Uncatalyzed diastereoselective synthesis of alkyliminofurochromone-derived benzylmalononitriles via a three-component cascade reaction: competition between Diels-Alder cycloaddition and Michael addition.

Diastereoselective Michael addition reactions of 3-(alkylamino)-9H-furo[3,4-b]chromen-9-one intermediate, produced from the [1 + 4] cycloaddition/tautomerization reaction between 3-formylchromones and alkyl isocyanide in dry CH2Cl2, with arylidene malononitrile were developed to afford a wide range of functionalized 2-((S)-((R,Z)-3-(alkylimino)-9-oxo-3,9-dihydro-1H-furo[3,4-b]chromen-1-yl)(aryl)methyl)malononitrile derivatives in good yields and excellent diastereoselectivities under mild conditions. Excellent diastereoselectivity has been achieved to yield products containing two stereogenic carbons and one stereogenic imine group. Two C-C and one C-O bonds were selectively formed to provide new alkylated iminofurochromones in good yields.

Anthracene-Tagged UiO-67-MOF as Highly Selective Aqueous Sensor for Nanoscale Detection of Arginine Amino Acid.

In the present paper, new functionalized UiO-67 metal-organic frameworks (MOF) which contain aromatic tagged groups such as phenyl, naphthyl, and anthracene have been synthesized, characterized, and used for sensing water-soluble amino acids. The results show that anthracene-tagged UiO-67-MOF is shown to act as a highly efficient and selective aqueous sensor for arginine over other water-soluble amino acids in nanoscale. Upon adding an increasing amount of arginine, PL bands of the anth-UiO-67 MOF quenched completely, while there is no perturbation in the PL bands for other amino acid observed. This MOF allows a selective ratiometric detection of arginine without any interference from other amino acids.

Diversity-Oriented Metal Decoration on UiO-Type Metal-Organic Frameworks: an Efficient Approach to Increase CO2 Uptake and Catalytic Conversion to Cyclic Carbonates.

A library of metallo-bipyridine UiO-type metal-organic frameworks (MOFs) has been successfully synthesized by postmetallation of a wide range of metal complexes into bidentate bipyridine moieties. Then, a systematic investigation is devoted to a catalytic evaluation of the resultant MOFs containing a binary Lewis acid function for the synthesis of cyclic carbonates from epoxides and carbon dioxide (CO2). The result indicated that the metal-grafted MOFs exhibit improvement in terms of CO2 uptake capacity and catalytic activity in comparison with their nonmetallated counterparts. The comprehensive investigation provides a valuable insight into the synergetic effects of MOF functionalities including metal node, grafted metal, and its counterion in the cycloaddition reaction. Furthermore, the metal coordination modulation due to its benefits such as being a solvent-free process, nearly full conversion to cyclic carbonates, high selectivity and high CO2 uptake, applying atmospheric CO2 pressure, and excellent stability and easy recyclability of the catalyst demonstrates them as promising candidates for practical utilization of CO2 conversion into value-added chemicals.

N-substituted noscapine derivatives as new antiprotozoal agents: Synthesis, antiparasitic activity and molecular docking study.

Novel N-substituted noscapine derivatives were synthesized by a three-component Strecker reaction of cyclic ether of N-nornoscapine with varied aldehydes, in the presence of cyanide ion. Moreover, the corresponding amides were synthesized by the oxidation of cyanide moieties in good yields. The in vitro antiprotozoal activity of the products was also investigated. Interestingly, some analogues did put on display promising antiparasitic activity against Trypanosoma brucei rhodesiense with IC50 values between 2.5 and 10.0 µM and selectivity index (SI) ranged from 0.8 to 13.2. Eight compounds exhibited activity against Plasmodium falciparum K1 strain with IC50 ranging 1.7-6.4 µM, and SI values between 2.8 and 10.5 against L6 rat myoblast cell lines. Molecular docking was carried out on trypanothione reductase (TbTR, PDB ID: 2WOW) and UDP-galactose 4' epimerase (TbUDPGE PDB: 1GY8) as targets for studying the envisaged mechanism of action. Compounds 6j2 and 6b2 displayed excellent docking scores with -8.59 and -8.86 kcal/mol for TbTR and TbUDPGE, respectively.

Is Gelation Behavior Predictable through a Crystal Engineering Approach? A Case Study in Four Similar Coordination Compounds.

In this paper, a detailed study on the gelation properties of a series of terpyridine and dipyrazine-pyridine ligands in the presence of metal salts is reported. To reveal the driving forces for the self-assembly of the metallogelators, their crystal structure is scrutinized. Inspired by the gelation of CuCl2[Terpy- nCN], where "Terpy- nCN" is 4'-( n-cyanophenyl)-2,2',6',2″-terpyridine, to look into the aggregation behavior of the related analogues, synthesis of CuCl2[Dipyz-py- nCN] derivatives, where "Dipyz-py- nCN" is 4-( n-cyanophenyl)-2,6-di-pyrazin-2-yl-pyridine, with the same cyano groups is performed. We then find that the Dipyz-py counterpart forms crystals when the molecules are stacked in an alternating way, instead of the unidirectional one required for gel formation. A crystal engineering approach is applied to determine the interactions that are favorable for fabricating a fiber network that is likely to be present in both crystalline and gel states and to find the interaction that disturbs this delicate balance between gelation and crystallization in coordination compounds; then, we conclude that the subtle balance between the molecular shape and intermolecular interactions is the origin of the gelation and crystallization of the current molecular system. This enables us to find the mutual connection among the structure of molecules, assembly behavior, and intermolecular interactions. With our experiments, a deep understanding of the balance among solution, gelation, and crystallization with subtle molecular diversions is provided.

Palladium-catalyzed, unsymmetrical homocoupling of thiophenes via carbon-sulfur bond activation: a new avenue to homocoupling reactions.

The Pd-catalyzed, CN-directed unsymmetrical synthesis of 2,4'-bithiophenes via an unprecedented homocoupling reaction is described. The NH2/CN/SMe arrangement breaks the routine. The cooperative performance of the functional groups in thiophenes would open up a new vision in the field of metal catalysis homocoupling reactions by joining the electrophilic and nucleophilic motifs of the substrate. Furthermore, it is found that the α-chelating effect of the carbonyl group in amino thiophene offers a new class of synthetic protocols for C-N cross-coupling with arylboronic acids. The bidentate N,O-chelation provides a series of advantages such as copper-catalyzed, ligand- and base-free under open-flask conditions. Interestingly, the combination of the C-N cross-coupling/homocoupling reactions in a domino fashion led to the bithiophene adducts featuring the C(Ar)-N bond cleavage in the nitrogen that bridged between the two thiophene units.

Pd-Catalyzed regioselective C-H halogenation of quinazolinones and benzoxazinones.

A Pd-catalyzed ortho-selective halogenation of benzoxazinone and quinazolinone scaffolds has been described employing N-halosuccinimide as both a halogen source and an oxidant reagent via C-H bond activation. This transformation shows high chemo- and regioselectivities and demonstrates a broad range of benzoxazinone and quinazolinone substrates with different functional groups and has been scaled up to the gram level.

Synthesis and in Vitro Antibacterial Evaluation of Novel 4-Substituted 1-Menthyl-1,2,3-triazoles.

Menthyl 1,4-disubstituted 1,2,3-triazole derivatives of hydroxybenzaldehydes, phenols and bile acids were synthesized via click chemistry. The novel synthesized compounds were evaluated for their in vitro antibacterial activity against Enterococcus faecium, and Staphylococcus aureus as Gram-positive bacteria. Some derivatives illustrated strong inhibitory effect against E. faecium with the minimum inhibitory concentration (MIC) values ranged from 1-3 µM, where cefixime as a positive control revealed MIC value of 35 µM. The structures of the synthesized compounds were confirmed by different spectroscopic techniques including 1H-NMR, 13C-NMR, high resolution (HR)-MS, IR and X-ray crystallographic analysis.

Labdane Diterpenoids from Salvia leriifolia: Absolute Configuration, Antimicrobial and Cytotoxic Activities.

Fractionation of an n-hexane extract of the aerial parts of Salvia leriifolia led to the isolation of two new (1, 2) and two known (3, 4) labdane diterpenoids, together with three other known compounds. The structures were established by a combination of 1D and 2D NMR, and HRESIMS. The structures of 1 and 3 were confirmed by single-crystal X-ray analysis. The absolute configuration of 1-4 was established by electronic circular dichroism spectroscopy. Compounds 1-4 were evaluated for their cytotoxic activities against MCF-7 human breast cancer cells. Labdanes 3 and 4 were additionally tested against MDA-MB231 human breast cancer and DU-145 human prostate cancer cell lines. Compound 4 showed IC50 values of 25, 50, and 50 µM against MCF-7, MDA-MB231, and DU-145 cells, respectively. Compounds 1-4 were tested for activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. Compound 3 showed an MIC of 213 µM against methicillin-resistant S. aureus.

Conformational variety of flexible mono-dentate ligands in coordination compounds: influence of π-involving interactions.

The effect of intermolecular interactions on the conformational variety of flexible mono-dentate ligands in coordination compounds has been investigated through the preparation of two series of mercury(ii) complexes. In this regard, the molecular and structural architecture of eight complexes, [HgCl2(L(amide-Cl))2] (), [HgCl2(L(amide-Br))2] (), [HgBr2(L(amide-Br))2] (), and [HgI2(L(amide-Br))2] (), as the first series and [HgBr2(L(imine-Cl))2] (), [HgBr2(L(imine-Br))2] (), [HgI2(L(imine-Cl))]n (), and [HgI2(L(imine-Br))]n (), as the second series, using two kind of flexible ligands, N-(1-halonaphthalen-4-yl)nicotinamide, L(amide-X), and 4-halo-N-((pyridin-3-yl)methylene)naphthalen-1-amine, L(imine-X), has been studied. Inspection of the packing of these compounds clearly shows the presence of conformational changes in the arrangement of the ligands in each series. Although there are slight differences between the crystal packing of these compounds, it seems that π-involving intermolecular interactions including πnaphπnaph in the first series and πimineπpy/naph in the second series with the cooperation of Hgπpy can lock the ligand conformational variety to a single conformer.

Structural and spectroscopic characterizations of aluminum phenoxide.

A synthetic route to obtain crystalline aluminum phenoxide was established. Its molecular structure in solid-state and solution is unambiguously determined by single-crystal X-ray diffraction and (1)H, (13)C and (27)Al NMR spectroscopy. The single-crystal X-ray analysis revealed the presence of the dimeric THF adduct [Al(OPh)3·THF]2 with a disordered trigonal bipyramidal geometry at the aluminum atom which is bonded to a THF ligand, two terminal and two bridging phenoxy groups (OPh). The solution behavior of the title compound was investigated by (27)Al NMR in non-coordinating (CDCl3) as well as coordinating (THF) solvents at different temperatures. The obtained results indicate the presence of four- and five-coordinate species in solution.

New ursane triterpenoids from Salvia urmiensis Bunge: Absolute configuration and anti-proliferative activity.

Two new triterpenoids, urmiensolide B (1) and urmiensic acid (2), with rare carbon skeletons together with three known compounds were isolated from the aerial parts of Salvia urmiensis Bunge, an endemic species of Iran. The structures were established by a combination of 1D and 2D NMR, and HRESIMS, and in the case of 2 and 3, their structures were confirmed by single-crystal X-ray analysis. The absolute configuration of 2 was established by electronic circular dichroism (ECD) spectra. The new compounds were evaluated for their anti-proliferative activities against A549 and MCF-7 human cancer cell lines. Compounds 1 and 2 showed IC50 values of 2.8 and 1.6 µM against MCF-7 cells, respectively.

Experimental and theoretical spectroscopic study and structural determination of nickel(II) tridentate Schiff base complexes.

Some new complexes of [NiL(PR3)] (where L=(E)-1-[(2-amino-5-nitrophenyl)iminio-methyl]naphthalene-2-olate (L(1)), (E)-1-[(2-hydroxiphenyl)iminio-methyl]naphthalene-2-olate (L(2)), R=Bu and Ph) containing tridentate ONN and ONO Schiff bases were synthesized and characterized by IR, UV-Vis, (1)H-NMR spectroscopy and elemental analysis. The geometry of [NiL(1)(PBu3)] and [NiL(2)(PBu3)] complexes were determined by X-ray crystallography. It was indicated that the complexes have a square planar structure and four coordinates in the solid state. Theoretical calculations were also performed to optimize the structures of the ligands and complexes in the gas phase and ethanol solvent, separately to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of the complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification.

Structural and spectroscopic characterizations of tetra-nuclear niobium(V) complexes of quinolinol derivatives.

Reactions between niobium ethoxide and 8-hydroxy-2-methylquinoline or 5-chloro-8-hydroxyquinoline have been explored. Two new tetranuclear heteroleptic niobium complexes containing oxo, ethoxo, and quinolinate chelate rings have been synthesized and characterized by (1)H, (13)C and (93)Nb NMR, UV-Vis, and FT-IR spectroscopies, and single-crystal X-ray diffraction. The molecular structures of the niobium complexes, [Nb4(µ-O)4(µ-OEt)2(ONC10H8)2(OEt)8] (I) and [Nb4(µ-O)4(µ-OEt)2(ONC9H5Cl)2(OEt)8] (II), are composed of a pair of edge-sharing bioctahedral moieties in which connected via two almost linear oxo-bridges, with a large difference in the NbO distances. Single-crystal structures showed both complexes are centrosymmetric and contain two distinct Nb centers, and results confirmed by observation of two niobium signals in the (93)Nb NMR spectra of complexes.

Influence of N-heteroaromatic π-π stacking on supramolecular assembly and coordination geometry; effect of a single-atom change in the ligand.

In order to understand how the polarization of aromatic systems, through the introduction of a nitrogen heteroatom, affects the π-π interactions and crystal packing of mercury coordination compounds, in this study, N-(quinolin-2-yl)pyrazine-2-carboxamide and N-(quinolin-3-yl)pyrazine-2-carboxamide ligands were employed in the synthesis of five Hg(II) complexes, [HgBr2(L2=quin)2]n, 1, [HgI2(L2=quin)], 2, [HgCl2(L3=quin)]n, 3, [Hg3Br6(L3=quin)2]n, 4, and [Hg3I6(L3=quin)2]n, 5. X-ray single crystal diffraction analysis of these compounds revealed that all the complexes have polymeric structures except complex 2, which is a discrete compound. Complexes 1 and 3 have 1D and 2D polymeric structures, respectively, while complexes 4 and 5 are 3D coordination polymers. In comparison to homologous complexes containing the N-(naphthalene-2-yl)pyrazine-2-carboxamide ligand, L2=naph, interestingly, the structural analysis clearly shows that the replacement of the naphthyl CH group with a nitrogen atom changes the spatial extent of the π-electron cloud and the polarity of the aromatic ring, from L2=naph adducts to L2=quin and L3=quin adducts, and the propensity to form π-π interactions increases. These π-π stacking interaction synthons affect the coordination geometry and structural assembly. This study reveals the undeniable contribution of π-π stacking interactions to the organization and stabilization of some of the crystal structures reported here.

Effect of robust π-π stacking synthon on the formation of mercury coordination compounds; an unusual pseudo-square planar geometry.

In this study, three Hg(II) complexes, [HgCl2(L(2-naph))]n, 1, [HgBr2(L(2-naph))]n, 2 and [HgI2(L(2-naph))2], 3 where L(2-naph) is N-(naphthalene-2-yl)pyrazine-2-carboxamide ligand have been synthesized and characterized. X-ray single crystal diffraction analysis of these compounds reveals that 1 and 2 are isostructural coordination polymers and 3 is a discrete compound. In comparison to homologue complexes containing N-(naphthalene-1-yl)pyrazine-2-carboxamide ligand, interestingly, structural analysis clearly shows that displacing substituent position plays an important role in the formation of the supramolecular organization of molecular complexes. The common feature in the crystal packing of these complexes is that there is a strong tendency to form π-π stacking interaction between pyrazine and naphthalene rings. These π-π stacking interaction synthons affect the coordination geometry and structural assembly. Also, theoretical methods show the π-π stacking interaction energies within a range of -64.13 to -70.51 kJ mol(-1). It is notable that in 3, cooperation of intermolecular π-π stacking synthon and intramolecular C-H(pyz)···I-Hg hydrogen bond resulted in the formation of unusual pseudo-square planar geometry around the Hg(II) center. This study reveals an undeniable contribution of π-π stacking interaction to the organization and stabilization of some of the crystal structures reported here.

Antitrypanosomal triterpenoid with an ε-lactone E-ring from Salvia urmiensis.

A new triterpenoid, urmiensolide (1), was isolated from Salvia urmiensis. The structure was elucidated by a combination of 1D and 2D NMR, HRESIMS, and X-ray crystallographic analyses. The absolute configuration was established by comparison of experimental and simulated ECD spectra. Urmiensolide is the first pentacyclic triterpenoid bearing a ε-lactone E-ring. The compound showed in vitro antitrypanosoal activity with an IC50 value of 5.6 µM against the Trypanosoma brucei rhodesiense STIB 900 strain and a selectivity index of 33. A possible biosynthetic pathway of 1 from α-amyrin is proposed.

Highly efficient construction of bisspirooxindoles containing vicinal spirocenters through an organocatalytic modified Feist-Bénary reaction.

We have developed an organocatalytic modified Feist-Bénary reaction of cyclic dicarbonyl compounds, isatins and cyclic α-bromo dicarbonyl compounds. This method affords bisspirooxindole-fused dihydrofurans containing two vicinal spiro centers. To the best of our knowledge, employing cyclic α-halo dicarbonyl compounds for the synthesis of bisspirooxindole-fused dihydrofurans has not been previously reported.

One-pot three-component synthesis of pyrano [3,2-b]pyrazolo[4,3-e]pyridin-8(1H)-ones.

An efficient one-pot synthesis of novel pyrano[3,2-b]pyrazolo[4,3-e]pyridin-8(1H)-ones via three-component condensation of kojic acid, 1-H-pyrazol-5-amines and aldehydes in the presence of a catalytic amount of Zn(OTf)(2) followed by H(2)O(2)-mediated oxidation is reported. Furthermore, the synthesis of 1'H-spiro[indoline-3,4'-pyrano[2,3-b]pyrazolo[3,4-e]pyridine]-2,8'(9'H)-diones were chosen for the library validation.