Dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate and bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ2N,N′)copper(I) tetrafluoroborate

The single‐crystal X‐ray structures of dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylate, C₁₄H₁₂N₂O₄, and the copper(I) coordination complex bis(dimethyl 2,2′‐bipyridine‐6,6′‐dicarboxylato‐κ²N,N′)copper(I) tetrafluoroborate, [Cu(C₁₄H₁₂N₂O₄)₂]BF₄, are reported. The uncoordinated ligand crystallizes across an inversion centre and adopts the anticipated anti pyridyl arrangement with coplanar pyridyl rings. In contrast, upon coordination of copper(I), the ligand adopts an arrangement of pyridyl donors facilitating chelating metal coordination and an increased inter‐pyridyl twisting within each ligand. The distortion of each ligand contrasts with comparable copper(I) complexes of unfunctionalized 2,2′‐bipyridine.     

catena‐Poly[bis[(η2‐1‐allyl‐3‐aminopyridinium)copper(I)]‐di‐μ‐chloro‐copper(I)‐di‐μ‐chloro‐copper(I)‐di‐μ‐chloro]

Crystals of the title π‐complex, [Cu₄Cl₆(C₈H₁₁N₂)₂]_n, were obtained by means of alternating‐current electrochemical synthesis. The structure consists of infinite copper–chlorine chains to which 1‐allyl‐3‐amino­pyridinium moieties are attached via a η² Cu—(C=C) interaction. The two independent Cu atoms have distinct coordination environments. One is three‐coordinate, surrounded by two chloro ligands and the olefinic bond, whereas the second copper center is surrounded by a tetrahedral arrangement of four Cl atoms. The lower basicity of 3‐amino­pyridine as compared with 2‐ and 4‐amino­pyridine lowers the capacity of the organic ligand for donating to N—H⋯Cl hydrogen bonds and results in the formation of a large inorganic fragment.     

catena‐Poly[[[2,4‐dichloro‐6‐(pyridin‐2‐ylmethyl­iminomethyl)phenolato]copper(II)]‐μ‐thio­cyanato]

The title complex, [Cu(C₁₃H₉Cl₂N₂O)(NCS)]_n, is a novel thio­cyanate‐bridged polynuclear copper(II) compound. The Cu^II atom is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base ligand and one terminal N atom of a bridging thio­cyanate ligand defining the basal plane, and one terminal S atom of another bridging thio­cyanate ligand occupying the axial position. The [2,4‐dichloro‐6‐(pyridin‐2‐ylmethyl­imino­methyl)­phenolato]­copper(II) moieties are linked by the bridging thio­cyanate ligands, forming polymeric chains running along the a axis.     

Synthesis,Characterization, and Crystal Structure of a Polymeric Copper(II) Complex Derived from 2‐(5‐Chloro‐2‐hydroxybenzylideneamino)‐2‐ethylpropane‐1,3‐diol with Catalytic Oxidation Property

The copper(II) complex [Cu₂L₂(μ_1,3‐NCS)₂]_n · nMeOH [HL = 2‐(5‐chloro‐2‐hydroxybenzylideneamino)‐2‐ethylpropane‐1,3‐diol] was synthesized and characterized by elemental analysis, as well as FT‐IR, and UV/Vis spectroscopy. The structures of the ligand and the complex were confirmed by single‐crystal X‐ray diffraction analyses. The Schiff base ligand coordinates to the copper atoms through the phenolate oxygen and imino nitrogen atoms, and one hydroxyl oxygen atom. The copper atoms are in octahedral coordination. The complex is an active catalyst for the oxidation of cyclooctene and styrene with tert‐butylhydroperoxide as the oxidant under mild conditions.     

catena‐Poly[[(2,2′‐diamino‐4,4′‐bithiazole){μ3‐cis‐N‐(2‐carboxylatophenyl)‐N′‐[3‐(dimethylamino)propyl]oxamidato(3−)}dicopper(II)] nitrate 0.6‐hydrate]

The title complex, {[Cu₂(C₁₄H₁₆N₃O₄)(C₆H₆N₄S₂)]NO₃·0.6H₂O}_n, is a one‐dimensional copper(II) coordination polymer bridged by cis‐oxamide and carboxylate groups. The asymmetric unit is composed of a dinuclear copper(II) cation, [Cu₂(dmapob)(dabt)]⁺ {dmapob is N‐(2‐carboxylatophenyl)‐N′‐[3‐(dimethylamino)propyl]oxamidate and dabt is 2,2′‐diamino‐4,4′‐bithiazole}, one nitrate anion and one partially occupied site for a solvent water molecule. The two Cu^II ions are located in square‐planar and square‐pyramidal coordination environments, respectively. The separations of the Cu atoms bridged by oxamide and carboxylate groups are 5.2053 (3) and 5.0971 (4) Å, respectively. The complex chains are linked by classical hydrogen bonds to form a layer and then assembled by π–π stacking interactions into a three‐dimensional network. The influence of the terminal ligand on the structure of the complex is discussed.     

Supramolecular architectures in CoII and CuII complexes with thiophene‐2‐carboxylate and 2‐amino‐4,6‐dimethoxypyrimidine ligands

The coordination chemistry of mixed‐ligand complexes continues to be an active area of research since these compounds have a wide range of applications. Many coordination polymers and metal–organic framworks are emerging as novel functional materials. Aminopyrimidine and its derivatives are flexible ligands with versatile binding and coordination modes which have been proven to be useful in the construction of organic–inorganic hybrid materials and coordination polymers. Thiophenecarboxylic acid, its derivatives and their complexes exhibit pharmacological properties. Cobalt(II) and copper(II) complexes of thiophenecarboxylate have many biological applications, for example, as antifungal and antitumor agents. Two new cobalt(II) and copper(II) complexes incorporating thiophene‐2‐carboxylate (2‐TPC) and 2‐amino‐4,6‐dimethoxypyrimidine (OMP) ligands have been synthesized and characterized by X‐ray diffraction studies, namely (2‐amino‐4,6‐dimethoxypyrimidine‐κN)aquachlorido(thiophene‐2‐carboxylato‐κO)cobalt(II) monohydrate, [Co(C₅H₃O₂S)Cl(C₆H₉N₃O₂)(H₂O)]·H₂O, (I), and catena‐poly[copper(II)‐tetrakis(μ‐thiophene‐2‐carboxylato‐κ²O:O′)‐copper(II)‐(μ‐2‐amino‐4,6‐dimethoxypyrimidine‐κ²N¹:N³)], [Cu₂(C₅H₃O₂S)₄(C₆H₉N₃O₂)]_n, (II). In (I), the Co^II ion has a distorted tetrahedral coordination environment involving one O atom from a monodentate 2‐TPC ligand, one N atom from an OMP ligand, one chloride ligand and one O atom of a water molecule. An additional water molecule is present in the asymmetric unit. The amino group of the coordinated OMP molecule and the coordinated carboxylate O atom of the 2‐TPC ligand form an interligand N—H…O hydrogen bond, generating an S(6) ring motif. The pyrimidine molecules also form a base pair [R₂²(8) motif] via a pair of N—H…N hydrogen bonds. These interactions, together with O—H…O and O—H…Cl hydrogen bonds and π–π stacking interactions, generate a three‐dimensional supramolecular architecture. The one‐dimensional coordination polymer (II) contains the classical paddle‐wheel [Cu₂(CH₃COO)₄(H₂O)₂] unit, where each carboxylate group of four 2‐TPC ligands bridges two square‐pyramidally coordinated Cu^II ions and the apically coordinated OMP ligands bridge the dinuclear copper units. Each dinuclear copper unit has a crystallographic inversion centre, whereas the bridging OMP ligand has crystallographic twofold symmetry. The one‐dimensional polymeric chains self‐assemble via N—H…O, π–π and C—H…π interactions, generating a three‐dimensional supramolecular architecture.     

Facile Synthesis of N‐(Benzyl‐1H‐1,2,3‐Triazol‐5‐yl) Methyl)‐4‐(6‐Methoxybenzo [d] Thiazol‐2‐yl)‐2‐Nitrobenzamides via Click Chemistry

A series of novel N‐((l‐benzyl‐lH‐l,2,3‐triazol‐5‐yl) methyl)‐4‐(6‐methoxy benzo[d ]thiazol‐2‐yl)‐2‐nitrobenzamide derivatives were prepared from 4‐(6‐methoxybenzo[d ]thiazol‐2‐yl)‐2‐nitro‐N‐(prop‐2‐ynyl) benzamide with benzyl azides by using click reaction (copper‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction) in the presence of CuSO₄.5H₂O and sodium ascaorbate. All the newly synthesized compounds were evaluated further in vitro antimicrobial activity against Gram‐positive bacteria (Staphylococcus aureus and Bacillus subtillis ), Gram‐negative bacteria (Echerichia coli and Pseudomonas aeuroginosa ), and fungi (Aspergillus niger and Aspergillusfumigatus ) strains. The new compounds were characterized based on spectroscopic evidence. Among them compounds 10a , 10h , and 10i were showed promising activity when compared with standard drugs Ciprofloxacin and Miconazole.     

2,6‐Bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine and its octahedral copper complex

In the tridentate ligand 2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine, C₂₃H₁₉N₇, both sets of triazole N atoms are anti with respect to the pyridine N atom, while in the copper complex aqua[2,6‐bis(1‐benzyl‐1H‐1,2,3‐triazol‐4‐yl)pyridine](pyridine)(tetrafluoroborato)copper(II) tetrafluoroborate, [Cu(BF₄)(C₅H₅N)(C₂₃H₁₉N₇)(H₂O)]BF₄, the triazole N atoms are in the syn–syn conformation. The coordination of the Cu^II atom is distorted octahedral. The ligand structure is stabilized through intermolecular C—H...N interactions, while the crystal structure of the Cu complex is stabilized through water‐ and BF₄‐mediated hydrogen bonds. Photoluminiscence studies of the ligand and complex show that the ligand is fluorescent due to triazole–pyridine conjugation, but that the fluorescence is quenched on complexation.     

Catalytic Asymmetric Mannich‐Type Reaction Enabled by Efficient Dienolization of α,β‐Unsaturated Pyrazoleamides†

(E)‐α,β‐Unsaturated pyrazoleamides undergo facile dienolization to furnish copper(I)‐(1Z,3Z)‐dienolates as the major in the presence of a copper(I)‐(R)‐DTBM‐SEGPHOS catalyst and Et₃N, which react with aldimines to afford syn‐vinylogous products as the major diastereoisomers in high regio‐ and enantioselectivities. In some cases, the diastereoselectivity is low, possibly due to the low ratio of copper(I)‐(1Z,3Z)‐dienolates to copper(I)‐(1Z,3E)‐dienolates. (Z)‐Allylcopper(I) species is proposed as effective intermediates, which may form an equilibrium with copper(I)‐(1Z,3Z)‐dienolates. Interestingly, the present methodology is a nice complement to our previous report, in which (E)‐β,γ‐unsaturated pyrazoleamides were employed as the prenucleophiles in the copper(I)‐catalyzed asymmetric vinylogous Mannich‐Type reaction and anti‐vinylogous products were obtained. In the previous reaction, copper(I)‐ (1Z,3E)‐dienolates were generated through α‐deprotonation, which might form an equilibrium with (E)‐allylcopper(I) species. Therefore, it is realized in the presence of a copper(I) catalyst that (E)‐α,β‐unsaturated pyrazoleamides lead to syn‐products and (E)‐β,γ‐unsaturated pyrazoleamides lead to anti‐products. Finally, by use of (E)‐β,γ‐unsaturated pyrazoleamide, (E)‐α,β‐unsaturated pyrazoleamide, (R)‐DTBM‐SEGPHOS, and (S)‐DTBM‐SEGPHOS, the stereodivergent synthesis of all four stereoisomers is successfully carried out. Then by following a three‐step reaction sequence, all four stereoisomers of N‐Boc‐2‐Ph‐3‐Me‐piperidine are synthesized in good yields, which potentially serve as common structure units in pharmaceutically active compounds.     

Catalytic,Conjugate Reduction‐Aldol Addition Reaction of β′‐Oxoalkyl α,β‐Unsaturated Carboxylates

Intramolecular conjugate reduction‐aldol addition reactions of β′‐oxoalkyl α,β‐unsaturated carboxylates were performed in the presence of copper catalysts generated in situ from copper salts, phosphine ligands and silanes. Moderate to good yields and high diastereoselectivities were obtained in 15 min to 3 h using bis[(2‐diphenylphosphino)phenyl] ether as the ligand.     

Two‐dimensional square‐grid frameworks formed by self‐associating copper(II) complexes with 1‐(3‐pyridyl)‐ and 1‐(4‐pyridyl)‐substituted butane‐1,3‐diones

In bis­[1‐(3‐pyridyl)butane‐1,3‐dionato]copper(II) (the Cu atom occupies a centre of inversion), [Cu(C₉H₈NO₂)₂], (I), and bis­[1‐(4‐pyridyl)butane‐1,3‐dionato]copper(II) methanol solvate, [Cu(C₉H₈NO₂)₂]·CH₃OH, (II), the O,O′‐chelating diketonate ligands support square‐planar coordination of the metal ions [Cu—O = 1.948 (1)–1.965 (1) Å]. Weaker Cu⋯N inter­actions [2.405 (2)–2.499 (2) Å], at both axial sides, occur between symmetry‐related bis­(1‐pyridylbutane‐1,3‐dion­ato)copper(II) mol­ecules. This causes their self‐organization into two‐dimensional square‐grid frameworks, with uniform [6.48 Å for (I)] or alternating [4.72 and 6.66 Å for (II)] inter­layer separations. Guest methanol mol­ecules in (II) reside between the distal layers and form weak hydrogen bonds to coordinated O atoms [O⋯O = 3.018 (4) Å].     

catena‐Poly[[{4‐bromo‐2‐[2‐(dimethyl­amino)ethyl­imino­methyl]­phenol­ato}­copper(II)]‐μ‐azido]

The title complex, [Cu(C₁₁H₁₄BrN₂O)(N₃)]_n, is an inter­esting azide‐bridged polynuclear copper(II) compound. The Cu^II atom is five‐coordinated in a square‐pyramidal configuration, with one O and two N atoms of one Schiff base and one terminal N atom of a bridging azide ligand defining the basal plane, and another terminal N atom of another bridging azide ligand occupying the axial position. The {4‐bromo‐2‐[2‐(dimethyl­amino)ethyl­imino­meth­yl]phenolato}copper(II) moieties are linked by the bridging azide ligands, forming polymeric chains running along the b axis. Adjacent chains are further linked by weak Br⋯Br inter­actions into a sheet.     

Four‐ and five‐coordinate copper(II) complexes with N‐(4,4‐diphenyl‐5‐oxo‐4,5‐dihydro‐1H‐imidazol‐2‐yl)glycine

The two title mononuclear compounds are four‐coordinate bis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂]·2C₃H₇NO, (I), and five‐coordinate aquabis[N‐(5‐oxo‐4,4‐diphenyl‐4,5‐dihydro‐1H‐imidazolidin‐2‐ylidene)glycinato]copper(II) dimethylformamide disolvate, [Cu(C₁₇H₁₄N₃O₃)₂(H₂O)]·2C₃H₇NO, (II). In (I), the Cu^II ion lies on an inversion centre with one‐half of the complex molecule in the asymmetric unit, while in (II) there are two independent ligand molecules in the asymmetric unit, with the Cu^II ion and coordinated water molecule located on a general position. In both crystal structures, the complex molecules assemble in ribbons via N—H...O hydrogen‐bond networks.     

Di‐μ‐hydroxo‐bis­[aqua(1,10‐phenanthroline‐κ2N,N′)copper(II)] trans‐bis(2‐{[(E)‐5‐formyl‐2‐oxido‐κO‐benzyl­idene]­amino‐κN}ethanesulfonato(2–))copper(II) hexahydrate

The title compound, [Cu₂(OH)₂(C₁₂H₈N₂)₂(H₂O)₂][Cu(C₁₀H₉NO₅S)₂]·6H₂O, is comprised of a copper‐centred complex cation and a copper‐centred complex anion; the cation lies about an inversion centre and in the anion the Cu atom lies on an inversion centre. In the doubly charged bridged dicopper cation, each Cu centre has distorted square‐pyramidal geometry. In the square‐planar dianion, two sulfonate ligands are trans coordinated to the Cu atom via a deprotonated hydroxyl O atom and an imine N atom, forming two six‐membered chelate rings. The structure is stabilized by an extensive hydrogen‐bond system and aromatic‐ring stacking interactions.     

3‐(4‐Cyano­phenyl)­pentane‐2,4‐dione and its copper(II) complex

The β‐diketone 3‐(4‐cyano­phenyl)­pentane‐2,4‐dione crystallizes as the enol tautomer 4‐(2‐hydroxy‐4‐oxopent‐2‐en‐3‐yl)­benzo­nitrile, C₁₂H₁₁NO₂, (I), with an intramolecular O—H⋯O hydrogen bond [O⋯O = 2.456 (2) Å]. Reaction of (I) with copper acetate monohydrate in the presence of triethyl­amine leads to the formation of the copper(II) complexbis­[3‐(4‐cyano­phenyl)­pentane‐2,4‐dionato‐κ²O,O]copper(II), [Cu(C₁₂H₁₀NO₂)₂], (II). In the structure of (II), the Cu atom is coordinated by four β‐diketonate O atoms in a slightly distorted square‐planar geometry, with Cu—O distances in the range 1.8946 (11)–1.9092 (11) Å. The nitrile moieties in (II) make it a candidate for reaction with other metal ions to produce supramolecular structures.     

Structural studies of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine hetero‐scorpionate copper complexes

The structures of five compounds consisting of (prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine complexed with copper in both the Cu^I and Cu^II oxidation states are presented, namely chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(I) 0.18‐hydrate, [CuCl(C₁₅H₁₇N₃)]·0.18H₂O, (1), catena‐poly[[copper(I)‐μ₂‐(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ⁵N,N′,N′′:C²,C³] perchlorate acetonitrile monosolvate], {[Cu(C₁₅H₁₇N₃)]ClO₄·CH₃CN}_n, (2), dichlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) dichloromethane monosolvate, [CuCl₂(C₁₅H₁₇N₃)]·CH₂Cl₂, (3), chlorido{(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II) perchlorate, [CuCl(C₁₅H₁₇N₃)]ClO₄, (4), and di‐μ‐chlorido‐bis({(prop‐2‐en‐1‐yl)bis[(pyridin‐2‐yl)methylidene]amine‐κ³N,N′,N′′}copper(II)) bis(tetraphenylborate), [Cu₂Cl₂(C₁₅H₁₇N₃)₂][(C₆H₅)₄B]₂, (5). Systematic variation of the anion from a coordinating chloride to a noncoordinating perchlorate for two Cu^I complexes results in either a discrete molecular species, as in (1), or a one‐dimensional chain structure, as in (2). In complex (1), there are two crystallographically independent molecules in the asymmetric unit. Complex (2) consists of the Cu^I atom coordinated by the amine and pyridyl N atoms of one ligand and by the vinyl moiety of another unit related by the crystallographic screw axis, yielding a one‐dimensional chain parallel to the crystallographic b axis. Three complexes with Cu^II show that varying the anion composition from two chlorides, to a chloride and a perchlorate to a chloride and a tetraphenylborate results in discrete molecular species, as in (3) and (4), or a bridged bis‐μ‐chlorido complex, as in (5). Complex (3) shows two strongly bound Cl atoms, while complex (4) has one strongly bound Cl atom and a weaker coordination by one perchlorate O atom. The large noncoordinating tetraphenylborate anion in complex (5) results in the core‐bridged Cu₂Cl₂ moiety.     

Copper‐Catalyzed γ‐Selective and Stereospecific Allylic Cross‐Coupling with Secondary Alkylboranes

The scope of the copper‐catalyzed coupling reactions between organoboron compounds and allylic phosphates is expanded significantly by employing triphenylphosphine as a ligand for copper, allowing the use of secondary alkylboron compounds. The reaction proceeds with complete γ‐E‐selectivity and preferential 1,3‐syn stereoselectivity. The reaction of γ‐silicon‐substituted allylic phosphates affords enantioenriched α‐stereogenic allylsilanes.     

One‐Pot,Three‐Component Synthesis of 1‐(2‐Hydroxyethyl)‐1H‐1,2,3‐triazole Derivatives by Copper‐Catalyzed 1,3‐Dipolar Cycloaddition of 2‐Azido Alcohols and Terminal Alkynes under Mild Conditions in Water

A safe, efficient, and improved procedure for the regioselective synthesis of 1‐(2‐hydroxyethyl)‐1H‐1,2,3‐triazole derivatives under ambient conditions is described. Terminal alkynes reacted with oxiranes and NaN₃ in the presence of a copper(I) catalyst, which is prepared by in situ reduction of the copper(II) complex 4 with ascorbic acid, in H₂O. The regioselective reactions exclusively gave the corresponding 1,4‐disubstituted 1H‐1,2,3‐triazoles in good to excellent yields. This procedure avoids the handling of organic azides as they are generated in situ, making this already powerful click process even more user‐friendly and safe. The remarkable features of this protocol are high yields, very short reaction times, a cleaner reaction profile in an environmentally benign solvent (H₂O), its straightforwardness, and the use of nontoxic catalysts. Furthermore, the catalyst could be recovered and recycled by simple filtration of the reaction mixture and reused for ten consecutive trials without significant loss of catalytic activity. No metal‐complex leaching was observed after the consecutive catalytic reactions.     

Copper‐Mediated Addition of Ethanolamine Affording 2‐Hydroxymethyl Naphtho[2,1‐d]oxazoles from 2‐Naphthols

A new and mild synthetic approach was presented for the synthesis of naphtho[2,1‐d]oxazoles. In the presence of copper (II)‐ethanolamine, 2‐hydroxymethyl naphtho[2,1‐d]oxazoles were one‐pot synthesized in moderate to good yields through copper‐mediated oxidation of 2‐naphthols followed with the addition of ethanolamine in acetonitrile.     

Synthesis of 5‐[2‐(guanin‐9‐yl)‐ and 5‐[2‐(2‐aminopurin‐9‐yl)ethyl]‐2‐D‐ribo‐(1,2′,3′,4′‐tetrahydroxybutyl)‐1,3‐dioxane

Stereoselective synthesis of 5‐[2‐(guanin‐9‐yl)‐ and 5‐[2‐(2‐aminopurin‐9‐yl)ethyl]‐2‐D‐ribo‐(1′,2′,3′,4′‐tetrahydroxybutyl)‐1,3‐dioxane, 2‐5, as potential prodrugs of penciclovir, has been accomplished in six steps from readily available 2,3,4,5‐tetra‐O‐acetyl‐aldehydo‐D‐ribose ( 6 ) and the 1,3‐diol 7 . It has been demonstrated that the use of boron trifluoride diethyl etherate (BF₃·Et₂O) in dichloromethane along with excess anhydrous copper(II) sulfate was crucial for the efficient formation of cyclic acetal 8 . In addition, the chromatographic separation of cis and trans isomers of the cyclic acetal at the bromide stage 10 was feasible, which was requisite for the successful stereoselective synthesis of the ribosyl derivatives 2–5 .