Lanthanide-benzophenone-3,3′-disulfonyl-4,4′-dicarboxylate Frameworks: Temperature and 1‑Hydroxypyren Luminescence Sensing and Proton Conduction

The benzophenone-3,3′-disulfonyl-4,4′-dicarboxylic acid (H₄–BODSDC) ligand and compounds, {(H₃O)­[Ln­(BODSDC)­(H₂O)₂]}_<i>n</i> (Ln = Tb­(<b>1</b>), Eu­(<b>2</b>), and Gd­(<b>3</b>)), were synthesized and structurally characterized. The lanthanide centers are bridged by the carboxylate groups of BODSDC^4– ligands to give a one-dimensional (1D) chain. The 1D chains are connected by the BODSDC^4– ligands to yield a three-dimensional (3D) structure featuring 1D channels. The lanthanide ions are efficiently sensitized by the BODSDC^4– ligand with an appropriate triplet excited state to generate characteristic Tb­(III) and Eu­(III) emissions in Tb­(<b>1</b>) and Eu­(<b>2</b>), respectively. Thus the binary compound, {(H₃O)­[Tb_0.93Eu_0.07(BODSDC)­(H₂O)₂]}_<i>n</i> (abbreviated as Tb_0.93Eu_0.07-BODSDC), was achieved for use as a ratiometric temperature sensor. The ratio values of Tb­(III) emission at 544 nm (<i>I</i>_Tb) and Eu­(III) emission at 616 nm (<i>I</i>_Eu) for Tb_0.93Eu_0.07-BODSDC linearly vary with temperature over a wide range, which indicates that the Tb_0.93Eu_0.07-BODSDC is a thermometer for ratiometric fluorescence sensing of temperature. Additionally, Tb­(<b>1</b>) is a fluorescent probe for detecting 1-hydroxypyrene (1-HP) by luminescence quenching. The uncoordinated sulfonate oxygens exposed on the channel surfaces serve as the binding sites for 1-HP. Finally, the enrichment of the solvent water molecules in the channels decorated by high-density hydrophilic sulfonate groups resulted in a high proton conductivity for Tb­(<b>1</b>)

Highly Enantioselective Synthesis of Propargyl Amides through Rh‑Catalyzed Asymmetric Hydroalkynylation of Enamides: Scope, Mechanism, and Origin of Selectivity

Chiral propargyl amides are particularly useful structural units in organic synthesis. The enantioselective synthesis of propargyl amide is highly desirable. Conventional approach involves the use of a stoichiometric amount of metal reagent or chiral auxiliary. In comparison, direct alkynylation with terminal alkyne is attractive because it avoids the use of stoichiometric organometallic reagent. The asymmetric coupling of aldehyde, amine, and alkyne (A³-coupling) provides an efficient method for the synthesis of <i>N</i>-alkyl and <i>N</i>-aryl-substituted propargyl amines, but this strategy is not amenable for the direct enantioselective synthesis of propargyl amide. We have developed a new strategy and report here a Rh-catalyzed asymmetric hydroalkynylation of enamides. Alkynylations occur regioselectively at the α position of an enamide to produce chiral propargyl amides. High yield and enantioselectivity were observed. Previous alkynylation methods to prepare chiral propargyl amine involve the nucleophilic addition to an electron-deficient imine. In contrast, our current approach proceeds through regioselective hydroalkynylation of an electron-rich alkene. Kinetic studies indicated that migratory insertion of the enamide to the rhodium hydride is turnover limiting. Computational studies revealed the origin of regio- and enantioselectivities. This novel strategy provides an efficient method to access chiral propargyl amides directly from terminal alkynes

Synthesis of Tribenzo[<i>b</i>,<i>e</i>,<i>g</i>]phosphindole Oxides via Radical Bicyclization Cascades of <i>o</i>‑Arylalkynylanilines

A new DTBP/Mg­(NO₃)₂-mediated bicyclization cascade of <i>o</i>-arylalkynylanilines with secondary arylphosphine oxides has been developed, enabling dual C­(sp²)–H functionalization along with the cleavage of the C–N bond. The combination between regioselective P-centered radical-triggered [3 + 2] cyclization and C-centered radical-induced cross-coupling in a one-pot manner delivered 27 examples of tribenzo­[<i>b</i>,<i>e</i>,<i>g</i>]­phosphindole oxides with generally high regioselectivity. A reasonable mechanism for forming such products involving radical addition–cyclization cascade is proposed

Radical Deaminative <i>ipso</i>-Cyclization of 4‑Methoxyanilines with 1,7-Enynes for Accessing Spirocyclohexadienone-Containing Cyclopenta[<i>c</i>]quinolin-4-ones

A new C-center radical-triggered bicyclization cascade of <i>N</i>-tethered 1,7-enynes for forming 28 examples of biologically interesting spirocyclohexadienone-containing cyclopenta­[<i>c</i>]­quinolin-4-ones with two all-carbon quaternary stereocenters has been established under mild conditions. The in situ generated diazonium salts from 4-methoxyanilines and <i>t</i>-BuONO are served as 4-methoxyphenyl precursors without additional oxidant, enabling 6-<i>exo</i>-<i>dig</i> cyclization/5-<i>exo</i>-<i>trig</i> <i>ipso</i>-cyclization to construct three new C–C bonds through metal-free dearomatization. The reaction also features broad substrate scope, annulation efficiency, and high functional group tolerance

Radical Deaminative <i>ipso</i>-Cyclization of 4‑Methoxyanilines with 1,7-Enynes for Accessing Spirocyclohexadienone-Containing Cyclopenta[<i>c</i>]quinolin-4-ones

A new C-center radical-triggered bicyclization cascade of <i>N</i>-tethered 1,7-enynes for forming 28 examples of biologically interesting spirocyclohexadienone-containing cyclopenta­[<i>c</i>]­quinolin-4-ones with two all-carbon quaternary stereocenters has been established under mild conditions. The in situ generated diazonium salts from 4-methoxyanilines and <i>t</i>-BuONO are served as 4-methoxyphenyl precursors without additional oxidant, enabling 6-<i>exo</i>-<i>dig</i> cyclization/5-<i>exo</i>-<i>trig</i> <i>ipso</i>-cyclization to construct three new C–C bonds through metal-free dearomatization. The reaction also features broad substrate scope, annulation efficiency, and high functional group tolerance