Motoi Kawatsura

Enantioselective Allylic Amination of Trifluoromethyl Group Substituted Racemic and Unsymmetrical 1,3-Disubstituted Allylic Esters by Palladium Catalysts

The palladium-catalyzed regio- and enantioselective allylic amination of trifluoromethyl group substituted racemic and unsymmetrical 1,3-disubstituted allylic esters has been accomplished. The enantioselective formation of the α-type allylic amines was attained by the dynamic kinetic asymmetric transformation (DYKAT).

Ruthenium-Catalyzed Regio- and Enantioselective Allylic Amination of Racemic 1-Arylallyl Esters

The regio- and enantioselective allylic amination of racemic monosubstituted allylic esters, such as 1-arylallyl acetates, with cyclic secondary amines has been accomplished. The RuCl3/(S,S)-ip-pybox catalyst system has effectively catalyzed the reaction to afford the enantiomerically enriched branch-type allylic amines with perfect regioselectivity and high enantioselectivity.

Retention of Regiochemistry and Chirality in the Ruthenium Catalyzed Allylic Alkylation of Disubstituted Allylic Esters

The regiospecific nucleophilic substitution during the ruthenium catalyzed allylic alkylation of 1,3-unsymmetrical disubstituted allylic esters was demonstrated. The nucleophile was selectively introduced at the position originally substituted with leaving group in the 2-DPPBA or ip-pybox ligated [RuCl(2)(p-cymene)](2) catalyzed allylic alkylation of 1,3-unsymmetrical disubstituted allylic esters. The chirality of the optically active allylic esters was also transferred to the alkylated products.

Palladium-catalyzed double alkylation of 3-aryl-2-fluoroallyl esters with malonate nucleophiles through the carbon-fluorine bond cleavage.

The alkylation of (Z)-3-aryl-2-fluoroallyl acetate with the malonate anion by the [Pd(C3H5)(cod)]BF4/2,2-bpy catalyst proceeds through the carbon-fluorine bond cleavage, and 2 equiv of the malonate nucleophile was introduced to the allyl substrate.

Iron-catalyzed [2 + 2 + 2] cycloaddition of trifluoromethyl group substituted unsymmetrical internal alkynes

Iron-catalyzed [2 + 2 + 2] intermolecular cycloaddition of trifluoromethyl group substituted unsymmetrical internal alkynes afforded the corresponding trifluoromethyl group substituted benzene derivatives in high yield with excellent selectivity.

Recent Progress on Nazarov Cyclizations: The Use of Iron Salts as Catalysts in Ionic Liquid Solvent Systems

Nazarov cyclization is an important and versatile method for the synthesis of five-membered carbocycles, and extensive studies have been conducted to optimize the reaction. Among recent studies, several trends are recognized. One is the combination of different reactions with Nazarov cyclization in a one-pot reaction system which enables the preparation of unique cyclization products. The second is the use of a transition-metal catalyst, though Lewis or Brønsted acids have generally been used for the reaction. The third is the realization of the asymmetric Nazarov cyclization. The fourth is the base-catalyzed Nazarov cyclization. Furthermore, several useful protocols for realizing Nazarov cyclization have also been developed. The recent progress on Nazarov cyclizations is summarized in Section 2. Section 3 is our chronicle in this field. We focused on the use of iron as the catalyst in Nazarov cyclizations and ionic liquids as solvents: Nazarov cyclization of thiophene derivatives using FeCl3 as the catalyst was accomplished and we succeeded in demonstrating the first example of an iron-catalyzed asymmetric Nazarov reaction. We next established Nazarov cyclization of pyrrole or indole derivatives using Fe(ClO4 )3 ·Al2 O3 as the catalyst with high trans selectivities in excellent yields. Since the cyclized product was reacted with a vinyl ketone in the presence of the same iron salt, the system allowed realization of the sequential type of Nazarov/Michael reaction of pyrrole derivatives. Furthermore, we demonstrated the recyclable use of the iron catalyst and obtained the desired Nazarov/Michael reaction products in good yields for five repetitions of the reactions without any addition of the catalyst using an ionic liquid, [bmim][NTf2 ], as the solvent. We expect that the iron-catalyzed Nazarov cyclization, in particular, in an ionic liquid solvent might become a useful method to synthesize functional molecules that include cycloalkene moieties.

Nickel-Catalyzed Asymmetric Propargylic Amination of Propargylic Carbonates Bearing an Internal Alkyne Group

We have achieved the nickel-catalyzed asymmetric propargylic amination of propargylic carbonates bearing an internal alkyne group. A wide variety of propargylic carbonates and N-methylaniline derivatives were tolerated under the reaction conditions, providing the corresponding chiral propargylic amines in up to 97% yield with up to 97% ee.