1,8-Bis(4-meth­oxy-3-nitro­phen­yl)naphthalene

Mol­ecules of the title compound, C24H18N2O6, are located on a twofold rotation axis passing through through the central C—C bond of the naphthalene ring system. The mol­ecular conformation is characterized by a roughly coplanar arrangement of the two substituted phenyl rings [dihedral angle 18.53 (5)°]. These two aryl rings are each twisted by 65.40 (5)° from the plane of the naphthyl unit

Synthesis, structure, spectral and electron-transfer properties of octahedral-[Co<SUP>III</SUP>(L)<SUB>2</SUB>]<SUP>+</SUP>/[Zn<SUP>II</SUP>(L)<SUB>2</SUB>] and square planar-[Cu<SUP>II</SUP>(L){OC(=O)CH<SUB>3</SUB>}] complexes incorporating anionic form of tridentate bis(8-quinolinyl)amine [N<SUP>1</SUP>C<SUB>9</SUB>H<SUB>6</SUB>-N<SUP>2</SUP>-C<SUB>9</SUB>H<SUB>6</SUB>N<SUP>3</SUP>, L<SUP>-</SUP>] ligand

The reaction of bis(8-quinolinyl)amine [N1C9H6-N2H-C9H6N3, LH] with CoII(ClO4)2 . 6H2O in methanol under aerobic conditions results in a new class of [CoIIIN6]+ (1+) chromophore incorporating an sp2-amido nitrogen center (N2) in the ligand frame. During the course of the reaction, the cobalt ion has been oxidized from its starting +2 oxidation state to +3 state in 1. The reaction of LH with the Cu-acetate yields monomeric square planar complex, [CuII(L){OC(=O)CH3}] (2). The same copper complex 2 is also obtained from Cu(ClO4) . 6H2O in presence of CH3COONa as base. On the other hand, the reaction of Zn(ClO4) . 6H2O with LH results in octahedral complex ZnII(L)2 (3). The Cu(II) complex 2 displays a four-line EPR spectrum at room temperature. Crystal structure of the free ligand (LH) shows that the amine proton [N(2)H] is hydrogen-bonded with the terminal quinoline nitrogen centers [N(1) and N(3)]. The crystal structure of 1 confirms the meridional geometry of the complex cation. The square planar geometry of copper complex 2 is confirmed by its crystal structure where the acetate function behaves as a monodentate ligand. The free ligand, LH, is found to be highly acidic in acetonitrile-water (1:1) medium and correspondingly the amine proton (NH) readily dissociates leading to its L- form even in absence of any external base. The pKb value of L- is determined to be 2.6. Both cobalt and copper complexes do not show any expected spin-allowed d-d transitions, possibly have masked by the intense charge-transfer transitions. However, in case of cobalt complex 1, one very weak unusual spin-forbidden 1A1g &#8594; 3T1g transition has been observed at 935 nm. The quasi-reversible cobalt (III)&#8596; cobalt(II) reduction of 1 is observed at E0, -1.0 V versus SCE. The reactions of bis(8-quinolinyl)amine [N1C9H6-N2H-C9H6N3, LH] with CoII(ClO4)2 . 6H2O, ZnII(ClO4)2 . 6H2O and CuII-acetate result in octahedral-[CoIII(L-)2]+ and [ZnII(L-)2] and square planar-[CuII(L-){-OC(=O)CH3}] complexes, respectively, incorporating an sp2-amido nitrogen center (N2) in the coordinated ligand frame of L. The structural, spectral and electrochemical aspects of the complexes have been described

Strong metal–metal coupling in mixed-valent intermediates [Cl(L)Ru(μ-tppz)Ru(L)Cl]+, L = β-diketonato ligands, tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine

Five diruthenium(II) complexes [Cl(L)Ru(μ-tppz)Ru(L)Cl] (1–5) containing differently substituted β-diketonato derivatives (1: L = 2,4-pentanedionato; 2: L = 3,5-heptanedionato; 3: L = 2,2,6,6-tetramethyl-3,5-heptanedionato; 4: L = 3-methyl-2,4-pentanedionato; 5: L = 3-ethyl-2,4-pentanedionato) as ancillary ligands (L) were synthesized and studied by spectroelectrochemistry (UV-Vis- NIR, electron paramagnetic resonance (EPR)). X-ray structural characterisation revealed anti (1, 2, 5) or syn (3) configuration as well as non-planarity of the bis-tridentate tppz bridge and strong dπ(RuII) → π*(pyrazine, tppz) back- bonding. The widely separated one-electron oxidation steps, RuIIRuII/RuIIRuIII and RuIIRuIII/RuIIIRuIII, result in large comproportionation constants (Kc) of ≥1010 for the mixed-valent intermediates. The syn-configurated 3n exhibits a particularly high Kc of 1012 for n = 1+, accompanied by density functional theory (DFT)-calculated minimum Ru–N bond lengths for this RuIIRuIII intermediate. The electrogenerated mixed-valent states 1+–5+ exhibit anisotropic EPR spectra at 110 K with average values of 2.304–2.234 and g anisotropies Δg = g1–g3 of 0.82–0.99. Metal-to-metal charge transfer (MMCT) absorptions occur for 1+–5+ in the NIR region at 1660 nm–1750 nm (ε ≈ 2700 dm3 mol−1 cm−1, Δν1/2 ≈ 1800 cm−1). DFT calculations of 1+ and 3+ yield comparable Mulliken spin densities of about 0.60 for the metal ions, corresponding to valence-delocalised situations (Ru2.5)2. Rather large spin densities of about −0.4 were calculated for the tppz bridges in 1+ and 3+. The calculated electronic interaction values (VAB) for 1+–5+ are about 3000 cm−1, comparable to that for the Creutz–Taube ion at 3185 cm−1. The DFT calculations predict that the RuIIIRuIII forms in 12+–52+ prefer a triplet (S = 1) ground state with ΔE (S = 0 − S = 1) [similar]5000 cm−1. One-electron reduction takes place at the tppz bridge which results in species [Cl(L)RuII(μ-tppz˙−)RuII(L)Cl]− (1˙−–3˙−, 5˙−) which exhibit free radical-type EPR signals and NIR transitions typical of the tppz radical anion. The system 4n is distinguished by lability of the Ru–Cl bonds

A novel structure of secondary alcohol derived from (+)-&#916;<SUP>3</SUP>-carene with pseudo three-fold symmetry

The crystal structure of C12OH20 (lR-6R-4R-2 R-3,7,7-trimethyl-4-(2-hydroxyethyl) bicyclo [4.1.0] hept-2-ene) has been determined by X-ray diffraction. The compound crystallizes in space group P212121 witha = 5.893(1),b = 22.572(2), c = 26.164(3) &#197;,V = 3480.3 &#197;3, Z= 12. The structure was solved by modified direct methods and refined to anR value of 0.081 for 607 unique reflections. Each asymmetric unit has three molecules which are held together through intermolecular hydrogen bonds resulting in a novel spiral-type arrangement of molecules. The six-membered ring has a half-chair conformation

The total synthesis and structural revision of stagonolide D

The total synthesis of the putative structure of stagonolide D has been completed. The relative and absolute configuration of stagonolide D was established by synthesizing its optical antipode. The adopted strategy involves the construction of the central macrolide employing ring-closing metathesis (RCM), followed by selective protecting group manipulations and a final concomitant −OTBS deprotection and displacement of an −OMs placed next to it, resulting in the formation of the epoxide ring

InCl<SUB>3</SUB>-Mediated Addition of Indole to Isatogens: An Expeditious Synthesis of 13-deoxy-Isatisine A

A strategy directed towards the total synthesis of isatisine A that involves several late-stage metal-catalyzed transformations that address the key carbon–carbon and carbon–heteroatom bond formations has been developed. As a part of this strategy, methods for the addition of indoles to isatogens that lead selectively to either 2,2-disubstituted N-hydroxyindolin-3-one or 2,2-disubstituted indolin-3-one compounds have been developed by employing InCl<SUB>3</SUB> as a catalyst or as the reagent. The present methods provide the first examples of the additions of indoles to the isatogen nucleus. To demonstrate its viability, the synthesis of 13-deoxy-isatisine A has been completed in ten steps from a known and easily available lactone

One-step stereospecific strategy for the construction of the core structure of the 5,11-methanomorphanthridine alkaloids in racemic as well as in optically pure form: synthesis of (±)-pancracine and (±)-brunsvigine

The unique core structure of the complex pentacyclic 5,11-methanomorphanthridine has been constructed stereospecifically in one step by an intramolecular [3+2] cycloaddition of a non-stabilized azomethine ylide (AMY), generated by the sequential double desilylation of 14 using AgIF as a one-electron oxidant. The formation of the single diastereomer in the key step is explained by the preferred transition state produced by endo attack of the AMY on the "Re" face of the dipolarophile. An asymmetric version of the cycloaddition using a chiral dipolarophile was applied to construct the core structure 68 with 63% ee. This strategy was successfully applied to the formal synthesis of (±)-pancracine and the total synthesis of (±)-brunsvigine. An unprecedented and interesting skeletal rearrangement product 49 was observed during the attempted assembly of the E ring from 46 through Horner-Wadsworth-Emmons reactions. Mechanisms involving azetidinium salt formation or the Grob-type fragmentation are advanced to explain the observed rearrangement

Synthesis of C1-and C8a-epimers of (+)-castanospermine from D-glucose derived γ,δ-epoxyazide: intramolecular 5-endo epoxide opening approach

A concise synthesis of two diastereomers of (+)-castanospermine namely 1- and 8a-epi-castanospermine 1b and 1c, respectively, is reported from D-glucose. The methodology involves stereoselective cross metathesis of D-glucose derived alkene 2 with 4-bromo-1-butene followed by azide displacement and m-CPBA oxidation to afford diastereomeric γ,δ-epoxyazides 5a/5b. The Staudinger reaction of epoxyazide 5a followed by reaction with benzylchloroformate (CbzCl) unexpectedly furnished 1,3-oxazinan-2-one derivative 7 whose stereochemistry was establish by single crystal X-ray. This helps to assign the stereochemistry in the epoxidation reaction. The reduction of 5a/5b was then carried out by transfer hydrogenation to provide γ,δ-epoxyamine that concomitantly undergoes intramolecular 5-endo-tet cyclization to afford hydroxypyrrolidine ring skeleton with sugar framework-a precursor to castanospermine analogues 1b/1c