Base-free palladium-catalyzed cross-coupling of arylsulfonium salts with sodium tetraarylborates
Palladium-catalyzed cross-coupling reactions of arylsulfonium salts with sodium tetraarylborates were found to proceed smoothly without recourse to an additional base, providing a new, reliable route to biaryls from organosulfur compounds.
Palladium-Assisted "Aromatic Metamorphosis" of Dibenzothiophenes into Triphenylenes
Abstract Two new palladium-catalyzed reactions of aromatic sulfur compounds enabled the conversion of dibenzothiophenes into triphenylenes in four steps. This transformation of one aromatic framework into another consists of 1) 4-chlorobutylation of the dibenzothiophene to form the corresponding sulfonium salt, 2) palladium-catalyzed arylative ring opening of the sulfonium salt with a sodium tetraarylborate, 3) an intramolecular SN2 reaction to form a teraryl sulfonium salt, and 4) palladium-catalyzed intramolecular C-S/C-H coupling through electrophilic palladation. Symmetrical as well as unsymmetrical triphenylenes of interest were synthesized in a tailor-made fashion in satisfactory overall yields. A change of heart: The invention of two palladium-catalyzed arylation reactions of organosulfur compounds enabled the transformation of dibenzothiophenes into triphenylenes and thus a fundamental change in the core aromatic structure (see scheme). Both symmetrical and unsymmetrical triphenylenes were synthesized in a tailor-made fashion in satisfactory overall yield.
Rhodium-Catalyzed asymmetric synthesis of spirocarbocycles: arylboron reagents as surrogates of 1,2-dimetalloarenes
(Figure Presented) Revolutionary Rh-oad: A rhodium/dienecatalyzed addition of sodium tetraarylborates to alkyne-tethered 2-cydoalken-lones has been developed for the synthesis of splrocarbocycles. The tetraarylborates catalytlcally form two new carbon-carbon bonds. A chlral diene ligand also asymmetrically creates quaternary spirocarbon stereocenters with high enantiomeric purity.
Ligand-free, atom-efficient Suzuki-Miyaura type cross-coupling reactions at room temperature
The atom-efficient cross-coupling reaction of sodium tetraarylborates with aryl iodides and bromides was reported. The reaction can be performed directly using a catalytic system composed of palladium chloride, sodium carbonate and methanol (PdCl2/Na2CO3/MeOH) under heat-free conditions at room temperature in an open air conditions. The reactions carried out in an atom-efficient way as 4 equiv of aryl halides coupled effectively with 1 equiv of sodium tetraarylborates to furnish 4 equiv of the corresponding functionalized biaryls in good to excellent yields.