds via the chiral α,β-unsaturated acylazolium intermediates. The annulation includes the formation of dihydropyranones, which undergo ring-opening methanolysis with Lewis acid activation, followed by deoxalation to afford chiral 1,5-ketoesters in moderate to good yields.

Tailoring the dimensionality of metal complexes via ligand modifications.

A series of Cu complexes obtained under the same reaction conditions has been analyzed to gain insight into the effect of the ligand composition on the final reaction product. Dipodal ligands containing N-donor imidazole rings and a benzene ring as a spacer with different numbers of methyl substituents on the aromatic rings were selected for the study such as 1,3-bis(imidazol-1-ylmethyl)benzene (L1), 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene (L2), 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (L3), 1,3-bis(2-methylimidazol-1-ylmethyl)-2,4,6-trimethylbenzene (L4). L4 has not been reported previously and was synthesized for this study.

Solvent-induced polymorphism in dipodal N-donor ligands containing a biphenyl core.

Polymorph screenings for two related dipodal N-donor ligands containing a biphenyl core, namely 4,4'-bis(pyridin-4-ylmethyl)-1,1'-biphenyl (1) and 4,4'-bis(1-imidazol-1-ylmethyl)-1,1'-biphenyl (2) were performed, and the new phases were isolated and their crystal structures analysed. Profiling included methods such as PXRD and thermal analysis. Hirshfeld surface analyses, as well as crystal lattice energy calculations provided deeper insight in the interplay of the intermolecular forces and the stability of the isolated phases.

Sawhorse-type ruthenium complexes with triazolopyrimidine ligands - what do they represent in terms of cytotoxic and CORM compounds?

Three sawhorse-type ruthenium(I) complexes containing purine analogs such as triazolopyrimidines of the general formula [Ru(CO)(μ-OOCCH)(L)], where L is 1,2,4-triazolo[1,5-]pyrimidine (tp for 1), 5,7-ditertbutyl-1,2,4-triazolo[1,5-]pyrimidine (dbtp for 2) and 5,7-diphenyl-1,2,4-triazolo[1,5-]pyrimidine (dptp for 3), have been synthesized and characterized by elemental analysis, infrared analysis, multinuclear magnetic resonance spectroscopic techniques (H, C, N), and single-crystal X-ray diffraction (for 1 and 2). By assay with myoglobin, the photo-activated CO-releasing molecule (PhotoCORM) character of (1-3) has been confirmed, thus indicating the possibility of use in CO-based therapies. The importance of UV-induced modification has been investigated in the context of anticancer properties.

From Isostructurality to Structural Diversity of Ag(I) Coordination Complexes Formed with Imidazole Based Bipodal Ligands, and Disclosure of a Unique Topology.

Two Ag(I) complexes with 1,3-bis(imidazol-1-ylmethyl)benzene () and counterions BF () and PF () were synthesized in order to check their behavior in forming molecular/crystal structures. This allows comparison with the final products of analogous syntheses performed with similar bidentate ligands containing methyl substituents on the benzene ring, namely 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene () and 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (). The Ag(I) complexes obtained with the methylated ligands mentioned above form isostructural pairs of waved 1D chains or dinuclear boxes, of general formula {[Ag()]X} and [Ag()]X, respectively (X = BF, PF), under the same reaction conditions.

Effect of conjugated system extension on structural features and electron-density distribution in charge-transfer difluoroborates.

A comparative structural study of two related donor-acceptor pyridine-based BF complexes, namely, 3-(dimethylamino)-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, CHBFNO (1), and 3-{(1E,3E)-4-[4-(dimethylamino)phenyl]buta-1,3-dien-1-yl}-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, CHBFNO (2), containing a dimethylamino group and either the shortest (in 1) or the longest (in 2) charge-transfer path known until now in this family of compounds, is presented. Single-crystal X-ray diffraction analysis supported by computational investigations shed more light on these systems, indicating, among other aspects, the predominance of C-H..

Solution/Ammonolysis Syntheses of Unsupported and Silica-Supported Copper(I) Nitride Nanostructures from Oxidic Precursors.

Herein we describe an alternative strategy to achieve the preparation of nanoscale CuN. Copper(II) oxide/hydroxide nanopowder precursors were successfully fabricated by solution methods. Ammonolysis of the oxidic precursors can be achieved essentially pseudomorphically to produce either unsupported or supported nanoparticles of the nitride.

Counterion Effect and Isostructurality in a Series of Ag(I) Complexes Containing a Flexible, Imidazole Based Dipodal Ligand.

The crystal structures of a series of Ag(I) complexes with 1,3-bis(imidazol-1-ylmethyl)-5-methylbenzene () and the counterions BF (), PF (), ClO (), and CFSO () were analysed to determine the effect of the latter on their formation. All resulting compounds crystallise in the non-centrosymmetric space group of a monoclinic system and show the formation of cationic, polymeric 1D Ag(I) complexes. SCXRD analyses revealed that compounds - are isostructural, though shows opposite handedness compared to and , resulting in an inversed packing arrangement.

New organometallic ruthenium(ii) complexes with purine analogs - a wide perspective on their biological application.

Three half-sandwich organometallic ruthenium(ii) complexes containing purine analogs such as triazolopyrimidines of general formula [(η-p-cym)Ru(L)Cl], where p-cym represents p-cymene and L is 5,6,7-trimethyl-1,2,4-triazolo[1,5-a]pyrimidine (tmtp for 1), 5,7-diethyl-1,2,4-triazolo[1,5-a]pyrimidine (detp for 2) and 5-methyl-1,2,4-triazolo[1,5-a]pyrimidin-7(4H)-one (HmtpO for 3), have been synthesized and characterized by elemental analysis, infrared, multinuclear magnetic resonance spectroscopic techniques (H, C, N), and single-crystal X-ray diffraction (for 1 and 2). All these complexes have been thoroughly screened for their in vitro cytotoxicity against MCF-7 and HeLa cell lines as well as L929 murine fibroblast cells, indicating [(η-p-cym)Ru(HmtpO)Cl] (3) as the most active representative against the HeLa cell line and simultaneously being 64-fold less toxic to normal L929 murine fibroblast cells than cisplatin. At the same time, 3 has shown antimetastatic activity comparable to NAMI-A against HeLa cells both after 24 and 48 h of treatment in a wound healing assay.

First dinuclear rhodium(II) complexes with triazolopyrimidines and the prospect of their potential biological use.

Five novel rhodium(II) complexes of general formula [Rh(μ-OOCCH)L], where L is a triazolopyrimidine derivative, in particular dimethyl-1,2,4-triazolo[1,5-a]pyrimidine (dmtp) for (1), 5,7-diethyl-1,2,4-triazolo[1,5-a]pyrimidine (detp) for (2), 7-isobutyl-5-methyl-1,2,4-triazolo[1,5-a]pyrimidine (ibmtp) for (3), 7-hydroxy-5-methyl-1,2,4-triazolo[1,5-a]pyrimidine (HmtpO) for (4) and 5,7-ditertbutyl-1,2,4-triazolo[1,5-a]pyrimidine (dbtp) for (5) are reported. These first representatives of paddle-wheel dirhodium complexes with triazolopyrimidines have been characterized by IR and NMR spectroscopy as well as by single-crystal X-ray diffraction studies. Three of the new complexes (1), (2) and (5) were thoroughly screened in vitro for their cytotoxicity against human breast cancer cell line MCF-7 and L929 murine fibroblast cells.

Synthesis, structure and biological evaluation of ruthenium(III) complexes of triazolopyrimidines with anticancer properties.

Six novel ruthenium(III) complexes of general formula [RuCl(L)] (1,3,5) and [RuCl(HO)(L)] (2,4,6), where L stands for three different triazolopyrimidine-derived ligands, are reported. The compounds have been structurally characterized (IR, EPR, SCXRD), and their magnetic moments have been determined. The single-crystal X-ray diffraction study revealed a slightly distorted octahedral geometry of the Ru(III) complexes with mer configuration in 1 and 5, and fac configuration in 3.

Allylation of Orthoquinones Towards Annulated Polycyclic Aromatic Systems.

Promising results of an efficient and convenient strategy for the annulation of polycyclic aromatic compounds (PACs), employing orthoquinones as starting material and comprising allylation, pinacol rearrangement, ring-closing metathesis (RCM), and one-pot reduction followed by Wagner-Meerwein rearrangement, are presented. The strategy involves introducing triallylborane prepared in situ in the allylation step. Moreover, a novel expedient method for the preparation of 9,10-diallylphenanthrene was introduced.

Homodiselenacalix[4]arenes: Molecules with Unique Channelled Crystal Structures.

A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert-butyl ester groups. Single-crystal X-ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level.

The gold-hydrogen bond, Au-H, and the hydrogen bond to gold, Au∙∙∙H-X.

In the first part of this review, the characteristics of Au-H bonds in gold hydrides are reviewed including the data of recently prepared stable organometallic complexes with gold(I) and gold(III) centers. In the second part, the reports are summarized where authors have tried to provide evidence for hydrogen bonds to gold of the type Au∙∙∙H-X. Such interactions have been proposed for gold atoms in the Au(-I), Au(0), Au(I), and Au(III) oxidation states as hydrogen bonding acceptors and H-X units with X = O, N, C as donors, based on both experimental and quantum chemistry studies.

A fragment-based approach toward substituted trioxa[7]helicenes.

A series of novel substituted trioxa[7]helicenes have been successfully prepared by a one-pot palladium catalyzed C-H arylation reaction starting from readily prepared dibenzofuran fragments. The dinitro-substituted helicene was analyzed by X-ray crystallography revealing the occurrence of two distinct enantiomers in the asymmetric unit, which forms interesting supramolecular motifs in the crystal, based on weak H-bonding interactions.

Homoselenacalix[4]arenes: synthetic exploration and metallosupramolecular chemistry.

Homoselenacalix[4]arenes were synthesized by a [2 + 2] reductive coupling protocol favouring the cyclotetramers. The inner and outer-rim decoration was varied and a bicyclic derivative was prepared by a similar one-pot procedure. Conformational analysis in solution and the solid state showed noticeable differences between the homoselenacalix[4]arenes and the analogous homothiacalix[4]arenes and provided insight into the metal binding potential of the Se-bridged macrocycles.

Amides of gold(I) diphosphines prepared from N-heterocyclic sources and their in vitro and in vivo screening for anticancer activity.

A series of new neutral mononuclear or dinuclear gold(I) complexes and a cyclic cationic tetranuclear amidogold(I) complex comprising of the phosphines 1,2-bis(dimethylphosphino)ethane (dmpe), μ-1,2-bis(diphenylphosphino)ethane (dppe), μ-1,3-bis(diphenylphosphino)propane (dppp), μ-1,5-bis(diphenylphosphino)pentane (dpppe), μ-1,6-bis(diphenylphosphino)hexane (dpph) or trimethylphosphine, and several N-heterocyclic ring systems (imidazolate, pyrazolate, 1,2,3-triazolate, 1,2,4-triazolate, pyrrolate, 9H-purine-9-ate or 9H-purine-6-amine-9-ate) as ligands, reveal intermolecular aurophilic interactions and 2D channels available for solvent molecules in some of their crystal structures. The antitumour activity of the acyclic gold(I) compounds is highly dependent on the substituents on the phosphorus atoms being highest for phenyl groups and lower for methyl groups. The activity of these compounds against selected cell lines is linked to the length of the carbon bridge between the two phosphorus atoms being highest with a bridge consisting of 5 or 6 carbons.

Synthesis of functionalized dioxa-aza[7]helicenes using palladium catalyzed arylations.

Despite the recent reports on transition-metal catalyzed cycloisomerization strategies toward helicenes, the amount of palladium catalyzed routes remains rather scarce. Within this letter the successful preparation and characterization of novel dioxa-aza[7]helicenes using palladium mediated coupling reactions is presented.

Bis(di-2-pyridyl-amine-κN,N')bis-(thio-cyanato-κN)nickel(II).

The mononuclear neutral title complex, [Ni(NCS)(2)(C(10)H(9)N(3))(2)], shows a cis-octa-hedral geometry around the Ni(II) ion, formed by two chelating di-2-pyridyl-amine (Hdpa) ligands and two thio-cyanate anions. Both amine H atoms are involved in N-H⋯S hydrogen bonding, resulting in the formation of layers of inter-linked mol-ecules parallel to the ab plane, which are further held together by weak π-π inter-actions between adjacent complexes, involving one ring of each dipyridyl-amine unit [centroid-centroid distance = 3.777 (4) Å], forming a three-dimensional assembly.

1,1,2,2-Tetra-kis(1,3-benzoxazol-2-yl)ethene.

The title compound, C(30)H(16)N(4)O(4), reveals [Formula: see text] crystallographic and mol-ecular symmetry and accordingly the asymmetric unit comprises one half-mol-ecule. The dihedral angle between the planes of the two geminal benzoxazole rings is 74.39 (5)°.

(Penta-fluoro-propionato-κO)tetra-kis-(trimethyl-phosphine oxide-κO)copper(II) penta-fluoro-propionate.

The title compound, [Cu(C(3)F(5)O(2))(C(3)H(9)OP)(4)](C(3)F(5)O(2)), comprises a cationic Cu(II) complex and a disordered penta-fluoro-propionate counter-ion. The metal atom has a distorted square-pyramidal coordination environment formed by four O atoms originating from trimethyl-phosphine oxide mol-ecules and the remaining one belonging to the monodentate penta-fluoro-propionate anion, which is situated in the basal plane of the pyramid. The mol-ecules are held together in the crystal by a net of weak C-H⋯O and C-H⋯F hydrogen bonds.

2-(4-Meth-oxy-benz-yl)-4,6-diphenyl-2,5-diaza-bicyclo-[2.2.2]oct-5-en-3-one.

In the crystal structure of the title compound, C(26)H(24)N(2)O(2), weak inter-molecular C-H⋯π inter-actions involving the benzene of the p-methoxy benzyl group and one of the phenyl rings result in the formation of chains consisting of alternating enanti-omers. Weak C-H ⋯O inter-actions with the methoxy O atom lead to the formation of layers, which are inter-linked by further C-H⋯O inter-actions into a three-dimensional assembly.

Novel N-heterocyclic ylideneamine gold(I) complexes: synthesis, characterisation and screening for antitumour and antimalarial activity.

Ylideneamine functionalised heterocyclic ligands, 1,3-dimethyl-1,3-dihydro-benzimidazol-2-ylideneamine (I), 3-methyl-3H-benzothiazol-2-ylideneamine (II) or 3,4-dimethyl-3H-thiazol-2-ylideneamine (III), were employed in the preparation of a series of both charged and neutral gold(I) complexes consisting either of a Au(C(6)F(5)) fragment (1-3), a [Au(PPh(3))](+) unit (4-6) or a [Au(NHC)](+) unit (7) coordinated to the imine nitrogen of the neutral ylideneamine ligand. These complexes were fully characterised by various techniques including X-ray diffraction. In addition, the antitumour and antimalarial potential of selected compounds were assessed in a preliminary study aimed at determining the medicinal value of such compounds.