1,721,061 research outputs found
The CeCl3.nH2O/NaI System in organic Synthesis: An efficient Water Tolerant Lewis Acid Promoter
No full text1-Methyl-1,4-cyclohexadiene as a Traceless Reducing Agent for the Synthesis of Catechols and Hydroquinones
No full textPro-aromatic and volatile 1-methyl-1,4-cyclohexadiene (MeCHD) was used for the first time as a valid H-atom source in an innovative method to reduce ortho or para quinones to obtain the corresponding catechols and hydroquinones in good to excellent yields. Notably, the excess of MeCHD and the toluene formed as the oxidation product can be easily removed by evaporation. In some cases, trifluoroacetic acid as a catalyst was added to obtain the desired products. The reaction proceeds in air and under mild conditions, without metal catalysts and sulfur derivatives, resulting in an excellent and competitive method to reduce quinones. The mechanism is attributed to a radical reaction triggered by a hydrogen atom transfer from MeCHD to quinones, or, in the presence of trifluoroacetic acid, to a hydride transfer process
Group 14 metalloles. Properties, synthesis and potential applications: From organic electronics to soft materials
No full textSince the discovery of the aggregation-induced emission (AIE) phenomenon of siloles in 2001, extensive research has been devoted to the synthesis of AIE-active group 14 metalloles and their applications. A large number of new systems have been designed, synthesized, and studied. It has been determined that the restriction of intramolecular rotation is the main cause for AIE, and the effect that the nature of the substituents has on the electronic structures allows one to control the properties of these materials. Siloles hold a number of favourable attributes for application in organic electronics; therefore many applications can be conceived for the siloles and other metalloles. In this mini-review we illustrate recent progress in the development of group 14 metallole-based OLEDs, bio/chemosensors and soft materials
Cerium (III) Chloride, a Novel Reagent for Nonaqueous Selective Conversion of Dioxolanes to Carbonyl Compounds
No full textExcited-State Engineering in Heteroleptic Ionic Iridium(III) Complexes
Full text linkIridium(III) complexes have assumed a prominent role in the areas of photochemistry and photophysics due to the peculiar properties of both the metal itself and the ligand environment that can be assembled around it. Ir(III) is larger, heavier, and bears a higher ionic charge than its analogue and widely used d6 ions such as Fe(II) and Ru(II). Accordingly, its complexes exhibit wider ligand-field d-d orbital splitting with electronic levels centered on the metal, typically nonemissive and photodissociative, not playing a relevant role in excited-state deactivations. In other words, iridium complexes are typically more stable and/or more emissive than Fe(II) and Ru(II) systems. Additionally, the particularly strong heavy-atom effect of iridium promotes singlet-triplet transitions, with characteristic absorption features in the UV-vis and relatively short excited-state lifetimes of emissive triplet levels. Ir(III) is also a platform for anchoring ligands of rather different sorts. Its versatile chemistry includes not only coordination with classic N∧N neutral ligands but also the binding of negatively charged chelators, typically having a cyclometalating C∧N anchor. The carbon-metal bond in these systems has some degree of covalent character, but this does not preclude a localized description of the excited states of the related complexes, which can be designated as metal-centered (MC), ligand-centered (LC), or charge transfer (CT), allowing a simplified description of electronic and photophysical properties. The possibility of binding different types of ligands and making heteroleptic complexes is a formidable tool for finely tuning the nature and energy of the lowest electronic excited state of cationic Ir(III) complexes by ligand design. Herein we give an account of our work on several families of iridium complexes typically equipped with two cyclometalating bidentate ligands (C∧N), in combination with mono or bidentate "ancillary"ligands with N∧N, C∧N, and C∧C motifs. We have explored new synthesis routes for both cyclometalating and ancillary ligands, obtaining primarily cationic complexes but also some neutral or even negatively charged systems. In the domain of the ancillary ligands, we have explored isocyanides, carbenes, mesoionic triazolylidenes, and bis-tetrazolic ligands. For the cyclometalating moiety, we have investigated carbene, mesoionic triazolylidene, and tetrazolic systems. Key results of our work include new strategies to modify both cyclometalating and ancillary ligands by relocating ionic charges, the determination of new factors affecting the stability of complexes, a demonstration of subtle structural effects that strongly modify the photophysical properties, new options to get blue-greenish emitters for optoelectronic devices, and a set of ligand modifications allowing the optimization of electrochemical and excited-state properties to obtain new promising Ir(III) complexes for photoredox catalysis. These results constitute a step forward in the preparation of custom iridium-based materials crafted by excited-state engineering, which is achieved through the concerted effort of computational and synthetic chemistry along with electrochemistry and photochemistr
Cerium(III) chloride promoted nucleophilic addition of organolithium reagents to alpha-alkyl-beta-ketophosphine oxides: a new protocol for the synthesis of stereodefined trisubstituted olefins.
No full textOpposite stereochemical effects exerted by CeCl3 and TiCl4 on the Lewis acid mediated reduction alfa-alkyl-beta-ketophosphine oxides
No full textA stereoselective synthesis of (E)-alpha,beta-unsaturated ketones involving the reactions of organocerium reagents with secondary beta-enamino ketones.
No full textEfficient diastereoselective synthesis of erythro- or threo-alpha-alkyl-beta-hydroxy sulfones by reductions of alpha-alkyl-beta-keto sulfones with TiCl4/BH3 or LiEt3BH/CeCl3 respectively.
No full textDiastereoselective synthesis of tertiary alcohols by nucleophilic addition to alpha-substituted-beta-keto esters
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