Jung Woon Yang

Fluoride-activated silicon catalysis enables transition-metal-free radical benzylic C(sp ³ )–H amination of cyclic benzylic ethers and amines using bench-stable chloramine-T as the nitrogen source.

Pre-organized control in water enables green chemistry, providing a platform for selective N -functionalization and sustainable molecular transformations.

Levulinic acid (LA) is a key biomass-derived platform molecule that provides access to a wide range of value-added chemicals through selective functional-group manipulation. Although transition-metal catalysis has traditionally dominated LA upgrading, recent years have witnessed rapid progress in transition-metal-free synthetic strategies based on main-group reagents, Brønsted (or Lewis) acids and bases, and organocatalytic activation modes. This Short Review summarizes recent advances in the metal-free synthesis and transformation of LA, with a particular focus on reaction design and mechanistic features relevant to organic synthesis. Key topics include chemoselective reduction to γ-valerolactone and related oxygenates, pH-controlled oxidative C–C bond cleavage to functional organic acids, acid-mediated condensation reactions toward polymer-relevant monomers, and metal-free amination and cyclization pathways affording nitrogen-containing heterocycles. By organizing these transformations according to reaction class and selectivity control, this review highlights how foundational organic reactivity can be leveraged to achieve efficient and sustainable valorization of LA without reliance on transition metals.

We report a transition‐metal‐free and highly selective chemical transformation of levulinic acid into citramalic acid via t ‐butoxide‐mediated enolate chemistry, complementing both the biotransformation of glucose and glycerol using E. coli as well as transition‐metal‐catalyzed processes based on levulinic acid. The atypical behavior of t ‐butoxide—classically recognized as a base that favors kinetic enolate formation in carbonyl chemistry—proves crucial for accessing the thermodynamic enolate under elevated temperatures and extended reaction times, thereby directing the reaction toward citramalic acid as the major product. Radical‐trapping experiments with TEMPO (2,2,6,6‐tetramethylpiperidine 1‐oxyl) and benzoic acid significantly diminished the product yield, indicating the involvement of radical intermediates in the initial oxygenation sequence and providing clear mechanistic insight into the operative pathway. Moreover, citramalic acid serves as a sustainable, bio‐based platform chemical that is amenable to downstream valorization into high‐value feedstocks, such as unnatural amino acid derivative and itaconic acid.

Efficient and selective amidation in water remains challenging because productive N-acylation competes with hydrolysis of the acylating agent. Although acyl fluorides exhibit greater hydrolytic stability than acyl chlorides, the mechanistic origins of their unusual reactivity and selectivity in water remain poorly understood. Combined kinetic, spectroscopic, and computational investigations reveal a previously unknown acyl-transfer pathway arising from the cooperative assembly of an acyl fluoride, a potassium ion (derived from K₂CO₃), and water, generating a water-solvated mimic of the 18-crown-6–K⁺ complex that fundamentally alters acyl-transfer reactivity under aqueous conditions. This activation mode enables carbonate-mediated formation of a carbonic mixed anhydride, whose enhanced resistance to hydrolysis relative to the corresponding acyl halide decisively favors productive N-functionalization over competing hydrolysis. Under the optimized K₂CO₃-mediated conditions, the model amidation afforded the amide in > 99% yield within 1 h, with no detectable hydrolysis product (> 99:n.d.), whereas the classical biphasic Schotten–Baumann reaction using benzoyl chloride and KOH in CH₂Cl₂/H₂O afforded the corresponding amide in 76% yield with an amide-to-hydrolysis-product ratio of 96:4. The resulting mechanism enables highly selective amidation under fully aqueous conditions and reveals a previously unrecognized mode of aqueous acyl transfer. Beyond elucidating the origins of acyl fluoride reactivity in water, this work establishes a kinetic and mechanistic foundation for the rational design of sustainable acylation chemistry and reveals a non-classical acyl-transfer mechanism that transcends the inherent limitations of classical Schotten–Baumann methodology.

We report a regioselective alkylation of quinolines enabled by activation of 1,1-diborylalkanes with organolithiums.

Large-scale simulations of atomic systems play a vital role in fields, including chemistry, materials science, and more. However, they often struggle with efficiency due to high computational costs. To overcome this, machine learning force fields (MLFFs) have emerged as a promising alternative, providing accuracy comparable to density functional theory (DFT) while lowering costs. Nonetheless, variations in potential energy based on atomic environments make it challenging to apply kernel-based models across different compounds. To address this issue, we present an MLFF using the Robust Bayesian Committee Machine (RBCM) for various compounds containing carbon, nitrogen, and hydrogen (C-N-H). The MLFF is trained with first-principles calculations and molecular dynamics simulations of various C-N-H molecules. Testing these models with longer amine structures and two Diels-Alder reactions shows excellent agreement with DFT results, demonstrating that machine learning models accurately predict potential energy surfaces of organic molecules and offer opportunity for studying a wide range of C-N-H compounds.