Transition-Metal-Free Synthesis of Fluorinated Arenes from Perfluorinated Arenes Coupled with Grignard Reagents

A simple method to obtain organofluorine compounds from perfluorinated arenes coupled with Grignard reagents in the absence of a transition-metal catalyst was reported. In particular, the perfluorinated arenes could react not only with aryl Grignard reagents but also with alkyl Grignard reagents in moderate to good yields

Fragments of 'Systema morborum'

Benzo­[1,4]­thiazin-3­(4<i>H</i>)-one derivatives are conveniently prepared in one pot via a Smiles rearrangement (SR) tandem reaction. In order to understand the reaction, we present here a theoretical study on the S–N type SR mechanism

Hydride Transfer from Iron(II) Hydride Compounds to NAD(P)⁺ Analogues

Iron­(II) hydride complexes of the “piano-stool” type, Cp*­(P-P)­FeH (P-P = dppe (<b>1H</b>), dppbz (<b>2H</b>), dppm (<b>3H</b>), dcpe (<b>4H</b>)) were examined as hydride donors in the reduction of <i>N</i>-benzylpyridinium and acridinium salts. Two pathways of hydride transfer, “single-step H^–” transfer to pyridinium and a “two-step (e^–/H^•)” transfer for acridinium reduction, were observed. When 1-benzylnicotinamide cation (BNA⁺) was used as an H^– acceptor, kinetic studies suggested that <b>BNA</b>^<b>+</b> was reduced at the C6 position, affording 1,6-BNAH, which can be converted to the more thermally stable 1,4-product. The rate constant <i>k</i> of H^– transfer was very sensitive to the bite angle of P–Fe–P in Cp*­(P-P)­FeH and ranged from 3.23 × 10^–3 M^–1 s^–1 for dppe to 1.74 × 10^–1 M^–1 s^–1 for dppm. The results obtained from reduction of a range of <i>N</i>-benzylpyridinium derivatives suggest that H^– transfer is more likely to be charge controlled. In the reduction of 10-methylacridinium ion (<b>Acr</b>^<b>+</b>), the reaction was initiated by an e^– transfer (ET) process and then followed by rapid disproportionation reactions to produce <b>Acr</b>_<b>2</b> dimer and release of H₂. To achieve H^• transfer after ET from [Cp*­(P-P)­FeH]⁺ to acridine radicals, the bulkier acridinium salt 9-phenyl-10-methylacridinium (<b>PhAcr</b>^<b>+</b>) was selected as an acceptor. More evidence for this “two-step (e^–/H^•)” process was derived from the characterization of <b>PhAcr^•</b> and [<b>4H</b>]^<b>+</b> radicals by EPR spectra and by the crystallographic structure confirmation of [<b>4H</b>]^<b>+</b>. Our mechanistic understanding of fundamental H^– transfer from iron­(II) hydrides to NAD⁺ analogues provides insight into establishing attractive bio-organometallic transformation cycles driven by iron catalysis

Hydride Transfer from Iron(II) Hydride Compounds to NAD(P)⁺ Analogues

Iron­(II) hydride complexes of the “piano-stool” type, Cp*­(P-P)­FeH (P-P = dppe (<b>1H</b>), dppbz (<b>2H</b>), dppm (<b>3H</b>), dcpe (<b>4H</b>)) were examined as hydride donors in the reduction of <i>N</i>-benzylpyridinium and acridinium salts. Two pathways of hydride transfer, “single-step H^–” transfer to pyridinium and a “two-step (e^–/H^•)” transfer for acridinium reduction, were observed. When 1-benzylnicotinamide cation (BNA⁺) was used as an H^– acceptor, kinetic studies suggested that <b>BNA</b>^<b>+</b> was reduced at the C6 position, affording 1,6-BNAH, which can be converted to the more thermally stable 1,4-product. The rate constant <i>k</i> of H^– transfer was very sensitive to the bite angle of P–Fe–P in Cp*­(P-P)­FeH and ranged from 3.23 × 10^–3 M^–1 s^–1 for dppe to 1.74 × 10^–1 M^–1 s^–1 for dppm. The results obtained from reduction of a range of <i>N</i>-benzylpyridinium derivatives suggest that H^– transfer is more likely to be charge controlled. In the reduction of 10-methylacridinium ion (<b>Acr</b>^<b>+</b>), the reaction was initiated by an e^– transfer (ET) process and then followed by rapid disproportionation reactions to produce <b>Acr</b>_<b>2</b> dimer and release of H₂. To achieve H^• transfer after ET from [Cp*­(P-P)­FeH]⁺ to acridine radicals, the bulkier acridinium salt 9-phenyl-10-methylacridinium (<b>PhAcr</b>^<b>+</b>) was selected as an acceptor. More evidence for this “two-step (e^–/H^•)” process was derived from the characterization of <b>PhAcr^•</b> and [<b>4H</b>]^<b>+</b> radicals by EPR spectra and by the crystallographic structure confirmation of [<b>4H</b>]^<b>+</b>. Our mechanistic understanding of fundamental H^– transfer from iron­(II) hydrides to NAD⁺ analogues provides insight into establishing attractive bio-organometallic transformation cycles driven by iron catalysis

Titanium-Oxide Host Clusters with Exchangeable Guests

A novel family of water-soluble, poly­oxo­cationic titanium-oxide host–guest clusters are reported herein. They exhibit an unprecedented hexagonal prismatic core structure for hosting univalent cationic guests like K⁺, Rb⁺, Cs⁺ and H₃O⁺. Guest exchange has been studied using ¹³³Cs NMR, showing the flexible pore of a host permits passage of a comparatively larger cation and giving an equilibrium constant of ca. 13 for displacing Rb⁺ by Cs⁺. Attractive ion-dipole interaction, depending on host–guest size complementarity, plays a dominant role for the preferential encapsulation of larger alkali-metal cationic guests

Gold/Lewis Acid Catalyzed Cycloisomerization/Diastereoselective [3 + 2] Cycloaddition Cascade: Synthesis of Diverse Nitrogen-Containing Spiro Heterocycles

A novel early and late transition-metal relay catalysis has been developed by combining a gold-catalyzed cycloisomerization and a Yb­(OTf)₃-catalyzed diastereoselective [3 + 2] cycloaddition with aziridines in a selective C–C bond cleavage mode. Various biologically significant complex nitrogen-containing spiro heterocycles were rapidly constructed from readily available starting materials under mild conditions

Hierarchical Assembly of a {Mn^II₁₅Mn^III₄} Brucite Disc: Step-by-Step Formation and Ferrimagnetism

In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn₇) to nonadecamer (Mn₁₉) satisfying the relation 1 + Σ_<i>n</i>6<i>n</i>, where <i>n</i> is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn₁₀, Mn₁₂, and Mn₁₄, were identified. Furthermore, the Mn₁₉ disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn₁₉­(<i>L</i>)_<i>x</i>­(OH)_<i>y</i>­(N₃)_{36–<i>x</i>−<i>y</i>}]²⁺ (<i>x</i> = 18, 17, 16; <i>y</i> = 8, 7, 6; H<i>L</i> = 1-(hydroxy­methyl)-3,5-dimethylpyrazole) indicating progressive exchange of N₃^– for OH^–. The high symmetry (<i>R</i>-3) Mn₁₉ crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn^II₁₅Mn^III₄]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH₃CN. The moment of nearly 50 Nμ_B suggests Mn^II–Mn^II and Mn^III–Mn^III are ferromagnetically coupled while Mn^II–Mn^III is antiferromagnetic which is likely if the Mn^III are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules

Hierarchical Assembly of a {Mn^II₁₅Mn^III₄} Brucite Disc: Step-by-Step Formation and Ferrimagnetism

In search of functional molecular materials and the study of their formation mechanism, we report the elucidation of a hierarchical step-by-step formation from monomer (Mn) to heptamer (Mn₇) to nonadecamer (Mn₁₉) satisfying the relation 1 + Σ_<i>n</i>6<i>n</i>, where <i>n</i> is the ring number of the Brucite structure using high-resolution electrospray ionization mass spectrometry (HRESI-MS). Three intermediate clusters, Mn₁₀, Mn₁₂, and Mn₁₄, were identified. Furthermore, the Mn₁₉ disc remains intact when dissolved in acetonitrile with a well-resolved general formula of [Mn₁₉­(<i>L</i>)_<i>x</i>­(OH)_<i>y</i>­(N₃)_{36–<i>x</i>−<i>y</i>}]²⁺ (<i>x</i> = 18, 17, 16; <i>y</i> = 8, 7, 6; H<i>L</i> = 1-(hydroxy­methyl)-3,5-dimethylpyrazole) indicating progressive exchange of N₃^– for OH^–. The high symmetry (<i>R</i>-3) Mn₁₉ crystal structure consists of a well-ordered discotic motif where the peripheral organic ligands form a double calix housing the anions and solvent molecules. From the formula and valence bond sums, the charge state is mixed-valent, [Mn^II₁₅Mn^III₄]. Its magnetic properties and electrochemistry have been studied. It behaves as a ferrimagnet below 40 K and has a coercive field of 2.7 kOe at 1.8 K, which can be possible by either weak exchange between clusters through the anions and solvents or through dipolar interaction through space as confirmed by the lack of ordering in frozen CH₃CN. The moment of nearly 50 Nμ_B suggests Mn^II–Mn^II and Mn^III–Mn^III are ferromagnetically coupled while Mn^II–Mn^III is antiferromagnetic which is likely if the Mn^III are centrally placed in the cluster. This compound displays the rare occurrence of magnetic ordering from nonconnected high-spin molecules