1,721,016 research outputs found
Real-Time Spectroscopic Analysis Enabling Quantitative and Safe Consumption of Fluoroform during Nucleophilic Trifluoromethylation in Flow
No full textThe productive use of toxic waste materials derived from industrial processes is one of the main goals of modern chemical research to increase sustainability of the large-scale production. Here we devise a simple and robust strategy for the utilization of trifluoromethane, obtained in large quantities from polytetrafluoroethylene manufacture, and the conversion of this greenhouse gas into valuable fluorinated compounds. The generation of the trifluoromethyl carbanion and its direct and complete consumption through trapping with a number of electrophiles were achieved by a fully contained flow reactor setup. The adoption of modern in-line analytical tools, such as portable Fourier transform infrared and nuclear magnetic resonance devices, allowed the accurate reagent dosing with considerable benefits in terms of controlling the environmental impact during this continuous process. The advantages of the method, with respect to the batch procedure, will be discussed and demonstrated experimentally
Microreactor Technology as Tool for the Development of a Sustainable Synthetic Chemistry
No full textThe microreactor technology has the potential to change the way to perform synthetic chemistry. Efforts in this field need to be
promoted at the best. This will reduce waste, increase the safety, save energy, improve the product quality, reduce the time for drug
discovery and improve the reliability and quality of commercially available microreactors. Research, education and training can play
a key role for the widespread use of this new technolog
Nitrogen-Bearing Lithium Compounds in Modern Synthesis
No full textNitrogen-containing compounds are ubiquitous and extremely important in synthesis. This chapter encompasses some general aspects on the generation, structure, and reactivity of nitrogen-bearing organolithiums showing the progress made over the last decade. In particular, the chemistry of reactive intermediates lithiated at sp3- hybridized carbon atoms adjacent (a) to a nitrogen atom is described. Recently developed strategies for the generation and use in synthesis of amino-organolithiums deriving from saturated nitrogenated heterocycles as well as from acyclic nitrogenated systems are reported. Starting from simple three-membered ring aziridines up to seven-membered ring azepines, the reactivity and structural features of the corresponding lithiated intermediates are covered. Special attention has been given to the stereochemistry of the reactions employing amino-organolithiums, and to the development of new and efficient protocols, such as the catalytic dynamic resolution and the catalytic asymmetric deprotonation, for controlling the absolute stereochemistry. The chapter underlines the role of substituents able to activate simple amines towards the lithiation as well as to stabilize the resulting intermediates, establishing the tight relationship between structure and reactivity, offering to researchers the background for testing the reactivity of unexplored nitrogenated systems
BH3-promoted stereoselective β-lithiation of N-alkyl-2-phenylaziridines
No full textBH3 complexes of N-alkyl-2-phenylaziridines have been synthesized and their structure and stereochemistry proved with DFT calculations and NMR experiments. It has been demonstrated that the Lewis acid complexation is able to promote a regioselective β-lithiation in 2-phenylaziridino- borane complexes. The lithiated intermediates were configurationally stable, allowing an enantioselective preparation of cis-2,3-disubstituted aziridines. © 2011 American Chemical Society
α- vs Ortho-Lithiation of N-Alkylarylaziridines: Probing the Role of the Nitrogen Inversion Process
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Regio- and Stereoselective Lithiation and Electrophilic Substitution Reactions of N-Alkyl-2,2-Diphenylaziridines: Solvent Effect
No full textThe lithiation reaction of cis- and trans-N-alkyl-2,3-diphenylaziridines has been investigated. While cis-diphenylaziridines do not undergo any lithiation upon treatment with organolithiums, the lithiation reaction of the trans counterparts is completely regioselective and the stereochemical course of the lithiation-trapping sequence is solvent dependent: inversion of configuration in coordinating solvents (THF or toluene/crown ether) and retention in hexane, ether, or toluene. The preparation of stereodefined functionalized N-alkyl-2,3-diphenylaziridines is described
Rapid, selective and stable HaloTag-Lb ADH immobilization directly from crude cell extract for the continuous biocatalytic production of chiral alcohols and epoxides
No full textA strategy for biocatalyst immobilization in flow directly from the crude cell extract is described. The efficiency and the stability of the immobilized enzyme were demonstrated during the asymmetric reduction of a range of ketones. The cascade two-step chemo-enzymatic preparation of chiral epoxides was possible through the initial ketone bioreduction to an intermediate halohydrin followed by its intramolecular cyclization
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