Interaction between Divalent Copper Fluoride and Carboxamide Group Enabling Stereoretentive Fluorination of Tertiary Alkyl Halides

Herein, we report a copper-catalyzed stereospecific fluorination involving CsF and α-bromocarboxamides as tertiary alkyl sources that, unlike traditional stereospecific routes involving stereoinversive S_N2 reactions, proceeds with retention of stereochemistry. The developed stereospecific Cu-catalyzed reaction is among the most efficient methods for synthesizing fluorinated molecules that possess highly congested stereogenic carbon centers. Mechanistic studies revealed that the combined reactivity of CuF₂ and Cs salt is essential for completing the catalytic cycle. Our catalytic system underwent fluorination exclusively with tertiary alkyl bromides and did not react with primary alkyl bromides, indicating that this stereospecific fluorination methodology is suitable for synthesizing fluorinated building blocks possessing stereo-defined F-containing tertiary carbon stereogenic center.     

Transition metal-catalyzed asymmetric reactions using P-chirogenic diaminophosphine oxides: DIAPHOXs

This review describes the development of a new class of chiral phosphorus ligands: amino acid-derived P-chirogenic diaminophosphine oxides, DIAPHOXs, and their application to several transition metal-catalyzed asymmetric allylic substitution reactions. Pd-catalyzed asymmetric allylic alkylation with cyclic beta-keto esters as prochiral nucleophiles was initially examined using P-chirogenic diaminophosphine oxide 1a, resulting in highly enantioselective construction of quaternary stereocenters. Mechanistic investigations revealed that 1a is activated by N,O-bis(trimethylsilyl)acetamide-induced tautomerization to afford a trivalent diamidophosphite species 13, which functions as the actual ligand. Pd-catalyzed asymmetric allylic substitutions of both acyclic and cyclic substrates were also examined using various nucleophiles such as malonate derivatives, nitromethane, aliphatic amines, and aromatic amines, providing a variety of chiral compounds with good to excellent enantioselectivity. In addition, Ir-catalyzed asymmetric allylic amination and alkylation of terminal allylic carbonates were examined using structurally optimized P-chirogenic diaminophosphine oxides, and the corresponding branched products were obtained in a highly regio- and enantioselective manner. Furthermore, the developed catalytic asymmetric process was successfully applied to the catalytic enantioselective synthesis of biologically active compounds, (R)-preclamol, (R)-baclofen hydrochloride, and (-)-paroxetine.     

Pd-catalyzed asymmetric allylic substitution reactions using P-chirogenic diaminophosphine oxides: DIAPHOXs

This paper describes the development of a new class of chiral phosphorus ligand: aspartic acid-derived P-chirogenic diaminophosphine oxides, DIAPHOXs, and their application to several Pd-catalyzed asymmetric allylic substitution reactions. Pd-catalyzed asymmetric allylic alkylation was initially examined in detail using diaminophosphine oxides 1a, resulting in the highly enantioselective construction of quaternary stereocenters. Mechanistic investigations revealed that 1a is activated by N,O-bis(trimethylsilyl)acetamide-induced tautomerization to afford a trivalent diamidophosphite species 12, which functions as the actual ligand. Furthermore, asymmetric allylic amination was examined using Pd-DIAPHOX catalyst systems, providing a variety of chiral allylic amines.     

Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxides: DIAPHOXs. Formal enantioselective synthesis of (−)-paroxetine

An Ir-catalyzed asymmetric allylic alkylation using chiral diaminophosphine oxide is described. Asymmetric allylic alkylation of terminal allylic carbonates proceeded using 5 mol % of Ir catalyst, 5 mol % of DIAPHOX 1i, 10 mol % of NaPF₆, 10 mol % of LiOAc, and N,O-bis(trimethylsilyl)acetamide (BSA), affording the corresponding branched products in excellent yield and in up to 95% ee. The developed catalytic asymmetric reaction was successfully applied to a formal enantioselective synthesis of (−)-paroxetine.     

Inclusion and dielectric properties of a vinylidene fluoride oligomer in coordination nanochannels

The dynamics of oligo(vinylidene fluoride) (OVDF) confined in regular nanochannels of a porous coordination polymer (PCP) was studied by means of dielectric spectroscopy. The OVDF chains in the PCP nanopores showed two Arrhenius-type relaxation processes at lower temperatures than the relaxation temperature observed for the neat OVDF, showing the enhanced mobility of the confined OVDF.     

Asymmetric synthesis of highly functionalized γ-lactams through an organocatalytic aza-Michael–Michael reaction cascade using fumaric acid amide esters as multi-reactive substrates

We developed a novel method for the asymmetric synthesis of highly functionalized γ-lactams through an organocatalytic aza-Michael–Michael reaction cascade using fumaric acid amide esters as multi-reactive substrates. Using chiral primary or secondary amine organocatalysts, we obtained two types of γ-lactams with three contiguous chiral centers in moderate to good yield with excellent enantioselectivity and diastereoselectivity.     

Polyacetylene and Polynorbornene Derivatives Carrying TEMPO. Synthesis and Properties as Organic Radical Battery Materials

Summary: 2,2,6,6‐Tetramethylpiperidine 1‐oxyl (TEMPO)‐containing N‐propargylamide HCCCH₂NHCO‐4‐TEMPO ( 1 ), propargyl ester HCCCH₂OCO‐4‐TEMPO ( 2 ), phenylacetylene derivative HCCC₆H₃‐3,4‐(CO₂‐4‐TEMPO)₂ ( 3 ), and norbornene diester monomers, NB‐2,3‐exo,exo‐(CH₂OCO‐4‐TEMPO)₂ ( 4 ), NB‐2,3‐endo,exo‐(COO‐4‐TEMPO)₂ ( 5a ), NB‐2,3‐endo,endo‐(COO‐4‐TEMPO)₂ ( 5b ) (NB = norbornene, TEMPO = 2,2,6,6‐tetramethyl‐1‐piperidinyloxyl) were synthesized and polymerized with rhodium and ruthenium catalysts. Monomers 2 , 5a , and 5b gave polymers with number‐average molecular weights of 47 000–185 000 in 59–100% yields, while 1 , 3 , and 4 gave polymers insoluble in common organic solvents in 88–100% yields. The capacities of cells fabricated with poly( 1 ), poly( 2 ), and poly( 3 ) were 67, 82, and 23 Ah · kg⁻¹ based on the weight, respectively. The capacity of poly( 5a )‐based cell reached the theoretical value (109 Ah · kg⁻¹) of the polymer.

Charge–discharge curves of poly( 5a ) at a current density of 0.13 mA · cm⁻² (100 mA · g⁻¹_{‐cathode active material}) in the voltage range of 2.5–4.2 V.     

Photon-stimulated ion desorption from DCOO/Si(100) near the O K-edge

Photon-stimulated ion desorption from deuterated formic acid chemisorbed on Si(100) has been studied using pulsed synchrotron radiation in the energy region of the oxygen 1s electron excitation. The O 1s electrons of hydroxyl oxygen and carbonyl oxygen could be selectively excited in the O K-edge region because the chemical environments are different. It is found that the CDO⁺ yield is enhanced at the O 1s(C---O)→σ*(C---O) resonance and the CD⁺ yield at the O 1s(C=O)→σ*(C---O) resonance. The results indicate that ion desorption is related both to the antibonding character of excited molecular orbitals and the local character of core hole orbitals.     

Helimagnetic resonance experiments in NiBr2 at millimetre wavelengths

The zero-field value of the high frequency mode of helimagnetic resonance in NiBr₂ and the g-value along the c-axis are precisely determined through the magnetic field dependence of the resonances. At 4.2 K we find v₂(0) = (204±2) GHz and g_{ = 2.17±0.02. From these precise values an accurate determination of the anisotropy parameter D is obtained.     

Applications of a photoion-photoion-coincidence technique to the study of photon-stimulated ion-desorption process following K-shell excitation

We have investigated the photon-stimulated ion-desorption from deuterated formic acid (DCOOD) monolayer chemisorbed on Si(100) crystal by applying a photoion-photoion-coincidence technique. The true-coincidence yields of an ion pair C⁺---D⁺ are given in the photon energy range (275–400 eV) above the C 1s absorption edge. The partial ion yields and Auger electron yields re presented for comparison. It was found that the multielectron (shake-off) excitation promotes the multiple bond-breaking of the adsorbate and the ion pair C⁺–D⁺ desorption events.