Yoshiji Takemoto

Palladium-catalyzed cascade process consisting of isocyanide insertion and benzylic C(sp3)-H activation: concise synthesis of indole derivatives.

Synthesis of the indole skeleton was achieved using a Pd-catalyzed cascade process consisting of isocyanide insertion and benzylic C(sp(3))-H activation. It was found that slow addition of isocyanide is effective for reducing the amount of catalyst needed and Ad(2)P(n)Bu is a good ligand for C(sp(3))-H activation. The construction of the tetracyclic carbazole skeleton was also achieved by a Pd-catalyzed domino reaction incorporating alkyne insertion.

Enantioselective Synthesis of 3,3-Disubstituted Oxindoles through Pd-Catalyzed Cyanoamidation

The first enantioselective cyanoamidation of olefins provides quick access to a variety of 3,3-disubstituted oxindoles. The combination of Pd(dba)2, an optically active phosphoramidite, and N, N-dimethylpropylene urea (DMPU) in decalin were found to be the best conditions.

Gold(I)-Catalyzed Polycyclizations of Polyenyne-Type Anilines Based on Hydroamination and Consecutive Hydroarylation Cascade

A hydroamination-double hydroarylation cascade using aniline derivatives bearing a trienyne moiety as the substrate was efficiently promoted by a gold(I) catalyst to produce benzo[a]naphtho[2,1-c]carbazole derivatives in good yields. This reaction is applicable to various substituted trienyne-type anilines, including 2,3-diethynylthiophene derivatives. The reaction of anilines bearing a tetraenyne and pentaenyne moiety allows direct construction of highly fused carbazoles by tetra- and pentacyclization, respectively, through hydroamination and consecutive hydroarylation without producing any theoretical waste products from the substrates.

Bifunctional hydrogen-bond donors that bear a quinazoline or benzothiadiazine skeleton for asymmetric organocatalysis.

Hydrogen-bond (HB)-donor catalysts that bear a 2-aminoquinazolin-4-(1H)-one or a 3-aminobenzothiadiazine-1,1-dioxide skeleton have been developed, and it has been shown that these catalyst motifs act similarly to other HB-donor catalysts such as thioureas. The highly enantioselective hydrazination of 1,3-dicarbonyl compounds was realized even at room temperature with up to 96% ee for 2-aminoquinazolin-4-(1H)-one-type catalysts, which were more effective than the corresponding urea and thiourea catalysts. In addition, benzothiadiazine-1,1-dioxide-type catalysts were shown to promote the isomerization of alkynoates to allenoates with high enantioselectivity. To overcome the problem that the products were obtained as mixtures with the starting alkynoates, we developed the tandem isomerization and cycloaddition of alkynoates for the synthesis of advanced chiral compounds such as bicyclo[2.2.1]heptenes and 3-alkylidene pyrrolidine without a significant loss of enantioselectivity.

Auto-Tandem Catalysis in the Synthesis of Substituted Quinolines from Aldimines and Electron-Rich Olefins: Cascade Povarov−Hydrogen-Transfer Reaction

We demonstrated a catalytic cascade inverse electron demand hetero-Diels-Alder reaction (Povarov reaction) and hydrogen-transfer process. The reaction of electron-rich olefins and excess amount of imines in the presence of acid catalysts under appropriate conditions affords substituted quinolines in a single operation. In the cascade process, the catalysts, such as Tf2NH, TfOH, and Lewis acids, catalyze two mechanistically distinct reactions (auto-tandem catalysis). We also describe the synthetic utility of the prepared quinolines.

NHC-catalyzed thioesterification of aldehydes by external redox activation

The NHC-catalyzed thioesterification of aromatic or aliphatic aldehydes with a range of thiols was developed in the presence of a stoichiometric amount of an organic oxidant. Among the oxidants examined, phenazine was shown to give the best results in terms of chemical yield and compatibility with thiols.

Gold(I)-Catalyzed Tandem Reactions Initiated by Hydroamination of Alkynyl Carbamates: Application to the Synthesis of Nitidine

As a convenient and direct synthesis of 1,2-dihydroisoquinolines, the gold(I)-catalyzed intramolecular hydroamination of (2-alkynyl)benzyl carbamates has been developed. The reaction with cationic gold(I) complex [AuCl(PPh(3))/AgNTf(2)] proceeded at room temperature, giving the desired 6-endo adducts. The addition of alcohol efficiently promoted the reaction, and the amount of the catalyst could be reduced to 1 mol %. However, the alkynes bearing either an electron-deficient aryl group or an alkyl group resulted in predominant production of 5-exo adducts. In such cases, use of a bulky gold catalyst, AuCl[(o-biPh)((t)Bu)(2)P]Cl/AgNTf(2), improved the regioselectivity, giving the 6-endo adducts in better yields. Furthermore, the hydroamination of alkynyl carbamates bearing an acetal or enone was successfully applied to the concise synthesis of tetracyclic heterocycles such as nitidine via the single catalyst-mediated tandem cyclization which consists of a condensation or a Michael addition of the resulting enecarbamates.

A novel synthesis of the (2R,3S)- and (2S3R)-3-amino-2-hydroxycarboxylic acid derivatives, the key components of a renin inhibitor and bestatin, from methyl (R)- and (S-mandelate

Abstract The title synthesis could be accomplished by featuring the [2+2]-cycloaddition reaction of a chiral imine with benzyloxyketene, alcoholysis of the formed 2-azetidinone derivative, and reductive removal of the mandelate-derived benzylic oxygen by way of a 2-oxazolidone derivative.

Palladium‐Catalyzed Amidation by Chemoselective C(sp3)H Activation: Concise Route to Oxindoles Using a Carbamoyl Chloride Precursor

Quite select: a new strategy was developed for the synthesis of various oxindoles from carbamoyl chlorides. Under the optimum reaction conditions, with Ad(2)PBu as a ligand, tBuCONHOH as an additive, and a CO atmosphere, selective C(sp(3))-H activation proceeded in the presence of a C(sp(2))-H bond. Ad=adamantyl.

Indium(III)-Catalyzed Tandem Reaction with Alkynylbenzaldehydes and Alkynylanilines to Heteroaromatic Compounds

Starting from ortho-alkynylbenzaldehydes and ortho-alkynylanilines, In(OTf)3-catalyzed synthesis of ring-condensed heteroaromatic compounds was developed via a domino intramolecular nucleophilic attack/intermolecular cycloaddition/dehydration reaction.