Abstract:A study on room temperature Suzuki cross-coupling in an aqueous medium was carried out using a simple hydrophilic palladium (II) complex, trans-PdCl 2 (NH 2 CH 2 COOH) 2 as catalyst in the presence of K 2 CO 3 in air. This approach with a comparatively inexpensive and hydrophilic catalyst, mild reaction condition and aqueous media exhibits excellent catalytic activity towards the Suzuki coupling of aryl bromides and arylboronic acids, and good yields were obtained in the Suzuki coupling of activated aryl chlorides.
Fourteen new C-23 carboxylated triterpenoids (stewartiacids A–N, 1–14) were obtained from the ‘vulnerable’ plant Stewartia sinensis. 11 and 12 showed inhibitory effects against ACL.
Commercially available reagents were used without further purification other than those detailed below. Toluene was distilled over sodium benzophenone ketyl under nitrogen. Dichloromethane and CH 3 CN were distilled over calcium hydride. Acetone was distilled from anhydrous CaSO 4 .All reactions were performed under a nitrogen atmosphere unless otherwise noted.Melting points are uncorrected. Melting points were determined on WRS-1 digital melting-point apparatus made by Shanghai Physical Instrument Factory (SPOIF), NMR spectra were recorded on a Varian MERCURY plus-400 spectrometer. The chemical shifts were reported in ppm downfield from tetramethylsilane (TMS) with the solvent resonance as the internal standard.Coupling constants (J) are reported in Hz and refer to apparent peak multiplications.
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