Hikaru Nishimura

Catalytic asymmetric induction of planar chirality by palladium-catalyzed asymmetric cross-coupling of a meso (arene)chromium complex

Abstract Asymmetric cross-coupling of tricarbonyl( o -dichlorobenzene) chromium with vinylic metals in the presence of a chiral palladium catalyst gave the mo

Catalytic asymmetric induction of planar chirality: Palladium-catalyzed asymmetric cross-coupling of meso tricarbonyl(arene) chromium complexes with alkenyl- and arylboronic acids

Abstract Asymmetric cross-coupling of tricarbonyl( o -dichlorobenzene)chromium with alkenyl- and arylmetals in the presence of a chiral phosphine-palladium catalyst gave the mono-coupling products at up to 69% ee.

Mono-Cr(CO)3 complexes of biphenyl compounds: Cross-coupling reactions of (η6-arene)chromium complexes with arylmetals

Abstract Cross-coupling reaction of tricarbonyl(η 6 -halobenzene)chromium complexes with arylmetals in the presence of palladium(0) catalyst produced mono-Cr(CO) 3 complexes of biphenyl compounds in good yield. Reaction of tricarbonyl(2,6-substituted 1-halobenzene)chromium complexes with ortho -substituted phenylboric acid gave stereoselectively cross-coupling products.

New chiral phosphine ligands containing (η6-arene)chromium and catalytic asymmetric cross-coupling reactions

Abstract New chiral monophosphine ligands 2–4 containing (η6-arene)chromium were prepared via the stereoselective ortho-lithiation of ((R)-N,N-dimethyl-1-phenylethylamine)-Cr(CO)3 (1). Asymmetric cross-coupling of 1-phenylethylmagnesium or -zinc reagent with vinyl bromides in the presence of palladium or nickel catalysts complexed with the chiral (ν6-arene)chromium ligands gave the coupling products of up to 61% ee.

REGIOSELECTIVITY OF NUCLEOPHILIC ADDITIONS TO (ARENE)CHROMIUM COMPLEXES : CONFORMATIONAL EFFECTS OF CR(CO)3 MOIETIES AND THE NATURE OF CARBANIONS

Abstract Nucleophilic addition of some carbon nucleophiles to tricarbonyl(1- exo -isopropyl-5-methoxytetralin)-chromium ( 4 ), tricarbonyl(1- endo -isopropyl-5-methoxytetralin)chromium ( 5 ), and tricarbonyl(1-isopropyl-5-methoxy-3,4-dihydronaphthalene)chromium ( 8 ) has been investigated. The regioselectivity of the nucleophilic addition using 2-lithio-1,3-dithiane under kinetic control conditions is dependent on the conformation of the Cr(CO) 3 group for the arene ring. exo -Isopropyl complex 4 gives the meta -substituted compound with high regioselectivity in good yield, while the corresponding endo -isopropyl complex 5 yields predominantly the ortho -substituted arene. The crystal structure of the endo -complex 5 has been determined by X-ray crystallography, indicating that three CO ligands adopt the staggered conformation for the aromatic ring. On the other hand, the addition reaction with nitriles or cyanohydrin-stabilized carbanions under thermodynamics conditions provide the high meta -selectivity, regardless of the conformation of the Cr(CO) 3 moiety.

Kinetic resolution of hydroxymethyl-substituted (arene)Cr(CO)3 and (diene)Fe(CO)3 by lipase

Abstract A kinetic resolution of (η 6 -arene)chromium complexes and (η 4 -diene)iron complexes by lipase has been developed. Racemic tricarbonyl( o -substituted benzylalcohol)chromium complexes were kinetically resolved to give (1 R )-alcohol complexes and the corresponding (1 S )-acetate complexes, respectively, in high yield and enantioselectivity by transesterification with isopropenyl acetate in the presence of Amano PS or Amano AK. On the other hand, Amano AY recognizes the antipode (1 R )-alcohol complex. Similarly, hydroxymethyl substituted tricarbonyl(2,4-diene)iron complexes produced optically active alcohol and acetate complexes with high enantioselectivity by lipase catalyzed transacetylation.

Synthesis and structure of Cr(CO)3 complexes of biphenyl compounds with axial chirality

Abstract Chromium complexation of a 2,6,2′-trisubstituted biphenyl compound gave four mono-Cr(CO) 3 and one di-Cr(CO) 3 complexation products in a variable ratio depending on the reaction conditions. However, cross-coupling of (2,6- disubstituted-1-bromobenzene)Cr(CO) 3 with 2-substituted phenylboronic acid catalyzed by palladium(0) produced a stereoselectively coupled product without the formation of the axial isomer. The crystal structures of these chromium complexes were determined by X-ray crystallography.

Kinetic resolution of hydroxymethyl substituted (diene)Fe(CO)3 complexes by lipase

Kinetic resolution of hydroxymethyl substituted (diene)Fe(CO)3 complexes using a lipase in the presence of isopropenyl acetate proceeds with high efficiency and enantioselectivity.

Synthesis of (±)-dihydroxyserrulatic acid via (arene)chromium complexes

Abstract The title compound has been synthesized with high selectivity by utilizing some characteristic properties of (arene)chromium complexes.

(η6-Arene)chromium complexes in organic synthesis: [2,3]-Wittig rearrangement of (benzyl crotyl ether)chromium complexes

Abstract The [2,3]-Wittig sigmatropic rearrangement of (benzyl ( E )-crotyl ether)chromium complexes is shown to give a syn stereoselection which is different from the anti selection reported for the corresponding chromium-free compounds.