Convergent Synthesis, Resolution, and Chiroptical Properties of Dimethoxychromenoacridinium Ions

Cationic azaoxa[4]­helicenes can be prepared in a single step from a common xanthenium precursor by addition of nucleophilic amines under monitored conditions (160 °C, 2 min, MW). The (−)-(<i>M</i>) and (+)-(<i>P</i>) enantiomers can be separated by chiral stationary-phase chromatography. Determination of the absolute configuration and racemization barrier (Δ<i>G</i>^⧧ (433 K) 33.3 ± 1.3 kcal·mol^–1) was achieved by VCD and ECD spectroscopy, respectively

General Ir-Catalyzed N–H Insertions of Diazomalonates into Aliphatic and Aromatic Amines

A general N–H insertion reactivity of acceptor–acceptor diazo malonate reagents is reported using [Ir(cod)Cl]2 as catalyst. A large range of amines, primary and secondary, aliphatic and aromatic, is possible. Mild temperatures, perfect substrate/reactant stoichiometry, and good functional group compatibility render the process particularly attractive for the (late-stage) functionalization of amines

One-Step Synthesis of Nitrogen-Containing Medium-Sized Rings via α‑Imino Diazo Intermediates

Eight- and 9-membered dioxazocines and dioxazonines are readily synthesized starting from <i>N</i>-sulfonyl-1,2,3-triazoles in a single-step procedure. A perfect regioselectivity and generally good yields (up to 92%) are obtained under dirhodium catalysis using 1,3-dioxolane and 1,3-dioxane as solvents and reagents

Efficient Synthesis of Imino-methano Tröger Bases by Nitrene Insertions into C–N Bonds

A direct nitrene insertion into C–N bonds is observed upon treatment of <i>methano</i>-Tröger bases with arylsulfonyl iminophenyliodinanes under copper and dirhodium catalysis. Novel cyclic imino-methano Tröger bases are obtained (55–88%). Enantiopure products (<i>ee</i> ≥ 99%) can be obtained with tailored substrates

Efficient Synthesis of Imino-methano Tröger Bases by Nitrene Insertions into C–N Bonds

A direct nitrene insertion into C–N bonds is observed upon treatment of <i>methano</i>-Tröger bases with arylsulfonyl iminophenyliodinanes under copper and dirhodium catalysis. Novel cyclic imino-methano Tröger bases are obtained (55–88%). Enantiopure products (<i>ee</i> ≥ 99%) can be obtained with tailored substrates

Synthesis, Structural Analysis, and Catalytic Properties of Tetrakis(binaphthyl or octahydrobinaphthyl phosphate) Dirhodium(II,II) Complexes

The X-ray structural analyses of homoleptic Rh­(II) complexes made of enantiopure (<i>R</i>)-1,1′-binaphthyl and (<i>R</i>)-(5,5′,6,6′,7,7′,8,8′-octahydro)­binaphthyl phosphate ligands are for the first time presented. The possibility to introduce halogen atoms at the 3,3′-positions is also reported. The isolated dirhodium complexes were further tested as catalysts (1 mol %) in enantioselective cyclopropanations and Si–H insertion reactions, affording chiral cyclopropanes and silanes in good yield but moderate enantioselectivity (ee max 63%)

Kinetics of Rh(II)-Catalyzed α‑Diazo-β-ketoester Decomposition and Application to the [3+6+3+6] Synthesis of Macrocycles on a Large Scale and at Low Catalyst Loadings

In the context of [3+6+3+6] macrocyclization reactions, precise kinetics of α-diazo-β-ketoester decomposition were measured by <i>in situ</i> infrared (IR) monitoring. Dirhodium complexes of Ikegami–Hashimoto typeand perchlorinated phthalimido derivatives in particularperformed better than classical achiral complexes. Clear correlations were found between speciation among dirhodium species and catalytic activity. With these results, novel cyclohexyl-derived catalysts were developed, affording good yields of macrocycles (up to 78%), at low catalyst loadings (from 0.01 mol % to 0.001 mol %) and on a large scale (from 1 g to 20 g)

Bright Electrochemiluminescence Tunable in the Near-Infrared of Chiral Cationic Helicene Chromophores

Cationic helicenes are <i>ortho</i>-fused polyaromatics which exhibit well-defined and stable helical conformations with original absorption and emission properties in the red to near-infrared spectral ranges. Herein, a selection of cationic [4] and [6]­helicenes are studied for their electrochemical, fluorescence, and electrochemiluminescence (ECL) properties in acetonitrile solutions. Their photophysical and redox responses are drastically tuned by the introduction of auxochrome substituents at their periphery or the interconversion of oxygen and nitrogen atoms within the helical core. All diaza helicenes exhibit a reversible reduction process, whereas in the presence of oxygen instead of nitrogen atoms in the helical core, irreversible oxidations and a decrease of ECL intensity are observed. ECL emission was successfully produced with two sacrificial coreactants (benzoyl peroxide and tri-<i>n</i>-propylamine, TPrA). [4]­Helicene <b>DMQA</b>^<b>+</b>, [6]­helicene <b>DIAZA­(Pr/Br)</b>^<b>+</b>, and <b>DIAZA­(Hex/Br)</b>^<b>+</b> exhibit similar ECL emission wavelength in the near-infrared region and generate very intense ECL signals. Their ECL efficiencies are up to 2.6 times higher than that of the reference compound [Ru­(bpy)₃]²⁺ when using TPrA as coreactant. A thermodynamic map gathering both oxidation and reduction potentials and fluorescence data is proposed for the prediction of energy sufficiency needed in both coreactant ECL systems. Such a systematic overview based on the photophysical and electrochemical properties may guide the conception and synthesis of new chromophores with a strong ECL proficiency

Asymmetric Epoxidation Using Iminium Salt Organocatalysts Featuring Dynamically Controlled Atropoisomerism

Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium salt organocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral substituent at nitrogen

Asymmetric Epoxidation Using Iminium Salt Organocatalysts Featuring Dynamically Controlled Atropoisomerism

Introduction of a pseudoaxial substituent at a stereogenic center adjacent to the nitrogen atom in binaphthyl- and biphenyl-derived azepinium salt organocatalysts affords improved enantioselectivities and yields in the epoxidation of unfunctionalized alkenes. In the biphenyl-derived catalysts, the atropoisomerism at the biphenyl axis is controlled by the interaction of this substituent with the chiral substituent at nitrogen