Aqueous Sodium Hydroxide Promoted Cross-Coupling Reactions of Alkenyltrialkoxysilanes under Ligand-Free Conditions

Abstract

Fluoride-free cross-coupling reactions of alkenyltrialkoxysilanes with aryl iodides, bromides, and chlorides are performed on water using sodium hydroxide as activator at 120 degrees C under normal or microwave heating. This process occurs in the presence of Pd(OAc)(2) or 4-hydroxyacetophenone oxime-derived palladacycle 1 as precatalysts under ligand-free conditions with low Pd loadings (0.01-1 mol %) and using tetra-n-butylammonium bromide as additive. Different commercially available vinylalkoxylsilanes can be cross-coupled under these reaction conditions to the corresponding styrenes, the best substrates being vinyltrimethoxy- or vinyltriethoxysilane. Alkenyltriethoxysilanes, prepared by Wilkinson-catalyzed hydrosilylation of alkynes with triethoxysilane, are stereospecifically arylated with aryl and vinyl halides under microwave irradiation in moderate to high beta/alpha regioselectivity affording unsymmetrical stilbenes, alkenylbenzenes, and conjugate dienes, respectively. This simple procedure allows the palladium recycling from the aqueous phase during three runs by extractive separation of the products, which contain very low levels of Pd (21-27.5 ppm for an aryl iodide and up to 76 ppm for a bromide).

(NHC)Palladium Complexes from Hydroxy‐Functionalized Imidazolium Salts as Catalyst for the Microwave‐Accelerated Fluorine‐Free Hiyama Reaction

“…The base (NaOH) was required to promote the Hiyama reaction and favour the transmetalation process;18c as expected, the use of lower amounts of base reduced the yield (Table 2, Entry 3). Thereafter, different bases were considered under the microwave conditions; however, no significant improvement over the results obtained with sodium hydroxide were observed.…”

Expanding the Scope of Replicable Unnatural DNA: Stepwise Optimization of a Predominantly Hydrophobic Base Pair

“…Potassium (trifluoromethyl)trimethoxyborate was used as a source of CF 3 nucleophiles for the copper-catalyzed trifluoromethylation, 21 and deprotection yielded d TfMO ( 10 ). Toward d VMO , we found that Suzuki-Miyaura cross-coupling with vinyltrifluoroborate, 22 palladium cross-coupling with vinylaluminium reagent 23 or vinyltriethoxysilane, 24 or Stille cross-coupling with vinyltributyltin 25 all resulted in the conversion of the aromatic iodide ( 9 ) to its vinyl analog with good yields. Because the Stille cross-coupling generated cleaner crude material, we proceeded with this route, and the d VMO ( 11 ) nucleoside was obtained after deprotection.…”

New series of monoamidoxime derivatives displaying versatile antiparasitic activity

“…This result suggests firstly that there is product metabolization by hepatocyte-specific metabolic enzymes in the HepG2 cell line, and secondly that these metabolites are less toxic in vitro than tested compounds. Several amidoximes possessing a methyl in R 2 , a benzyl in R 3 and a variously monosubstituted phenyl group in R 1 (32)(33)(34)(35) 13 C chemical shifts were referenced to the solvent peaks: CDCl 3 (76.9 ppm) or DMSO-d6 (39.6 ppm). Coupling constants (J values) are given in hertz.…”