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A range of bromothiophenes reacted with lithium boranato(tert-butyl)methylphosphide in the absence of transition-metal catalysts under mild conditions to provide the same 2,5-disubstituted and 2-monosubstituted products regardless of the substitution patterns of the starting bromothiophenes. [ABSTRACT FROM AUTHOR]

This article describes recent developments in the understanding of the mechanism of enantioselection in one of the most efficient artificial catalytic reactions—Rh-catalyzed asymmetric hydrogenation. Numerous experimental and computational data are consistent with the idea that the enantioselection takes place through the reversible coordination of the double bond in octahedral dihydride complexes, which can happen only if the resulting chelate cycle is formed in the less hindered quadrant. In its main features, this mechanism of generating chirality resembles the recently uncovered three-stage recognition process occurring in enzymatic reactions. [ABSTRACT FROM AUTHOR]

A simple synthetic approach to aromatic compounds using combinations of RCM, dehydration, oxidation, and tautomerization is described. [ABSTRACT FROM AUTHOR]

A Pd-catalyzed asymmetric allylic substitution with 1,3-dithianes as acyl anion equivalents has been developed in high yields and excellent enantioselectivities. The reaction was performed on a gram scale, and the corresponding alkylated products were conveniently converted into several biologically active products. This work provides an alternative strategy utilizing electrophilic carbonyl compounds as nucleophilic species in a Pd-catalyzed allylic substitution. [ABSTRACT FROM AUTHOR]

Novel P-stereogenic pincer-Ni complexes{κP,κC,κP-3,5-Me2-2,6-(MetBuPCH2)2C6H}NiCl(3), {κP,κC,κP-3,5-Me2-2,6-(MetBuPCH2)2C6H}NiOTf (4),[{κP,κN,κP-2,6-(MetBuPCH2)2C5H3N}NiCl]Cl (7), [{κP,κN,κP-2,6-(MetBuPCH2)2C5H3N}NiCl]BF4(8), and [{κP,κN,κP-2,6-(MetBuPCH2)2C5H3N}Ni(NCMe)](BF4)2(9) were synthesized in 55–84%yields and characterized by 1H NMR, 13C{1H} NMR, 31P{1H} NMR, 19F{1H} NMR, and/or single-crystal X-ray diffractions. The ORTEPdiagrams of complexes 3, 7, 8, and 9show that the coordination geometries aroundthe Ni center in all these structures are approximately square planarbut have different bond lengths and angles. These complexes were shownto be active catalysts for the asymmetric aza-Michael addition ofα,β-unsaturated nitriles. For most examplesgood to excellent yields (up to 99%) and moderate enantiomeric excesses(up to 46% ee) were obtained. Notably, the PCP complex 3exhibited higher catalytic activity in the aza-Michael additionthan the PNP complexes 7, 8, and 9. Two achiral PCP-type pincer-Ni complexes, {κP,κC,κP-3,5-Me2-2,6-(tBu2PCH2)2C6H}NiCl (11) and {κP,κC,κP-3,5-Me2-2,6-(Ph2PCH2)2C6H}NiCl (13), were also synthesized and fully characterized in order to revealthe structural differences between the chiral and achiral complexes. [ABSTRACT FROM AUTHOR]

An electron-rich P-stereogenic bisphosphine ligand named “BenzP*” was conveniently prepared from o-dibromobenzene and enantiopure tert-butylmethylphosphine-borane. Its rhodium complex exhibited excellent enantioselectivities of up to 99.9% and high catalytic activity of up to 10 000 h−1TOF in asymmetric hydrogenations of various functionalized alkenes. [ABSTRACT FROM AUTHOR]

Optically active dinuclear palladium complexes containing a Pd−Pd bond were prepared by using (R,R)-bis(tert-butylmethylphosphino)methane ((R,R)-t-Bu-MiniPHOS). The dinuclear palladium complexes coupled with silver triflate exhibited good to excellent enantioselectivities up to 99% in palladium-catalyzed alkylative ring-opening reactions of azabenzonorbornadienes. [ABSTRACT FROM AUTHOR]

New synthetic routes to substituted 3-hydroxypyridines 6are presented. Ring-closing olefin metathesis (RCM)/elimination and RCM/oxidation/deprotection of nitrogen-containing dienes 4are the key processes of the routes. An application of RCM/oxidation/deprotection to the synthesis of 3-aminopyridine 13fis also described. [ABSTRACT FROM AUTHOR]

The synthesis of substituted styrenes was achieved by ring-closing enyne metathesis (RCEM)/elimination of enyne substrates 12. The synthetic approach was also effective for a different type of enyne substrate 14, yielding corresponding styrene 15. [ABSTRACT FROM AUTHOR]

A screening method for asymmetric catalysts is reported in which a metal-containing optically-active product of an asymmetric reaction is employed as a chiral catalyst in another asymmetric reaction; the rapid preparation and instant testing system of catalysts resulted in a considerable reduction in the time required for the screening process. [ABSTRACT FROM AUTHOR]