American Chemical Society Acta Medica Okayama 15237060 21 17 2019 Rhenium-Catalyzed Cyclization via 1,2-Iodine and 1,5-Hydrogen Migration for the Synthesis of 2-Iodo-1H-indenes 6756 6760 EN Masahito Murai Graduate School of Natural Science and Technology, Okayama University Kazuhiko Takai Graduate School of Natural Science and Technology, Okayama University A rhenium complex catalyzed the formation of 2-iodo-1H-indene derivatives through iodine and hydrogen migration of 3-iodopropargyl ethers. The reaction proceeded via generation of 1-iodoalkenylrhenium carbene species by sequential 1,2-iodine and 1,5-hydrogen shifts with readily available precursors under neutral conditions. The reaction mechanism and the reactivity of the generated alkenylcarbene species were also investigated. No potential conflict of interest relevant to this article was reported.

American Chemical Society Acta Medica Okayama 15237060 21 9 2019 Rhenium-Catalyzed Regioselective ortho-Alkenylation and [3 + 2 + 1] Cycloaddition of Phenols with Internal Alkynes 3441 3445 EN Masahito Murai Graduate School of Natural Science and Technology, Okayama University Masaki Yamamoto Graduate School of Natural Science and Technology, Okayama University Kazuhiko Takai Graduate School of Natural Science and Technology, Okayama University An operationally simple and direct rhenium-catalyzed ortho-alkenylation (C-alkenylation) of unprotected phenols with alkynes was developed. The protocol provided ortho-alkenylphenols exclusively, and formation of para- or multiply alkenylated phenols and hydrophenoxylation (O-alkenylation) products were not observed. The [3 + 2 + 1] cycloaddition of phenols and two alkynes via ortho-alkenylation was also demonstrated, in which the alkynes functioned as both two- and one-carbon units. These reactions proceeded with readily available starting materials under neutral conditions without additional ligands. No potential conflict of interest relevant to this article was reported.

American Chemical Society Acta Medica Okayama 15237060 21 8 2019 Chromium-Mediated Stannylcyclopropanation of Alkenes with (Diiodomethyl)stannanes 2668 2672 EN Masahito Murai Graduate School of Natural Science and Technology, Okayama University Ryuji Taniguchi Graduate School of Natural Science and Technology, Okayama University Chisato Mizuta Graduate School of Natural Science and Technology, Okayama University Kazuhiko Takai Graduate School of Natural Science and Technology, Okayama University A stannyl-group-substituted gem-dichromiomethane species, generated in situ from CrCl2, TMEDA, and tributyl(diiodomethyl)stannane, worked as an efficient stannylcarbene equivalent to promote cyclopropanation of alkenes. The reaction provided synthetically useful stannylcyclopropanes directly from commercially available unactivated alkenes without using potentially flammable alkylzinc and diazo compounds. Structural characterization of stannyl- and germyl-group-substituted gem-dichromiomethane complexes and the effect of group 14 elements containing substituents for cyclopropanation are also described. No potential conflict of interest relevant to this article was reported.

Wiley Acta Medica Okayama 0947-6539 25 66 2019 Mechanistic Insights into Rhenium-Catalyzed Regioselective C-Alkenylation of Phenols with Internal Alkynes 15189 15197 EN Masahito Murai Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Masaki Yamamoto Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Kazuhiko Takai Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University A (ƒÊ-aryloxo)rhenium complex was isolated and confirmed as a key precatalyst for rhenium-catalyzed ortho-alkenylation (C-alkenylation) of unprotected phenols with alkynes. The reaction exclusively provided ortho-alkenylphenols; the formation of para or multiply alkenylated phenols and hydrophenoxylation (O-alkenylation) products was not observed. Several mechanistic experiments excluded a classical Friedel-Crafts-type mechanism, leading to the proposed phenolic hydroxyl group assisted electrophilic alkenylation as the most plausible reaction mechanism. For this purpose, the use of rhenium, a metal between the early and late transition metals in the periodic table, was key for the activation of both the soft carbon-carbon triple bond of the alkyne and the hard oxygen atom of the phenol, at the same time. ortho-Selective alkenylation with allenes also provided the corresponding adducts with a substitution pattern different from that obtained by the addition reaction with alkynes. No potential conflict of interest relevant to this article was reported.

American Chemical Society Acta Medica Okayama 2155-5435 8 6 2018 Amine-Promoted anti-Markovnikov Addition of 1,3-Dicarbonyl Compounds with Terminal Alkynes under Rhenium Catalysis 5454 5459 EN Masahito Murai Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Erika Uemura Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Kazuhiko Takai Division of Applied Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University Amines have been identified to greatly accelerate the intermolecular anti-Markovnikov addition of carbon nucleophiles to unactivated terminal alkynes. Using a combination of [ReBr(CO)3(thf)]2 and iPr2NEt, construction of cyclic all-carbon quaternary centers was achieved with various 1,3-ketoesters, diketones, and diesters with lower catalyst loading under milder conditions. The type of addition could be easily controlled by choice of additive, highlighting the unique features of rhenium catalysis No potential conflict of interest relevant to this article was reported.

American Chemical Society Acta Medica Okayama 1523-7060 18 17 2016 Synthesis and Properties of Sila[n]helicenes via Dehydrogenative Silylation of C-H Bonds under Rhodium Catalysis 4380 4383 EN Masahito Murai Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Ryo Okada Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Atsushi Nishiyama Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Kazuhiko Takai Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University Use of a rhodium catalyst with (R)-(S)-BPPFA ligand allows efficient synthesis of sila[n]helicenes via dehydrogenative silylation of C-H bonds. By selecting the proper ligands, the current method provides the ability to prepare unsymmetrical sila[n]helicene derivatives without any oxidants. The resulting sila[6]helicene is a rare example of a five-membered ring-fused [6]helicene, which was isolated as a single pure enantiomer without substituents on the terminal benzene rings. No potential conflict of interest relevant to this article was reported.