Transition-Metal-Mediated Nucleophilic Aromatic Substitution with Acids

Abstract

Index Page Experimental General Considerations S2 Synthesis of Q 2 FB (2) S2 Synthesis of (Q 2 FB)Rh(TFA)(COE) (3) S2-S3 Synthesis of (Q 2 FB)Rh(TFA) 3 (1) S3 General procedure for catalytic S N Ar in HTFA S3 NMR spectra Table of NMR chemical shifts S4 NMR spectra of 2 S5-S6 NMR spectra of 3 S6-S10 NMR spectra of 1 S10-S13 19 F NMR spectra of CF 3 C(O)F S13 19 F NMR spectra of CH 3 C(O)F S14 NMR spectra of intermediate 4 S14-S16 NMR spectra of proposed 5a and 5b S17-S18 NMR spectra of catalytic defluorination S19 Kinetics Defluorination of 1 S20-S21 References S22 DFT Calculations S23-S30 S2 Experimental General Considerations. Unless otherwise noted, all synthetic procedures were performed under anaerobic conditions in a nitrogen filled glovebox or by using standard Schlenk techniques. Glovebox purity was maintained by periodic nitrogen purges and was monitored by an oxygen analyzer (O 2 < 15 ppm for all reactions). Tetrahydrofuran, pentane and diethyl ether were dried by distillation from sodium/benzophenone. Benzene, hexanes, and methylene chloride were purified by passage through a column of activated alumina. Benzene-d 6 , chloroform-d 1 , and tetrahydrofuran-d 8 were stored over 4Å molecular sieves in a nitrogen atmosphere. 1 H NMR spectra were recorded on a Varian Mercury Plus 300 MHz or a Varian Inova 500 MHz spectrometer, and the 13 C NMR spectra were recorded on a Varian Inova 500 MHz spectrometer (operating frequency 126 MHz). All 1 H and 13 C NMR spectra are referenced against residual proton signals (1 H NMR) or the 13 C resonances of the deuterated solvent (13 C NMR). {(COE) 2 Rh(μ-TFA)} 2 was prepared according to published literature procedures. 2 All other reagents were used as purchased from commercial sources. Synthesis of 8,8'-(4,5-difluorobenzene)diquinoline (Q 2 FB) (2). Quinolin-8-ylboronic acid (1.50 g, 8.67 x10-3 mol, 2.4 equiv.), 1,2-dibromo-4,5-difluorobenzene (0.985 g, 3.62 x10-3 mol, 1 equiv.), Pd(PPh 3) 4 (0.418 g, 3.62 x10-4 mol, 0.10 equivalents), and K 3 PO 4 (17.0 g, 8.01 x10-2 mol, 22 equiv.) were combined into the 250 mL Schlenk flask. Under an inert atmosphere, degassed dimethylformaldehyde (60 mL) and degassed DI water (60 mL) were added to the Schlenk flask, and the flask was fitted with a glass stopper and sealed. The glass stopper was secured to the Schlenk flask with several rubber bands, and then the reaction mixture was heated in an oil bath at 110 °C with stirring for 14 h. Afterwards, the reaction mixture was allowed to cool to room temperature, during which the aqueous and organic layers separated. The lower aqueous phase was separated from the organic phase by separatory funnel and discarded. The organic layer was collected, and a copious amount of DI water (500 mL) was added to precipitate a yellow oily solid. The solid was collected by filtration and then dissolved in Et 2 O (30 mL) and filtered. The filtrate was collected and reduced under mild pressure to an oil. The product was purified by column chromatography (silica). The mono-coupled product was removed as ...

Defluorosilylation of fluoroarenes and fluoroalkanes

“…In pathway a, the silyl anion performs a nucleophilic attack on the fluorine-substituted carbon of the aryl ring by intramolecular S N Ar (I-S N Ar), assisted by a transfer of the π-bond density of the aryl ring to the d-orbital of nickel (Fig. 5b , path a) 34 , 36 , 37 . The fluorine atom coordinates to the Ni center, where K + also assists the C–F bond cleavage to provide G via F .…”

A Mild and Ligand-Free Ni-Catalyzed Silylation via C–OMe Cleavage

“…This conclusion is reminiscent of the structurally well-defined, yet exceptionally sensitive, Ni(0)-ate complex 21 reported by Pörschke that can be obtained by reaction of Ni­(COD) 2 with MeLi in ethylene atmospheres, the identity of which was rigorously proven by X-ray diffraction analysis. , Unfortunately, and despite extensive experimentation, isolation of 20 or direct spectroscopic evidence for such putative intermediate was not possible, probably due to its expected exceptional sensitivity and limited lifetime. In a formal sense, the reaction of 20 with an aryl methyl ether could be visualized as an internal metal-catalyzed nucleophilic aromatic substitution assisted by complexation of the K + counterion with the lone pair of the ethereal oxygen atom (Scheme , path a) . Alternatively, one could also envision a “ nonclassical ” oxidative addition of the C­(sp 2 )–OMe bond via Ni(0)-ate complexes assisted by the K + counterion (Scheme , path b). , These interpretations could explain the strikingly different behavior found for potassium counterions, in which a Lewis acid might aid the targeted C–O cleavage. ,, …”

Catalytic Synthesis of Superlinear Alkenyl Arenes Using a Rh(I) Catalyst Supported by a “Capping Arene” Ligand: Access to Aerobic Catalysis

“…We speculated that the ligand 5-FP [5-FP = 1,2-bis­( N -7-azaindoly)­benzene], which we have termed a “capping arene” ligand, would prevent the coordination of a sixth strongly donating ligand to the metal center upon its oxidation to Rh­(III) and, hence, stabilize Rh­(I) against oxidation by oxygen and permit catalysis under aerobic conditions (Scheme ). − Using this design, we report a new Rh catalyst precursor that achieves efficient oxidative olefin hydroarylation using air either to recycle Cu­(II) oxidants or as the sole oxidant. The new Rh complex, (5-FP)­Rh­(TFA)­(η 2 -C 2 H 4 ) ( 1 ), catalyzes the conversion of benzene and propylene to linear alkenyl arenes in the presence of oxygen or using air as the in situ oxidant.…”