Direct Amidation of 2′-Aminoacetophenones Using I₂‑TBHP: A Unimolecular Domino Approach toward Isatin and Iodoisatin

Synthesis of isatin and iodoisatin from 2′-aminoacetophenone was achieved via oxidative amido cyclization of the sp³ C–H bond using I₂–TBHP as the catalytic system. The reaction proceeds through sequential iodination, Kornblum oxidation, and amidation in one pot. This method is simple, atom economic, and works under metal- and base-free conditions

Copper-Mediated Selective C–H Activation and Cross-Dehydrogenative C–N Coupling of 2′‑Aminoacetophenones

Isatins were obtained by cross-dehydrogenative C–N annulation and dealkylative C–N annulation of 2′-<i>N</i>-aryl/alkylaminoacetophenones and 2′-<i>N</i>,<i>N</i>-dialkylaminoacetophenones respectively in the presence of Cu(OAc)_<i>2</i>·H₂O/NaOAc/air. However, on reaction with CuBr, 2′-<i>N</i>-benzylaminoacetophenones underwent selective oxidation of an α-methylene group of amine rather than the 2-acetyl group to provide corresponding benzamides exclusively. Base played an important role in selective oxidation by lowering the temperature and time

γ‑Carbonyl Quinones: Radical Strategy for the Synthesis of Evelynin and Its Analogues by C–H Activation of Quinones Using Cyclopropanols

Cyclopropanols, on oxidative ring opening with AgNO₃–K₂S₂O₈ in DCM–H₂O at room temperature and under open flask conditions, produced β-keto radicals which were successfully added to quinones to furnish γ-carbonyl quinones. This mild method has been applied to the synthesis of cytotoxic natural products, 4,6-dimethoxy-2,5-quino­dihydro­chalcone and evelynin

Electrophilic Hydrazination of Cyclopropanols Using Azodicarboxylates via Copper(II) Catalysis: An Umpolung Strategy to Access β‑Hydrazino Ketone Motifs

The scope of an umpolung approach to expand synthetic access to bifunctional γ-keto hydrazine intermediates via electrophilic amination of β-homoenolates derived from cyclopropanol precursors that took advantage of azodicarboxylates or azodicarboxamides as electron-deficient nitrogen sources was examined. This new synthetic procedure avails commercially available or readily accessible starting materials along with a ligand-free Cu(II) salt as an inexpensive catalyst. Using this operationally simple reaction, which proceeds under mild conditions (open-flask and ambient temperature) and is suitable for multigram scale, preparative applications were established with a range of aryl- and alkyl-substituted cyclopropanols and azodicarboxylate/azodicarboxamide substrates (26 examples, 74–95% yields). Further, the obtained products have been shown to provide convenient synthetic access to γ-hydroxy hydrazide, γ-amino hydrazide, and heterocyclic derivatives

Visible-Light Activation of the Bimetallic Chromophore–Catalyst Dyad: Analysis of Transient Intermediates and Reactivity toward Organic Sulfides

In order to develop a new photocatalytic system, we designed a new redox-active module (<b>5</b>) to hold both a photosensitizer part, [Ru^II(terpy)­(bpy)­X]^<i>n</i>+ (where terpy = 2,2′:6′,2′′-terpyridine and bpy = 2,2′-bipyridine), and a popular Jacobsen catalytic part, salen–Mn­(III), covalently linked through a pyridine-based electron-relay moiety. On the basis of nanosecond laser flash photolysis studies, an intramolecular electron transfer mechanism from salen–Mn^III to photooxidized Ru^III chromophore yielding the catalytically active high-valent salen–Mn^IV species was proposed. To examine the reactivity of such photogenerated salen–Mn^IV, we employed organic sulfide as substrate. Detection of the formation of a Mn^III–phenoxyl radical and a sulfur radical cation during the course of reaction using time-resolved transient absorption spectroscopy confirms the electron transfer nature of the reaction. This is the first report for the electron transfer reaction of organic sulfide with the photochemically generated salen–Mn^IV catalytic center

Relating the Structure of Geminal Amido Esters to their Molecular Hyperpolarizability

Advanced organic nonlinear optical (NLO) materials have attracted increasing attention due to their multitude of applications in modern telecommunication devices. Arguably the most important advantage of organic NLO materials, relative to traditionally used inorganic NLO materials, is their short optical response time. Geminal amido esters with their donor-π-acceptor (D-π-A) architecture exhibit high levels of electron delocalization and substantial intramolecular charge transfer, which should endow these materials with short optical response times and large molecular (hyper)­polarizabilities. In order to test this hypothesis, the linear and second-order nonlinear optical properties of five geminal amido esters, (<i>E</i>)-ethyl 3-(X-phenylamino)-2-(Y-phenylcarbamoyl)­acrylate (<b>1</b>, X = 4-H, Y = 4-H; <b>2</b>, X = 4-CH₃, Y = 4-CH₃; <b>3</b>, X = 4-NO₂, Y = 2,5–OCH₃; <b>4</b>, X = 2-Cl, Y = 2-Cl; <b>5</b>, X = 4-Cl, Y = 4-Cl) were synthesized and characterized, whereby NLO structure–function relationships were established including intramolecular charge transfer characteristics, crystal field effects, and molecular first hyperpolarizabilities (β). Given the typically large errors (10–30%) associated with the determination of β coefficients, three independent methods were used: (i) density functional theory, (ii) hyper-Rayleigh scattering, and (iii) high-resolution X-ray diffraction data analysis based on multipolar modeling of electron densities at each atom. These three methods delivered consistent values of β, and based on these results, <b>3</b> should hold the most promise for NLO applications. The correlation between the molecular structure of these geminal amido esters and their linear and nonlinear optical properties thus provide molecular design guidelines for organic NLO materials; this leads to the ultimate goal of generating bespoke organic molecules to suit a given NLO device application