Carbon monoxide as a building block in organic synthesis. Part V. Involvement of palladium-hydride species in carbonylation reactions of monoterpenes. X-ray crystal structure of [Ph3PCH2CH=CHPh]4[PdCl6][SnCl6]

A palladium precursor and SnCl₂ as cocatalyst were used under 4 MPa of carbon monoxide for the catalytic alkoxycarbonylation of several monoterpenes into C₁₁ esters. The active catalyst involves a palladium-hydride species whose formation was investigated. In the case of the model substrate 3-phenylpropene, the source of the hydrido ligand was determined to be the alkene itself. Allylic hydrogen abstraction seems to be a general way to produce the active hydridopalladium species since monoterpenes having labile allylic hydrogens were converted under exceptional mild conditions. An X-ray crystal structure analysis was carried out on [(Ph₃PCH₂CH =MPh)₄(PdCl₆)(SnCl₆)]. kw]Palladium; X-ray structure; Terpenes; Carbonylation; Hydroesterification     

Lanthanide complexes derived from (R)-1,1'-binaphthyl-2,2'-bis(neopentylamine)--(Li(THF)4)(Ln[(R)-C20H12N2(C10H22)]2) (Ln = Sm, Yb)--novel catalysts for enantioselective intramolecular hydroamination

The complexes (Li(THF)4)(Ln[(R)-C20H12N2(C10H22)]2) (Ln = Sm, Yb) have been synthesized, fully characterized and found to be efficient and enantioselective catalysts for intramolecular hydroamination of 1-(aminomethyl)-1-allylcyclohexane.     

Replacement of Volatile Acetic Acid by Solid SiO2@COOH Silica (Nano)Beads for (Ep)Oxidation Using Mn and Fe Complexes Containing BPMEN Ligand

Mn and Fe BPMEN complexes showed excellent reactivity in catalytic oxidation with an excess of co-reagent (CH₃COOH). In the straight line of a cleaner catalytic system, volatile acetic acid was replaced by SiO₂ (nano)particles with two different sizes to which pending carboxylic functions were added (SiO₂@COOH). The SiO₂@COOH beads were obtained by the functionalization of SiO₂ with pending nitrile functions (SiO₂@CN) followed by CN hydrolysis. All complexes and silica beads were characterized by NMR, infrared, DLS, TEM, X-ray diffraction. The replacement of CH₃COOH by SiO₂@COOH (100 times less on molar ratio) has been evaluated for (ep)oxidation on several substrates (cyclooctene, cyclohexene, cyclohexanol) and discussed in terms of activity and green metrics.     

Organometallic cluster complexes containing ynamine ligands

A comprehensive review of the chemistry of metal carbonyl cluster complexes containing ynamine ligands including syntheses, structures, bonding, and reactivity is presented.     

Lanthanide complexes coordinated by N-substituted (R)-1,1'-binaphthyl-2,2'-diamido ligands in the catalysis of enantioselective intramolecular hydroamination

A new family of lanthanide ionic complexes derived from chiral, substituted (R)-binaphthylamine ligands, [Li(thf)(4)][Ln{(R)-C(20)H(12)(NR)(2)}(2)] (Ln=Yb, Sm, Nd, or Lu), has been synthesized and characterized by X-ray crystal structure analyses. All complexes have been tested as new catalysts for the hydroamination/cyclization of 1-(aminomethyl)-1-allylcyclohexane. Ytterbium complexes proved to be both the most active and the most enantioselective, and the use of the complex [Li(thf)(4)][Yb{(R)-C(20)H(12)(NC(3)H(7))(2)}(2)], bearing isopropyl radicals on the nitrogen atoms, allowed the formation of the corresponding spiropyrrolidine in high yield with up to 70 % ee.     

A mechanistic investigation of oxidative addition of methyl iodide to [Tp*Rh(CO)(L)

Reaction of methyl iodide with square planar [kappa(2)-Tp*Rh(CO)(PMe(3))] 1a (Tp* = HB(3,5-Me(2)pz)(3)) at room temperature affords [kappa(3)-Tp*Rh(CO)(PMe(3))(Me)]I 2a, which was fully characterized by spectroscopy and X-ray crystallography. The pseudooctahedral geometry of cationic 2a, which contains a kappa(3)-coordinated Tp* ligand, indicates a reaction mechanism in which nucleophilic attack by Rh on MeI is accompanied by coordination of the pendant pyrazolyl group. In solution 2a transforms slowly into a neutral (acetyl)(iodo) rhodium complex [kappa(3)-Tp*Rh(PMe(3))(COMe)I] 3a, for which an X-ray crystal structure is also reported. Kinetic studies on the reactions of [kappa(2)-Tp*Rh(CO)(L)] (L = PMe(3), PMe(2)Ph, PMePh(2), PPh(3), CO)] with MeI show second-order behavior with large negative activation entropies, consistent with an S(N)2 mechanism. The second-order rate constants correlate well with phosphine basicity. For L = CO, reaction with MeI gives an acetyl complex, [kappa(3)-Tp*Rh(CO)(COMe)I]. The bis(pyrazolyl)borate complexes [kappa(2)-Bp*Rh(CO)(L)] (L = PPh(3), CO) are much less reactive toward MeI than the Tp* analogues, indicating the importance of the third pyrazolyl group and the accessibility of a kappa(3) coordination mode. The results strengthen the evidence in favor of an S(N)2 mechanism for oxidative addition of MeI to square planar d(8) transition metal complexes.     

Chirality control in 2,2'-biphosphole ligand leading to enantiopure Pd complex

Asymmetric alkylation of the 3,4-dimethyl-5-phenyl-2,2'-biphospholyl anion with the (2R,4R)-(-)-pentaneditosylate leads to a new chirally flexible 2,2'-biphosphole ligand as a mixture of three diasteroisomers. By complexation with Pd(II), a chirality control occurs to afford enantiopure Pd complex.     

[Yb(H2O)8][Cd3Cl9(H2O)]·6H2O

The title compound, namely octa­aqua­ytterbium(III) aqua­nona­chloro­tricadmate(II) hexa­hydrate, [Yb(H₂O)₈][Cd₃Cl₉(H₂O)]·6H₂O, was prepared by evaporation at 278 K from an aqueous solution of the ternary system YbCl₃–CdCl₂–H₂O and was characterized by elemental chemical analysis and by X‐ray powder and single‐crystal diffraction studies. The crystal structure can be viewed as being built from layers of double chains of CdCl₆ and CdCl₅(H₂O) octahedra separated by antiprismatic [Yb(H₂O)₈]³⁺ cations. The stabilization of the structure is ensured by O—H⋯O and O—H⋯Cl hydrogen bonds. A comparison with the structures of SrCd₂Cl₆·8H₂O and CeCd₄Cl₁₁·13H₂O is presented.     

Investigating the role of c-Jun N-terminal kinases in the proliferation of Werner syndrome fibroblasts using diaminopyridine inhibitors

To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H₂O₂ was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation.