Delocalization Effects and Tunable Emission in a Class of Charged Cyclazines with Nitrogen on the Periphery.

A new class of cyclazine analogues with periphery reminiscent of an aza[10]annulene framework, tethered internally by an sp carbon, is presented. In depth structure analysis based on NMR and X-ray diffraction data gave a deeper insight into the effect of electron delocalization on their structure and properties. A characteristic change in chemical shift positions suggested an aromatic ring current in these systems.

Synthesis and in vitro study of antiproliferative benzyloxy dihydropyrimidinones.

In this study, we report on antiproliferative benzyloxy dihydropyrimidinones (DHPMs) produced by the Biginelli reaction of benzyloxy benzaldehyde, urea, and diverse 1,3-diones. The reaction was catalyzed by lanthanum triflate and completed within 1-1.5 h, with 74-97% yield.

Palladium catalyzed carbonylative annulation of the C(sp)-H bond of N,1-diaryl-1H-tetrazol-5-amines and N,4-diaryl-4H-triazol-3-amines to quinazolinones.

Pd(ii) catalyzed direct C-H carbonylative annulation of N,1-diaryl-1H-tetrazol-5-amines and N,4-diaryl-4H-1,2,4-triazol-3-amines gave the corresponding triazole and tetrazole fused quinazolinones in good yields. This methodology offers a convenient method for the synthesis of these important heterocyclic scaffolds in a highly atom economical process. On the mechanistic aspect weakly nucleophilic triazole and tetrazole moieties function as both directing as well as intramolecular nucleophiles.

Electron Precise Group 5 Dimetallaheteroboranes [{CpV(μ-EPh)}{μ-η:η-BHE}] and [{CpNb(μ-EPh)}{μ-η:η-BHE}] (E = S or Se).

Synthesis and structural elucidation of various electron precise group 5 dimetallaheteroboranes have been described. Room temperature reaction of [CpVCl] with Li[BH(EPh)], generated from the treatment of LiBH·THF and PhE (E = S or Se), for 1 h in toluene, followed by thermolysis, led to the formation of bimetallic complexes [{CpV(μ-EPh)}{μ-η:η-BHE}], 1 and 2 (1: E = S and 2: E = Se), and [{CpV(μ-SePh)}{μ-η:η-BH(OCH)Se}], 3. One of the striking features of these compounds is that they represent a rare class of distorted tetrahedral clusters having bridging hydrogens.

Nb and Ta benzotriazole or benzoxazole phenoxide complexes as catalysts for the ring-opening polymerization of glycidol to synthesize hyperbranched polyglycerols.

A series of novel mononuclear (1a-7a and 1b-6b) as well as tetranuclear (8a and 9a) niobium (Nb) and tantalum (Ta) complexes of benzotriazole or benzoxazole phenoxide pro-ligands bearing different substituents at the ortho and para positions of the phenol rings were synthesized and characterized. The reaction of NbCl or TaCl with one equivalent of benzotriazole or benzoxazole phenoxide pro-ligands (L1H-L6H) in dry toluene or chloroform produced the corresponding chloride (1a-6a and 1b-6b) and ethoxy (7a) mononuclear Nb and Ta complexes in high yields. Furthermore, from the mononuclear Nb complexes (1a or 4a), a new structural form of tetrameric niobium complexes (8a and 9a) was synthesized through a controlled hydrolysis reaction.

Correction: Triamide macrocyclic chloride receptors via a one-pot tandem reduction-condensation-cyclization reaction.

Correction for 'Triamide macrocyclic chloride receptors via a one-pot tandem reduction-condensation-cyclization reaction' by Harekrushna Behera, et al., Org. Biomol.

Bite-Angle-Regulated Coordination Geometries: Tetrahedral and Trigonal Bipyramidal in Ni(II) with Biphenyl-Appended (2-Pyridyl)alkylamine ,'-Bidentate Ligands.

Two simple biphenyl-appended (2-pyridyl)alkylamine -bidentate ligands, L and L, having ethylene and methylene spacers between donor groups, with bite angles L ≈ 100° and L ≈ 80°, dictate pseudotetrahedral and trigonal-bipyramidal geometries in six high-spin Ni(II)-halide complexes, [Ni(L)X] and [Ni(L)X](ClO) (where X = Cl, Br, I), respectively. The structures in the solid state, determined using X-ray crystallography, and in solution, determined using spectroscopic methods (UV-vis-NIR and paramagnetic H NMR), which complement each other, are described.

Triamide macrocyclic chloride receptors via a one-pot tandem reduction-condensation-cyclization reaction.

A pyridine containing triamide macrocycle and its substituted analog have been synthesized in one pot from the corresponding monomer without the use of coupling reagents. The macrocycle can selectively bind chloride ions. The ease of synthesis and chloride-binding properties of the macrocycle make it a highly attractive scaffold for ion-encapsulation, ion-transport and water purification.

Sulfamide-Lattice Restructuring To Form Dimensionally Controlled Molecular Arrays and Gel-Forming Systems.

A design approach that incorporates structural requirements for the formation of a 1D assembly, fibril stability, and fibril-fibril interactions for gelation was attempted by using amino acid-based sulfamides with the general structure Aa-NH-SO -NH-Aa (Aa=amino acid). A preference for 1D assembly alone was not a sufficient condition for gelation, which became evident from studies involving sulfamide esters 1-5. Reducing the crystallization tendency without hindering unidirectional growth was executed through diacids of the sulfamide precursors with various amines that form an envelope around the sulfamide core through salt bridges.

Group 4 metal complexes of Trost's semi-crown ligand: synthesis, structural characterization and studies on the ring-opening polymerization of lactides and ε-caprolactone.

The synthesis of titanium(IV), zirconium(IV) and hafnium(IV) complexes of Trost's semi-crown ligand is described. All complexes were fully characterized by 1H and 13C NMR and mass spectroscopy. The molecular structures of the representative complexes 2, 3 and 4 were determined by single-crystal X-ray diffraction studies.

Cation-Transporting Peptides: Scaffolds for Functionalized Pores?

Protein pores that selectively transport ions across membranes are among nature's most efficient machines. The selectivity of these pores can be exploited for ion sensing and water purification. Since it is difficult to reconstitute membrane proteins in their active form for practical applications it is desirable to develop robust synthetic compounds that selectively transport ions across cell membranes.

Synthesis and characterization of group 4 metal alkoxide complexes containing imine based bis-bidentate ligands: effective catalysts for the ring opening polymerization of lactides, epoxides and polymerization of ethylene.

A series of Ti(iv), Zr(iv) and Hf(iv) complexes containing imine based bis-bidentate ligands were synthesized and characterized by various spectroscopic techniques, elemental analysis and X-ray crystallography. The ligands m-xysal-((t)Bu)4 (L(1)((t)Bu)4), m-xysal-(Me)2((t)Bu)2 (L(2)Me2((t)Bu)2) and m-xysal-(Cl)4 (L(3)Cl4) were reacted with Ti(O(i)Pr)4, Zr(O(i)Pr)4·(i)PrOH and Hf(O(t)Bu)4 in a 1 : 1 stoichiometric ratio to form complexes (L2M2(OR)4, where L = m-xysal-((t)Bu)4, m-xysal-(Me)2((t)Bu)2 and m-xysal-(Cl)4, M = Ti and R = (i)Pr, (L2M2(OR)4, where L = m-xysal-((t)Bu)4, m-xysal-(Me)2((t)Bu)2 and m-xysal-(Cl)4, M = Zr and R = (i)Pr and (L3M3(OR)6, where L = m-xysal-((t)Bu)4, m-xysal-(Me)2((t)Bu)2 and m-xysal-(Cl)4, M = Hf and R = (t)Bu respectively. Complex was crystallized from a 1 : 1 : 1 mixture of chloroform, ethanol and toluene to yield an ethoxy substituted complex (L2M2(OR)4, L = m-xysal-(Me)2((t)Bu)2, M = Zr and R = Et.

Facile base-free in situ generation and palladation of mesoionic and normal N-heterocyclic carbenes at ambient conditions.

Synthesis of normal and mesoionic N-heterocyclic carbene Pd(II) complexes in near quantitative yields from the corresponding NHC precursor salts under base free and ambient conditions is reported. A plausible mechanism involving charge-assisted hydrogen bonded intermediates is proposed.

Efficient and versatile catalysis of N-alkylation of heterocyclic amines with alcohols and one-pot synthesis of 2-aryl substituted benzazoles with newly designed ruthenium(II) complexes of PNS thiosemicarbazones.

Ruthenium(II) carbonyl complexes with phosphine-functionalized PNS type thiosemicarbazone ligands [RuCl(CO)(EPh3)(L)] (1-6) (E = P or As, L = 2-(2-(diphenylphosphino)benzylidene) thiosemicarbazone (PNS-H), 2-(2-(diphenylphosphino)benzylidene)-N-methylthiosemicarbazone (PNS-Me), 2-(2-(diphenylphosphino)benzylidene)-N-phenylthiosemicarbazone (PNS-Ph)) have been synthesized and characterized by elemental analysis and spectroscopy (IR, UV-Vis, (1)H, (13)C, (31)P-NMR) as well as ESI mass spectrometry. The molecular structures of complexes 1, 2 and 6 were identified by means of single-crystal X-ray diffraction analysis. The analysis revealed that all the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate PNS fashion.

Effect of distal sugars and interglycosidic linkage on the N-glycoprotein linkage region conformation: synthesis and X-ray crystallographic investigation of β-1-N-alkanamide derivatives of cellobiose and maltose as disaccharide analogs of the conserved chitobiosylasparagine linkage.

The linkage region constituents, 2-deoxy-2-acetamido-β-D-glucopyranose (GlcNAc) and L-asparagine (Asn) are conserved in the N-glycoproteins of all eukaryotes. Elucidation of the structure and conformation of the linkage region of glycoproteins is important to understand the presentation and dynamics of the carbohydrate chain at the protein/cell surface. Earlier crystallographic studies using monosaccharide models and analogs of N-glycoprotein linkage region have shown that the N-glycosidic torsion, ϕN, is more influenced by the structural variation in the sugar part than that of the aglycon moiety.

Group IV complexes containing the benzotriazole phenoxide ligand as catalysts for the ring-opening polymerization of lactides, epoxides and as precatalysts for the polymerization of ethylene.

A series of Ti(IV), Zr(IV) and Hf(IV) benzotriazole phenoxide (BTP) complexes were synthesized and characterized by various spectroscopic techniques, elemental analysis and X-ray crystallography. The monosubstituted Zr(IV) BTP complexes [(μ-L)Zr(O(i)Pr)3]2 1-3 [L = (C1)BTP-H (1), (TCl)BTP-H (2), (pent)BTP-H (3)] and tetrasubstituted Zr(IV), Hf(IV) complexes ZrL4 4-6 [L = (C1)BTP-H (4), (TCl)BTP-H (5), (pent)BTP-H (6)] and HfL4 7-9 [L = (C1)BTP-H (7), (TCl)BTP-H (8), (pent)BTP-H (9)] were prepared by the reaction of Zr(O(i)Pr)4·((i)PrOH) and Hf(O(t)Bu)4 in toluene with the respective ligands in different stoichiometric proportions. The reaction between BTP and TiCl4 and ZrCl4 and HfCl4 in a 2 : 1 stoichiometric reaction resulted in the formation of disubstituted group IV chloride complexes L2MCl2 10-12 [L = (C1)BTP-H, M = Ti, Zr and Hf].

Imino phenoxide complexes of niobium and tantalum as catalysts for the polymerization of lactides, ε-caprolactone and ethylene.

Imino phenoxide complexes of Nb and Ta show precise control towards the solvent free ring-opening polymerization of lactides (LA) and ε-caprolactone (CL). There is a close proximity between the observed number average molecular weight (M(n)) and theoretical molecular weight and the molecular weight distributions (MWDs) were found to be narrow. Analysis of low molecular weight oligomers of LA synthesized from these compounds revealed that the ligand is incorporated as one of the end terminal groups in the polymer chain.

Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki-Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies.

trans-Bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride has been shown to be an excellent catalyst for the multiple Suzuki-Miyaura coupling reactions of polybromoarenes to the corresponding fully substituted polyarylarenes. The reactions proceeded in excellent yields and with high turnover numbers. With 1,4-dibromobenzene the catalyst was found to be active for up to 13 consecutive cycles with a turnover number of 1260.

1,1'-Binaphthyl-2,2'-diyl benzyl-phos-phoramidate.

In the title compound, C(27)H(20)NO(3)P, the P atom exhibits a somewhat distorted PNO(3) tetra-hedral geometry, with the O-P-O angle for the binaphthyl fragment being 102.82 (6)°. The dihedral angle between the naphthyl ring systems is 59.

Salen complexes of zirconium and hafnium: synthesis, structural characterization, controlled hydrolysis, and solvent-free ring-opening polymerization of cyclic esters and lactides.

Dinuclear salen compounds of zirconium and hafnium are efficient initiators for the solvent-free ring-opening polymerization of cyclic ester monomers and lactides. There is a correlation between the theoretical and experimental number-average molecular weights (M(n)'s) in these polymerizations. Polymerization of β-butyrolactone gives poly(3-hydroxybutyrate) with a good M(n) and molecular weight distribution.

Multi-chelation approach towards natural product-like skeletons: one-pot access to a nitrogen-containing tetracyclic framework from AlaAla dipeptide.

Reductive transformation of the dipeptide BocAlaAlaOMe to a complex, internally charge-stabilized, natural product-like skeleton in one synthetic step is discussed. Stepwise replacement of the B-H bonds in borane by B-N or B-O resulted in incorporation of three boron atoms in a tetracyclic framework whereby one is stereogenic!

Stereocontrolled facile synthesis and antimicrobial activity of oximes and oxime ethers of diversely substituted bispidines.

A small library of diversely substituted 2,4,6,8-tetraaryl-3,7-diazabicyco[3.3.1]nonan-9-ones, their oximes and O-methyloximes were achieved in a stereocontrolled manner by an easiest synthetic strategy as single isomers with high yields.

Stereospecific synthesis of oximes and oxime ethers of 3-azabicycles: A SAR study towards antimicrobial agents.

Libraries of 1-methyl-2,4-diaryl-3-azabicyclo[3.3.1]nonan-9-ones/oximes/O-methyloximes 1-14/15-28/29-42 and 7-methyl-2,4-diaryl-3-azabicyclo[3.

p-Tolyl-methanaminium cyclo-hexane-1,2-diyl phosphate.

In the title mol-ecular salt, C(8)H(12)N(+)·C(6)H(10)O(4)P(-), the cation and anion are connected by N-H⋯O hydrogen bonds. The C atoms of the cyclo-hexane ring are disordered over two sets of sites in a 0.51 (4):0.

Triethyl-ammonium 1,1'-binaphthyl-2,2'-diyl phosphate.

In the crystal structure of the title compound, C(6)H(16)N(+)·C(20)H(12)O(4)P(-), an N-H⋯O inter-action links the cation to the anion. The N atom in the triethyl-ammonium cation exhibits a trigonal-bipyramidal coordination geometry and forms an N-H⋯O inter-action with one phosphate O atom of the 1,1'-binaphthyl-2,2'-diyl phosphate ligand. A bifurcated C-H⋯O inter-action with the other phosphate O atom links molecules along the a axis.