1,6-Nucleophilic Di- and Trifluoromethylation of para-Quinone Methides with Me3SiCF2H/Me3SiCF3 Facilitated by CsF/18-Crown-6
摘要:
The direct 1,6-nucleophilic difluoromethylation, trifluoromethylation, and difluoroalkylation of para-quinone methides (p-QMs) with Me3SiRf (Rf = CF2H, CF3, CF2CF3, CF2COOEt, and CF2SPh) under mild conditions are described. Although Me3SiCF2H shows lower reactivity than Me3SiCF3, it can react with p-QMs promoted by CsF/18-Crown-6 to give structurally diverse difluoromethyl products in good yields. The products can then be further converted into fluoroalkylated para-quinone methides and α-fluoroalkylated diarylmethanes.
1,6-Nucleophilic Di- and Trifluoromethylation of para-Quinone Methides with Me3SiCF2H/Me3SiCF3 Facilitated by CsF/18-Crown-6
摘要:
The direct 1,6-nucleophilic difluoromethylation, trifluoromethylation, and difluoroalkylation of para-quinone methides (p-QMs) with Me3SiRf (Rf = CF2H, CF3, CF2CF3, CF2COOEt, and CF2SPh) under mild conditions are described. Although Me3SiCF2H shows lower reactivity than Me3SiCF3, it can react with p-QMs promoted by CsF/18-Crown-6 to give structurally diverse difluoromethyl products in good yields. The products can then be further converted into fluoroalkylated para-quinone methides and α-fluoroalkylated diarylmethanes.
Photoactivation of (<i>p</i>-Methoxyphenyl)(trifluoromethyl)diazirine in the Presence of Phenolic Reaction Partners
作者:Björn Raimer、Thomas Lindel
DOI:10.1002/chem.201203479
日期:2013.5.17
Shine light on your chemistry! Irradiating 3‐(4‐methoxyphenyl)‐3‐(trifluoromethyl)‐3H‐diazirine in the presence of equimolar solutions of phenol and tyrosine derivatives leads to Friedel–Crafts alkylations (see scheme), which suggests a strategy for the development of “cleaner” diazirines for chemical biology.
Cross-dehydrogenative coupling enables enantioselective access to CF<sub>3</sub>-substituted all-carbon quaternary stereocenters
作者:Xiaoguang Pan、Zehua Wang、Linglong Kan、Ying Mao、Yasheng Zhu、Lei Liu
DOI:10.1039/c9sc05894j
日期:——
strategy for enantioselective access to acyclic CF3-substituted all-carbonquaternarystereocenters has been established. By using catalytic DDQ with MnO2 as an inexpensive terminal oxidant, asymmetric cross coupling of racemic δ-CF3-substituted phenols with indoles proceeded smoothly, providing CF3-bearing all-carbonquaternarystereocenters with excellent chemo- and enantioselectivities. The generality
Quantum chemical calculation of 19F NMR chemical shifts of trifluoromethyl diazirine photoproducts and precursors
作者:Björn Raimer、Peter G. Jones、Thomas Lindel
DOI:10.1016/j.jfluchem.2014.06.027
日期:2014.10
Irradiation of aryl(trifluoromethyl)diazirines may result in a multitude of products, which are difficult to assign in the F-19 NMR spectrum. In this article, it is demonstrated that an average accuracy of 2.9 ppm (standard deviation) can be achieved by quantum chemical calculations at the B3LYP 6-311G++(2d,2p) level of theory, followed by a Boltzmann weighting of the optimized conformers. A set of 30 compounds was investigated both-experimentally and theoretically. F-19 NMR chemical shifts of precursor Z-oximes and Z-tosyloximes ranged from delta(F) -62.9 to -61.8 ppm, whereas their E counterparts showed shifts between delta(F) -67.2 and -66.2 ppm. Stereochemical assignments were confirmed by two X-ray analyses. Quantum chemical calculation also allowed the assignment of the configuration of an (E,E) azine. Trifluoromethyl diazirines exhibited a delta(F) between -66.1 and -65.6, diaziridines between -76.2 and -75.9 ppm. The smallest delta(F) values were observed for alpha-oxygenated trifluoromethyl compounds (delta(F) -78.9 to -77.4 ppm). The average deviation of the calculated from the experimental values corresponds to only about 1% of the standard F-19 NMR chemical shift range. (C) 2014 Elsevier B.V. All rights reserved.