86093-76-7Relevant academic research and scientific papers
Air-Sensitive Photoredox Catalysis Performed under Aerobic Conditions in Gel Networks
H?ring, Marleen,Abramov, Alex,Okumura, Keisuke,Ghosh, Indrajit,K?nig, Burkhard,Yanai, Nobuhiro,Kimizuka, Nobuo,Díaz Díaz, David
, p. 7928 - 7938 (2018/06/04)
In this work, we demonstrate that useful C-C bond-forming photoredox catalysis can be performed in air using easily prepared gel networks as reaction media to give similar results as are obtained under inert atmosphere conditions. These reactions are completely inhibited in homogeneous solution in air. However, the supramolecular fibrillar gel networks confine the reactants and block oxygen diffusion, allowing air-sensitive catalytic activity under ambient conditions. We investigate the mechanism of this remarkable protection, focusing on the boundary effect in the self-assembled supramolecular gels that enhances the rates of productive reactions over diffusion-controlled quenching of excited states. Our observations suggest the occurrence of triplet-sensitized chemical reactions in the gel networks within the compartmentalized solvent pools held between the nanofibers. The combination of enhanced viscosity and added interfaces in supramolecular gel media seems to be a key factor in facilitating the reactions under aerobic conditions.
Trifluoromethylation of aryl and heteroaryl halides with fluoroform-derived CuCF3: Scope, limitations, and mechanistic features
Lishchynskyi, Anton,Novikov, Maxim A.,Martin, Eddy,Escudero-Adan, Eduardo C.,Novak, Petr,Grushin, Vladimir V.
, p. 11126 - 11146 (2013/12/04)
Fluoroform-derived CuCF3 recently discovered in our group exhibits remarkably high reactivity toward aryl and heteroaryl halides, performing best in the absence of extra ligands. A broad variety of iodoarenes undergo smooth trifluoromethylation with the ligandless CuCF3 at 23-50 C to give the corresponding benzotrifluorides in nearly quantitative yield. A number of much less reactive aromatic bromides also have been trifluoromethylated, including pyridine, pyrimidine, pyrazine, and thiazole derivatives as well as aryl bromides bearing electron-withdrawing groups and/or ortho substituents. Only the most electrophilic chloroarenes can be trifluoromethylated, e.g., 2-chloronicotinic acid. Exceptionally high chemoselectivity of the reactions (no side-formation of arenes, biaryls, and C2F5 derivatives) has allowed for the isolation of a large number of trifluoromethylated products in high yield on a gram scale (up to 20 mmol). The CuCF3 reagent is destabilized by CuX coproduced in the reaction, the magnitude of the effect paralleling the Lewis acidity of CuX: CuCl > CuBr > CuI. While SNAr and SRN1 mechanisms are not operational, there is a well-pronounced ortho effect, i.e., the enhanced reactivity of ortho-substituted aryl halides 2-RC6H4X toward CuCF3. Intriguingly, this ortho-effect is observed for R = NO2, COOH, CHO, COOEt, COCH3, OCH3, and even CH3, but not for R = CN. The fluoroform-derived CuCF3 reagent and its reactions with haloarenes provide an unmatched combination of reactivity, selectivity, and low cost.
The gas-phase reaction of the CF3 radical with thiophene
Herrera, Olga S.,Nieto, Jorge D.,Lane, Silvia I.,Oexler, Elena V.
, p. 1477 - 1481 (2007/10/03)
The reaction of CF3 radicals, generated by photolysis of CF 3I or hexafluoroacetone with thiophene, was studied in the gas phase at 25°C. At conversion of thiophene less than 20%, monosubstituted CF 3-thiophenes were found as the main reaction products, in addition to CF3H, C2F6, and monosubstituted dihydro-CF3-thiophene, the latter in very low proportion. An isomeric mixture of 2- and 3-CF3-thiophene was obtained in a ratio of about 16, independent of the radical source used (CF3I or hexafluoroacetone) to produce the CF3 radicals. A plausible mechanism that accounts for the observed products is proposed, and the reactivity of thiophene toward the CF3 radical at 25°C was determined as kadd/kc1/2 = 106 ± 4 cm3/2 mol-1/2 s-1/2.
TRIFLUORMETHYLIERUNGSREAKTIONEN VON CF3I, Te(CF3)2, Sb(CF3)3, Hg(CF3)2, UND Cd(CF3)2*D MIT FURAN, THIOPHEN, PYRROL UND p-BENZOCHINON
Naumann, Dieter,Kischkewitz, Juergen
, p. 265 - 281 (2007/10/02)
The trifluoromethylation reactions of Cd(CF3)2*glyme, Hg(CF3)2, Sb(CF3)3, CF3I, and Te(CF3)2 with furan, thiophene, pyrrol, and p-benzoquinone are compared under similar conditions.During the photochemical reactions the reactivity increases in the series
Thiirene formation in the reactions of sulfur atoms with alkynes
Verkoczy, Bela,Sherwood, Alden G.,Safarik, Imre,Strausz, Otto P.
, p. 2268 - 2281 (2007/10/02)
The gas phase reactions of S(1D2) and S(3PJ) atoms with alkynes have been studied by photolyzing COS in the presence of CHCH, CF3CCH, and CF3CCCF3.In the reactions with CHCH, CS2, benzene, and thiophene were formed; with CF3CCH, eight products found with disubstituted thiophenes and trisubstituted benzenes as the major products.In the case of CF3CCCF3, only perfluorotetramethylthiophene was detected at low conversion but at long photolysis several new products were observed.Many of the reaction products characterized here have not been reported before.The formation and distribution of the reaction products could be rationalized by an overall mechanism in which the formation of the highly reactive primary adducts, thiirene and thioformylmethylene, is followed by bimolecular reactions yielding the principal end products.The formation of minor products could be explained by secondary photoisomerizations, secondary photolysis, and by secondary decompositions and the secondary reactions of sulfur atoms with primary products.
