Ken Tanaka

Our research group was the first to discover that cationic rhodium(I)/BINAP-type bisphosphine complexes are versatile new catalysts for highly chemo-, regio-, and enantioselective [2+2+2] cycloadditions. The high chemo- and regioselectivity of these ­cycloadditions enabled efficient catalytic synthesis of substituted benzenes, cyclophanes, and nitrogen heterocycles. Furthermore, enantioselective variants of these cycloadditions were also developed that realized efficient catalytic constructions

We have developed a rhodium-catalyzed enantioselective intermolecular [2+2+2] cycloaddition of 1,6-diynes with trimethylsilylynamides for the synthesis of axially chiral anilides. The axial chirality is constructed at the formation of benzene rings with high enantioselectivity (up to 98% ee). It should be noted that the present reaction employs the readily prepared trimethylsilylynamides starting from commercially available bis(trimethysilyl)acetylene and the trimethylsilyl group of the product

Three become one: The cationic rhodium(I) complex [Rh(cod)2]BF4 catalyzes the [2+2+1] cross-cyclotrimerization of silylacetylenes and two alkynyl esters, leading to substituted silylfulvenes (see scheme; cod=1,5-cyclooctadiene). The reductive complexation of the silylfulvene product with RhCl3 in EtOH furnished the corresponding dinuclear electron-deficient cyclopentadienyl rhodium(III) complex.

We have developed highly enantioselective synthesis of functionalized helically chiral molecules via a Rh-catalyzed [2 + 2 + 2] cycloaddition and synthesis of ladder-type molecules via an unprecedented Rh-catalyzed formal [2 + 1 + 2 + 1] cycloaddition involving C−C triple bond cleavage.

A Rh(I)/(R)-Tol-BINAP catalyst reacts with a racemic mixture of 4-alkynals to selectively furnish a cyclobutanone from the (R)-substrate and a cyclopentenone from the (S)-substrate. This method is noteworthy from several standpoints, including the scarcity of parallel kinetic resolutions (especially those that are catalyzed or that involve carbon-carbon bond formation) and the dearth of catalytic processes that generate enantioenriched cyclobutanones.

[reaction: see text] Cationic rhodium(I)/modified BINAP complexes are effective catalysts for highly regioselective intermolecular cyclotrimerization of terminal alkynes and highly chemo- and regioselective intermolecular cocyclotrimerization of diethyl acetylenedicarboxylate (DEAD) and terminal alkynes. It is a noteworthy example of intermolecular cocyclotrimerization of two different alkynes in terms of catalytic activity, chemo- and regioselectivity, scope of substrates, and ease of operation

A belt-shaped [8]cycloparaphenylene (CPP) and an enantioenriched Möbius-shaped [10]CPP have been synthesized by high-yielding rhodium-catalyzed intramolecular cyclotrimerizations of a cyclic dodecayne and a pentadecayne, respectively. This Möbius-shaped [10]CPP possesses stable chirality and isolated with high enantiomeric purity. It is evident from the reaction Gibbs energy calculation that the above irreversible cyclotrimerizations are highly exothermic; therefore establishing that the intramo

Planar chiral zigzag-type [8]- and [12]cyclophenylene (CP) belts have been synthesized in good yields with high ee values of 98% and 83%, respectively, by the rhodium-catalyzed enantioselective intramolecular sequential cyclotrimerizations of the corresponding cyclic polyynes. The observed high enantioselectivity arises from the regioselective formation of a rhodacycle intermediate from an unsymmetric triyne unit. The X-ray crystal structural analysis of the racemic planar chiral zigzag-type [8]

The oxidative olefination of sp(2) C-H bonds of anilides with both activated and unactivated alkenes using an (electron-deficient η(5) -cyclopentadienyl)rhodium(III) complex is reported. In contrast to reactions using this electron-deficient rhodium(III) catalyst, [Cp*RhCl2 ]2 showed no activity against olefination with unactivated alkenes. In addition, the deuterium kinetic isotope effect (DKIE) study revealed that the C-H bond cleavage step is thought to be the turnover-limiting step.

Two quaternary carbon centers are created in the title reaction to form fused dihydropyrans (see scheme). The same catalyst promotes the ortho functionalization of aryl ketones with 1,6-enynes with excellent regio- and enantioselectivity. Z=amide, C(CO2Me)2, O; E=CO2Et, Ac; R1=Me, aryl, CO2Me; R2=Me; R3=Me, CO2Et. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2008/z704758_s.pdf or from the author. Please note: The publisher is not

Enantioenriched N-aryl-2-pyridones with axially chiral C-N bonds were prepared by a cationic rhodium(I)-BINAP or tol-BINAP-catalyzed enantioselective [2+2+2] cycloaddition of alkynes with ortho-substituted phenyl isocyanates.

Put a ring on it: A cationic rhodium(I)/binap complex catalyzes the intramolecular cyclization reactions of naphthol- or phenol-linked 1,6-enynes to produce vinylnaphtho- or vinylbenzofurans and vinylnaphtho- or vinylbenzopyrans through the cleavage and formation of sp2 CO bonds. Mechanistic studies imply that the present cyclization reactions proceed through β-oxygen elimination from cationic rhodacycle intermediates.

Dibenzo[7]helicenes were synthesized with up to 99 % ee by rhodium(I)/binap-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of 2-phenylnaphthalene-linked triynes. Additionally, [2+1+2+1] cycloaddition products, that is, twisted anthracenes, were also synthesized by using difluorphos as ligand. Although these compounds are not configurationally stable at elevated temperature, their Scholl reactions afforded configurationally stable double dibenzo[6]helicenes. The thus-obtained dib

Abstract An S‐shaped double helicene‐like molecule (>99 % ee ), possessing stable helical chirality, has been synthesized by the rhodium(I)/difluorphos complex‐catalyzed highly diastereo‐ and enantioselective intramolecular double [2+2+2] cycloaddition of a 2‐naphthol‐ and benzene‐linked hexayne. The collision between two terminal naphthalene rings destabilizes the helical chirality of the S‐shaped double helicene‐like molecule, but the introduction of two additional fused benzene rings signi

Planar chiral carbon nanorings and nanobelts (CNRs and CNBs), the sidewall segment molecules of chiral-type carbon nanotubes (CNTs), have attracted attention owing to their characteristic chiroptical properties. From the appropriate CNTs, axially or planar chiral CNRs and CNBs have been designed and synthesized, but multiply helical sidewall segments were almost unexplored due to the difficulty in simultaneous control of multiple chiralities. In this article, we have succeeded in the perfectly d