Publications by authors named "Motoi Kawatsura"

The nickel-catalyzed highly enantioselective Friedel-Crafts propargylation of 3-substituted indoles with propargylic carbonates bearing an internal alkyne group was developed. A wide array of the propargylic carbonates as well as 3-substituted indoles can be applicable to the asymmetric nickel catalysis, providing the corresponding chiral C-3 propargylated indolenine derivatives bearing two vicinal chiral centers in up to 89% yield with up to >99% ee and 94:6 dr (24 examples).

View Article and Find Full Text PDF

We have accomplished the ruthenium-catalyzed benzylic substitution of benzyl esters with a stabilized carbon nucleophile. A [Cp*RuCl2]2/picolinic acid catalyst system promoted the reaction of 2-naphthylmethyl-2,3,4,5,6-pentafluorobenzoates with a series of stabilized carbon nucleophiles such as malonates, β-ketoesters, and diketones to give the corresponding benzylic alkylation products in moderate to high yields. We proposed a plausible reaction mechanism that could involve a (π-benzyl)ruthenium intermediate.

View Article and Find Full Text PDF

The nickel-catalyzed hydroarylation of 1,3-dienes with arylboronic acids using a secondary homoallyl carbonate as a surrogate for the 1,3-diene and hydride source has been developed. The synthetic strategy allowed an efficient access to a wide array of hydroarylation products in high yields with high functional group compatibility without the use of an external hydride source. Mechanistic experiments indicated that the alkene-directed oxidative addition and subsequent β-hydride elimination would be a critical process in this transformation.

View Article and Find Full Text PDF

We have developed a novel synthetic method accessing benzo[b][1,4]oxazepines that are one of the rare classes of benzoxazepine derivatives by reaction of 2-aminophenols with alkynones in 1,4-dioxane at 100 °C. A series of benzo[b][1,4]oxazepine derivatives can be prepared by using this synthetic protocol. Mechanistic experiments indicated that the hydroxy proton of the aminophenol could play a crucial role in the formation of an alkynylketimine intermediate that undergoes 7-endo-dig cyclization.

View Article and Find Full Text PDF

Nickel-catalyzed transformation of alkene-tethered oxime ethers to nitriles using a traceless directing group strategy has been developed. A series of alkene-tethered oxime ethers derived from benzaldehyde and cinnamyl aldehyde derivatives were converted into the corresponding benzonitriles and cinnamonitriles in 46-98% yields using the nickel catalyst system. Control experiments showed that the alkene group tethered to an oxygen atom on the oximes via one methylene unit plays a key role as a traceless directing group during the catalysis.

View Article and Find Full Text PDF

The nickel-catalyzed benzylic substitution of benzyl alcohol derivatives with a soft carbon nucleophile is extremely rare compared to that with a hard carbon nucleophile. We have achieved the nickel-catalyzed benzylic substitution of benzyl esters with malonates as a soft carbon nucleophile. Primary and secondary benzyl 2,3,4,5,6-pentafluorobenzoates as well as a wide variety of malonate derivatives were well tolerated in the nickel-catalyzed reaction, providing the corresponding alkylation products in 46-86% yields (34 examples).

View Article and Find Full Text PDF

We describe herein the synthetic method to benzoxazole derivatives via the copper-catalyzed hydroamination of alkynones with 2-aminophenols. The method produced a wide variety of functionalized benzoxazole derivatives in good yields. Preliminary mechanistic experiments revealed that the reaction would proceed through the copper-catalyzed hydroamination of alkynones and the sequential intramolecular cyclization of β-iminoketones/elimination of acetophenone promoted by the copper catalyst.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

We demonstrate the iron-catalyzed intermolecular coupling of internal alkynes and thiosalicylic acid derivatives. The reaction was effectively catalyzed by the Fe(acac)/1,10-phenanthroline catalyst in toluene/HFIP (hexafluoroisopropyl alcohol) as the reaction solvent and afforded several types of 1,3-oxathiine derivatives in moderate to high yields through the intermolecular hydrothiolation and sequential intramolecular cyclization.

View Article and Find Full Text PDF

We demonstrated the ruthenium-catalyzed allylic amination of 2,3,3-trifluoroallylic carbonates with several types of amines. The reactions proceeded with several types of amines, and succeeded in obtaining polyfluorinated terminal alkenes possessing branched allylic amines as a single regioisomer.

View Article and Find Full Text PDF

The palladium-catalyzed alkylation reaction of 2,3,3-trifluoroallylic carbonates with indoles afforded a trifluoromethyl group possessing 3-substituted indole derivatives. The reaction proceeded via attack of the C-3 carbon of the indoles onto the C-2 position of the allylic moiety and intramolecular construction of the trifluoromethyl group by the intramolecular fluorine atom shift from the C-2 position to the C-3 position of the allyl unit.

View Article and Find Full Text PDF

The ruthenium-catalyzed regioselective allylic amination of tertiary allylic acetates with several types of amines has been accomplished. The reaction was effectively catalyzed by Cp*RuCl/5,5'-dimethyl-2,2'-bipyridine or its related ruthenium catalyst systems, and α,α-disubstituted allylic amines were formed as a single regioisomer in moderate to high yields.

View Article and Find Full Text PDF

We demonstrated the kinetic resolution of racemic and branched monosubstituted allylic acetates by a ruthenium-catalyzed regioselective allylic etherification. The reaction was effectively catalyzed by the chiral ruthenium catalyst, which was generated by [RuCl2(p-cymene)]2 and (S,S)-iPr-pybox and a catalytic amount of TFA, and both the allylic etherification product and recovered allylic acetate were obtained as an enantiomerically enriched form with up to a 103 s value.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

We examined the palladium-catalyzed allylic alkylation of trifluoromethyl group-substituted racemic and acyclic unsymmetrical 1,3-disubstituted allylic benzoate with a malonate anion, and succeeded in obtaining an enantiomerically enriched product in high yields with high ee values through the dynamic kinetic asymmetric transformation (DYKAT). The best result was attained by the [Pd(C3H5)(cod)]BF4/(S)-tol-BINAP in the presence of BSA or DMAP as a base.

View Article and Find Full Text PDF

The copper-catalyzed regioselective intermolecular hydroamination of the aryl and trifluoromethyl group or electron-withdrawing group substituted internal alkynes with amines has been accomplished. The reaction was effectively catalyzed by the ligand-free Cu(OTf)2 and afforded the intended amine derivatives in good yields after treatment of NaBH3CN.

View Article and Find Full Text PDF

The palladium-catalyzed reaction of 2,3,3-trifluoroallyl esters with several types of amines afforded trifluoromethylenamines, which were formed by the addition of a nitrogen nucleophile at the C-2 position and the intramolecular construction of the trifluoromethyl group via the fluorine atom shift from the C-2 to the C-3 position.

View Article and Find Full Text PDF

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).

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

Optical resolution of 2-methyl-2-nitrobut-3-en-1-ol has been accomplished using a "low-temperature lipase-catalyzed transesterification" carried out at -40 °C.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

The regio- and stereoselective addition of carboxylic acids to aryl and trifluoromethyl group substituted unsymmetrical internal alkynes has been accomplished: the Ru(3)(CO)(12)/3PPh(3) catalyst system has effectively catalyzed the reaction to afford the trifluoromethyl group substituted (E)-enol esters with high regio- and stereoselectivities.

View Article and Find Full Text PDF

It found that the Ru(3)(CO)(12) coordinated with 2-(diphenylphosphino)benzonitrile (2-DPPBN) to effectively catalyze the [2 + 2 + 2] cyclotrimerization of the trifluoromethyl group substituted internal alkynes in high yields with up to >98% regioselectivity. Isolation of a ruthenacyclopentadiene was successful and confirmed that the complex is a reaction intermediate.

View Article and Find Full Text PDF