ABSTRACT
A new method is presented for 1,3-difluorination and 1,3-oxyfluorination reactions. The process is based on iodonium mediated opening of 1,1-disubstituted cyclopropanes. The reaction proceeds with high chemo- and regioselectivity under mild reaction conditions typically at room temperature in a couple of hours. The reaction probably occurs via electrophilic ring-opening of cyclopropanes.
ABSTRACT
An air- and moisture-stable fluoroiodane in the presence of AgBF4 is suitable for selective geminal difluorination of styrenes under mild reaction conditions. One of the CF bonds is formed by transfer of electrophilic fluorine from the hypervalent iodine reagent, while the other one arises from the tetrafluoroborate counterion of silver. Deuterium-isotope-labelling experiments and rearrangement of methyl styrene substrates suggest that the reaction proceeds through a phenonium ion intermediate.
Subject(s)
Borates/chemistry , Heterocyclic Compounds, 2-Ring/chemistry , Hydrocarbons, Fluorinated/chemical synthesis , Onium Compounds/chemistry , Silver Compounds/chemistry , Styrenes/chemistry , Air , Deuterium/chemistry , Halogenation , Hydrocarbons, Fluorinated/chemistry , Molecular Structure , Water/chemistryABSTRACT
Styrenes with an electron-deficient double bond undergo cyanotrifluoromethylation with a trifluoromethylated hypervalent iodine reagent in the presence of CuCN. The reaction proceeds under mild conditions in the presence of bulky phosphines or B2pin2 additives. The process is highly regioselective and involves the consecutive formation of two C-C bonds in a single addition reaction. In the presence of a p-methoxy substituent in the styrene, oxytrifluoromethylation occurs instead of the cyanotrifluoromethylation.
Subject(s)
Copper/chemistry , Hydrocarbons, Fluorinated/chemistry , Hydrocarbons, Fluorinated/chemical synthesis , Styrenes/chemistry , Electrons , Methylation , Molecular Structure , StereoisomerismABSTRACT
Quinones undergo copper-mediated C-H trifluoromethylation reactions using a hypervalent iodine reagent. The reactions have a broad synthetic scope involving naphtho, alkyl, chloro and methoxy quinones.
Subject(s)
Copper/chemistry , Hydrocarbons, Fluorinated/chemical synthesis , Quinones/chemistry , Hydrocarbons, Fluorinated/chemistry , Molecular StructureABSTRACT
Coumarin-sensitized, long-wavelength-absorbing luminescent Eu(III)-complexes have been synthesized and characterized. The lanthanide binding site consists of a cyclen-based chelating framework that is attached through a short linker to a 7-hydroxycoumarin, a 7-B(OH)(2)-coumarin, a 7-O-(4-pinacolatoboronbenzyl)-coumarin or a 7-O-(4-methoxybenzyl)-coumarin. The syntheses are straightforward, use readily available building blocks, and proceed through a small number of high-yielding steps. The sensitivity of coumarin photophysics to the 7-substituent enables modulation of the antenna-absorption properties, and thus the lanthanide excitation spectrum. Reactions of the boronate-based functionalities (cages) with H(2)O(2) yielded the corresponding 7-hydroxycoumarin species. The same species was produced with peroxynitrite in a ×10(6)-10(7)-fold faster reaction. Both reactions resulted in the emergence of a strong ≈407 nm excitation band, with concomitant decrease of the 366 nm band of the caged probe. In aqueous solution the methoxybenzyl caged Eu-complex was quenched by ONOO(-). We have shown that preliminary screening of simple coumarin-based antennae through UV/Vis absorption spectroscopy is possible as the changes in absorption profile translate with good fidelity to changes in Eu(III)-excitation profile in the fully elaborated complex. Taken together, our results show that the 7-hydroxycoumarin antenna is a viable scaffold for the construction of turn-on and ratiometric luminescent probes.
Subject(s)
Chelating Agents/chemistry , Coumarins/chemistry , Europium/chemistry , Lanthanoid Series Elements/chemistry , Umbelliferones/chemistry , Absorption , Luminescence , Luminescent Measurements , Molecular Structure , Spectrophotometry, UltravioletABSTRACT
Regio- and stereoselective Cu-catalyzed addition of the above hypervalent iodine reagent to alkynes and alkenes was achieved. In the presence of CuI, the reaction is suitable to perform trifluoromethyl-benzoyloxylation and trifluoromethyl-halogenation of alkenes and alkynes. Electron-donating substituents accelerate the process, and alkenes react faster than alkynes emphasizing the electrophilic character of the addition reaction.
