A novel three-component reaction of anilines,formaldehyde and dimedone: simple synthesis of spirosubstituted piperidines

A three-component condensation of anilines with dimedone and formaldehyde leads to the formation of 3,5-dispirosubstituted piperidines. This simple reaction can serve as a convenient source of 3,5-disubstituted piperidines as well as polyfunctional 3-spirofused piperidines.     

Covalency in the f element-chalcogen bond. computational studies of M[N(EPR2)2]3 (M = La, Ce, Pr, Pm, Eu, U, Np, Pu, Am, Cm; E = O, S, Se, Te; R = H, (i)Pr, Ph)

The geometric and electronic structures of the title complexes have been studied using scalar relativistic, gradient-corrected density functional theory. Extension of our previous work on six-coordinate M[N(EPH 2) 2] 3 (M = La, Ce, U, Pu; E = O, S, Se, Te), models for the experimentally characterized M[N(EP (i)Pr 2) 2] 3, yields converged geometries for all of the other 4f and 5f metals studied and for all four group 16 elements. By contrast, converged geometries for nine-coordinate M[N(EPPh 2) 2] 3 are obtained only for E = S and Se. Comparison of the electronic structures of six- and nine-coordinate M[N(EPH 2) 2] 3 suggests that coordination of the N atoms produces only minor changes in the metal-chalcogen interactions. Six-coordinate Eu[N(EPH 2) 2] 3 and Am[N(EPH 2) 2] 3 with the heavier group 16 donors display geometric and electronic properties rather different from those of the other members of the 4f and 5f series, in particular, longer than expected Eu-E and Am-E bond lengths, smaller reductions in charge difference between M and E down group 16, and larger f populations. The latter are interpreted not as evidence of f-based metal-ligand covalency but rather as being indicative of ionic metal centers closer to M (II) than M (III). The Cm complexes are found to be very ionic, with very metal-localized f orbitals and Cm (III) centers. The implications of the results for the separation of the minor actinides from nuclear wastes are discussed, as is the validity of using La (III)/U (III) comparisons as models for minor actinide/Eu systems.     

Energy decomposition analysis of metal-metal bonding in [M2X8]2- (X=Cl, br) complexes of 5f (U, Np, Pu), 5d (W, Re, Os), and 4d (Mo, Tc, Ru) elements

The electronic structures of a series of [M2X8]2- (X=Cl, Br) complexes involving 5f (U, Np, Pu), 5d (W, Re, Os), and 4d (Mo, Tc, Ru) elements have been calculated using density functional theory, and an energy decomposition approach has been used to carry out a detailed analysis of the metal-metal interactions. The energy decomposition analysis involves contributions from orbital interactions (mixing of occupied and unoccupied orbitals), electrostatic effects (Coulombic attraction and repulsion), and Pauli repulsion (associated with four-electron two-orbital interactions). As previously observed for Mo, W, and U M2X6 species, the general results suggest that the overall metal-metal interaction is considerably weaker or unfavorable in the actinide systems relative to the d-block analogues, as a consequence of a significantly more destabilizing contribution from the combined Pauli and electrostatic (prerelaxation) effects. Although the orbital-mixing (postrelaxation) contribution to the total bonding energy is predicted to be larger in the actinide complexes, this is not sufficiently strong to compensate for the comparatively greater destabilization originating from the Pauli-plus-electrostatic effects. A generally weak electrostatic contribution accounts for the large prerelaxation destabilization in the f-block systems, and ultimately for the weak or unfavorable nature of metal-metal bonding between the actinide elements. There is a greater variation in the energy decomposition results across the [M2Cl8]2- series for the actinide than for the d-block elements, both in the general behavior and in some particular properties.     

Phenalenannulations: Three-Point Double Annulation Reactions that Convert Benzenes into Pyrenes

3-Point annulations, or phenalenannulations, transform a benzene ring directly into a substituted pyrene by “wrapping” two new cycles around the perimeter of the central ring at three consecutive carbon atoms. This efficient, modular, and general method for π-extension opens access to non-symmetric pyrenes and their expanded analogues. Potentially, this approach can convert any aromatic ring bearing a -CH₂Br or a -CHO group into a pyrene moiety. Depending upon the workup choices, the process can be directed towards either tin- or iodo-substituted product formation, giving complementary choices for further various cross-coupling reactions. The two-directional bis-double annulation adds two new polyaromatic extensions with a total of six new aromatic rings at a central core.     

The Norbornene Shuttle: Multicomponent Domino Synthesis of Tetrasubstituted Helical Alkenes through Multiple C?H Functionalization

Shall we dance? Within the proposed mechanism for the palladium‐catalyzed title reaction, the strained alkene norbornene (or norbornadiene) enters and exits the catalytic cycle in a catalytic “square dance”, acting as both a promoter and a coupling partner in the formation of four carbon–carbon bonds, two of them by challenging C? H activation processes.

     

On the paucity of molecular actinide complexes with unsupported metal-metal bonds: a comparative investigation of the electronic structure and metal-metal bonding in U2X6 (X = Cl, F, OH, NH2, CH3) complexes and d-block analogues

Density functional calculations have been performed on M2X6 complexes (where M = U, W, and Mo and X = Cl, F, OH, NH2, and CH3) to investigate general aspects of their electronic structures and explore the similarities and differences in metal-metal bonding between f-block and d-block elements. A detailed analysis of the metal-metal interactions has been conducted using molecular orbital theory and energy decomposition methods. Multiple (sigma and pi) bonding is predicted for all species investigated, with predominant f-f and d-d metal orbital character, respectively, for U and W or Mo complexes. The energy decomposition analysis involves contributions from orbital interactions (mixing of occupied and unoccupied orbitals), electrostatic effects (Coulombic attraction and repulsion), and Pauli repulsion (associated with four-electron two-orbital interactions). The general results suggest that the overall metal-metal interaction is stronger in the Mo and W species, relative to the U analogues, as a consequence of a significantly less destabilizing contribution from the combined Pauli and electrostatic ("pre-relaxation") effects. Although the orbital-mixing ("post-relaxation") contribution to the total bonding energy is predicted to have a larger magnitude in the U complexes, this is not sufficiently strong to compensate for the comparatively greater destabilization that originates from the Pauli-plus-electrostatic effects. Of the pre-relaxation terms, the Pauli repulsion is comparable in analogous U and d-block compounds, contrary to the electrostatic term, which is (much) less favorable in the U systems than in the W and Mo systems. This generally weak electrostatic stabilization accounts for the large pre-relaxation destabilization in the U complexes and, ultimately, for the relative weakness of the U-U bonds. The origin of the small electrostatic term in the U compounds is traced primarily to MX(3) fragment overlap effects.     

A stable two-coordinate acyclic silylene

Simple two-coordinate acyclic silylenes, SiR(2), have hitherto been identified only as transient intermediates or thermally labile species. By making use of the strong σ-donor properties and high steric loading of the B(NDippCH)(2) substituent (Dipp = 2,6-(i)Pr(2)C(6)H(3)), an isolable monomeric species, Si{B(NDippCH)(2)}{N(SiMe(3))Dipp}, can be synthesized which is stable in the solid state up to 130 °C. This silylene species undergoes facile oxidative addition reactions with dihydrogen (at sub-ambient temperatures) and with alkyl C-H bonds, consistent with a low singlet-triplet gap (103.9 kJ mol(-1)), thus demonstrating fundamental modes of reactivity more characteristic of transition metal systems.     

Submerged fermentation of the edible mushroom Pleurotus ostreatus in a batch stirred tank bioreactor as a promising alternative for the effective production of bioactive metabolites

The aim of this study was to investigate the potential of the submerged fermentation procedure in the production of bioactive metabolites of the common edible mushroom Pleurotus ostreatus. The biomass of the mushroom strain was produced by submerged fermentation in a batch stirred tank bioreactor and extracted by solvents of increasing polarity. The dichloromethane and methanol extract were fractioned by different techniques including Adsorption Chromatography and Fast Centrifugal Partition Chromatography (FCPC). The structures of pure compounds were elucidated with 1D/2D NMR-spectroscopic analyses, and chemical correlations combined with GC/MS and LC/MS experiments. Nineteen metabolites (e.g., fatty acids, phenolic metabolites, nucleotides and alkaloids) were isolated. Beyond the production of known metabolites, we report herein the production also of trans-3,4-dihydro-3,4,8-trihydroxynapthalen-1(2H)-one, indolo-3-carboxylic acid, 3-formylpyrrole and 4-hydroxybenzoic acid, that have pharmaceutical interest and are isolated for the first time from Pleurotus strains. This work indicates the great potential of the established bioprocess for the production of P. ostreatus mycelia with enhanced metabolic profile.     

Bonding Trends Traversing the Tetravalent Actinide Series: Synthesis, Structural, and Computational Analysis of An(IV)((Ar)acnac)(4) Complexes (An = Th, U, Np, Pu; (Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3))

A series of tetravalent An(IV) complexes with a bis-phenyl β-ketoiminate N,O donor ligand has been synthesized with the aim of identifying bonding trends and changes across the actinide series. The neutral molecules are homoleptic with the formula An((Ar)acnac)(4) (An = Th (1), U (2), Np (3), Pu (4); (Ar)acnac = ArNC(Ph)CHC(Ph)O; Ar = 3,5-(t)Bu(2)C(6)H(3)) and were synthesized through salt metathesis reactions with actinide chloride precursors. NMR and electronic absorption spectroscopy confirm the purity of all four new compounds and demonstrate stability in both solution and the solid state. The Th, U, and Pu complexes were structurally elucidated by single-crystal X-ray diffraction and shown to be isostructural in space group C2/c. Analysis of the bond lengths reveals shortening of the An-O and An-N distances arising from the actinide contraction upon moving from 1 to 2. The shortening is more pronounced upon moving from 2 to 4, and the steric constraints of the tetrakis complexes appear to prevent the enhanced U-O versus Pu-O orbital interactions previously observed in the comparison of UI(2)((Ar)acnac)(2) and PuI(2)((Ar)acnac)(2) bis-complexes. Computational analysis of models for 1, 2, and 4 (1a, 2a, and 4a, respectively) concludes that both the An-O and the An-N bonds are predominantly ionic for all three molecules, with the An-O bonds being slightly more covalent. Molecular orbital energy level diagrams indicate the largest 5f-ligand orbital mixing for 4a (Pu), but spatial overlap considerations do not lead to the conclusion that this implies significantly greater covalency in the Pu-ligand bonding. QTAIM bond critical point data suggest that both U-O/U-N and Pu-O/Pu-N are marginally more covalent than the Th analogues.