Secododecahedradienes – Syntheses,Reactivity, in‐Plane Homoconjugated 3C/2e Cations, 4C/3e Radical Cations,and σ‐Bishomoaromatic 4C/2e Dications?

Secodecahedradiene 2a , featuring very proximate, perfectly syn‐periplanar and significantly pyramidalized C=C bonds, was synthesized as testing object for in‐plane(σ)‐homoconjugational electron delocalization, starting from the available pagodane 15b . The response of 2a (and in part its diester 2b ) – in π,π‐distance (average 3.08 Å), olefinic pyramidalization (average 26.9°), and π,π‐split (PE, 1.15 eV) intermediate between disecododecahedradiene 1a and 1,16‐dodecahedradiene 3a – to selected 4π‐reagents, electrophiles, and radicals was explored experimentally and by calculations. Intriguing multistep reaction sequences attest to the ease of competing stabilization pathways for the 3C/2e in‐plane homoconjugated cationic intermediates. PE, CV, and ESR measurements and calculations (DFT) characterize the radical cation generated from 2a as in‐plane homoconjugated 4C/3e‐species 2a ^.+, persistent in a Freon matrix, but only very shortly existent in solution (CIDNP). Consequently, NMR control of the two‐electron oxidation in SbF₅/SO₂ClF did not disclose the σ‐bis‐homoaromatic dication 4C/2e (see 2a ^{2 +} ), but a bis‐allylic dication 75 as persistent species. In support of 2a ^{2 +} as intermediate, evidence is presented for very limited kinetic protection offered by the secododecahedral framework to through H‐cage σ‐homoconjugated cations.     

A Facile Total Synthesis of (±)-Selina-3, 11-Dien-9-Ol

A facile total synthesis of (±)-selina-3, 11-dien-9-ol (1) has been described. The key step is the one-pot reductive deoxygenation of α, β-unsaturated p-tosylhydrazone and reduction of 9-carbonyl of 9 with sodium borohydride.     

Lamellare Schichtstrukturen von M[N(SO2C6H4‐4‐COOCH3)2] · n H2O (M = Na,n = 1; M = K,n = 0): Gibt es schwache Wasserstoffbrücken CH2–H…O=C zwischen den Schichten?

Structures of Ionic Di(arenesulfonyl)amides. 5. Lamellar Layer Structures of M[N(SO₂C₆H₄‐4‐COOCH₃)₂] · n H₂O (M = Na, n = 1; M = K, n = 0): Are there Weak Hydrogen Bonds CH₂–H…O=C between the Layers? The new lamellar compounds NaN(SO₂C₆H₄‐4‐COOMe)₂ · H₂O ( 1 a ) and KN(SO₂C₆H₄‐4‐COOMe)₂ ( 2 a ), obtained by neutralizing the corresponding strong NH acid with aqueous NaOH or KOH, were characterized by low‐temperature X‐ray diffraction ( 1 a : orthorhombic, space group Pbca, Z = 8, Z′ = 1; 2 a : orthorhombic, P2₁2₁2₁, Z = 8, Z′ = 2). Both crystals are further examples of layered inorgano‐organic solids where the inorganic component is comprised of metal cations, coordinating N(SO₂)₂ groups and water molecules (in 1 a ) and the outer regions are formed by the 4‐substituted phenyl rings of the folded anions, which approximate to mirror symmetry. In the two‐dimensional networks, the cations adopt respectively a distorted octahedral [Na(O–S)₄(OH₂)₂], an irregular [K(1)O₆N₂], or an irregular [K(2)O₉] coordination. In contrast to the previously reported carboxylic congeners, where an extensive series of C–O–H…O=C hydrogen bonds is observed between layers, the esterified materials do not display any O–CH₂–H…O=C interlayer bonding, although such interactions and short C_ar–H…O=C/O=S contacts exist within the lamellae.     

Enantioselective synthesis of a potential 1,5-syn-polyol C1–C24 subunit of (−)-caylobolide A

The synthesis of a possible 1,5-syn-polyol C1–C24 subunit resident in (−)-caylobolide A has been accomplished. The key reaction sequence was a repetitive protocol for the construction of the syn-1,5-diol segment by means of Ru-catalyzed cross-metathesis and boron-mediated allylation reactions.     

A Cu/Cinchona P,N-ligand system enabled general asymmetric C(sp~3)–C(sp) coupling

正Due to the special structural feature and versatile reactivity towards various types of transformations, alkynes have inspired continuous research interest for their generation, incorporation and application in organic synthesis, chemical biology and material science [1]. Notably, since its invention in 1975, the Sonogashira reaction, which efficiently couples aryl halides with aryl or vinyl terminal alkynes via Pd(0)/Cu(I) synergistic catalysis, has proven to be one of the most     

A NEW RARE-EARTH VANADATE LaBa_2V_3O_(11)

A new rare-earth vanadate LaBa_2V_3O_(11)is synthesized by the conventional solidstate reaction.The single phase can be obtained at sintering temperature of 1010°C.TheX-ray powder diffraction shows that the new compound has tetragonal structure with cellparameters a of 7.94 and c of 24.27 The LaBaaV_3O_(11)can be decomposed to LaVO_4.Ba3(VO_2)_2 and V_2O_5 by higher sitering temperature than 1010°C.The as-sintered sample isinsulator with resistivity of 10 12 ohm cm.Furthermore,if the as-sintered sample wasannealed under H_2 atmosphere,the LaBa_2V_3O_(11)decomposed to LaVO_3 and BaYO_4 despite ofthe lower annealing temperature of 950°C.     

[Cu3(C11H12N3OS)3(C11H10N3OS)]SO4 · 3H2O, a trinuclear heteroleptic copper(II) complex with N-allyl-N′-salicylidenethiosemicarbazone and its cyclization product: Synthesis and X-ray diffraction study

Single crystals of a trinuclear copper(II) complex with N-allyl-N′-salicylidenethiosemicarbazone and its cyclization product were obtained and examined by X-ray diffraction. Prolonged keeping of the reaction mixture in aqueous ethanol at room temperature resulted in partial cyclization of the starting ligand into 2-(4-allyl-5-mercapto-4H-1,2,4-triazol-3-yl)phenol followed by coordination of both ligands to copper ions, giving a cluster-type trinuclear complex of the empirical formula C₄₄H₅₀N₁₂O₁₁S₅Cu₃. The crystals are monoclinic, space group P2₁/n, a = 14.1169(4) Å, b = 20.1006(5) Å, c = 19.6852(5) 0A, β = 107.065(2)°, Z = 4, R ₁ = 0.0586 (I > 4σ(I)). The structure of the complex consists of three square fragments; in each fragment, the Cu atom is coordinated in a tridentate fashion by the starting organic ligand in the thione form. The cyclization product of this ligand is coordinated through two triazole N atoms and the thiol S atom, thus extending the square environment of copper. The cluster structure of the complex is formed by the bridging bonds Cu-O-Cu between the Cu(1) and Cu(2) atoms and by the bridging bonds Cu-S-Cu between the Cu(2) and Cu(3) atoms.     

Mechanism,reactivity, and selectivity of the iridium-catalyzed C(sp3)–H borylation of chlorosilanes

The iridium-catalyzed C(sp³)–H borylation of methylchlorosilanes is investigated by means of density functional theory, using the B3LYP and M06 functionals. The calculations establish that the resting state of the catalyst is a seven-coordinate Ir(v) species that has to be converted into an Ir(iii)tris(boryl) complex in order to effect the oxidative addition of the C–H bond. This is then followed by a C–B reductive elimination to yield the borylated product, and the catalytic cycle is finally completed by the regeneration of the active catalyst over two facile steps. The two employed functionals give somewhat different conclusions concerning the nature of the rate-determining step, and whether reductive elimination occurs directly or after a prior isomerization of the Ir(v) hydride intermediate complex. The calculations reproduce quite well the experimentally-observed trends in the reactivities of substrates with different substituents. It is demonstrated that the reactivity can be correlated to the Ir–C bond dissociation energies of the corresponding Ir(v) hydride intermediates. The effect of the chlorosilyl group is identified to originate from the α-carbanion-stabilizing effect of the silicon, which is further reinforced by the presence of an electron-withdrawing chlorine substituent. Furthermore, the source of selectivity for the borylation of primary over secondary C(sp³)–H can be explained on a steric basis, by repulsion between the alkyl group and the Ir/ligand moiety. Finally, the difference in the reactivity between C(sp³)–H and C(sp²)–H borylation is investigated and rationalized in terms of distortion/interaction analysis.     

RuH3[P(C6H5)3] 3 − as a ligand in complexes withM(CO)3 Fragments (M = Cr,Mo, W)

The reactions of RuH₃[P(C₆H₅)₃] ₃ ^– with Cr(CO)₃(CH₃CN)₃, Mo(CO)₃ (diglyme), or W(CO)₃(C₃H₂CN)₃ resulted in the formation of the appropriate [(H₅C₆)₃P]₃Ru(-H)₃ M(CO) ₃ ^– complexes, which have been characterized analytically, spectroscopically, and in one case (M = Cr) by an X-ray diffraction study of the K [N(C₂H₄OC₂H₄OCH₃)₃]⁺ salt. This complex crystallizes in the triclinic space group Pl witha = 13.666(6),b= 13.7901(7),c = 18.147(8) A,a = 93.23(3)°, = 94.07(4)° = 90.43(4)°, andV = 3405.6 A³ for Z = 2. Final discrepancy indices ofR = 0.048 and Rù = 0.056 were obtained. The hydride ligands, all of which could be located and their positional coordinates refined, completed local pseudo-octahedral coordination about both the ruthenium and thechromium centers. The Ru-H bonds are significantly shorter than the Cr-H ones, 1.65(4) vs. 1.92(4) A, and the Ru-Cr bond distance is 2.5474(9) A.     

Triethanolamine zinc phosphite, (C6H13NO3)Zn2(HPO3): a templated network or a network of clusters?

(C6H13NO3)Zn2(HPO3) (I) displays an extended hybrid organic/inorganic structure in which the triethanolamine organic species acts as an anionic tetradentate ligand, rather than a typical protonated cationic template. Crystal data for I: Mr = 357.89, monoclinic, P2(1)/c (no. 14), a = 8.4216(4) angstroms, b = 9.9262(5) angstroms, c = 12.8494(6) angstroms, beta = 91.824(1) degrees, V = 1073.6(1) angstroms3, Z = 4.     

A porphyrin with a C═C unit at its center

The molecule (C═C)TTP (TTP = tetra-p-tolylporphyrin) and the triflate salt of its dication, [(C═C)TTP][OTf](2), have been synthesized and characterized. NMR spectroscopy, nucleus-independent chemical shift calculations, and the crystal structure of (C═C)TTP indicate that (C═C)TTP is antiaromatic and (C═C)TTP(2+) is aromatic.     

反常蓝移单电子锂键Y…Li-CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]体系的结构与性质

在密度泛函理论B3LYP/6-311++G(d,p)及MP2/6-311++G(d,p)水平上研究了单电子锂键复合物Y…Li—CH3[Y=CH3, CH2CH3, CH(CH3)2, C(CH3)3]的结构与性质. 结果表明, 三种单电子锂键复合物H3CH2C…Li—CH3(II), (H3C)2HC…Li—CH3(III)和(H3C)3C…Li—CH3(IV)单电子锂键强度依II(-26.7 kJ·mol-1)相似文献   

Does a Concerted Non‐Insertive Mechanism Prevail over a σ‐Insertive Mechanism in Catalytic Cyclohydroamination by Magnesium Tris(oxazolinyl)phenylborate Compounds? A Computational Study

The present study comprehensively explores alternative mechanistic pathways for intramolecular hydroamination of 2,2-dimethyl-4-penten-1-amine (1) by [{To(M)}MgMe] (To(M)=tris(4,4-dimethyl-2-oxazolinyl)phenylborate) (2) with the aid of density functional theory (DFT) calculations. A single-step amidoalkene → cycloamine conversion through a concerted proton transfer associated with N-C ring closure has been explored as one possible mechanism; its key features have been described. This non-insertive pathway evolves via a six-centre TS structure featuring activation of the olefin unit towards nucleophilic amido attack outside the immediate vicinity of the metal centre by amino proton delivery and describes a viable mechanistic variant for alkaline-earth metal-mediated aminoalkene hydroamination. However, herein is presented sound evidence for the operation of the Mg-N amido σ-bond insertive mechanism, its turnover-limiting activation barrier is found to be 5.0 kcal mol(-1) lower than for the non-insertive mechanism, for the cyclohydroamination of 2,2-disubstituted 4-aminoalkenes by a [{To(M)}Mg-NHR] catalyst. The operative mechanism involves rapid equilibria of the {To(M)}Mg-amidoalkene resting state 3 with its amine adduct, easily accessible and thermodynamically disfavoured, hence reversible, 1,2-olefin insertion into the Mg-N amido σ-bond with ring closure at 3, linked to turnover-limiting Mg-C azacycle tether aminolysis by an adduct substrate molecule, followed by facile cycloamine liberation to regenerate the active catalyst species 3. The following aspects are in support of this scenario: 1) the derived rate law is consistent with the experimentally obtained empirical rate law; 2) the reasonable agreement between the computationally estimated and the observed value of the primary KIE; 3) the assessed effective activation barrier for turnover-limiting aminolysis matches empirically determined Eyring parameters remarkably well; and 4) the observed resistance of isolated 3 to undergo amidoalkene cycloamine/cycloamido transformation until further quantities of substrate is added is consistently explained. The herein unveiled insights into the structure-reactivity relationships will undoubtedly govern the rational design of alkaline-earth metal-based catalysts and likely facilitate further advances in the area.     

Solubility in the LaCl<Subscript>3</Subscript>-LnCl<Subscript>3</Subscript>-HCl-H<Subscript>2</Subscript>O (Ln = Pr,Nd) Systems at 25°C

The solubility in the quaternary water-salt systems LaCl₃-NdCl₃-HCl-H₂O (1) and LaCl₃-PrCl₃-HCl-H₂O (2) at 25°C was studied in the section of 40 wt % hydrochloric acid, a system with a eutonic discontinuity. The composition at the point of discontinuity for the eutonic solution is the following. In system 1: 4.67 wt % LaCl₃ · 7H₂O, 0.37 wt % PrCl₃ · 7H₂O, 37.98 wt % HCl, and 56.98 wt % H₂O; in system 2: 4.37 wt % LaCl₃ · 7H₂O, 0.93 wt % NdCl₃ · 6H₂O, 37.88 wt % HCl, and 56.82 wt % H₂O.