Ruphos-mediated Suzuki cross-coupling of secondary alkyl trifluoroborates (original) (raw)
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Tetrahedron, 2015
An efficient protocol for Pd-catalyzed 2,2,2-trifluoroethoxylation of activated aryl bromides and bromochalcones has been developed. We unveil a fascinating insight into the Pd-catalyzed CeO cross-coupling reaction. Pd/tBuXPhos (L1) ligand system facilitates the CeO cross-coupling reaction between 2,2,2trifluoroethanol and activated aryl bromides at both higher (115 C) and lower temperatures (40 C). Unprecedentedly, this catalyst system facilitates the CeO cross-coupling reaction in short span of reaction times, generally 5e25 min (at 115 C). The structurally simple analogue of tBuXPhos ligand so called John-Phos (L2) ligand is also facilitated the CeO bond formation with activated aryl bromides and bromochalcones. Interestingly, under the optimal conditions (L1), methanol is also coupled rapidly with activated aryl bromides. These catalyst systems (L1 and L2) fail to couple electron rich aryl bromides with 2,2,2trifluoroethanol, thus these catalyst systems allow the reductive elimination through an electronic pathway of reductive elimination. The unusual reactivity of 2,2,2-trifluoroethanol in Pd-catalyzed CeO cross-coupling reaction makes that the chemistry of fluorinated molecules is unique than that of non-fluorinated analogues. The bromo-chalcones can be used as a new coupling partner in the cross-coupling reaction.
The Journal of Organic Chemistry, 2012
The introduction of an alkoxyethyl moiety onto aromatic substructures has remained a longstanding challenge for synthetic organic chemists. The main reasons are the inherent instability of alkoxyethylmetallic species and the lack of general procedures to access them. A new method utilizing a cross-coupling strategy based on the exceptional properties of organotrifluoroborates has been developed, and the method allows an easy and efficient installation of this unit on a broad range of aryl and heteroaryl bromides.
Synthesis and Reactivity of Solid-Supported Organotrifluoroborates in Suzuki Cross-Coupling
Organic Letters, 2012
Solid-supported organotrifluoroborates were prepared in high yields by ion exchange with Amberlyst resins. The reactivity of solid supported aryltrifluoroborates was evaluated in Suzuki-Miyaura couplings with numerous aryl bromide partners. Electron rich and electron poor substituents were tolerated on both substrates, providing yields up to 90%. Examples of alkyl-, alkenyl-, alkynyl-and heteroaryltrifluoborates were also successfully cross-coupled to aryl halides.
Chemical Communications, 2007
General Methods. Difluoroenol silyl ethers 1 2a-2e and monofluoro silyl enol ether 2 4 were prepared as described previously. Tri-n-butyltin fluoride and a 1M toluene solution of P(t-Bu)3, were purchased from Aldrich Chemical Co. and used as received. Toluene was distilled under nitrogen over sodium prior to use. All other chemicals were used as received from commercial sources. 1 H NMR spectra were obtained on a 300-or 500-MHz spectrometer, and chemical shifts were recorded relative to a residual protonated solvent. 13 C NMR spectra were obtained at 75.5 MHz on a 300-MHz instrument, and chemical shifts were recorded relative to the solvent resonance. Both 1 H NMR and 13 C NMR chemical shifts are reported in parts per million relative to tetramethylsilane. 19 F NMR chemical shifts are reported in parts per million from CFCl 3. The solvent was CDCl 3 unless otherwise stated. The purity of products was determined by CH&N elemental analyses. Column chromatography was carried out using ACROS silicagel (0.060-0.200 mm). Thin layer chromatography (TLC) was carried out on commercially available pre-coated plates (Whatman UV 254 silica).