Publications by authors named "Yoshio Kasashima"

The reaction of -alkyl--cinnamyl-2-ethynylaniline derivatives via annulation and aza-Claisen-type rearrangement easily afforded corresponding branch-type 3-allylindoles with high regioselectivities in good yields using π-allylpalladium chloride complex as a catalyst.

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We synthesized -alkyl--cinnamoyl amide type phosphine-olefin compounds 1 and found axial chirality in a C(aryl)-N(amide) bond in compounds 1 by HPLC analysis using a chiral stationary phase column. We successfully obtained enantiomeric isomers of 1 and demonstrated the use of (-)-1 for chiral ligands in Pd-catalyzed asymmetric allylic substitution reactions of allylic esters with indoles (up to 97% ee).

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Annulation of -allyl-2-ethynylaniline derivatives easily afforded the corresponding 2-substituted 3-allylindole derivatives in good to excellent yields using P,olefin ligand/palladium catalst systems.

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Atroposelective resolution for axially chiral nicotinamides was achieved by dynamic chiral salt formation with L-DBTA using six types of nicotinamides that could not be optically resolved by the preferential crystallization method. Kinetic studies of their racemization indicated that the chiral conformation was retained for a significant period of time. Two methods of crystallization-induced asymmetric transformation were examined by dynamic diastereomeric salt formation: solvent evaporation from a supersaturated solution, and attrition-enhanced asymmetric transformation.

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We synthesized cinnamoyl amide type chiral P,olefin ligand ()-4. We successfully obtained separable diastereomers of 4d and demonstrated Pd-catalyzed asymmetric allylic substitution reactions of indoles using (,a)-4d as a chiral ligand with high enantioselectivities (up to 98% ee).

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Asymmetric synthesis was performed by combining the photochemical reaction of an achiral substrate followed by crystallization-induced deracemization. The results indicated that a fused indoline produced by photochemical intramolecular δ-hydrogen abstraction and cyclization of N-(5-chloro-2-methylphenyl)phthalimide crystallized as a racemic conglomerate. Since this substrate has an aminal skeleton, racemization involving a ring-opening and ring-closing equilibrium process occurred under suitable conditions.

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Dynamic enantioselective crystallization enabled the chiral symmetry breaking of two spiropyrans and one spirooxazine. The three spiro compounds afforded racemic conglomerate crystals, and easily racemized in alcoholic solution without irradiation. Optically pure enantiomorphic crystals were obtained by vapor-diffusion crystallization or attrition-enhanced deracemization (Viedma ripening).

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A novel regioselective cyclization reaction of N-cinnamoylthioureas leading to six- or five-membered heterocyclic compounds was developed. N-Cinnamoylthioureas in the presence of trifluoroacetic acid (TFA) underwent the well-established intramolecular cycloaddition reaction to give 2-imino-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones in good yields. On the other hand, the reaction with 1,8-diazabicyclo[5.

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Asymmetric Diels-Alder reaction was achieved under achiral conditions. Reaction of prochiral 2-methylfuran and N-phenylmaleimide in heptane or hexane solution at 80 °C efficiently gave a conglomerate crystal of exo-type Diels-Alder adduct selectively, and continuous suspension of the reaction mixture with glass beads promoted attrition-enhanced deracemization, leading to an optically active exo-adduct in 90% ee.

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Photodimerization of 3-arylindenones in solution and in the solid state was examined. Irradiation of 3-arylindenones in benzene exclusively gave C-symmetric anti-HH cyclobutane dimers in good yields. In contrast, photolysis in the solid state afforded syn-HH cyclobutane dimers efficiently, which was considerably influenced by the molecular arrangement in the crystal lattice.

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Irradiation of prochiral (E)-aroylacrylamide with sunlight gave single-handed pyrrolinone quantitatively and with an enantiomeric excess (ee) of over 99 % under absolutely achiral conditions. The phenomenon was explained by photoisomerization and reversible cyclization followed by dynamic crystallization involving deracemization.

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Single-handed α-amino acid derivatives were generated from achiral precursors without an external chiral source. Conjugate addition of phenethylamine to an achiral aroyl acrylamide under homogeneous conditions gave the α-amino amides in quantitative yields, which crystallized as a conglomerate of a P2 crystal system. Dynamic preferential crystallization or attrition-enhanced deracemization resulted in the formation of enantiomorphic crystals of 99 % ee.

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Irradiation of three chromone-2-carboxamides with a chiral auxiliary resulted in diastereoselective formation of a C2-chiral anti-HH dimer scaffold. Selection of the solvent polarity and decreasing the temperature resulted in asymmetric induction with up to 84% diastereomeric excess (de).

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Optically active materials could be generated by simple solidification of achiral materials without an external chiral source. When achiral cis-3,4-diphenylsuccinimides were solidified in the presence of a catalytic amount of DBU by evaporating the solvent with stirring, optically active trans-3,4-diphenylsuccinimides were obtained quantitatively with high enantiomeric excesses.

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The reaction of vinyl ethers with carboxylic acids using iodine as a catalyst under solvent-free conditions was investigated. The reaction of saturated carboxylic acids with vinyl ethers gave the corresponding esters. Mechanistic studies revealed the production of the adduct of the vinyl ether with the carboxylic acid, which then rearranged to form the ester.

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The reaction of olefins with nitriles using iodine as a catalyst under solvent-free conditions was investigated. The reaction of cycloolefins, such as cyclopentene and cyclohexene, with benzonitrile using iodine as a catalyst produced both amide and heterocyclic compounds. The reaction of chiral (+)-camphene with benzonitrile produced racemic (±)-N-isobornylbenzamide (N-((1S,2S,4S)-1,7,7-trimethylbicyclo[2.

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3-hydroxy acids, 3-hydroxy-3,7-dimethyloct-6-enoic acid (1) and 3-hydroxy-2,2,3,7-tetramethyloct-6-enoic acid (2), were prepared from 6-methyl-5-hepten-2-one, and they were subsequently used to prepare (2,6,6-trimethyltetrahydropyran-2-yl)acetic acid (3) and 2-methyl-2-(2,6,6-trimethyltetrahydropyran-2-yl)propanoic acid (4), respectively, via cyclization with an acidic catalyst such as boron trifluoride diethyl etherate or iodine. The reaction of carboxylic acids 3 and 4 with alcohols, including methanol, ethanol, and 1-propanol, produced the corresponding methyl, ethyl, and propyl esters, which all contained a tetrahydropyran ring. Reduction of carboxylic acids 3 and 4 afforded the corresponding alcohols.

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The reaction of esters with nitriles, using iodine as a catalyst under solvent-free conditions, was investigated. For example, 1-phenylethyl acetate reacted with benzonitrile in the presence of iodine to afford the amide, N-(1-phenylethyl)benzamide. Addition of water was effective in promoting amidation.

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The reactions of alcohols with nitriles under solvent-free conditions, using molecular iodine as a catalyst, were investigated. The reaction of 1-phenylethanol with propanenitrile produced the amide N-(1-phenylethyl)propanamide, by dehydration and tautomerization, in 71% yield, under the following conditions: temperature=90°C, alcohol:iodine molar ratio=1:0.2, alcohol:nitrile molar ratio=1:5, and reaction time=5 h.

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Reactions of α-vinylbenzyl alcohol with other alcohols using iodine as a catalyst were investigated. The corresponding cinnamyl ethers were obtained as products. This suggested that α-vinylbenzyl alcohol was converted to cinnamyl ethers via 1-phenylallyl cation.

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The irradiation of chromone-2-carboxylic esters resulted in the stereo- and regioselective formation of C(2) chiral anti-HH dimers from the triplet excited state. On the contrary, photolysis in the solid-state gave anti-HT dimers exclusively controlled by molecular arrangement in the crystal.

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X-Ray crystallographic analysis of N-(1-naphthyl)-2(1H)-pyrimidinethione revealed that the space group was tetragonal and chiral P4(3). The rate of racemization due to the C-N bond rotation was considerably influenced by the solvent properties. A nonpolar solvent lowers the ΔG(‡)value by about 3.

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Intramolecular etherification of 1,3-diols was investigated using iodine as a catalyst under solvent-free conditions. The reaction proceeded to completion in a heterogeneous system. Five-membered cyclic ethers were obtained by intramolecular cyclization of 1,3-diols with dehydration.

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Intramolecular cyclic etherification of 1,3-diols was investigated using iodine as a catalyst under solution reaction conditions. Compounds containing five-membered ether rings were obtained. Propella ether (11-oxatricyclo[4.

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2-Quinolone-4-carboxamide derived from (S)-proline, which exists as a mixture of two diastereomers before crystallization, converged to a single diastereomer by crystallization (CIDT), and the homochirality was transferred by a intermolecular 2 + 2 photocycloaddition reaction with high optical activity.

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