Shigeki Matsunaga

Reductive metal-hydride hydrogen atom transfer (MHAT) catalysis generates metal hydride species through electron and proton transfer. Recent advances in photocatalytic and electrocatalytic cobalt-based systems offer sustainable alternatives to conventional oxidative MHAT methods. However, reductive MHAT processes involving other transition metals remain underdeveloped, highlighting the need for more versatile and environmentally benign platforms. Herein, we report an intramolecular hydroarylation of unactivated alkenes under an iron/photocatalyst dual catalytic system. In this process, reductive generation of a low-valent iron intermediate, followed by protonation, affords the key iron hydride species, thereby expanding reductive MHAT catalysis beyond the previously established cobalt-based paradigm.

The isomerization of readily available terminal alkenes is a valuable transformation for the synthesis of internal alkenes; however, competing overisomerization and the formation of E / Z isomers are inevitable issues. Herein, we report the Z ‐selective monoisomerization of terminal alkenes at ambient temperature using a combination of NiI ₂ , 1,3‐bis(dicyclohexylphosphino)propane, and 2,4,5,6‐tetrakis(9H‐carbazol‐9‐yl)isophthalonitrile (4CzIPN) under visible‐light irradiation. Various homoallyl arenes and simple terminal alkenes underwent the selective isomerization to 2‐alkenes with good Z ‐selectivity. The reaction is proposed to proceed via a Ni–hydride pathway, and experimental studies revealed that photoinduced processes generate the active catalytic species.

Selective E / Z isomerization of diaryl oxime derivatives, in which the two isomers have similar geometric and electronic characteristics, was achieved using photosensitizers with appropriate triplet energies. We found that suitable substituents can modulate conjugation in methoximes, thereby generating a triplet energy gap between the E and Z isomers. In addition, Z ‐isomer‐enriched methoximes enabled site‐selective C(sp ² )–H functionalization.

Masked sulfinates with sulfinate protecting groups are important precursors for sulfonyl fluorides, which are versatile synthetic intermediates and biologically useful tools. We have designed and developed α-diazo masked sulfinates with an additional carbonyl group (aDAMAS reagents). These aDAMAS reagents combine a reactive α-diazo unit and a masked sulfinate moiety to provide new opportunities for the synthesis of functionalized sulfonyl fluorides. As a demonstration of the synthetic utility of these reagents, they were utilized for the Ru-catalyzed synthesis of benzothiazine-1-oxides bearing a sulfonyl fluoride group and other preliminary transformation reactions.

Catalytic Markovnikov-selective hydroboration of unactivated alkenes is a powerful tool for accessing alkyl boronic esters. Here, we report Markovnikov-selective MHAT hydroboration of unactivated alkenes enabled by cobalt/photoredox dual catalysis. The reaction proceeded via radical intermediates, providing high regioselectivity with mono-, di-, and trisubstituted alkenes.

Dedicated to Professor Masakatsu Shibasaki on the occasion of his 80th birthday. N,N-Dimethyl tertiary sulfonamides were efficiently activated by Me-λ³-iodane through N-methylation, and the generated electrophilic sulfonyl ammonium salts were converted into sulfonyl fluorides in one pot. The use of Et3N·3HF as the nucleophilic fluoride source is key to obtaining good-to-high yields for various substrates. The optimized protocol enables the utilization of readily available and highly stable sulfonamides as a protecting group for the corresponding sulfonyl fluorides. We have demonstrated the multistep synthesis of sulfonyl fluorides, during which the sulfonyl moiety was protected from strong nucleophiles as a sulfonamide. Received: 01 December 2025 Accepted after revision: 07 January 2026 Article published online: 29 January 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

The direct functionalization of C(sp³)-H bonds assisted by native carbonyl functional groups is a promising strategy for the streamlined synthesis of complex molecules. Here, we report native amide-directed C(sp³)-H alkynylation reactions using an electron-deficient iridium catalyst and an electron-deficient pyridone ligand. Under the optimized conditions, the C(sp³)-H alkynylation of terminal methyl groups and internal methylene groups of cyclobutane carboxamides afforded the desired products in moderate to good yields.

Hypervalent iodine compounds have found various applications in organic chemistry and related research fields. Compared with aryl‐, alkynyl‐, and alkenyl‐substituted iodanes and iodonium salts, alkyl–λ³–iodanes have been much less studied due to their infamous instability and the lack of convenient methods for their generation. Herein, it is reported that the reaction between a tetraalkylsilane and iodine tris(trifluoroacetate) at low temperature cleanly generates the corresponding alkyl–λ³–iodane in commonly used chlorinated solvents. The in situ‐generated alkyl–λ³–iodanes are reasonably stable at low temperature, and Me–λ³–iodane serves as a soft and highly electrophilic methylating agent for tertiary sulfonamides. This alkylative activation of tertiary sulfonamides provides reactive sulfonyl ammonium intermediates that can achieve transamidation and fluorination reactions, thus demonstrating the synthetic utility of the in situ‐generated alkyl–λ³–iodane.