Takeshi Yasui 교수

The metal-free ring expansion of cyclopropanols containing a pendant styrene moiety was successfully achieved using a proton-coupled electron transfer enabled by an organic photoredox catalyst. Through this, variants of 1-tetralone and 1-benzosuberone bearing a substituent at the benzylic position were selectively obtained through the regioselective ring closure of alkyl radical intermediates depending on the substitution pattern of the alkene moiety.

Herein, we report dual cobalt and photoredox catalysis enabled [2+2+2] cycloaddition of enediynes to produce tricyclic cyclohexadienes bearing a quaternary bridgehead carbon. A variety of enediynes were used, and the corresponding cyclohexadienes were obtained in good to high yields. The use of a chiral ligand, (S)-Segphos, enabled a highly enantioselective reaction allowing access to highly enantio-enriched cyclohexadienes.

Endosperm starch isolated from an amylose-free waxy mutant hull-less barley line, Shikoku Hadaka 97, had an amylose content of 0.3% and higher swelling power than ordinary waxy barley cultivars/lines with amylose contents of 2.2—6.5%. A highly significant correlation was observed between amylose content and swelling power among waxy barley starches. No clear differences were detected in the chain-length distribution profiles or thermal properties between the amylose-free starch and ordinary waxy

Herein, we report a method for the generation of vinylallenes via cobalt/photoredox dual-catalysis-enabled formal 1,8-acyloxy migration of 1,6-diynyl esters. We demonstrated a 1,8-acyloxy migration/6π-electrocyclization cascade using (hetero)aryl-substituted 1,6-diynyl esters as substrates, leading to the formation of arenol derivatives. Several control experiments suggested that the β-oxygen elimination of a cobaltacyclopentadiene intermediate enabled formal 1,8-acyloxy migration to generate th

The rhodium-catalyzed cycloisomerization of ester-tethered 1,6-diynes bearing a cyclopropanol moiety produced tetralone/exocyclic diene hybrid molecules with thermodynamically unfavorable alkene geometry. The results of control experiments and density functional theory calculations suggest that the ester tether plays an important role in the efficiency of E/Z isomerization processes.

Abstract Herein, we report a Rh‐catalyzed asymmetric [2+2+2] cycloaddition of ene‐yne‐yne enediynes to generate enantio‐enriched tricyclic cyclohexadienes bearing a quaternary bridgehead carbon. We found that the Rh‐Phanephos complex is an appropriate catalyst for the cycloaddition of enediynes bearing an unsubstituted propiolate terminus, whereas Rh‐biaryl bisphosphine catalysts, which have been widely used for asymmetric cycloadditions of alkynes and alkenes, are not applicable for the reactio

[in Japanese]

Transition-metal-mediated carbon–carbon single-bond cleavage of cyclopropenes has been widely exploited in organic synthesis. However, the ring-opening of cyclopropenes via the cleavage of their carbon–carbon double bond remains a formidable challenge. Herein, we report an intramolecular cycloaddition of cyclopropenes with alkynes via cleavage of the carbon–carbon double bond of cyclopropenes enabled by a ruthenium catalyst to afford 1,2-fused cyclopentadienes, which are difficult to access by c

Transition-metal-catalyzed C(sp3)–H functionalization has been much less investigated compared to C(sp2)–H functionalization because the site-selectivity control in C(sp3)–H bond activation is much more challenging than that in C(sp2)–H bond activation. Site-selective C(sp3)–H functionalization without the assistance of directing groups is highly desirable, because the installation and removal of directing groups are not required. Hence, cycloaddition through a site-selective C–H bond activation

高速液体クロマトグラフィーを用いる乳製品中の糖類の定量法を設定した。試料は必要ならば水で溶解または希釈した後, 80%エタノールで処理し,遠心分離し,その上清を試料液とした。 LiChrosorb NH2(10μm)カラム(2.6 I. D.×250mm)を用い,移動相(アセトニトリル:水=75:25)を1.0ml/minの流速で送液することにより,フラクトース,グルコース,シュクロース,ラクトースを10分間以内で分析することができた。この方法におけるラクトースの添加回収率は平均102.3%であった。また市販乳製品を分析した際の測定値の変動係数は平均4.5%であった。

Abstract Cobalt catalysts have recently gained considerable attention as alternatives to catalysts based on precious transition metals such as Rh and Ir. Recently, Co/photoredox cooperative catalysis has emerged as a powerful tool that enables versatile transformations, including cycloaddition reactions of unsaturated compounds. In particular, 1,6‐diyne derivatives are fascinating substrates for these reactions because the corresponding exocyclic 1,3‐diene products can be further transformed int