Takeshi Hanamoto

Asymmetric [2,3]wittig rearrangement of 2′-alkenyloxyacetamide bearing trans-2,5-bis(methoxymethoxymethyl)pyrrolidine moiety as a chiral auxiliary

[2,3]Wittig rearrangement of (2S,5S)-N-(alkenyloxyacetyl)-2,5-bis- (methoxymethoxymethyl)pyrrolidine enolate was studied and zirconium enolates of the corresponding (E)-alkenyloxyacetyl compounds were found to rearrange with high syn-diastereo and diastereoface selection.

Highly enantioselective homogeneous catalysis of chiral rare earth phosphates in the hetero-Diels–Alder reaction

Abstract Two types of novel rare earth (RE) complexes were synthesized and used as a chiral Lewis acid catalyst for the hetero-Diels–Alder reaction of carbonyl compounds with the Danishefskys diene under homogeneous conditions. The Y[( R )-H 8 -BNP] 3 ( 3 -Y )-catalyzed reaction of aromatic aldehydes and the Yb[( R )-BNP] 3 ( 1 -Yb )-catalyzed reaction of phenylglyoxylates afforded the corresponding cycloadducts with excellent optical purities (up to 99% ee) in high yields at room temperature. The successful recycling uses of the scandium catalyst ( 3 -Sc ) are also described.

Asymmetric dialkylation of α-cyanoacetic acid

Abstract Formation of the quarternary asymmetric center by double alkylation of cyanoacetamide enolate bearing trans -2,5-bis(methoxymethoxymethyl)pyrrolidine moiety as a chiral auxiliary, was carried out with high diastereoselectivity.

Diastereo- and enantioselective hydrodimerization of β-monosubstituted acrylic acid amides induced by chiral samarium(II) complexes

Abstract The chiral samarium(II) complex prepared from SmI2, (R)-BINOL, and an achiral tertiary amine promoted the reductive homo-coupling reaction of β-monosubstituted acrylic acid amides to give the corresponding 3,4-trans-disubstituted adipamides with high enantioselectivities (up to 85% ee).

Palladium(0)-catalyzed reaction of propargylic phosphates with SmI2: A highly regioselective route to the synthesis of allenes and acetylenes

Abstract A highly regioselective reaction of propargylic phosphates has been established by using SmI 2 and a Pd(0) catalyst to give allenes and acetylenes in high isolated yields depending on the substrate used.

Regiodivergent reduction of allylic esters with samarium(II) iodide by tuning ester groups and proton sources

Abstract Samarium(II) iodide reduced allylic esters in the presence or the absence of palladium(0) catalyst to give α- and γ-protonated products in a regiodivergent fashion by tuning ester functionality and proton sources.

Construction of four consecutive asymmetric centers I. Anti- and syn- selective epoxydation of β-methyl-cis-homoallylic alcohols

Abstract All the diastereomers of 2,3- cis -epoxy-4-methyl-5-decanol and of 8,9- cis -epoxy-7-methyl-6-tridecanol were stereoselectively synthesized as key intermediates in a model approach toward the stereoselective construction of four consecutive asymmetric centers.

Stereoselectivity in [2,3]wittig rearrangement of isopropyl [(2E)-1 -(ω-benzyloxyalkyl)-2-butenyl]oxyacetate. Preparation of potent building blocks for the synthesis of polyoxo compounds

Abstract The stereochemistry of [2,3]Wittig rearrangement of isopropyl [(2 E )-1-(ω-benzyloxyalkyl)-2-butenyl]oxyacetates was found to depend on the position of benzyloxy group and the metal ion used, and in some suitable combinations, ( syn , E )- or ( syn , Z )-product was obtained with high selectivity.

Construction of four consecutive asymmetric centers II. Regioselectiveepoxide-ring opening of γ,δ-cis-epoxy-β-methyl alcohols by alkylation

Abstract The regioselective epoxide-ring opening of diastereomeric cis -epoxy alcohol intermediates by higher order mixed cuprates mostly in the presence of tributylphosphine led to all eight possible diastereomers of a model compound of four consecutive asymmetric centers.

Cleavage of t-butyldimethylsilyl ether with t-butyl hydroperoxide and dioxobis(2,4-pentanedionato)molybdenum(vi) system

A combination of t-butyl hydroperoxide (TBHP) and MoO2(acac)2 which is a mild epoxidation system, was found to be also effective for the cleavage of t-butyldimethylsilyl (TBDMS) ethers.