Ryo Irie

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).

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 .

Catalytic asymmetric and chemoselective aerobic oxidation: kinetic resolution of sec-alcohols

Optically active (nitroso)(salen)ruthenium(II) chloride (2) was found to be an efficient catalyst for aerobic oxidation of racemic secondary alcohols under irradiation with a halogen or fluorescent lamp, which proceeded with good enantiomer-differentiation (krel=11–20). Furthermore, no epoxidation was observed in the oxidation of racemic 4-phenyl-3-buten-2-ol.

Rational design of Mn-Salen epoxidation catalysts: Preliminary results

Abstract (Salen)manganese(III) complex 7 designed on the basis of the new proposal on the olefins access to metal-oxo bond and complex 10 having axial chirality in salicylaldehyde part were found to be effective catalysts for the epoxidation of unfunctionalized olefins, especially for cis-olefins.

Catalytic asymmetric oxidation of sulfides using (salen)manganese(III) complex as a catalyst

Abstract Asymmetric oxidation of sulfides was examined by using (salen)manganese(III) complexes as catalysts and (8S,8′S,1″S,2″S)-complex

Co(II)-salen-catalyzed highly cis- and enantioselective cyclopropanation

Abstract The reactions of styrene derivatives and t-butyl α-diazoacetate using (R,R)-(salen)cobalt(II) complex 6 as a catalyst in the presence of N-methylimidazole gave the corresponding cyclopropanecarboxylates with excellent enantio- (>95% ee) and high cis-stereoselectivity (98%) as well as good chemical yields.

Highly enantioselective benzylic hydroxylation with concave type of (salen)manganese(III) complex

Abstract Newly-designed optically active (salen)manganese(III) complexes (5) catalyze highly enantioselective benzylic hydroxylation and moderate level of enantiomer-differentiating oxidation (kinetic resolution) of the resulting benzylic alcohols. Thus, the enantiomeric excess of hydroxylation product was increased through kinetic resolution, as the reaction time was prolonged. For example, enantiomeric excess of 3,3-dimethylindan-1-ol, the hydroxylation product of 1,1-dimethylindan using 5a as a catalyst in chlorobenzene, was 84% after 10 min and 90% after 20 h.

Highly Enantioselective Cyclopropanation with Co(II)-Salen Complexes: Control of cis- and trans-Selectivity by Rational Ligand-Design

Cyclopropanation of styrene derivatives with alkyl α-diazoacetate in the presence of the second-generation (salen)cobalt(II) complex 6 proceeded with excellent cis- and enantioselectivity. On the other hand, the cyclopropanation in the presence of complex 14 which was designed on the basis of the mechanism of asymmetric induction by complex 6 showed good trans- and excellent enantioselectivity.

Chemoselective aerobic oxidation of primary alcohols catalyzed by a ruthenium complex

Abstract In the presence of secondary alcohols, primary alcohols are selectively oxidized to aldehydes under aerobic conditions by using a (nitrosyl)Ru(salen) complex as catalyst.