Efficient copper-catalyzed trifluoromethylation of aromatic iodides was achieved with TMSCF 3 in the presence of trimethoxyborane. The Lewis acid was used to anchor the in situ generated trifluoromethyl anion and suppress its rapid decomposition. Broad applicability of the new trifluoromethylating reaction was demonstrated in the functionalization of different aromatic and heteroaromatic iodides.
Several o-(trimethylsilyl)aryl imidazolylsulfonates were synthesized in a simple process and successfully applied in cycloadditions involving benzyne intermediates. The precursor offers an efficient alternative for generating benzynes compared to widely used ortho TMS triflates under similar reaction conditions. With the utilization of this new precursor, the formation of potentially genotoxic trifluoromethanesulfonate side product is eliminated. The applicability of the new benzyne precursor was demonstrated in different types of cycloaddition reactions to prepare heterocyclic molecules.
Poly(N-vinylimidazole) homopolymer (PVIm) and poly(N-vinylimidazole)-l-poly(tetrahydrofuran) (PVIm-l-PTHF), a novel amphiphilic polymer conetwork (APCN), were synthesized to compare their solid state structure and investigate the swelling behavior of this unique conetwork in water. A short-range ordered structure stabilized by second-order interactions between the imidazole pendant groups was found in the PVIm homopolymer and in the PVIm phase of the dry conetwork as revealed by solid-state NMR 13 C cross-polarization magic angle spinning (CP MAS) and two-dimensional 1 H− 13 C frequencyswitched Lee−Goldburg (FSLG) HETCOR measurements. With increasing swelling ratio, structural and conformational changes were recognized in the hydrophilic PVIm phase of the APCN. In the kinetic swelling study, unexpectedly, four different swelling ranges were identified by gravimetric measurements, solid-state NMR methods, and positron annihilation lifetime (PAL) spectroscopy before the APCN reached its equilibrium swelling state. In the first period, which takes place in several minutes, the ordered structure disintegrates in the PVIm phase and the water uptake is relatively slow. This structural realignment is followed by the main course of water uptake governed by Fickian diffusion in the second stage. Close to the equilibrium swelling ratio, the swelling curve becomes nonmonotonic caused by a realignment of main chains of the hydrophilic phase in the third stage of swelling. Thus, by the unique combination of conventional swelling kinetics and solid-state NMR as well as PAL spectroscopies for investigating the aqueous swelling of the PVIm-l-PTHF amphiphilic polymeric conetwork, it was revealed that unexpected noncontinuous swelling occurs which is due to structural changes of the PVIm component in the conetwork in the course of this process.
The introduction of trifluoroalkyl groups into aromatic molecules is an important transformation in the field of organic and medicinal chemistry. However, the direct installation of fluoroalkyl groups onto aromatic molecules still represents a challenging and highly demanding synthetic task. Herein, a simple trifluoroethylation process that relies on the palladium-catalyzed C-H activation of aromatic compounds is described. With the utilization of a highly active trifluoroethyl(mesityl)iodonium salt, the developed catalytic method enables the first highly efficient and selective trifluoroethylation of aromatic compounds. The robust catalytic procedure provides the desired products in up to 95 % yield at 25 °C in 1.5 to 3 hours and tolerates a broad range of functional groups. The utilization of hypervalent reagents opens new synthetic possibilities for direct alkylations and fluoroalkylations in the field of transition-metal-catalyzed C-H activation.
Development of direct late-stage installation of key fluorinated functional groups into aromatic systems is an important and challenging task of current organic chemistry. Herein, we report a novel palladium catalyzed trifluoroethylation process by C-H activation for the access of ortho trifluoroethylated aromatic ureas. The application of novel, highly active trifluoroethyl(mesityl)iodonium salt enables the efficient introduction of the trifluoroethyl group at 25 °C in 3 hours in high yields (up to 95%) with good functional group tolerance. Abstract: Development of direct late-stage installation of key fluorinated functional groups into aromatic systems is an important and challenging task of current organic chemistry. Herein, we report a novel palladium catalyzed
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