Takayuki Yakura

Iodoarene catalysts immobilized on magnetite (Fe₃O₄) were developed. The reactivity of catalysts 4 a and 4 b were similar to that of 4-iodophenoxyacetic acid (3) for the oxidation of 4-alkoxyphenols in the presence of Oxone^® as a co-oxidant to give the corresponding p-quinones in high yields. In addition, 4 b was readily recovered by the use of an external magnet and was recycled up to eight times. This is the first example of a magnetic, nanoparticle-supported iodoarene catalyst.

Stereoselective Total Synthesis of Myriocin Using Rhodium(II)-Catalyzed CH Amination Followed by Alkylation

Co-reporter:Dr. Hisanori Nambu;Narumi Noda;Wenqi Niu;Dr. Tomoya Fujiwara ;Dr. Takayuki Yakura

Asian Journal of Organic Chemistry 2015 Volume 4( Issue 11) pp:1246-1249

Publication Date(Web):

DOI:10.1002/ajoc.201500318

Abstract

The stereoselective total synthesis of myriocin was achieved by using the Du Bois Rh^II-catalyzed C−H amination of sulfamate 6, derived from diethyl l-tartrate, and a subsequent alkylation. The reaction of sulfamate 6 with PhI(OAc)₂ and MgO in the presence of Rh₂(OAc)₄ gave an oxathiazinane N,O-acetal as the sole product in high yield. Alkylation of the N,O-acetal with vinylmagnesium bromide in the presence of ZnCl₂ proceeded stereoselectively to provide an oxathiazinane bearing a quaternary chiral center in high yield. This route includes the first application of the Du Bois procedure for the construction of a quaternary chiral center.

An efficient synthesis of cycloalkane-1,3-dione-2-spirocyclopropanes from 1,3-cycloalkanediones using (1-aryl-2-bromoethyl)-dimethylsulfonium bromides: application to a one-pot synthesis of tetrahydroindol-4(5H)-one

Co-reporter:Hisanori Nambu, Masahiro Fukumoto, Wataru Hirota, Naoki Ono, Takayuki Yakura

Tetrahedron Letters 2015 Volume 56(Issue 29) pp:4312-4315

Publication Date(Web):15 July 2015

DOI:10.1016/j.tetlet.2015.05.069

An efficient synthesis of cyclohexane- and cyclopentane-1,3-dione-2-spirocyclopropanes from 1,3-cycloalkanediones using sulfonium salts was achieved. The reaction of 1,3-cycloalkanediones with (1-aryl-2-bromoethyl)-dimethylsulfonium bromides and powdered K2CO3 in EtOAc provided the corresponding spirocyclopropanes in high yields. Furthermore, a one-pot synthesis of tetrahydroindol-4(5H)-one from 1,3-cyclohexanedione was achieved using the present protocol and a sequential ring-opening cyclization of spirocyclopropane with a primary amine.

Ring-Opening Cyclization of Cyclohexane-1,3-dione-2-spirocyclopropanes with Amines: Rapid Access to 2-Substituted 4-Hydroxyindole

Co-reporter:Hisanori Nambu, Masahiro Fukumoto, Wataru Hirota, and Takayuki Yakura

Organic Letters 2014 Volume 16(Issue 15) pp:4012-4015

Publication Date(Web):July 17, 2014

DOI:10.1021/ol501837b

An efficient ring-opening cyclization of cyclohexane-1,3-dione-2-spirocyclopropanes with primary amines has been developed. The reaction proceeded at room temperature without any additives to provide 2-substituted tetrahydroindol-4-ones in good to excellent yields without the formation of the 3-substituted isomers. The obtained product was readily converted into a 2-substituted 4-hydroxyindole derivative via a synthetically useful indoline intermediate.

A 2-Iodobenzamide Catalyst for Oxidation of Alcohols at Room Temperature

Co-reporter:Dr. Takayuki Yakura;Akihiro Yamada;Narumi Noda;Dr. Tomoya Fujiwara ;Dr. Hisanori Nambu

Asian Journal of Organic Chemistry 2014 Volume 3( Issue 4) pp:421-424

Publication Date(Web):

DOI:10.1002/ajoc.201300279

Abstract

A 2-iodobenzamide catalyst for the oxidation of alcohols was developed. Reaction of alcohols with a catalytic amount of 2-iodobenzamide in the presence of oxone as a co-oxidant at room temperature gave the corresponding carbonyl compounds in excellent yields. Primary alcohols were directly converted into the corresponding carboxylic acids, whereas secondary alcohols were oxidized to ketones. A 2-iodobenzoic acid-type catalyst for alcohol oxidation at room temperature has not been reported before.

Novel 2,2,6,6-Tetramethylpiperidine 1-OxylIodobenzene Hybrid Catalyst for Oxidation of Primary Alcohols to Carboxylic Acids

Co-reporter:Takayuki Yakura;Ayaka Ozono

Advanced Synthesis & Catalysis 2011 Volume 353( Issue 6) pp:855-859

Publication Date(Web):

DOI:10.1002/adsc.201100024

Abstract

Novel bifunctional hybrid-type catalysts bearing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and iodobenzene moieties (1a and 1b) were developed and used for the environmentally benign oxidation of primary alcohols to carboxylic acids. Reaction of primary alcohols 2 with a catalytic amount of 1 in the presence of peracetic acid as a co-oxidant under mild conditions gave the corresponding carboxylic acids 3 in excellent yields.

Hypervalent iodine oxidation of phenol derivatives using a catalytic amount of 4-iodophenoxyacetic acid and Oxone® as a co-oxidant

Co-reporter:Takayuki Yakura, Masanori Omoto, Yû Yamauchi, Yuan Tian, Ayaka Ozono

Tetrahedron 2010 66(31) pp: 5833-5840

Publication Date(Web):

DOI:10.1016/j.tet.2010.04.124

Total synthesis of myriocin and mycestericin D employing Rh(II)-catalyzed CH amination followed by stereoselective alkylation

Co-reporter:Narumi Noda, Hisanori Nambu, Kana Ubukata, Tomoya Fujiwara, Kiyoshi Tsuge, Takayuki Yakura

Tetrahedron (16 February 2017) Volume 73(Issue 7) pp:

Publication Date(Web):16 February 2017

DOI:10.1016/j.tet.2016.12.066

Total synthesis of myriocin and mycestericin D was achieved using the Du Bois Rh(II)-catalyzed CH amination of a sulfamate and subsequent alkylation as a key step. The reaction of a sulfamate with PhI(OAc)2 and MgO in the presence of Rh2(OAc)4 gave oxathiazinane N,O-acetal as the sole product in high yield. Alkylation of N,O-acetal using vinylmagnesium bromide in the presence of ZnCl2 proceeded stereoselectively to provide an oxathiazinane bearing a quaternary chiral center in high yield. Myriocin and mycestericin D were synthesized from a common synthetic intermediate. This route includes the first application of the Du Bois procedure for constructing a quaternary chiral center.Figure optionsDownload full-size imageDownload high-quality image (156 K)Download as PowerPoint slide