Recyclable Hypervalent-Iodine-Mediated Dehydrogenative Cyclopropanation under Metal-Free Conditions

A method is developed for the synthesis of cyclopropanes from the C­(sp²)–C­(sp³) single bonds of β-keto esters with activated methylene compounds under metal-free conditions in the presence of 5-trimethyl­ammonio-1,3-dioxo-1,3-dihydro-1λ⁵-benzo­[<i>d</i>]­[1,2]­iodoxol-1-ol anion (AIBX), a recyclable water-soluble hypervalent iodine­(V) reagent developed by our group. This mild, efficient method has a wide substrate scope and good functional group tolerance and is complementary to existing cyclopropanation strategies. The method can be used to construct polysubstituted ring-fused cyclopropanes and is amenable to further synthetic transformations for construction of complex biologically active molecules as well as asymmetric cyclopropanes (90% de) when a chiral ester auxiliary is used

Electrochemiluminescence Properties of [Pt₂Ag₄(CCC₆H₄R)₈]_<i>n</i> (R = CH₃, <i>n</i> = 1; R = H, <i>n</i> = 1 and 2) with Amine (TPrA and DBAE) as the Coreactant and Determination of Sudan I

Two hexanuclear clusters, [Pt₂Ag₄(CCC₆H₄R)₈] (R = CH₃, <b>1</b>; R = H, <b>2</b>), together with dimer [Pt₂Ag₄(CCC₆H₅)₈]₂ (<b>3</b>), have been synthesized and characterized by elemental analyses, electrospray ionization mass spectrometry, and ¹H NMR spectroscopy and by X-ray crystallography for <b>1</b> and <b>3</b>. A considerable enhancement of photoluminescence (PL) and a notable red shift in the emission maximum of <b>1</b> (λ_max 600 nm) relative to <b>2</b> (λ_max 545 nm) are observed. Electrogenerated chemiluminescence (ECL) of <b>1</b> and <b>2</b> in the absence or presence of coreactant tri-<i>n</i>-propylamine (TPrA) or 2-(dibutylamino)­ethanol (DBAE) at different working electrodes in different solvents (CH₂Cl₂, CH₂ClCH₂Cl, or CH₃CN) has been studied. The ECL spectra are identical with the PL spectra, indicating that ECL emissions are also due to a MLM′CT [Pt­(d)/π (CCC₆H₄R-4) → Pt­(p_<i>z</i>)/Ag­(sp)/π* (CCC₆H₄R-4)] state modified by Pt···Ag and Ag···Ag contacts. ECL of <b>1</b>- and <b>2</b>/amine systems in CH₂ClCH₂Cl was produced at the potentials of 1.14–1.19 V vs SCE, notably negatively shifted by about 0.38 V compared to those of the Ru­(bpy)₃²⁺/amine system. In all cases, ECL quantum efficiencies of <b>2</b> are higher than those of <b>1</b> and on the same order of magnitude as that of the [Ru­(bpy)₃]­(PF₆)₂/amine system. It is noted that Sudan I tends to decrease the ECL intensity of the <b>1</b>/DBAE system in CH₂ClCH₂Cl at a platinum working electrode. A new ECL method for the determination of Sudan I was developed with a linear range of 2.5 × 10^–5–1.0 × 10^–3 M and a detection limit of 8.0 × 10^–6 M based on 3 times the ratio of signal-to-noise

Integration of Milstein Ru–PNN and Rh–Tribi/Tetrabi for Isomerization Linear Selective Hydroformylation of Far Internal Alkenes

Converting cheap and abundant internal alkenes to value-added linear aldehydes is of great importance but not an addressed issue. In this paper, an integration of a Milstein-type Ru–PNN catalyst and our Rh–Tribi/Tetrabi catalyst was first demonstrated in highly improved isomerization linear selective hydroformylation of 2-, 3-, and 4-alkenes, yielding excellent linear selectivities and activities (linear selectivity improvements of 2.2–58%, up to 94.2–98.6%, and turnover numbers improvements of 61–335 TON, up to 385–851) compared to the Ru–PNN/Rh–Bisbi system