Sungyul Lee

Due to the tremendous interest in carbon-fluorine bond-forming reactions, research efforts in this area have been dedicated to the development of facile processes to synthesize small fluorine-containing organic molecules. Among others, PET (Positron Emission Tomography) is one of the most important applications of fluorine chemistry. Recognizing the specific requirements of PET processes, some groups have focused on fluorination reactions using alkali metal fluorides, particularly through SN2-ty

Abstract Highly enantioselective biomimetic Michael addition reactions of malonic acid half thioesters (MAHTs) to a variety of nitroolefins, affording the optically active γ‐amino acid precursors, were developed by employing the Cinchona ‐based squaramides (up to >99% ee ). Remarkably, this biomimetic process is enantioconvergent, a highly desirable feature of a catalytic asymmetric reaction, whereby E / Z ‐isomers of the nitroolefins afford the same product enantiomer. The synthetic utility

Herein, we report the promising use of n-oligoethylene glycols (oligoEGs) as mutifunctional promoters for nucleophilic-substitution reactions employing alkali metal salts. Among the various oligoEGs tested, pentaethylene glycol (pentaEG) had the most efficient catalytic activity. In particular, when compared with other nucleophiles examined, a fluorine nucleophile generated from CsF was significantly activated by the pentaEG promoter. We also performed various facile nucleophilic-displacement re

Abstract Calculations are presented for the structure and the isomerization reaction of various conformers of the bare serine, neutral serine–(H 2 O) n and serine zwitterion–(H 2 O) n ( n = 1, 2) clusters. The effects of binding water molecules on the relative stability and the isomerization processes are examined. Hydrogen bonding between serine and the water molecule(s) may significantly affect the relative stability of conformers of the neutral serine–(H 2 O) n ( n = 1, 2) clusters. The sidec

Interdiffusion coefficient \\ ildeD in the β-phase of Ti-Al alloys has been determined by Matano’s method in the temperature range 1323 to 1823 K with (pure Ti)-(Ti-8.5 at% Al alloy), (pure Ti)-(Ti-16.5 at% Al alloy) and (Ti-8.5 at% Al alloy)-(Ti-16.5 at% Al alloy) couples. In the whole temperature range the value of \\ ildeD increases gradually with increasing aluminum content. The Arrhenius plot of \\ ildeD up to 6 at% Al shows an upward curvature similar to that recognized in the self-diffusi

Interdiffusion coefficients in the β phase of Ti–Cr and Ti–Pd alloys have been determined by Matano’s method in the temperature range between 1173 and 1823 K with (pure Ti)–(Ti-4.62 at% Cr alloy) and (pure Ti)–(Ti-1.84 at% Pd alloy) couples. The impurity diffusion coefficients of Cr and Pd in β-Ti have been determined by extrapolating concentration dependence of the interdiffusion coefficient to the infinite dilution of solute, and the following results have been obtained. In the whole temperatu

This review highlights the effects of explicit water molecules on the structures of amino acids and dipeptides, focusing on the relative stability of canonical<italic>vs.</italic>zwitterionic conformers.

A bis-tert-alcohol-functionalized crown-6-calix[4]arene (BACCA) was designed and prepared as a multifunctional organic promoter for nucleophilic fluorinations with CsF. By formation of a CsF/BACCA complex, BACCA could release a significantly active and selective fluoride source for SN2 fluorination reactions. The origin of the promoting effects of BACCA was studied by quantum chemical methods. The role of BACCA was revealed to be separation of the metal fluoride to a large distance (>8 Å), there

A quantum mechanical theory is described for diatomic photodissociation processes to atomic fine structure states for which more than one atomic term limit must be explicitly considered. The theory is employed to treat the photodissociation of OH molecule. Two frame transformation matrices are constructed and incorporated, for the first time, to describe the correlations between two oxygen terms [O(3P) and O(1D)] and the adiabatic Born–Oppenheimer states. We find that very interesting dynamics r

Achirale Polyetherderivate beschleunigen SN2-Reaktionen, indem sie sowohl das Nucleophil (KF) als auch das Elektrophil (eine Sulfonatgruppe) aktivieren (siehe Bild). Mit einer chiralen Variante der Katalysatoren gelingt die desilylierende kinetische Racematspaltung der Silylether von sekundären Alkoholen. Die Ergebnisse von Dichtefunktionalrechnungen erklären, wie derartige organische Promotoren funktionieren.

Ferromagnetic single-crystalline Co nanowires (NWs) aligned in a vertical orientation are epitaxially grown on <italic>m</italic>-cut sapphire substrates by a rapid and versatile chemical vapor deposition method. They were transformed into Co₃O₄ nanotubes by thermal annealing under dilute O₂ conditions.

Multichannel scattering calculations are used to determine the role of nonadiabatic interactions on the predissociation dynamics of several vibrational levels of the A 2Σ+ state of OH and the resulting oxygen atom fine structure branching ratios. Nonadiabatic effects are found to be very strong for the lower predissociative vibrational A 2Σ+ levels and to remain nonnegligible even for the higher vibrational states of A 2Σ+ despite the considerable degree to which the asymptotic fragment kinetic