Search results for "OCA"

TiO2 Nanoparticles Functionalized with Non-innocent Ligands Allow Oxidative Photocyanation of Amines with Visible/Near-Infrared Photons

2018

Photosynthesis is an efficient mechanism for converting solar light energy into chemical energy. We report on a strategy for the aerobic photocyanation of tertiary amines with visible and near-infrared (NIR) light. Panchromatic sensitization was achieved by functionalizing TiO2 with a 2-methylisoquinolinium chromophore, which captures essential features of the extended π-system of 2,7-diazapyrenium (DAP2+) dications or graphitic carbon nitride. Two phenolic hydroxy groups make this ligand highly redox-active and allow for efficient surface binding and enhanced electron transfer to the TiO2 surface. Non-innocent ligands have energetically accessible levels that allow redox reactions to chang…

Understanding the Participation of Fluorinated Azomethine Ylides in Carbenoid-Type [3 + 2] Cycloaddition Reactions with Ynal Systems: A Molecular Ele…

2021

The carbenoid-type (cb-type) 32CA reaction of 1,1-difluoroated azomethine ylide (DFAY) with phenylpropynal has been studied using the molecular electron density theory (MEDT). Electron localization function (ELF) characterizes DFAY as a carbenoid species participating in cb-type 32CA reactions. The supernucleophilic character of DFAY and the strong electrophilic character of the ynal cause this polar 32CA reaction to have an unappreciable barrier; the reaction, which is highly exothermic, presents total chemo- and regioselectivity. ELF topological analysis of the bonding changes along the reaction establishes its non-concerted two-stage one-step mechanism, in which the nucleophilic attack o…

Photocatalytic Giese Addition of 1,4-Dihydroquinoxalin-2-ones to Electron-Poor Alkenes Using Visible Light.

2020

The visible-light photoredox-catalyzed coupling of 1,4-dihydroquinoxalin-2-ones and Michael acceptors was achieved using Ru(bpy)3Cl2 as the photocatalyst and (PhO)2PO2H as an additive. The optimized reaction conditions provide a good yield for the radical conjugate addition products (44 examples) with a wide range of structurally different Michael acceptors. A gram scale reaction using sunlight irradiation is also described. Furthermore, several transformations were carried out with the Giese addition products.

Organocatalytic enantioselective Strecker reaction with seven-membered cyclic imines

2018

[EN] A highly enantioselective Strecker reaction with dibenzo[b,f][1,4]oxazepines has been described using a dihydroquinine-derived thiourea as organocatalyst. The reaction affords chiral 10,11-dihydrodibenzo[b,f][1,4] oxazepine 11-carbonitrile derivatives in excellent yields (up to 99%) and excellent enantioselectivities (up to 98%) under mild reaction conditions.

Organocatalytic Oxidation of Secondary Alcohols Using 1,2-Di(1-naphthyl)-1,2-ethanediamine (NEDA) (Eur. J. Org. Chem. 28/2014)

2014

Role of the Open-Shell Character on the Pressure-Induced Conductivity of an Organic Donor-Acceptor Radical Dyad

2018

Single‐component conductors based on neutral organic radicals have received a lot of attention due to the possibility that the unpaired electron can serve as a charge carrier without the need of a previous doping process. Although most of these systems are based on delocalized planar radicals, we present here a nonplanar and spin localized radical based on a tetrathiafulvalene (TTF) moiety, linked to a perchlorotriphenylmethyl (PTM) radical by a conjugated bridge, which exhibits a semiconducting behavior upon application of high pressure. The synthesis, electronic properties, and crystal structure of this neutral radical TTF‐Ph‐PTM derivative (1) are reported and implications of its crystal…

Asymmetric Synthesis of Spiro β-Lactamsviaa Squaramide- Catalyzed Sulfa-Michael Addition/Desymmetrization Protocol

2016

An efficient asymmetric synthesis of spirocyclohexenone β-lactams bearing three contiguous stereocenters has been achieved in moderate to good yields and high stereoselectivities. The protocol involves the combination of a squaramide-catalyzed sulfa-Michael addition under desymmetrization via a dynamic kinetic resolution of racemic 2,5-cyclohexadienones.

A Decade of Electrochemical Dehydrogenative C,C-Coupling of Aryls.

2019

The importance of sustainable and green synthetic protocols for the synthesis of fine chemicals has rapidly increased during the last decades in an effort to reduce the use of fossil fuels and other finite resources. The replacement of common reagents by electricity provides a cost- and atom-efficient, environmentally friendly, and inherently safe access to novel synthetic routes. The selective formation of carbon-carbon bonds between two distinct substrates is a crucial tool in organic chemistry. This fundamental transformation enables access to a broad variety of complex molecular architectures. In particular, the aryl-aryl bond formation has high significance for the preparation of organ…

Synthesis, molecular structures and EPR spectra of the paramagnetic cuboidal clusters with Mo3S4Ga cores

2017

Electron precise [Mo3(l3-S)(l-S)3(diphos)3Br3]Br (diphos = dppe, dmpe) incomplete cuboidal clusters with six cluster skeletal electrons (CSE) were converted into paramagnetic cuboidal [Mo3(GaBr)(l3-S)4- (diphos)3Br3] clusters by treatment with elemental Ga. The new heterobimetallic complexes with nine CSE possess a doublet ground state with the unpaired electron density delocalized over the three molybdenum atoms.

Squaramide-Catalyzed Asymmetric aza-Friedel-Crafts/N,O-Acetalization Domino Reactions Between 2-Naphthols and Pyrazolinone Ketimines

2017

N-Boc ketimines derived from pyrazolin-5-ones were explored to develop an unprecedented domino aza-Friedel-Crafts/N,O-acetalization reaction with 2-naphthols. The novel method requires a catalyst loading of only 0.5 mol % of a bifunctional squaramide catalyst, is scalable to gram amounts, and provides a new series of furanonaphthopyrazolidinone derivatives bearing two vicinal tetra-substituted stereogenic centers in excellent yields (95-98 %) and stereoselectivity (>99:1 d.r. and 97-98 % ee). A different reactivity was observed in the case of 1-naphthols and other electron-rich phenols, which led to the aza-Friedel-Crafts adducts in 70-98 % yield and 47-98 % ee.