DMSO promoted catalyst-free oxidative C-N/C-O couplings towards synthesis of imidazoles and oxazoles.

Dimethyl sulfoxide (DMSO)-promoted catalyst-free oxidative C-N coupling and C-O coupling under oxidant-free conditions are outlined. This protocol is operationally simple and leads to various functionalized substituted imidazoles or oxazoles in good yields. To date, a very limited number of oxidation protocols have been established, where DMSO acts solely as a catalyst or an oxidant or both.

Substrate Switchable Pathway for Selective Construction of Bridged Dibenzo[b,f][1,5]diazocines and Bridged Spiromethanodibenzo[,]azepines.

An operationally simple method for the synthesis of bridged dibenzo[b,f][1,5]diazocines and bridged spiromethanodibenzo[,]azepines exhibiting bridged eight-membered and seven-membered molecular architecture is reported. This unique approach is based on substrate selective mechanistic pathway, including an unprecendented aerial oxidation-driven mechanism for the synthesis of bridged spiromethanodibenzo[,]azepines. The reaction is highly atom economic, and in addition, it allows the construction of two rings and four bonds in a single operation under metal-free condition.

Steric-Hindrance-Induced Diastereoselective Radical Nitration of 3-Alkylidene-2-oxindoles Followed by Tosylhydrazine-Mediated Sulfonation.

Metal-free radical nitration of the β C-H bond of 3-alkylidene-2-oxindoles with -butyl nitrite (TBN) has been explored. Interestingly, ()-3-(2-(aryl)-2-oxoethylidene)oxindole and ()-3-ylidene oxindole give different diastereomers on nitration. The mechanistic investigation revealed that the diastereoselectivity was controlled by the size of the functional group.

Metal-free, I-promoted direct synthesis of 2-cyano-substituted maleimides a unique 3,3-dicyano-2-arylacrylic acid intermediate.

A robust, I-mediated cyclization reaction was developed for the synthesis of 2-cyano-substituted maleimides from arylethylidene malononitriles and amines unique a 3,3-dicyano-2-arylacrylic acid intermediate. The reaction duration was short and devoid of an expensive transition-metal catalyst, ligands or toxic carbon monoxide. We executed an I/DMSO-mediated desirable oxidation of the C(sp)-H bond of the carbonyl precursor followed by the formation of a 3,3-dicyano-2-arylacrylic acid intermediate.

FeCl-Catalyzed Synthesis of 6-Thioxo-hexahydroindeno[1',2':4,5]imidazo[1,5-]pyridin-12(6)-ones via an Interesting [1,2] Oxygen Shift Pathway.

An iron-catalyst mediated one-pot multicomponent route for the synthesis of novel 6-thioxo-hexahydroindeno[1',2':4,5]imidazo[1,5-]pyridin-12(6)-one scaffolds has been developed using ninhydrin, l-proline, and aryl isothiocyanates in ethanol medium. This methodology offers an interesting [1,2] oxygen shift mechanism pathway via a number of ring-opening and ring-closing cascade steps to provide diverse substituted hexahydroindeno-imidazo[1,5-]pyridinones in excellent to good yields. The stereochemistry of the proline ring is lost during the course of the reaction.

Green synthesis of C5-C6-unsubstituted 1,4-DHP scaffolds using an efficient Ni-chitosan nanocatalyst under ultrasonic conditions.

A heterogeneous and magnetically recyclable Ni-chitosan nanocatalyst was synthesized and thoroughly characterized by powder Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) spectroscopy, etc. It was effectively utilized in the eco-friendly synthesis of new C5-C6-unsubstituted 1,4-DHPs under ultrasonic irradiation. The important focus of the methodology was to develop an environmentally friendly protocol with a short reaction time and a simple reaction procedure.

A combined experimental and theoretical study on a single, unsupported oxo-bridged Mn(III,III) dimer coordinated to two iminobenzosemiquinone π-radical anions.

Ligand H2LAP comprises a non-innocent 2-aminophenol unit and an innocent bis(pyridin-2-ylmethyl)amine unit. The ligand, upon reaction with an equivalent amount of Mn(ClO4)2·6H2O in the presence of Et3N under air in MeOH, provided a mono(oxo)-bridged dinuclear Mn2 complex ({[(LISQ)MnIII-O-MnIII(LISQ)][(ClO4)]2}; 1). X-ray crystal structure analysis of complex 1 revealed that in the dicationic unit, the physical oxidation state of each Mn ion was +III and the 2-aminophenol unit of ligand H2LAP was in its one-electron oxidized iminobenzosemiquinone form.

Coordination polymers of Ag(i) and Hg(i) ions with 2,2'-azobispyridine: synthesis, characterization and enhancement of conductivity in the presence of Cu(ii) ions.

The cationic coordination polymers (CPs) of the types [Hg(abpy)][PF] (1) and [Ag(abpy)][PF] (2) (abpy = 2,2'-azobispyridine) were synthesized and characterized. Experimentation using the crystals confirmed that 1 and 2 are conductors of electricity. The relative conductivity of 1 is 62 times greater than that of 2.

A Chemodosimetric Approach for Fluorimetric Detection of Hg Ions by Trinuclear Zn(II)/Cd(II) Schiff Base Complex: First Case of Intermediate Trapping in a Chemodosimetric Approach.

The present work discloses the application of two fluorescent zinc and cadmium complexes ( and ) for sensing of Hg(II) ions through a chemodosimetric approach. The ligand under consideration in this work is a NO donor Schiff base ligand ()-4-bromo-2-(((2-morpholinoethyl)imino)methyl)phenol (), which has been harnessed to generate complexes [ZnL(OAc)] () and [CdL(OAc)] (). X-ray single crystal diffraction studies unveil the trinuclear skeleton of complexes and .

Biporous Cd(II) Coordination Polymer via Disulfide Bond Formation: Self-Healing and Application to Photosensitive Optoelectronic Device.

A heteroporous metal-organic framework, [Cd(2,2'-DSB)(INH)(HO)] (), is fabricated by the reaction of CdI, 2-mercaptobenzoic acid (2-MBAH), and isoniazid (INH). The X-ray structure of the compound shows the bridging INH and 2,2'-disulfanediyldibenzoic acid (H2,2'-DSBA) around the Cd(II) ion center. 2-MBAH has been dimerized to the formation of 2,2'-DSB (S-S-bonded dianion), which has further extended to form the 2D network.

Metal promoted conversion of aromatic amines to ortho-phenylenediimine derivatives by a radical coupling path.

A radical path for the conversion of o-substituted arylamines to o-phenylenediimine derivatives is reported. In the presence of [RuII(PPh3)3Cl2] (RuP), 2-(phenylthio)aniline (LSNH2) acts as an o-amination agent. Reaction of LSNH2 with RuP in toluene promotes (4e + 4H+) oxidative dimerization affording an o-phenylenediimine complex of ruthenium(ii).

Proton-Coupled Oxidation of Aldimines and Stabilization of H-Bonded Phenoxyl Radical-Phenol Skeletons.

Stable phenoxyl radicals H-bonded to phenols were successfully isolated. The effect of the intermolecular H-bonding to the concerted proton coupled electron transfer (CPET) reactions of the aldimines and the stability and spin distribution of the H-bonded phenoxyls are reported. Salts of iminium-phenol derivatives as cations and the corresponding imine-phenolato derivatives coordinated to zinc(II) as anions, [Zn(ArO)Cl][ArOH], were isolated, where ArOH are aldimine derivatives.

Exploration of catecholase-like activity of a series of magnetically coupled transition metal complexes of Mn, Co and Ni: new insights into the solution state behavior of Mn complexes.

A series of tri-nuclear complexes of general formula [ML(OAc)], where M = Mn (1), Co (2) and Ni (3), (HL = (E)-4-bromo-2-(((2-morpholinoethyl)imino)methyl)phenol), have been synthesized. Single crystal X-ray crystallography reveals that each molecule contains three metal ions which are bridged by four acetate moieties. In the solution phase, the complexes are present as mononuclear species.

Orthometalated -(Benzophenoxazine)--aminophenol: Phenolato versus Phenoxyl States.

The molecular and electronic structures of the orthometalated ruthenium(III) and osmium(III) complexes of -(benzophenoxazine)--aminophenol (LH) that exhibits versatile redox activities are reported. The redox chemistry of LH is remarkably different from that of -(aryl)--aminophenol (LH). The study established that LH is redox noninnocent and is a precursor of a phenoxyl radical.

A Diruthenium Complex of an N-Pyridyl-o-aminophenol Derivative: A Route to Mixed Valency.

An N-pyridyl-o-aminophenol derivative that stabilises mixed-valence states of ruthenium ions is disclosed. A diruthenium complex, [(L )Ru Cl ]⋅MeOH (1⋅MeOH) is successfully isolated, in which L is the o-iminobenzoquinone form of 2-[(3-nitropyridin-2-yl)amino]phenol (L H ). In 1, L oriented towards one ruthenium centre is a non-innocent NO-donor redox ligand, whereas another oriented towards another ruthenium centre is an innocent pyridine-donor redox ligand.

Redox Cascades and Making of a C-C Bond: 1,2-Benzodiazinyl Radicals and a Copper Complex of a Benzodiazine.

Two 1,2-benzodiazinyl radicals, cinnolinyl radicals by name, were successfully isolated by cascade routes using 1,4-naphthoquinone as a precursor. Reaction of 1,4-naphthoquinone with hydrazine hydrate promotes a (5e + 5H) redox cascade affording benzo[ g]naphtho[1,2- c]cinnolinyl-7,12,14-trione (Cn) in 69% yields, while the similar reaction with 2-hydrazinopyridine is a (7e + 7H) oxidative cascade and furnishes N-pyridinecinnolinyl radical (Cn). The cascades are composed of C-N and C-C bond making reactions.

Proton-Coupled Oxidation of a Diarylamine: Amido and Aminyl Radical Complexes of Ruthenium(II).

Diarylamido, Q-N-Py (L), complexes of ruthenium(II), trans-[(LH)Ru(PPh)Cl] (1H) and trans-[(L)Ru(PPh)(CO)Cl] (2), using N-(5-nitropyridin-2-yl)quinolin-8-amine (HL) as a ligand are disclosed (Q and Py refer to quinoline and 5-nitropyridine fragments). 1H contains a zwitterionic amido ligand (Q-N-PyH) that undergoes a concerted proton electron transfer (CPET) reaction in air, generating trans-[(L)Ru(PPh)Cl] (1·CHCl). The ground electronic state of 1 is delocalized as [(L)Ru ↔ (L)Ru] (L is an aminyl radical of type Q-N-Py).

Geometry-Driven Iminosemiquinone Radical to Cu(II) Electron Transfer and Stabilization of an Elusive Five-Coordinate Cu(I) Complex: Synthesis, Characterization, and Reactivity with KO.

The noninnocent ligand HL contained a bulky phenyl substituent at the ortho position to the aniline moiety. The ligand reacted with 0.5 equiv of CuCl·2HO in the presence of EtN under air and provided the corresponding Cu(II)-bis(imonosemiquinone) complex (1).

Cobalt Ion Promoted Redox Cascade: A Route to Spiro Oxazine-Oxazepine Derivatives and a Dinuclear Cobalt(III) Complex of an N-(1,4-Naphthoquinone)-o-aminophenol Derivative.

The study discloses that the redox activity of N-(1,4-naphthoquinone)-o-aminophenol derivatives (LH) containing a (phenol)-NH-(1,4-naphthoquinone) fragment is notably different from that of a (phenol)-NH-(phenol) precursor. The former is a platform for a redox cascade. LH is redox noninnocent and exists in Cat-N-(1,4-naphthoquinone)(2-) (L) and SQ-N-(1,4-naphthoquinone) (L) states in the complexes.

A Redox-Active Cascade Precursor: Isolation of a Zwitterionic Triphenylphosphonio-Hydrazyl Radical and an Indazolo-Indazole Derivative.

A redox-active [ML] unit (M = Co and Mn; LH = N'-(1,4-dioxo-1,4-dihydronaphthalen-2-yl)benzohydrazide) defined as a cascade precursor that undergoes a multicomponent redox reaction comprising of a C-N bond formation, tautomerization, oxidation, C-C coupling, demetalation, and affording 6,14-dibenzoylbenzo[f]benzo[5,6]indazolo[3a,3-c]indazole-5,8,13,16-tetraone (L) is reported. Conversion of LH → L in air is overall a (6H+6e) oxidation reaction, and it opens a route for the syntheses of bioactive diarylindazolo[3a,3-c]indazole derivatives. The reaction occurs via a radical coupling reaction, and the radical intermediate was isolated as a triphenylphosphonio adduct.

An Iminosemiquinone-Coordinated Oxidovanadium(V) Complex: A Combined Experimental and Computational Study.

Ligand HSar contained two terminal amidophenolate units that were connected by a disulfane bridge. The ligand reacted with VOSO·5HO in the presence of EtN under air and provided a mononuclear octahedral oxidovanadium complex (1). X-ray crystal structure analysis of complex 1 revealed that the oxidation state of the V ion was V and the VO unit was coordinated to an iminosemiquinone radical anion.

Molecular and Electronic Structures of Ruthenium Complexes Containing an ONS-Coordinated Open-Shell π Radical and an Oxidative Aromatic Ring Cleavage Reaction.

The coordination chemistry of 2,4-di-tert-butyl-6-[(2-mercaptophenyl)amino]phenol (LH), which was isolated as a diaryl disulfide form, (LH), with a Ru ion is disclosed. It was established that the trianionic L is redox-noninnocent and undergoes oxidation to either a closed-shell singlet (CSS), L, or an open-shell π-radical state, L, and the reactivities of the [Ru(L)] and [Ru(L)] states are different. The reaction of (LH) with [Ru(PPh)Cl] in toluene in the presence of PPh affords a ruthenium complex of the type trans-[Ru(L)(PPh)Cl] (1), while the similar reaction with [Ru(PPh)(H)(CO)Cl] yields a L complex of ruthenium(II) of the type trans-[Ru(L)(PPh)(CO)] (2).

Arylamino radical complexes of ruthenium and osmium: dual radical counter in a molecule.

Radical and non-radical ruthenium and osmium complexes of 1-amino-9,10-anthraquinone (AqNH), which is defined as a molecule of dual radical counter, are disclosed. 1-Amido-9,10-anthraquinone (AqNH) complexes of the types trans-[Ru(AqNH)(PPh)(CO)Cl] (1), trans-[Os(AqNH)(PPh)(CO)Br] (2) and trans-[Ru(AqNH)(PPh)Cl] (3) were isolated. AqNH of 1-3 is redox active and undergoes oxidation reversibly at +(0.

Radical and Non-Radical States of the [Os(PIQ)] Core (PIQ = 9,10-Phenanthreneiminoquinone): Iminosemiquinone to Iminoquinone Conversion Promoted o-Metalation Reaction.

The coordination and redox chemistry of 9,10-phenanthreneiminoquinone (PIQ) with osmium ion authenticating the [Os(II)(PIQ(•-))], [Os(III)(PIQ(•-))], [Os(III)(C,N-PIQ)], [Os(III)(PIQ)], and [Os(III)(PIQ(2-)) ] states of the [Os(PIQ)] core in the complexes of types trans-[Os(II)(PIQ(•-))(PPh3)2(CO)Br] (1), trans-[Os(III)(PIQ(•-))(PPh3)2Br2] (2), trans-[Os(III)(C,N-PIQ)(PPh3)2Br2]·2CH2Cl2 (3·2CH2Cl2), trans-[Os(III)(C,N-PIQ(Br))(PPh3)2Br2]·2CH2Cl2 (4·2CH2Cl2), trans-[Os(III)(C,N-PIQ(Cl2))(PPh3)2Br2] (6), trans-[Os(III)(PIQ(•-))(PPh3)2Br2](+)1/2I3(-)1/2Br(-) (1(+)1/2I3(-)1/2Br(-)), [Os(III)(PIQ)(PPh3)2Br2](+) (2(+)), and [Os(III)(PIQ(2-))(PPh3)2Br2](-) (2(-)) are reported (PIQ(•-) = 9,10-phenanthreneiminosemiquinonate anion radical; C,N-PIQ = ortho-metalated PIQ, C,N-PIQ(Br) = ortho-metalated 4-bromo PIQ, and C,N-PIQ(Cl2) = ortho-metalated 3,4-dichloro PIQ). Reduction of PIQ by [Os(II)(PPh3)3(H)(CO)Br] affords 1, while the reaction of PIQ with [Os(II)(PPh3)3Br2] furnishes 2. Oxidation of 1 with I2 affords 1(+)1/2I3(-)1/2Br(-), while the similar reactions of 2 with X2 (X = I, Br, Cl) produce the ortho-metalated derivatives 3·2CH2Cl2, 4·2CH2Cl2, and 6.

Radical non-radical states of the [Ru(PIQ)] core in complexes (PIQ = 9,10-phenanthreneiminoquinone).

9,10-Phenanthreneiminosemiquinonate anion radical (PIQ˙(-)) complexes of ruthenium of types trans-[Ru(II)(PIQ˙(-))(PPh3)2(CO)Cl] () and trans-[Ru(III)(PIQ˙(-))(PPh3)2Cl2] () are reported. Reactions of and with I2 afford trans-[Ru(III)(PIQ˙(-))(PPh3)2(CO)Cl](+)I3(-)·½CH2Cl2 ((+)I3(-)·½CH2Cl2) and trans-[Ru(PIQ˙(-))2(PPh3)2(μ-Cl)3](+)I3(-)·¼I2·¼toluene) ((+)I3(-)·¼I2·¼toluene), while the reaction of with Br2 yields a 9,10-phenanthreneiminoquinone (PIQ) complex of the type mer-[Ru(III)(PIQ)(PPh3)Br3]·½CH2Cl2 (·½CH2Cl2). In comparison, the reaction of trans-[Ru(III)(PQ˙(-))(PPh3)2Cl2] (PQ), a 9,10-phenanthrenequinone (PQ) analogue of affords only trans-[Ru(III)(PQ)(PPh3)2Cl2](+)Br3(-) ((+)Br3(-)).