Vinyl tris(trimethylsilyl)silanes: substrates for Hiyama coupling

Abstract

The oxidative treatment of vinyl tris(trimethylsilyl)silanes with hydrogen peroxide in aqueous sodium hydroxide in tetrahydrofuran generates reactive silanol or siloxane species that undergo Pdcatalyzed cross-couplings with aryl, heterocyclic and alkenyl halides in the presence of Pd(PPh 3 ) 4 and tetrabutylammonium fluoride. Hydrogen peroxide and base are necessary for the coupling to occur while activation of the silanes with fluoride is not required. The conjugated and unconjugated tris(trimethylsilyl)silanes serve as good cross-coupling substrates. The (E)-silanes undergo coupling with retention of stereochemistry while coupling of (Z)-silanes occurred with lower stereoselectivity to produce an E/Z mixture of products.

Trans‐Selective Radical Silylzincation of Ynamides

“…[23,25] The prepared b-bromoenamides participated readily in Suzuki-Miyaura-type cross couplings. Reaction of Z-26 with 4-anisylboronic acid afforded a-carbonyl b-substituted enamide Z-27 [23,26] in 73 % isolated yield in spite of a partial isomerization during the coupling reaction. Z-29 was prepared similarly from Z-28 and phenylboronic acid in 50 % yield, and no isomerization was observed.…”

“…Finally, a-carbonylated b-silylenamides Z-21-Z-25 were prepared by reaction with aromatic, vinylic, or aliphatic acyl chlorides. The Z configuration of Z-13 was established by X-ray crystallographic analysis [23] (see the Supporting Information).…”

Cobalt-Catalyzed Cross-Coupling of Grignards with Allylic and Vinylic Bromides: Use of Sarcosine as a Natural Ligand

“…34 Methyl 2-benzylacrylate (8). 35 Colorless liquid (508 mg, 96% yield); 1 H NMR (400 MHz, CDCl 3 ): δ (ppm) 3.62 (s, 2H), 3.71 (s, 3H), 5.44 (dt, J = 1.5 Hz, 1.4 Hz, 1H), 6.22 (dt, J = 1.5, 0.7 Hz, 1H), 7.15-7.22 (m, 3H), 7.25-7.31 (m, 2H).…”

Cross‐Coupling Reactions of Organosilicon Compounds in the Stereocontrolled Synthesis of Retinoids

“…A solution of trienyl iodides 6 or 6' (1.0 equiv) in THF and [Pd 2 A C H T U N G T R E N N U N G (dba) 3 ]·CHCl 3 (0.05-0.1 equiv) were sequentially added at RT, and the mixture was stirred for 1 h. Diethyl ether was added and the mixture was filtered through a short pad of silica gel. The solvent was removed under vacuum and the crude mixture was purified by column chromatography (SiO 2 , 95:5 hexane/AcOEt) to afford the corresponding retinyl ethers (15)(16)(17)(18)(19)(20)(21)(22) as yellow oils. Silylhydride coupling: By following the general procedure, treatment of a solution of silylhydride 8 e (28 mg, 0.096 mmol) in THF (2 mL) with TBAF (1.0 m in THF, 96 mL, 0.96 mmol) for 30 min at 0 8C, followed by addition of a solution of iodide 6 (15 mg, 0.05 mmol) in THF (1 mL) and [Pd 2 A C H T U N G T R E N N U N G (dba) 3 ]·CHCl 3 (2 mg, 0.002 mmol) afforded compound 18 in 85 % yield (15 mg).…”

“…To determine the influence of the substituent on the silicon atom, the protected analogues were synthesized by using as many as possible of a large set of organosilicon reagents that included representatives of two families of oxygen-activated silanes and of the whole array of "masked silanols" reported to date. [20] These organosilicon reagents were prepared by existing methods and evaluated and compared with regard to their chemical stability, activation conditions (fluoride-promoted or fluoride-free) and suitability for these specific cross-coupling reactions. [21]…”