22185-97-3Relevant academic research and scientific papers
Catalyst-Free Decarbonylative Trifluoromethylthiolation Enabled by Electron Donor-Acceptor Complex Photoactivation
Lipp, Alexander,Badir, Shorouk O.,Dykstra, Ryan,Gutierrez, Osvaldo,Molander, Gary A.
supporting information, p. 3507 - 3520 (2021/06/11)
A catalyst- and additive-free decarbonylative trifluoromethylthiolation of aldehyde feedstocks has been developed. This operationally simple, scalable, and open-to-air transformation is driven by the selective photoexcitation of electron donor-acceptor (EDA) complexes, stemming from the association of 1,4-dihydropyridines (donor) with N-(trifluoromethylthio)phthalimide (acceptor), to trigger intermolecular single-electron transfer events under ambient- and visible light-promoted conditions. Extension to other electron acceptors enables the synthesis of thiocyanates and thioesters, as well as the difunctionalization of [1.1.1]propellane. The mechanistic intricacies of this photochemical paradigm are elucidated through a combination of experimental efforts and high-level quantum mechanical calculations [dispersion-corrected (U)DFT, DLPNO-CCSD(T), and TD-DFT]. This comprehensive study highlights the necessity for EDA complexation for efficient alkyl radical generation. Computation of subsequent ground state pathways reveals that SH2 addition of the alkyl radical to the intermediate radical EDA complex is extremely exergonic and results in a charge transfer event from the dihydropyridine donor to the N-(trifluoromethylthio)phthalimide acceptor of the EDA complex. Experimental and computational results further suggest that product formation also occurs via SH2 reaction of alkyl radicals with 1,2-bis(trifluoromethyl)disulfane, generated in-situ through combination of thiyl radicals. (Figure presented.).
Stereocontrolled Synthesis of 1,4-Dicarbonyl Compounds by Photochemical Organocatalytic Acyl Radical Addition to Enals
Goti, Giulio,Bieszczad, Bartosz,Vega-Pe?aloza, Alberto,Melchiorre, Paolo
supporting information, p. 1213 - 1217 (2019/01/04)
We report a visible-light-mediated organocatalytic strategy for the enantioselective acyl radical conjugate addition to enals, leading to valuable 1,4-dicarbonyl compounds. The process capitalizes upon the excited-state reactivity of 4-acyl-1,4-dihydropyridines that, upon visible-light absorption, can trigger the generation of acyl radicals. By means of a chiral amine catalyst, iminium ion activation of enals ensures a stereoselective radical trap. We also demonstrate how the combination of this acylation process with a second catalyst-controlled bond-forming event allows to selectively access the full matrix of all possible stereoisomers of the resulting 2,3-substituted 1,4-dicarbonyl products.
Visible-light assisted one-pot preparation of aryl glyoxals from acetoarylones via in-situ arylacyl bromides formation: Selenium-free approach to acetoarylones oxidation
Natarajan, Palani,Manjeet,Kumar, Naveen,Devi, Sapna,Mer, Kalyani
supporting information, p. 658 - 662 (2017/01/25)
A novel visible-light (blue LEDs: hν?=?425?±?15?nm) photocatalyzed one-pot method for the synthesis of electronically diverse aryl glyoxals in good to excellent yields from acetoarylones and green regents such as air, vitamin C and dioxane dibromide has been described. In addition, an application of the current methodology has been demonstrated for the oxidation of monoamine oxidase-B inhibitors, i.e., 1-(4-((4-fluorobenzyl)oxy)phenyl)ethanone and 1-(3-((4-chlorobenzyl)oxy)phenyl)ethanone. This finding may serves as a valuable alternative to the traditional acetoarylones oxidation reactions conducted using selenium dioxide a harmful and unselective reagent known to simultaneously oxidize allylic, benzylic, [sbnd]CH3and so on.
Quantitative comparison of the mesitoyl vs the benzoyl fragment in photoinitiation: A question of origin
Voll, Dominik,Junkers, Thomas,Barner-Kowollik, Christopher
experimental part, p. 2542 - 2551 (2012/03/26)
Photolytically generated radicals (at a wavelength of 351 nm) derived from the acetophenone-type photoinitiators benzoin (2-hydroxy-1,2-diphenylethanone) and 2,4,6-trimethylbenzoin (2-hydroxy-1-mesityl-2-phenylethanone, TMB) (specifically the benzoyl and
Hydration of Bis(pentamethylphenyl)- and Bismesityl-ketenes leading to Ene-1,1-diols (Enols of Carboxylic Acids)
Allen, Barbara M.,Hegarty, Anthony F.,O'Neill, Pat,Nguyen, Minh Tho
, p. 927 - 934 (2007/10/02)
The reaction of the sterically hindered diarylketenes (Ar = Me5C6 or 2,4,6-Me3C6H2) with water is pH independent over the range 1-9 and is not subject to strong buffer catalysis.The primary products formed are the corresponding ene-1,1-diols which result from addition across the C=O (rather than the C=C) of the ketene.These "enols of carboxylic acids" are relatively long lived owing to slow protonation of the β-carbon (because of steric hindrance caused by the o-Me groups) and evidence for their structures in solution is presented.On attempted isolation of theene-1,1-diols facile oxidation to a stable free radical, as well as ketonisation to the corresponding acids, occurs.Evidence is presented in terms of the large negative entropy of activation (ca. 200 J K-1 mol-1), solvent isotope effects and the absence of significant general-base catalysis, that (despite the sterically hindered nature of these ketenes) the characteristics of their hydration are typical of other ketenes and that this most likely involves an initial concerted reaction with a water oligomer.Updated ab initio calculations are also presented, which are consistent with this view.
