Hiroshi Furuno

Chiral rare earth metal complex-catalyzed conjugate addition of O-alkylhydroxylamines. An efficient synthetic entry into optically active 2-acyl aziridines

The conjugate addition of O-alkylhydroxylamines to α,β-unsaturated ketones is effectively catalyzed by chiral rare earth metal complexes to afford the corresponding β-amino ketones with high enantioselectivities (up to 99% ee) in almost quantitative yields, which are, upon treatment with a base catalyst, quantitatively converted into the 2-acyl aziridines without losing their enantiopurities. The protocol is highly practical thus providing an easy access to enantiopure 2-acyl aziridines and their derivatives in good quantities.

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.

Catalytic conversion of conjugated enones into optically active α-keto aziridines using chiral rare earth metal complexes

Optically active N -unsubstituted α-keto aziridines 2 were synthesized from conjugated enones 1 via the Sc[( R )-BNP] 3 -catalyzed enantioselective Michael addition of O -methylhydroxylamine followed by the La(O- i -Pr) 3 -catalyzed ring closure of the corresponding β-methoxyamino ketones 3 . A remarkably high asymmetric amplification was observed during the Michael addition, and notable kinetic resolution was also realized during the ring closure reaction when a La(O- i -Pr) 3 –( R )-BINOL catalyst system was employed.

AgSbF6-promoted cycloaddition reaction of 2-trifluoromethyl-N-tosylaziridine with aldehydes.

2-Trifluoromethyl-N-tosylaziridine reacted with various aldehydes in the presence of a catalytic amount of AgSbF(6) to provide the corresponding cis-4-trifluoromethyl-2-substituted-N-tosyl-1,3-oxazolidines with excellent regio- and stereoselectivity.

Remarkable effect of tris(4-fluorophenyl)phosphine oxide on the stabilization of chiral lanthanum complex catalysts. A new and practical protocol for the highly enantioselective epoxidation of conjugated enones

A new and efficient chiral catalyst system, lanthanum-chiral BINOL-tris(4-fluorophenyl)phosphine oxide-cumene hydroperoxide, was developed for the epoxidation of alpha, beta-unsaturated ketones thus providing the corresponding epoxy ketones with excellent enantioselectivities (up to >99% ee) in good to excellent yields at room temperature.

Asymmetric double aldol reaction of chiral acetyloxazolidinone

Abstract Treatment of chiral oxazolidinone with Bu 2 BOTf (2.5 equiv.) and Et 3 N (3.0 equiv.) quantitatively produced the doubly borylated enolate, which afforded the double aldol products with high diastereoselectivity after reaction with aldehydes.

Reaction of N-methyl-5-tributylstannyl-4-fluoro-1H-pyrazole and its application to N-methyl-chromeno[2,3-d]pyrazol-9-one synthesis

N-Methylation by sequential treatment of 5-tributylstannyl-4-fluoro-1H-pyrazole 1 with LDA and iodomethane regioselectively afforded the compound 2a in high yield. The addition reaction of 5-lithiated-4-fluoro-1H-pyrazole generated from 2a with a wide range of electrophiles allowed a facile introduction of different substituents at position 5 in good yields. The adduct 3d was efficiently converted to N-methyl-chromeno[2,3-d]pyrazol-9-one 9 in 3 steps.

Silica Gel-Mediated Organic Reactions under Organic Solvent-Free Conditions

Silica gel was found to be an excellent medium for some useful organic transformations under organic solvent-free conditions, such as (1) the Friedel-Crafts-type nitration of arenes using commercial aqueous 69% nitric acid alone at room temperature, (2) one-pot Wittig-type olefination of aldehydes with activated organic halides in the presence of tributyl- or triphenylphosphine and Hunig’s base, and (3) the Morita-Baylis-Hillman reaction of aldehydes with methyl acrylate. After the reactions, the desired products were easily obtained in good to excellent yields through simple manipulation.

Hetero-Diels-Alder Reaction Catalyzed by Self-organized Polymeric Rare Earth Complexes under Solvent-free Conditions

2-Substituted 2,3-dihydropyran-4-one derivatives were conveniently synthesized under solvent-free conditions by Lewis acid-catalysis with a polymeric scandium sulfonate complex, which can be prepared in a self-organized manner in one step and successfully reused for the next round of reactions.

Secondary metabolites with antiproliferative effects from Albizia glaberrima var glabrescens Oliv. (Mimosoideae)

Abstract A new 5-dehydroxyflavan, namely Albiziaflavan B or (+)-(2R, 3S, 4R)-3′,4′, 7-trihydroxy-4-methoxy-2,3-trans-flavan-3,4-trans-diol (1) was isolated from the root bark of Albizia glaberrima, together with six known compounds including three flavans: (+)-mollisacacidin (2), (+)-fustin (3) and butin (4); two steroids: chondrillasterol (5) and chondrillasterone (6), and a triterpenoid: lupeol (7). The structure of 1 was established by detailed analysis of its spectroscopic data, especially 1D and 2D NMR spectra, HRESIMS and CD data. Compounds 1–6 were assayed for their antiproliferative effects on two human cancer cells, HeLa at 50 μM (n = 2) and HL60 at 20 μM (n = 2). Compound 3 and 4 were the most active on HL60 with IC50 of 8.1 and 8.3 μM, respectively. Compound 6 was the most active with an IC50 of 4.6 μM on HeLa.