24437-41-0Relevant articles and documents
A visible-light mediated three-component radical process using dithiocarbamate anion catalysis
Cuadros, Sara,Horwitz, Matthew A.,Schweitzer-Chaput, Bertrand,Melchiorre, Paolo
, p. 5484 - 5488 (2019)
We report a photoinduced three-component radical process, which couples readily available alkyl chlorides, maleimides, and heteroaromatic fragments to rapidly generate complex chiral products with high diastereocontrol. This method generates radicals via an SN2-based photochemical catalytic mechanism, which is not reliant on the redox properties of the precursors. It therefore grants access to open-shell intermediates from substrates that would be incompatible with or inert to classical radical-generating strategies. The redox-neutral conditions of this process make it tolerant of redox-sensitive substrates and allow the installation of multiple biologically relevant heterocycles within the cascade products.
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Carson et al.
, p. 1096 (1977)
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Visible-light induced disproportionation of pyrrole derivatives for photocatalyst-free aryl halides reduction
Li, Zhi-Jun,Li, Shuya,Hofman, Elan,Hunter Davis, Andrew,Leem, Gyu,Zheng, Weiwei
supporting information, p. 1911 - 1918 (2020/04/07)
As a green synthetic approach, visible light-driven photosynthesis is highly desirable in arylation of inert alkyl halides, as they are important precursors in the total synthesis of natural products and pharmaceuticals. However, the high bond dissociation energy of aryl halides is typically out of the range of a single visible-light photon. Here, we propose an essential initiation and subsequent electron-transfer step process for visible light-driven aryl halide reduction, and identify the key pyrrole radical anion intermediate, that acts as the strong reduction species. We propose a photoinduced disproportionation (PDP) approach without the addition of any photocatalysts or additives to afford radical anions of pyrrole derivatives, which have enough reduction power to transfer an electron to aryl halide, giving rise to the corresponding aryl radical to afford the desired C-H arylated heterocyclic product. Once generated, the heterocyclic product can undergo the same photoinduced disproportionation (PDP) process to activate aryl halides, thereby promoting the reaction rate. This unprecedented initiation step, which was carried out in the absence of photocatalysts and additives under ambient conditions, can also be used for coupling a wide range of (hetero)aryl halides and pyrrole derivatives, as well as the synthesis of drug intermediates and biorelevant compounds.
Continuous Flow Homolytic Aromatic Substitution with Electrophilic Radicals: A Fast and Scalable Protocol for Trifluoromethylation
Monteiro, Júlia L.,Carneiro, Paula F.,Elsner, Petteri,Roberge, Dominique M.,Wuts, Peter G. M.,Kurjan, Katherine C.,Gutmann, Bernhard,Kappe, C. Oliver
supporting information, p. 176 - 186 (2017/01/09)
We report an operationally simple and rapid continuous flow radical C?C bond formation under Minisci-type reaction conditions. The transformations are performed at or below room temperature employing hydrogen peroxide (H2O2) and dimethylsulfoxide (DMSO) as reagents in the presence of an FeIIcatalyst. For electron-rich aromatic and heteroaromatic substrates, C?C bond formation proceeds satisfactorily with electrophilic radicals including.CF3,.C4F9,.CH2CN, and.CH2CO2Et. In contrast, electron-poor substrates exhibit minimal reactivity. Importantly, trifluoromethylations and nonafluororobutylations using CF3I and C4F9I as reagents proceed exceedingly fast with high conversion for selected substrates in residence times of a few seconds. The attractive features of the present process are the low cost of the reagents and the extraordinarily high reaction rates. The direct application of the protocol to dihydroergotamine, a complex ergot alkaloid, yielded the corresponding trifluoromethyl ergoline derivative within 12 seconds in a continuous flow microreactor on a 0.6 kg scale. The trifluoromethyl derivative of dihydroergotamine is a promising therapeutic agent for the treatment of migraines.
