Visible Light-Enhanced C−H Amination of Cyclic Ethers with Iminoiodinanes

A two-step protocol allowing the C−H amination of cyclic ethers with iminoiodinanes, followed by the reduction of the resulting intermediate has been developed for the preparation of amino alcohols. The initial C−H functionalization is accelerated by visible light, improving the reactivity compared to the thermal process performed in the dark. The effect of different substituents on the photochemical reactivity of iminoiodinanes has been studied both experimentally and computationally. Photophysical measurements and DFT calculations were performed to better understand the observed reactivities and corroborate the proposed mechanistic proposal

Rhodium- and non-metal-catalyzed approaches for the conversion of isoxazol-5-ones to 2,3-dihydro-6H-1,3-oxazin-6-ones

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPTwo approaches were developed for the conversion of isoxazol-5-ones to 2,3-dihydro-6H-1,3-oxazin-6-ones. The first involves dirhodium-catalyzed reaction of aryl diazoacetates, leading to rhodium carbene intermediates that undergo insertion into the N–O bo191951585161FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2015/20809-4I.D.J. acknowledges the Fulbright Foundation for a Junior Faculty Award and the support of Fapesp (2015/20809-4). H.M.L.D. was supported by the National Science Foundation (CHE 1465189). Instrumentation used in this work was supported by the National Sci

Activating imides with triflic acid: a general intramolecular aldol condensation strategy toward indolizidine, quinolizidine, and valmerin alkaloids

A simple, inexpensive, step economic, and highly modular synthetic strategy to access izidine alkaloids is described. The key step is a TfOH-promoted intramolecular aldol condensation between enol and cyclic imide moieties. This cyclization strategy can be employed within an aza-Robinson annulation framework and represents a general tool to build fused bicyclic amines. To illustrate the power of this method, we describe the preparation of (+/-)-coniceine, (+/-)-quinolizidine, (+/-)-tashiromine, (+/-)-epilupinine, and the core of (+/-)-valmerins221239243sem informaçãosem informaçãoY.Q.-A acknowledges the Chemistry Department of Uni-versidad de los Andes (UniAndes) for a PhD fellowship and itsFaculty of Science for providingfinancial support for aninternship. Financial support for this work was provided by theFaculty of Science of UniAndes (INV-2018-48-1337) to Y.Q.-A and D.G.-S., and a Fapesp Grant (2017/24017-0) wasawarded to I.D.J. The authors also greatly appreciate thesupport of Dr. Deborah Simoni (Unicamp, Brazil) for X-rayanalyses and Dr. Mario Macias (UniAndes, Colombia) forcareful refinement of the X-ray structure of3

Rhodium- and Non-Metal-Catalyzed Approaches for the Conversion of Isoxazol-5-ones to 2,3-Dihydro‑6<i>H</i>‑1,3-oxazin-6-ones

Two approaches were developed for the conversion of isoxazol-5-ones to 2,3-dihydro-6<i>H</i>-1,3-oxazin-6-ones. The first involves dirhodium-catalyzed reaction of aryl diazoacetates, leading to rhodium carbene intermediates that undergo insertion into the N–O bond of isoxazol-5-ones. The second approach involves conversion of the aryldiazoacetates to the corresponding tosylates, followed by reaction with the isoxazol-5-one in a metal-free one-pot procedure. These studies illustrate an alternative method to achieve a carbene-like transformation without requiring a metal catalyst

Michael Addition of Soft Carbon Nucleophiles to Alkylidene Isoxazol-5-ones: A Divergent Entry to β‑Branched Carbonyl Compounds

A novel, divergent strategy toward the synthesis of β-branched (and linear) carbonyl compounds is developed by taking advantage of alkylidene isoxazol-5-ones as key building blocks. The yields obtained range from good to excellent, therefore making the described methods attractive options for building such molecules

Enantioselective Organocatalytic Alkylation of Aldehydes and Enals Driven by the Direct Photoexcitation of Enamines

Disclosed herein is a photo-organocatalytic enantioselective ?- and ?-alkylation of aldehydes and enals, respectively, with bromomalonates. The chemistry uses a commercially available aminocatalyst and occurs under illumination by a fluorescent light bulb in the absence of any external photoredox catalyst. Mechanistic investigations reveal the previously hidden ability of transiently generated enamines to directly reach an electronically excited state upon light absorption while successively triggering the formation of reactive radical species from the organic halides. At the same time, the ground state chiral enamines provide effective stereochemical induction for the enantioselective alkylation process

RuCl3/ PPh3 : catalyzed direct conversion of isoxazol‐5‐ones to 2,3‐disubstituted pyridines

A novel catalytic system employing RuCl3/ PPh3 is described for the preparation of 2,3‐disubstituted pyridines starting from 3,4‐disubstituted isoxazol‐5‐ones and acrolein. Mechanistic studies involving 31P NMR, HRMS analyses and control experiments have been performed in order to support key events and intermediates proposed for this transformation41233603365FAPESP – Fundação de Amparo à Pesquisa Do Estado De São Paulo2017/22164-6; 2017/24017-

X-Ray Characterization of an EDA Complex which Drives the Photochemical

Disclosed herein is a metal-free, photochemical strategy for the direct alkylation of indoles. The reaction, which occurs at ambient temperature, is driven by the photochemical activity of electron donor-acceptor (EDA) complexes, generated upon association of substituted 1H-indoles with electron-accepting benzyl and phenacyl bromides. Significant mechanistic insights are provided by the X-ray single-crystal analysis of an EDA complex relevant to the photo-alkylation and the determination of the quantum yield (&Phi;) of the process.</p

X‐Ray Characterization of an Electron Donor–Acceptor Complex that Drives the Photochemical Alkylation of Indoles

A metal-free, photochemical strategy for the direct alkylation of indoles was developed. The reaction, which occurs at ambient temperature, is driven by the photochemical activity of electron donor-acceptor (EDA) complexes, generated upon association of substituted 1H-indoles with electron-accepting benzyl and phenacyl bromides. Significant mechanistic insights are provided by the X-ray single-crystal analysis of an EDA complex relevant to the photoalkylation and the determination of the quantum yield (Φ) of the process

Blue light-promoted N-H insertion of carbazoles, pyrazoles and 1,2,3-triazoles into aryldiazoacetates

Blue light irradiation of aryldiazoacetates leads to the formation of free carbenes, which can react with carbazoles, pyrazoles and 1,2,3-triazoles to afford the corresponding N-H inserted products. These reactions are performed under air and at room temperature, allowing the mild preparation of a variety of motifs found in biologically relevant targets362511061111CAPES - Coordenação de Aperfeiçoamento de Pessoal e Nível SuperiorCNPQ - Conselho Nacional de Desenvolvimento Científico e TecnológicoFAPESP – Fundação de Amparo à Pesquisa Do Estado De São Paulo2017/24017-0sem informaçãosem informaçã