6 research outputs found
Direct Amidation of 2′-Aminoacetophenones Using I<sub>2</sub>‑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 sp<sup>3</sup> C–H bond using I<sub>2</sub>–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)<sub><i>2</i></sub>·H<sub>2</sub>O/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 AgNO<sub>3</sub>–K<sub>2</sub>S<sub>2</sub>O<sub>8</sub> in DCM–H<sub>2</sub>O at room temperature and under open flask conditions, produced β-keto radicals which were successfully added to quinones to furnish Îł-carbonyl quinones. This mild method has been applied to the synthesis of cytotoxic natural products, 4,6-dimethoxy-2,5-quinoÂdihydroÂchalcone 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
Îł-hydroxy hydrazide, Îł-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<sup>II</sup>(terpy)Â(bpy)ÂX]<sup><i>n</i>+</sup> (where terpy = 2,2′:6′,2′′-terpyridine and bpy = 2,2′-bipyridine),
and a popular Jacobsen catalytic part, salen–MnÂ(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<sup>III</sup> to photooxidized
Ru<sup>III</sup> chromophore yielding the catalytically active high-valent
salen–Mn<sup>IV</sup> species was proposed. To examine the
reactivity of such photogenerated salen–Mn<sup>IV</sup>, we
employed organic sulfide as substrate. Detection of the formation
of a Mn<sup>III</sup>–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<sup>IV</sup> 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-Ď€-acceptor (D-Ď€-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)Âpolarizabilities. 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)Âacrylate (<b>1</b>, X
= 4-H, Y = 4-H; <b>2</b>, X = 4-CH<sub>3</sub>, Y = 4-CH<sub>3</sub>; <b>3</b>, X = 4-NO<sub>2</sub>, Y = 2,5–OCH<sub>3</sub>; <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