Hiroaki Iwamoto

Chemical mechanical planarization (CMP) employing ceria (CeO2) abrasives is widely regarded as a critical process in semiconductor manufacturing due to their superior removal rates for SiO ₂ films compared to other abrasives. However, the efficient removal of ceria residues from the surface remains a significant challenge. Ceria particles are strongly adhered to SiO ₂ surfaces through both chemical and electrostatic interactions. In this study, we developed a post-CMP cleaning solution capable of chemically dissolving ceria residues. Fundamental investigations revealed that the combined use of fluoride, acid, and a reductant significantly enhances cerium dissolution efficiency. The fluoride-containing cleaner also demonstrated excellent performance in post-CMP cleaning of surfaces polished with ceria-based slurries. Moreover, we discovered that non-fluorinated additives exhibit cerium removal efficiencies comparable to fluoride-containing chemicals. The cleaner formulated with these additives is more compatible with various films compared to fluoride-based formulations.

A new C₂-symmetrical P-chirogenic bisphosphine ligand with silyl substituents on the ligand backbone, (R,R)-5,8-TMS-QuinoxP*, has been developed. This ligand showed higher reactivity and enantioselectivity for the direct enantioconvergent borylation of cyclic allyl electrophiles than its parent ligand, (R,R)-QuinoxP* (e.g., for a piperidine-type substrate: 95% ee vs 76% ee). The borylative kinetic resolution of linear allyl electrophiles was also achieved using (R,R)-5,8-TMS-QuinoxP* (up to 90% ee, s = 46.4). An investigation into the role of the silyl groups on the ligand backbone using X-ray crystallography and computational studies displayed interlocking structures between the phosphine and silyl moieties of (R,R)-5,8-TMS-QuinoxP*. The results of DFT calculations revealed that the entropy effect thermodynamically destabilizes the dormant dimer species in the catalytic cycle to improve the reactivity. Furthermore, in the direct enantioconvergent case, detailed calculations indicated a pronounced enantioselective recognition of carbon–carbon double bonds, which is virtually unaffected by the chirality at the allylic position, as a key for the borylation from both enantiomers of racemic allyl electrophiles.

A modular synthetic method, involving a hydrothiolation, silylation, and fluoroalkylation, for the construction of highly functionalized fluoroalkyl sulfides has been developed. The use of aprotic polar solvents enables the additive-free chemoselective hydrothiolation of tetrafluoroethylene, trifluorochloroethylene, and hexafluoropropene with various thiols. The stepwise functionalization reactions convert the hydrothiolated intermediates into the tetrafluoroethyl sulfides in high efficiency. The method avoids the use of the environmental pollutant Halon-2402, which was employed as a building block in a reported synthetic route.

The first copper(I)‐catalyzed enantioselective borylation of racemic benzyl chlorides has been realized by a quadrant‐by‐quadrant structure modulation of QuinoxP*‐type bisphosphine ligands. This reaction converts racemic mixtures of secondary benzyl chlorides into the corresponding chiral benzylboronates with high enantioselectivity (up to 92 % ee). The results of mechanistic studies suggest the formation of a benzylic radical intermediate. The results of DFT calculations indicate that the optimal bisphosphine‐copper(I) catalyst engages in noncovalent interactions that efficiently recognize the radical intermediate, and leads to high levels of enantioselectivity.

The first copper(I)‐catalyzed enantioselective borylation of racemic benzyl chlorides has been realized by a quadrant‐by‐quadrant structure modulation of QuinoxP*‐type bisphosphine ligands. This reaction converts racemic mixtures of secondary benzyl chlorides into the corresponding chiral benzylboronates with high enantioselectivity (up to 92 % ee). The results of mechanistic studies suggest the formation of a benzylic radical intermediate. The results of DFT calculations indicate that the optimal bisphosphine‐copper(I) catalyst engages in noncovalent interactions that efficiently recognize the radical intermediate, and leads to high levels of enantioselectivity.

Metal-free asymmetric catalysis for the synthesis of sterically encumbered amino-acids was developed using allyl- and allenylboronic acid reagents.

Finding optimal chiral ligands for transition-metal-catalyzed asymmetric reactions using trial-and-error methods is often time-consuming and costly, even if the details of the reaction mechanism are already known. Although modern computational analyses allow the prediction of the stereoselectivity, there are only very few examples for the attempted design of chiral ligands using a computational approach for the improvement of the stereoselectivity. Herein, we report a systematic method for the design of chiral ligands for the enantioselective Markovnikov hydroboration of aliphatic terminal alkenes based on a computational and experimental evaluation sequence. We developed a three-hindered-quadrant P-chirogenic bisphosphine ligand that was designed in accordance with the design guidelines derived from this method, which allowed the Markovnikov hydroboration to proceed with high enantioselectivity (up to 99% ee).

We report the first copper(i)-catalysed intramolecular alkylboration of terminal allenes with an alkyl halide moiety.

The first C–B bond-forming dearomative carboborylation of heteroaromatic compounds has been achieved using copper(I) catalysis. This reaction includes the regioselective addition of a borylcopper(I) intermediate to indoles, followed by the diastereoselective methylation of the resulting copper(I) enolate intermediate to afford the corresponding 3-boryl-2-methylindolines bearing a quaternary stereogenic center with excellent regio- and diastereoselectivity. 3-Boryl-2-methylindoline derivatives bearing a quaternary stereogenic center were obtained with excellent regio- and diastereoselectivities through the dearomative carboborylation of Boc-protected methyl indole-2-carboxylate using a copper(I) catalyst, bis(pinacolato)diboron, K(O-t-Bu), and MeOTs, which was used as an alkyl electrophile, in THF. The products of this reaction could be useful synthetic intermediates in the combination of a boron functionalization process.