Yasuhiro Ohki

Asymmetric metathesis dimerization/desymmetrization (AMD/DS) reaction on C _s ‐symmetric planar‐prochiral divinylphosphaferrocene/divinylferrocene substrates 1 was realized in the highly enantioselective fashion. For the substrates having a proper substituent in the position adjacent to the vinyl groups in 1 , the molybdenum‐alkylidene precatalyst coordinated with either ( R )‐ or ( S )‐3,3'‐bis(diphenylmethyl)‐5,5',6,6',7,7',8,8'‐octahydro‐2,2'‐binaphtholate ( L1 ) was capable of distinguishing between the two enantiotopic vinyl groups in 1 , and facilitated the AMD reaction at one of the two vinyl groups predominantly providing the corresponding planar‐chiral metathesis dimer 2 in >99% ee. The presence of a substituent neighboring to the vinyl group was critical for the successful AMD/DS reaction, and both enantio‐ and chemoselectivities were poor without it. The reactions using an achiral or a racemic molybdenum‐alkylidene precatalyst did not halt at the dimerization stage and proceeded further to furnish the oligomers/polymers through the acyclic diene metathesis polymerization (ADMET) pathway. The excellent enantio‐ and chemoselectivities in the present AMD/DS process stems from the following two factors: (i) the highly enantioselective deactivation of one of the two enantiotopic vinyl groups in 1 , which prevents the dimers 2 from oligomerizing/polymerizing, and (ii) the subsequent kinetic resolution (KR) on the initially formed planar‐chiral dimeric products 2 , which predominantly consumes the minor enantiomers/diastereomers through ADMET.

Metal-sulfur (M-S) clusters are ancient biological cofactors that catalyze CO2 and N2 reduction, yet no biological or synthetic M-S cluster has achieved sustained, high-turnover conversion of CO2 to hydrocarbons at a single active site. We reasoned that effective CO2-to-CH4 catalysis requires not only CO2 activation but also retention of a metal-bound CO intermediate for subsequent six-electron reduction. Here, a bioinspired [Cp*3Mo3S4Fe] cubane (Cp* = C5Me5) catalyzes the direct eight-electron reduction of CO2 to CH4 under ambient conditions with turnover numbers exceeding 150,000 and only trace CO formation. A structurally characterized CO2-derived anionic Fe-CO intermediate was identified, and a neutral Fe-CO cubane undergoes nearly quantitative conversion to CH4 under the catalytic conditions. These results identify synthetic M-S clusters as a competent framework for advancing catalytic CO2 reduction beyond the two-electron stage, with appropriate molecular design and reaction conditions. More broadly, they establish productive retention of a metal-bound CO intermediate as a key molecular design principle for CO2-to-hydrocarbon catalysis.

Azulene has long resisted functionalization owing to the fleeting nature of its lithiated intermediates. Here, we demonstrate that flow microreactors, featuring rapid mixing, short residence times, and precise temperature control, enable controlled generation of these highly reactive species, providing regioselective access to 6- or 1-substituted azulenes in yields of up to 89% under noncryogenic conditions. This methodology allows the synthesis of 6-diethylboryl-1-(pyridin-4-yl)azulene (3), which spontaneously self-assembles into a cyclic trimer (3₃) via intermolecular B–N coordination. The trimer displays a pronounced blue shift relative to the monomer, while addition of 4-dimethylaminopyridine (DMAP) induces visible red-shifted disassembly into a monomeric DMAP adduct. Notably, this DMAP-driven supramolecular disassembly was monitored in real time using a flow microreactor equipped with in-line UV–vis spectroscopy. These results demonstrate that flow microreactors not only address a long-standing challenge in azulene chemistry but also enable real-time visualization of supramolecular switching, providing a basis for color-responsive functional materials.

Highly diastereo- and enantioselective kinetic resolution (KR) of a series of racemic planar-chiral 1-R-2-vinylcymantrenes ( rac - 1 ; R = Br, Me, I) was realized by an asymmetric metathesis dimerization (AMD) reaction catalyzed by a chiral molybdenum-alkylidene precatalyst. The Mo/( R )- L1 precatalyst promoted the AMD/KR reaction of rac - 1a (R = Br) to give ( E )-( R , R )- 2a of 99% ee together with unreacted recovered ( S )- 1a of 45% ee at 37% conversion. The diastereoselectivity of this reaction was excellent with chiral - 2a / meso - 2a = 96:4 molar ratio, and the selectivity factor ( k _rel ) was calculated to be 754 based on a second-order equation. In all the three substrates examined, the dimerized products, chiral - 2 , were obtained in >98% ee thanks to the outstanding enantioselectivity.

The synthesis and full characterization of 1,4-dilithio-1,4-bis(triisopropylsilyl)-2,3-diphenylbuta-1,3-diene (1b) are reported. This molecule featuring extremely bulky silyl groups at the 1- and 4-positions serves as a precursor for the synthesis of 2,5-bis(triisopropylsilyl)-3,4-diphenyl-1-silacyclopenta-1,3-dienes (siloles) bearing various substituents at the silicon atom (SiR₂ = SiH₂ (4), SiH(OMe) (5), SiF₂ (6), SiBr₂ (7), SiBr(OMe) (8)). Importantly, compounds 6 and 7 reacted with lithium to afford 2,5-bis(triisopropylsilyl)-3,4-diphenyldilithiosilole (9). The solid-state molecular structure and solution NMR spectra reveal the formation of an aromatic ring system, as opposed to the precursors 6 and 7, with two Li cations coordinated by the silacycle in η⁵-fashions. The sterically bulky dilithiosilole 9 can be applied as an important starting material in the pursuit of low-valent silicon species without donor stabilization.

Nanoclusters are nanometer-sized molecular compounds characterized by significant metal-metal bonding and low average oxidation states, and they exhibit unique properties distinct from those of small metal complexes or nanoparticles. Unlike noble metals stable in metallic forms, the synthesis of nanometer-sized iron clusters has been precluded by the relatively weak iron-iron bonds and the high reactivity of low oxidation state iron, despite the extensive history of molecular iron compounds. Here, we report the synthesis and characterization of a cationic 55-atom iron cluster with a 1.2 nm icosahedral core. Its 12 vertices are occupied by tri-tert-butylphosphines, while multiple hydrides cover the surface. This core can be viewed as a substructure of the face-centered cubic (fcc), in contrast to the body-centered cubic (bcc) for the stable bulk phase. This work reveals a stable structure and fundamental properties of a nanometer-sized iron cluster, which have remained elusive for decades, and the simple synthetic protocol provides a route to explore molecular nanochemistry.