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Yoshie Tanaka

Publications and source records attributed to Yoshie Tanaka.

7 recordsLinked to original sources
PubMed2006

Double helix-to-double helix transformation, using platinum(II) acetylide complexes as surrogate linkers.

We describe novel optically active double helices consisting of complementary strands stabilized by amidinium-carboxylate salt bridges. The m-terphenyl groups of each strand are joined by trans-Pt(II) acetylide complexes with pendant PPh(3) ligands as the surrogate linker, which converts to cis counterparts by a ligand exchange reaction with cis-1,2-bis(diphenylphosphino)ethylene, resulting in the formation of double helices with different structures. Subsequent iodine-promoted reductive elimination on the Pt(II) atoms generates the fully organic, enantiomerically pure double helices. [structure: see text]

Journal Article↗
PubMed2006

Construction of double-stranded metallosupramolecular polymers with a controlled helicity by combination of salt bridges and metal coordination.

We describe the construction of the first double-stranded metallosupramolecular helical polymers. We designed and synthesized a supramolecular duplex comprised of complementary m-terphenyl-based strands bearing a chiral amidine or achiral carboxylic acid together with two pyridine groups at the four ends. Supramolecular polymerization of the duplex with cis-PtPh2(DMSO)2 in 1,1,2,2-tetrachloroethane produced the double-stranded metallosupramolecular polymer with a controlled helicity of which the two complementary metallostrands are intertwined through the amidinium-carboxylate salt bridges. The structures and hydrodynamic dimensions of the metallosupramolecular polymers were characterized by 1H NMR, diffusion-ordered NMR, dynamic light scattering, absorption, and CD measurements. The polymeric structure was also visualized by atomic force microscopy.

Chemistry, Organic↗
PubMed2004

Stereoselective synthesis of atropisomeric korupensamines A and B utilizing planar chiral arene chromium complex.

Naphthyl tetrahydroisoquinoline alkaloids, atropisomeric korupensamines A and B and ent-korupensamine B, were synthesized by syn-selective cross-coupling of a planar chiral arene chromium complex with naphthylboronic acid and subsequent axial isomerization or tricarbonylchromium migration to the inverted arene face as a key step. Palladium(0)-catalyzed cross-coupling of planar chiral arene chromium complex 12 with naphthylboronic acid 9 gave syn-biaryl coupling product 13. syn-Biaryl chromium complex 13 was heated in 1:1 mixture of di-n-butyl ether and 1,2-dichloroethane to give a face-inverted anti-biaryl chromium complex 14 without axial isomerization. Korupensamine A was synthesized from the syn-biaryl chromium complex 13 via o-formyl syn-biaryl chromium complex 10, and ent-korupensamine B was prepared from the face-inverted anti-biaryl chromium complex 14. On the other hand, difluoro-substituted syn-biaryl chromium complex 40 with a formyl group afforded anti-biaryl chromium complex 41 containing a rotated central bond by heating in xylene. The chromium-complexed fluorine atom was easily substituted with an isopropoxy group by nucleophilic substitution. Use of these reactions allowed (+)-2-bromo-3,5-difluorobenzaldehyde chromium complex (37) as a single chiral source to be converted to atropisomeric korupensamines A and B, respectively.

Chromium Compounds↗
PubMed2003

Asymmetric synthesis of axially chiral biaryls: inversion of planar chirality vs axial isomerization and functionalization at the side chain of biaryl chromium complexes.

Axially chiral syn-biaryl chromium complexes having a coordinating heteroatom substituent at the benzylic position gave anti-biaryl chromium complexes 5 with inversion of the planar chirality by heating in a nonaromatic solvent, while syn-biaryl chromium complexes with an o-methyl or formyl substituent afforded axially isomerized anti-biaryl chromium complexes under heating in an aromatic solvent. syn-biaryl and both enantiomeric anti-biaryl chromium complexes with the o-formyl group were stereoselectively prepared from an identical planar chiral arene chromium complex as chiral source. The formyl group of the axially chiral chromium complexes was functionalized by radical cyclization and beta-lactam formation, and hetero-Diels-Alder reaction.

Journal Article↗
PubMed2002

Asymmetric synthesis of anti- and syn-beta-amino alcohols by reductive cross-coupling of transition metal-coordinated planar chiral arylaldehydes with aldimines.

Samarium iodide-mediated cross-coupling of N-tosyl ferrocenylideneamine with planar chiral ferrocenecarboxaldehydes or benzaldehyde chromium complexes gave diastereoselectively the corresponding anti-beta-amino alcohol derivatives in good yields, while N-tosyl benzylideneamine produced syn-beta-amino alcohols by coupling with planar chiral arylaldehydes. Dynamic kinetic resolution of a configurationally equilibrated reactive species generated from achiral N-tosyl ferrocenilideneamine and benzylideneamine by reduction with samarium iodide was observed in the cross-coupling with planar chiral arylaldehydes giving both antipodes of beta-amino alcohols depending on the planar chirality. The obtained anti-beta-amino alcohol with the ferrocene ring was utilized as a chiral ligand for catalytic asymmetric reduction of acetophenone.

Journal Article↗
PubMed2002

Asymmetric synthesis of beta-amino alcohols by reductive cross-coupling of benzylideneamine with planar chiral benzaldehydes.

[reaction: see text] Samarium iodide mediated reductive cross-coupling of N-tosyl benzylideneamine with benzaldehydes or the corresponding chromium complexes gave syn-beta-amino alcohol derivatives. A dynamic kinetic resolution of a configurationally equilibrated reactive species occurred in the cross-coupling with planar chiral benzaldehyde chromium complexes.

Amines↗