Which do endohedral Ti2C80 metallofullerenes prefer energetically: Ti2@C80 or Ti2C2@C78? A theoretical study

Four possible isomers of the Ti2C80 metallofullerene are discussed in detail at the B3LYP DFT level of theory: two isomers in Ti2@C80 formula with two Ti atoms encapsulated inside a C80 cage and the other two in Ti2C2@C78 formula with a Ti2C2 cluster involved inside a C78 cage. In the encaged Ti2C2 cluster, there are end-on and side-on C2 bridging modes into the two Ti atoms. The optimized end-on cluster has a linear Ti-C-C-Ti array, whereas the side-on cluster has a butterfly-like structure where the two Ti atoms and the C2 unit do not lie in a plane. DFT calculations show that the Ti2C2@C78 molecule with the end-on Ti2C2 cluster is energetically most favorable in the four isomers. Stabilities of the Ti2C80 molecules are essentially dominated by Ti binding sites inside fullerene cages. The Ti atoms bind over the hexagon rings in preference to a junction between hexagon and pentagon rings. In the Ti2C2@C78 molecules, orbital interactions between the Ti2C2 cluster and the outer cage play a significant role in determining the C2 bridging modes into the dititanium center and their relative stabilities.     

Mono- and di-t-butyl substituted 2,2′-bis(1,3-dithia[3]ferrocenophane-2-ylidene) derivatives: TTF-like ferrocene analogs

Mono- and di-t-butyl substituted 2,2′-bis(1,3-dithia[3]ferrocenophane-2-ylidene) derivatives were prepared. These derivatives showed the E_1/2(1) in lower potential region than that of differrocenyl-ethene and -ethyne. Also, the ΔE_1/2 value declined according to the increase of a t-butyl group.     

An efficient catalytic enantioselective fluorination of β-ketophosphonates using chiral palladium complexes

On the basis of our Pd enolate chemistry, we have succeeded in developing an efficient catalytic enantioselective fluorination of β-ketophosphonates. In the presence of chiral Pd complexes 1 (1-10 mol %), various substrates including cyclic and acyclic β-ketophosphonates underwent the reaction with N-fluorobenzenesulfonimide (NFSI) in EtOH to give the corresponding fluorinated products in a highly enantioselective manner (94-98% ee).     

Rhenium-catalyzed synthesis of naphthalene derivatives via insertion of aldehydes into a C-H bond

A rhenium complex, [ReBr(CO)₃(THF)]₂, catalyzed reactions of aromatic ketimines and aldehydes with dienophiles, followed by dehydration, to give naphthalene derivatives in good to excellent yields. This reaction proceeds via C-H bond activation, insertion of an aldehyde, intramolecular nucleophilic cyclization, reductive elimination, elimination of aniline and Diels-Alder reaction. After dehydration, naphthalene derivatives were formed.     

Crown Ethers as Synergist in the 2-Thenoyltrifluoroacetone Extraction of Lanthanoids in 1,2-Dichloroethane

Summary. The solvent extraction of 14 trivalent lanthanoid ions (Ln ³⁺) from a nitrate medium into 1,2-dichloroethane containing 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione (HTTA) was investigated at 25.0°C. The extraction of Ln(TTA)₃ species was confirmed and the extraction constants were determined. The extraction of Ln with the synergistic mixture of HTTA and a crown ether (CE: 12-crown-4, 18-crown-6, cyclohexano-18-crown-6 or benzo-18-crown-6) was also investigated at 25.0°C. The 1:1 adducts of the complex and crown ether, Ln(TTA)₃·(CE) are formed for all the lanthanoid ions and the CEs used in this study. The formation constants, β_add, of the adduct Ln(TTA)₃·(CE) from Ln(TTA)₃ in the organic phase were determined by nonlinear least-squares method. The stabilities and structures of the formed adducts were discussed with respect to the cavity size, steric effect, and basicity of the CE.     

Cyclic Guanidine Compounds from Toxic Newts Support the Hypothesis that Tetrodotoxin is Derived from a Monoterpene

The biosynthesis of tetrodotoxin (TTX), a potent neurotoxin consisting of a 2,4‐dioxaadamantane skeleton and a guanidine moiety, is an unsolved problem in natural product chemistry. Recently, the first C5–C10 directly bonded TTX analogue, 4,9‐anhydro‐10‐hemiketal‐5‐deoxyTTX, was obtained from toxic newts and its carbon skeleton suggested a possible monoterpene origin. On the basis of this hypothesis, screening of predicted biosynthetic intermediates of TTX was performed using two MS‐guided methods. Herein, five novel cyclic guanidine compounds from toxic newts are reported which commonly contain a cis‐fused bicyclic structure including a six‐membered cyclic guanidine. These structures could be biosynthetically derived from geranyl guanidine through oxidation, cyclization, and/or isomerization steps. LC–MS analysis confirmed the widespread distribution of the five novel compounds in toxic newt species. These results support the hypothesis that TTX is derived from a monoterpene.     

Macrocyclic 2,7‐Anthrylene Oligomers

A macrocyclic compound consisting of six 2,7‐anthrylene units was successfully synthesized by Ni‐mediated coupling of the corresponding dibromo precursor as a novel π‐conjugated compound. This compound was sufficiently stable and soluble in organic solvents due to the presence of mesityl groups. X‐ray analysis showed that the molecule had a nonplanar and hexagonal wheel‐shaped framework of approximately S₆ symmetry. The dynamic process between two S₆ structures was observed by using the dynamic NMR technique, the barrier being 58 kJ mol^?1. The spectroscopic properties of the hexamer were compared with those of analogous linear oligomers.     

Copper-Catalyzed Coupling Reaction of Secondary Alkyl 2-Pyridinesulfonates with Alkyl Lithium-Based Reagents

The Cu(OTf)₂-catalyzed alkyl–alkyl coupling reaction of a secondary substrate MeCH(OSO₂Py)CH₂CH₂C₆H₄(4-OMe) with a nBuLi-based reagent prepared by transmetalation with MgBr₂ ⋅ THF₃ in THF produced a coupling product in 74 % yield. The use of soluble MgBr₂ ⋅ THF₃ in THF was required for this reaction. This method was applied to sBuLi and Ph(CH₂)₄Li. In contrast, transmetalation of MeLi with soluble MgCl₂ ⋅ THF₂ in THF produced the Me reagent, which was reactive for the coupling reaction. The reaction proceeded with inversion of the stereogenic carbon. Furthermore, (S)-14-methyloctadecan-2-one, a sex pheromone produced by lichen moths, was synthesized.     

BF(2) complexes of alpha-alkyl-substituted dipyrrolyldiketones as acyclic anion receptors

alpha-Alkyl-substituted dipyrrolyldiketones have exhibited anion binding behaviours with pyrrole rotations, whose rates depend on the alkyl chain lengths.