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A novel method for the preparation of tetrahydropentaleno[1,2

A series of benzylidene-3-pyrrolines were prepared from chalcone derivatives, arylacetylene and sulfonamide via a three-step sequence without the isolation of intermediates. Typically, the reaction of 1,3-di-p-tolylprop-2-en-1-one with lithium phenylacetylide was followed by substitution with tosylamide and then silver-catalyzed 5-exo-dig cyclization to give N-tosyl-2-benzylidene-3,5-di-p-tolyl-2,5-dihydro-1H-pyrrole with a 86% yield. Furthermore, transformation to the corresponding substituted 3-pyrrolin-2-one and pyrrole by m-chloroperbenzoic acid (mcpba)-oxidation and acid-catalyzed aromatization, respectively, was investigated.

An easy manipulation method for the preparation of N-arylquinazolinium salts is described from readily available aryldiazonium salts, nitriles, and 2-aminoarylketones in a one-pot operation. This method relies on the in situ generation of the N-arylnitrilium intermediate from the reaction of aryldiazonium salt with nitrile, which undergoes amination/cascade cyclization/aromatization, leading to N-arylquinazolinium salts in excellent yields. Nucleophilic addition of alkoxide to these N-arylquinazolinium salts provides functionalized dihydro- N-arylquinazoline.

A diruthenium complex, [(L)Ru2(η6-C6H6)2Cl2](PF6)2 (1) (L = 5-phenyl-2,8-di-2-pyridinylanthyridine), was prepared and characterized. This diruthenium complex 1 was found to be an efficient catalyst for the reduction of aromatic nitro compounds leading to the corresponding aniline derivatives with the use of hydrazine as the reducing agent at 80 °C in an ethanol solution. Catalytic activity of 1 towards various possible intermediates leading to anilines was investigated to understand the reaction pathway. These studies indicate that this reduction proceeds via a direct route as evidenced by hydroxylamines being observed as the major intermediate followed by the appearance of aniline under the catalytic conditions. Thus, the reaction pathway of this catalytic system is discussed.

Rhodium(I)-catalyzed intermolecular cycloadditions of alkynes with vinyl aziridines bearing a conjugated carbonyl group in the olefin moiety followed by the double migration resulted in the formation of pyrrole derivatives in a one pot fashion.

One-pot synthesis of 3-aryl-4(3H)-quinazolinones has been realized through a cascade annulation. Reaction of aryldiazonium salt with a nitrile provides in situ generation of a reactive nitrilium ion, which is attacked by the amino group of 2-aminobenzoate followed by cyclization to deliver the desired product. This strategy offers a convenient and easy access to a wide range of functionalized quinazolinone.

A new method for the preparation of 2-amino-3-cyanoquinolines from readily available aryldiazonium salts, 2-aminoarylketones, and malononitrile via a cascade reaction is reported. This one-pot approach involves the in situ generation of an N-arylnitrilium intermediate from the direct reaction of aryldiazonium salts and malononitrile, which undergoes intermolecular amination, Knoevenagel condensation, and then aromatization to yield the desired compound in moderate to good yields. This methodology features a quick assembly of C2 and C3 functionalized quinolines.

A transition-metal-free approach for the preparation of N-arylketimines has been developed from the direct reaction of aryldiazonium salts, arenes, and nitriles in a one-pot fashion with the consecutive formation of N-C and C-C bonds. This approach proceeds via an in situ generation of N-arylnitrilium intermediate, which then undergoes intermolecular arylation. This three-component strategy offers a step- and atom-efficient way to N-arylketimines from easily accessible reagents under mild reaction conditions. The characterization of stereochemistry of ketimine was achieved by X-ray crystallographic structure and theoretical calculation. Operational simplicity, shorter reaction time, excellent functional group compatibility, and scalability are the key features of this report.

Copper complexes containing a N-heterocylic carbene (NHC)/amidate/pyridine tridentate, 3-mesityl-1-(2-oxo-2-[{pyridin-2-ylmethyl}amino]ethyl)-imidazolin-2-ylidene (HL), were synthesized and characterized. By X-ray single crystal analysis, both Cu(L)(OAc) (3a) and Cu(L)Br (3b) show that the metal center is coordinated by a CNN-tridentate and a anionic donor in a slightly distorted square-planar geometry. These copper complexes are active as catalysts for oxidative bromination of dimethoxybenzene and styrene with the use of LiBr as the bromine source and oxygen as the terminal oxidant.

The direct reaction between 2,7-bis(2-pyridinyl)-1,8-naphthyridine (bpnp) and Pd(CH3COO)2 in CF3COOH yields the new dinuclear palladium(II) complex [Pd2(bpnp)(μ-OH)(CF3CO2)2](CF3CO2) (1). Similarly, substitution of Pd(CH3CN)4(BF4)2 with bpnp in DMF gives [Pd2(bpnp)(μ-OH)(DMF)2](BF4)3 (2). Treatment of 1 or 2 with Cl– readily provide the chloro-substituted species [Pd(bpnp)(μ-OH)(Cl)2]+. All complexes were characterized by spectroscopic methods, and the structure of 2 was further confirmed by X-ray crystallography. Complex 1 is an efficient catalyst for the reduction of aromatic nitro compounds leading to the corresponding aniline derivatives under atmospheric pressure of hydrogen at 50 °C. The mechanistic pathway of the catalysis is investigated. From the reaction pathway, it is suggested that a facile condensation of nitroso and hydroxylamine intermediates is enabled by the dipalladium system and the desired transformation proceeds smoothly under mild reaction conditions to yield the reduced product.

Synthesis and catalytic activity of palladium complexes with 8-(pyridin-2-ylmethoxy)quinolinone (3) were investigated. Complexation of 3 with (CH3CN)2PdCl2 gave the dimeric palladium complex [N,N-(3)PdCl]2 (4). The structure of 4 was characterized by 1H/13C NMR and mass spectroscopic methods, and further confirmed by X-ray crystallography. Complex 4 acts as a catalyst for oxidative cleavage of C=C bonds. In this work, the hydration of styrenes catalysed by 4, via an anti-Markovnikov's Wacker manner, provided the terminal aldehyde as the initial product, which then underwent C-C cleavage to yield the corresponding benzaldehydes. Systematic studies of this catalysis were discussed.

A one-pot synthesis of quinazolino[3,4- a]quinazolin-13-ones was realized from the direct reaction of o-(methoxycarbonyl)benzenediazonium salts, nitriles, and 2-cyanoanilines in moderate to good yields. This method utilizes the in situ generation of reactive N-arylnitrilium ion, which undergoes further amination/tandem cyclization/amidation to deliver the desired polycyclic scaffolds with consecutive formation of four N-C bonds. Flexibility in substitution patterns, mild reaction conditions, and operational simplicity are the salient features of this methodology.

Complexation of 1,8-naphthyridine(Np)-2-carboxylic derivatives L1-L3 [L1 = Np-2-COOH, L2 = Np-2-CONH2, L3 = Np-2-CONHCH2Py] with [Ir(COD)(µ-OMe)]2 yielded the corresponding complexes [Ir(COD)(Ln)] (1~3, n = 1~3, respectively). The potential tridentate L3 behaves as a bidentate donor in the complex 3. Treatment of L1 with [Ir(COD)Cl]2 under nitrogen atmosphere gave a Ir(III) hydride complex [Ir(COD)(L1)HCl] (4). However, carrying out the reaction in the presence of oxygen rendered a Ir(III) dichloride species [Ir(COD)(L1)Cl2] (5). All these complexes were characterized by spectroscopic analyses and X-ray single crystal determination. Catalytic activity of iridium complexes in amination of amines with alcohols was screened. It appears that iridium amido complexes 2 and 3 show excellent catalytic activity on amination of anilines with alcohols in the presence of Cs2CO3 at 120 °C.

An unsymmetrical ligand, 2-(2-pyridinyl)-7-(pyrazol-1-yl)-1,8-naphthyridine (L5) was prepared for the construction of a series of dinuclear complexes. Treatment of L5 with [Ru2(µ-OAc)4Cl] followed by anion metathesis afforded [(L5)(µ-OAc)3Ru2](PF6) (3). Reaction of L5 with 2 equiv. of Ni(OAc)2 provided [Ni4(L5)2(µ-OH)4(CF3COO)2](CF3COO)2 (5). Reaction of [Re2(CO)8(CH3CN)2] with L5 in a refluxing chlorobenzene solution gave a mixture of dirhenium (6) and monorhenium (7) complexes. The monocobalt complex 8 was obtained from complexation of L5 with CoCl2. These new complexes were characterized by elemental analysis and spectroscopic techniques. The structures of complexes 3, 5 and 8 were further confirmed by X-ray crystallography. Nickel complex 5 was evaluated as a catalyst for reduction reactions involving the conversion of ester functionalities into their corresponding alcohols.

Two new anthyridine-based ligands, 5-phenyl-2,8-bis(2-pyridinyl)-1,9,10-anthyridine (L3) and 5-phenyl-2,8-bis(6′-bipyridinyl)-1,9,10-anthyridine (L4), were designed for accommodation of dimetallic systems with the metal ions separated by ∼5 A. Complexation of Cu(ClO4)2 with L3 and L4 provided the corresponding dicopper complexes [{Cu2(L3)(H2O)4(CH3CN)2}(ClO4)4] (3) and [{Cu2(L4)(μ-ClO4)2}(PF6)2] (4), respectively. Both complexes were characterized by spectroscopic methods, and the detail structural features were further confirmed by X-ray crystallography. Structural analyses of 3 and 4 reveal the Cu···Cu distances in the complexes being 4.9612(7) and 5.013 (2) A, respectively. Both complexes are active in the catalytic oxidation of benzyl alcohols into the corresponding aldehydes. Furthermore, complex 4 appears to be a good catalyst for the oxidative coupling of primary alcohols into the corresponding esters with the use of hydrogen peroxide as the oxidant in an aqueous medium. The possible cooperative in...

Two new dinickel complexes with anthyridine-based ligands, 5-phenyl-2,8-bis(2-pyridinyl)-1,9,10-anthyridine (L2) and 5-phenyl-2,8-bis(6′-bipyridinyl)-1,9,10-anthyridine (L3), are reported. Complexation of Ni(OAc)2 with L2 and L3 in trifluoroacetic acid provided the corresponding dinickel complexes [{Ni2(L2)(H2O)6(CF3COO)2}(CF3COO)2] (2) and [Ni2(L3)(CF3COO)4(H2O)] (3), respectively. Both complexes were characterized by spectroscopic methods and further confirmed by X-ray crystallography. Structural analyses of 2 and 3 revealed the Ni⋯Ni distances in the complexes to be 5.4086(6) and 5.0138(7) A, respectively. The catalytic activities of complexes 2 and 3 toward the reduction of carboxylic acids were evaluated. It appears that complex 3 shows a good catalytic activity toward the reduction of carboxylates into the corresponding alcohols by diphenylsilane.

One-pot and metal free synthesis of α-ketoamides has been described through in situ generation of aryl ketones from easily available ethylarenes followed by amidation with various amines. This multiple oxidation protocol involves catalytic I2–pyridine–TBHP (t-butyl hydroperoxide) mediated oxidative benzylic carbonylation and sequential NaI–TBHP mediated oxidative amidation without using any solvent.

A series of functionalized 3,4-dihydroquinolinium salts were prepared from the reaction of aryldiazonium salt with alkene in a nitrile solution. Further oxidation yielding either 3-hydroxyquinoline or quinoline products was investigated. A one-pot process from aryldiazonium salts, alkenes and nitriles leading to 3-hydroxyquinolines was also developed. Furthermore, an intramolecular trapping of an N-arylnitrilium ion with a vinyl group at the ortho position leading to 2-substituted quinolines was revealed.

A transition metal-free synthesis of multisubstituted quinazolin-4(3H)-imines has been realized by the direct reaction of aryldiazonium salts, nitriles, and 2-cyanoanilines in a one-pot fashion. This strategy utilizes the in situ formation of reactive N-arylnitrilium intermediate, which undergoes further tandem cyclization with consecutive formation of N–C bonds. Broad functional group compatibility, mild conditions, shorter time, and operational simplicity are the notable features of this report.

A series of aza-polycyles containing octahydroacridine core were prepared via an intramolecular aza-Diels-Alder reaction of a dimerized citral with various aromatic amines. This reaction is efficiently catalyzed by InCl3 at ambient temperature to afford the corresponding cyclized products in moderate to good yields.

A transition metal free approach for the synthesis of substituted phenanthridines from the coupling reaction of aryldiazonium tetrafluoroborates with nitriles has been developed. This operationally simple protocol proceeds through a substitution of aryldiazonium with nitriles followed by an intramolecular arylation to provide the corresponding phenanthridines in moderate to excellent yields.

Ruthenium arene complexes, [(η6-p-cymene)2Ru2(L)Cl2](PF6)2 [3b, L = 2, 7-bis(di-2-pyridinyl)-1,8-naphthyridine] and [(η6-p-cymene)Ru(L′)Cl](PF6) [4, L′ = tri(2-pyridinyl)amine], were synthesized and characterized by spectroscopic and analytical techniques. The molecular structure of [(η6-p-cymene)2Ru2(L)Cl2]Cl2 (3a) was further determined by single-crystal X-ray analysis. The use of these ruthenium complexes as pre-catalysts for oxidative coupling of 1,2-diols/1,2-aminoalcohol with o-phenylenediamines leading to quinoxalines was investigated. Complex 3b appeared to be a good catalyst for this transformation.

A new methodology has been developed to construct C–N and C–P bonds through direct coupling of C–OH and N–H/P–H bonds via dehydrative cross coupling reaction. Furthermore, this protocol offers an efficient and straightforward way to access a biologically important nitrogen-heterocycle, namely, 3,4-dihydroquinazoline utilizing either an inexpensive iron catalyst or under metal-free conditions.

A (2+2+2) modular synthesis of multisubstituted quinazolines has been realized by the direct reaction of aryldiazonium salts with two equivalent of nitriles. Reaction of aryldiazonium salt with a nitrile provides the initial formation of a reactive nitrilium ion, which is attacked by another molecule of nitrile followed by electrophilic cyclization to deliver the desired product. Notable flexibility in the substitution patterns, readily available substrates, short reaction time, transition metal-free, and gram-scale synthesis are the advantages of this method.

Dicopper(I) complexes {Cu2(bpnp)(CH3CN)4}(PF6)2] (2), [{Cu2(bpnp)(CH3CN)4}(BAr4F)2] (3) and [Cu2(bpnp)Cl2] (4) were prepared from the complexation of [Cu(CH3CN)4](PF6) with 2,7-bis(2-pyridyl)-1,8-naphthyridine (bpnp) followed by anion metathesis and treatment of chloride sequentially. The X-ray structural analysis of 4 indicates the molecule to have a twofold axis passing through the Cu2Cl2 core, which has the shape of a butterfly, and that the Cu atom is tetrahedrally coordinated with in a Cl2N2 donor set. In preliminary experiments 2 was found to be an effective catalyst in the coupling/cyclization of 2-bromobenzoic acids with amidines, providing the corresponding quinazolinones in good yields. Copyright © 2014 John Wiley & Sons, Ltd.

Conversion of substituted cyclohexenones into the corresponding phenols can be achieved using copper acetate as the catalyst in the presence of LiBr and CF3COOH under oxygen. With the use of excess LiBr, electrophilic aromatic bromination afforded the corresponding bromophenol under similar catalytic conditions.

Thermal reaction of 2,7-bis(2-pyridinyl)-l,8-naphthyridine (bpnp) with Ru3(CO)12 in the presence of moisture resulted in the formation of a formate-bridged diruthenium complex [(bpnp-H3)Ru2(μ-HCOO)(CO)4] (1), in which the ligand was partially hydrogenated. Complex 1 was fully characterized by spectroscopic analyses and X-ray single crystal determination. Regarding the partially reduced ligand in 1, it occurs through a water–gas shift type reduction. The bridging formate ligand can be substituted by other carboxylate ligands. Physical and chemical properties of the newly prepared complexes were investigated.

Correction for ‘Synthesis of N-heterocyclic carbene rhenium(i) carbonyl complexes’ by Chang-Hong Chen, et al., Dalton Trans., 2012, 41, 2747–2754.

A simple and straightforward approach to access C4-substituted-3,4-dihydroquinazolines has been achieved, where copper-catalyzed activation of α-amino peroxide and hydroxide intermediates to iminium ion precursors has been realized as an important step. Reactions of these intermediates with alkynes, indoles, pyrrole, and silylenol ether afforded the structurally diverse C4-substituted-3,4-dihydroquinazoline derivatives in good yields.

Coordination of 2,8-Ar2-5-phenylanthyridines (Ar = 2-thienyl, 1a; Ar = 2-ClC6H4–, 1b) with dirhodium tetraacetate yielded the cyclometalated complexes [Rh2(OAc)3(metalated-1a)] (3a) and [Rh2(OAc)3(...

Complexation of 2,7-bis(2-pyridyl)-1,8-naphthyridine (bpnp) with Cu2O in formic acid under aerobic conditions provided a dicopper complex [Cu2(bpnp)(μ-OH)(HCOO)3] (1). This complex has been characterized by X-ray crystallographic and spectroscopic analysis. With O2 as the oxidant, complex 1 is an efficient catalyst for the oxidative coupling of alcohols with amines or diamines, leading to the corresponding imines or diimines in good to excellent yields.

An efficient ruthenium-catalyzed oxidative cyclization of enamides with alkynes in water or dimethoxyethane leading to the pyrrole derivatives is reported. Typically, a mixture of ethyl 2-(acetylamino)acrylate, diphenylacetylene, [Ru( p -cymene)Cl 2 ] (2 mol %), KPF 6 , and Cu(OAc) 2 in water was heated under refluxing conditions providing the N-acetylated pyrrole product in 95% yield.

Complexation of 2,7-bis(2-pyridinyl)-9-phenylanthyridine (4) with [RuCl2(CO)3(THF)] and [(η6-p-cymene)RuCl2]2 provided the mono-nuclear complex [(4)Ru(CO)3Cl][RuCl3(CO)3] (5) and the dinuclear complex [(4)Ru2(p-cymene)2Cl2] (6), respectively. Both complexes have been characterized by spectroscopic, elemental and crystallographic analyses. Complex 6 is an efficient catalyst for the oxidative cyanation of various tertiary arylamines.

Substitution of [RuCl2(CO)3(THF)], [RuCl2(dmso)4] and [RuCl2(PPh3)3] with a macrocyclic ligand, 2,3,4,5,6,7,8,9-octahydro-1,9-diphenyl-1H-5,1,9-benzazadiphosphacyclo undecine (11-P2NH), provided [Ru(11-P2NH)Cl2(CO)] (3), [Ru(11-P2NH)Cl2(dmso)] (4) and [Ru(11-P2NH)Cl2(CH3CN)] (5), respectively. These complexes were characterized by elemental analyses as well as NMR spectroscopy. The structure of 3 was further confirmed by X-ray diffraction analysis. The octahedral geometry around the ruthenium center is in agreement with the Werner’s “coordination” bonding concepts. The chelate rings of the macrocycle toward Ru(II) center adopting into chair conformations were revealed. Furthermore, these ruthenium complexes were found to be active for N-alkylation of dibenzylamine with alcohols.

Treatment of [Re2(CO)8(CH3CN)2] with 2,7-dipyridinyl-1,8-naphthyridine (bpnp) thermally provided mononuclear [(N,N′-bpnp)Re(CO)3Cl] (1). Further reaction of 1 with rhenium carbonyls yielded ortho-metallation dinuclear rhenium complex 2. Both complexes were characterized by spectroscopic analyses and single-crystal X-ray determination. Complex 1 also reacted with [PdMeCl(COD)] and [Ir(COD)Cl]2 by means of ortho-metallation to yield the corresponding heterodinuclear species. Complex 2 appears to be an excellent precatalyst to promote the insertion of terminal alkynes into acetoacetates, which subsequently undergo cyclization to form 2-pyranones.