Tsutomu Katsuki

Catalytic asymmetric oxidations using optically active (salen)manganese(III) complexes as catalysts

Abstract This review deals with enantioselective one oxygen atom transfer reactions (epoxidation, oxidation of enolates, and oxidation of sulphide to sulphoxides) catlaysed by optically active (salen)manganese(III)complexes. Asymmetric aziridination is also discussed briefly.

Mn-salen catalyst, competitor of enzymes, for asymmetric epoxidation

Asymmetric epoxidation of simple olefins using (salen)manganese(III) complexes as catalysts has made a great advances in the last half decade and now finds wide application in organic synthesis. In this article, we describe the scope of the reaction, and the principal achievements to date are presented in Tables. The mechanistic aspect of the reaction is also discussed briefly.

Chiral Metallosalen Complexes: Structures and Catalyst Tuning for Asymmetric Epoxidation and Cyclopropanation

Optically active metallosalens are currently one of the most widely used catalysts for asymmetric synthesis. This is mainly due to the following reasons: various salen [N,N′-ethylenebis(salicyldeneaminato)] ligands form complexes with many metal ions and the resulting metallosalens adopt versatile structures, therefore, metallosalens show a variety of catalytic performances. Thus, selection of a metal ion serving the aimed reaction and regulation of ligand conformation to be suitable for the reaction are indispensable for achieving metallosalen-catalyzed asymmetric reactions. Recently, several factors controlling ligand-conformation in metallosalens have been clarified. This article provides selected examples of tuning the structures of metallosalens in compliance to the aimed reaction, by taking asymmetric oxene or carbene transfer reaction as the instance.

Stereo and regioselective openings of chiral 2,3-epoxy alcohols. Versatile routes to optically pure natural products and drugs. Unusual kinetic resolutions

A diverse selection of new synthetic applications of the titaniumcatalyzed asymmetric epoxidation (AE) process is described. These include asymmetric syntheses of (+)_DarvonR Alcohol, (-)-bestatin, (+)-2-methyl bestatin, (-)-propranolol, (-)-u-amino--hydroxybutyric acid, and (_) and (+)_frontalin. The kinetic resolution mode of the AE process was used to prepare chiral insect pheromones in very high (>99% e.e.) optical purity; these include (+)-and (-)-ct-caprolactone, (-)-exobrevicomin, (-)-endobrevicomin, (+)_and (-)-ipsdienol, and (+)-trans-verbenol. A number of unusual kinetic resolutions based on the AE process are presented; these include resolutions of allenic alcohols, n-acetylenic carbinols, -hydroxy sulfides, and a dienol. Almost two years ago we first reported on the titanium-catalyzed asymmetric epoxidation process shown in Scheme 11a In the interim this new chiral catalyst system has rapidly become accepted as one of the best means for synthesizing a great variety of optically pure

Rational design of Mn-salen catalyst (2): Highly enantioselective epoxidation of conjugated cis olefins

Abstract On the basis of the newly proposed hypothesis on the mechanism of asymmetric induction, highly efficient (salen)manganese(III) complex (3) was constructed as a catalyst for asymmetric epoxidation. With this catalyst, the highest level of enantioselectivity was realized in the epoxidation of various conjugated cis-olefins.

Catalytic asymmetric epoxidation of unfunctionalized olefins using chiral (salen)manganese(III) complexes

Abstract Several kinds of chiral (salen)manganese(III) complexes ( 2 and 3 ) having chiral salicylaldehyde and chiral ethylenediamine moieties were prepared and used for catalytic asymmetric epoxidation of unfunctionalized olefins with iodosobenzene as a terminal oxidant. Catalysts 2 and 3 were found to show the characteristic substrate specificity for the enantiofacial selection of olefins, respectively. Furthermore, the addition of donor ligands such as pyridine N -oxide or 2-methylimidazole to the epoxidation reaction system was found to alter the enantioselectivity. As a result, the highest enantioselectivity for nonenzaymatic catalytic epoxidation was achieved for ( E )-1-phenylpropene (56% ee, with 2c in the presence of 2-methylimidazole), ( E )-stilbene (48% ee, with 3a ), and dihydronaphthalene (83% ee, with 3a in the presence of pyridine N -oxide).

Iron-catalyzed asymmetric aerobic oxidation: oxidative coupling of 2-naphthols.

Fe(salan) complexes were found to be efficient catalysts for the asymmetric aerobic oxidative coupling of 2-naphthol derivatives. This reaction can be carried out in air at 60 degrees C with high enantioselectivity up to 97% ee. This is the first report for asymmetric aerobic oxidation using molecular oxygen in air in the absence of additives.

Enantioenriched Synthesis of C1-Symmetric BINOLs: Iron-Catalyzed Cross-Coupling of 2-Naphthols and Some Mechanistic Insight

Highly enantioselective aerobic oxidative cross-coupling of 2-naphthols with broad substrate scope was achieved using an iron(salan) complex as the catalyst. Enantiomeric excesses of the products ranged from 87 to 95%. The scope of the cross-coupling reaction was found to be different from that of the homocoupling reaction under the same reaction conditions.

Ti(salen)-catalyzed enantioselective sulfoxidation using hydrogen peroxide as a terminal oxidant

(R,R)-Di-μ-oxo Ti(salen) 4 was found to serve as an efficient catalyst for asymmetric oxidation of various sulfides with hydrogen peroxide. For example, oxidation of methyl phenyl sulfide by using 4 as the catalyst in the presence of a urea·H2O2 adduct showed high enantioselectivity of 94% ee. The high enantioselectivity of this reaction was considered to be related to the cis-β-structure of a monomeric Ti(salen) species generated from 4 in a methanol–hydrogen peroxide solution.

Enantioselective epoxidation of unfunctionalized olefins using chiral (salen)manganese(III) complexes

Abstract Chiral (salen)manganese(III) complexes ( 3 and 4 ) were prepared and used for the enantioselective epoxidation of unfunctionalized olfefins. The highest enantioselectivity of 48% ee for the catalytic epoxidation of (E)-stilbene was realized by using 3 as a catalyst though much lower enantioselectivity (7% ee) was obtained for that of (E)-1-phenyl-1-propene. In the epoxidation of (Z)-olefins, enantioselectivities were in the range of 68–72% ee by using 3 as a catalyst and 60% ee by using 4 .