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55. Tandem Reaction Approaches to Isoquinolones from 2-Vinylbenzaldehydes and Anilines via Imine Formation–6π-Electrocyclization–Aerobic Oxidation Sequence

Author

Lee, Jiyeon, Kim, Hun Young, and Oh, Kyungsoo

Abstract

Two distinctive transition-metal-promoted aerobic oxidation protocols have been developed for the synthesis of isoquinolones from 2-vinylbenzaldehydes and aniline derivatives. Thus, the one-pot tandem reaction sequence of imine formation, thermal 6π-electrocyclization, followed by either Cu(OAc)2-mediated or Pd(OAc)2-catalyzed aerobic oxidation protocol allowed the ready access to isoquinolone derivatives. The control experiments revealed that the 1,2-dihydroisoquinoline intermediates from the 6π-electrocyclization of 1-azatrienes were aerobically oxidized to isoquinolones in the presence of either Cu(OAc)2or Pd(OAc)2catalyst.

Published
2020
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56. Silver-Catalyzed Asymmetric Desymmetrization of Cyclopentenediones via [3 + 2] Cycloaddition with α-Substituted Isocyanoacetates

Author

George, Jimil, Kim, Hun Young, and Oh, Kyungsoo

Abstract

A highly selective and practical asymmetric Ag(I) catalyst system has been developed for the [3 + 2] cycloaddition reactions between isocyanoacetates and cyclopentenediones. The current Ag(I) catalyst system tolerates moisture and air and readily utilizes class III solvents such as EtOAc and acetone. The development of on demandgeneration of an active chiral catalyst in the presence of isocyanides paves a way to the efficient asymmetric preparation of bicyclic pyrrolidines with four stereogenic centers, including two quaternary centers in 80–97% ee.

Published
2024
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57. Rhodium(I)-Catalyzed Decarbonylative Aerobic Oxidation of Cyclic α-Diketones: A Regioselective Single Carbon Extrusion Strategy

Author

Golime, Gangadhararao, Kim, Hun Young, and Oh, Kyungsoo

Abstract

A rhodium-catalyzed decarbonylative aerobicoxidation of cyclic α-diketones has been developed for the first time, where the regioselective formations of α-pyrones and isocoumarins have been achieved. The current decarbonylative aerobicoxidation pathway proceeds via the C–C bond cleavage followed by a C–O bond formation, representing a biomimetic oxidation approach to unsaturated six-membered cyclic lactones. The unique ability of rhodium catalysts to induce the decarbonylative aerobicoxidation opens up a new synthetic toolbox that utilizes the “regioselective single carbon” extrusion strategy.

Published
2024
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58. A One-Pot Synthesis of Pyranone and Pyrrole Derivatives from β-Chlorovinyl Ketones via Direct Conjugate Addition Approach

Author

Kim, Hun Young and Oh, Kyungsoo

Abstract

The direct conjugate addition reactions of imino esters to β-chlorovinyl ketones have been accomplished in the presence of a substoichiometric amount of hard base, LiHMDS. An in situgenerated species from the conjugate addition reaction readily acted as autocatalyst to convert the imino esters to its corresponding enolates. By utilizing a sequence of conjugate addition/elimination/lactonization followed by either reduction or reaction with amines, the novel one-pot syntheses of highly functionalized pyranone and pyrrole derivatives were accomplished in good to excellent yields.

Published
2024
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65. Effects of N2/CO2 dilution on flame propagation velocities and quenching distances of oxy-methane premixed mixtures using an Annular-Stepwise-Diverging-Tube (ASDT).

Author

KIM, HUN YOUNG, LEE, JISEOP, and KIM, NAM IL

Subjects
*DILUTION, *QUENCHING (Chemistry), *METHANE, *GAS mixtures, *SCALAR field theory
Abstract

Many combustion systems use the technique called exhaust gas recirculation. Thus, the effects of N2/CO2 dilution on the combustion characteristics have been of interest. In this study, the dilution effects on the flame propagation velocity (FPV) of an oxy-methane premixed mixture were investigated using a state-of-the-art annular stepwise diverging tube. The relationship between FPV and the length scale was measured for various equivalence ratios in the dilution ratio range 65–75% N2 and 50–65% CO2. The characteristic variations of FPV in each dilution case could be described as a surface in a concentration–length–velocity diagram, and this provides a bird's eye view of the dilution effects on flame propagation. Two distinctive scalar values of the quenching distance and the critical FPV were investigated. At the same dilution ratio, CO2 dilution caused more significant variation than N2 dilution did regarding FPV, quenching distance, and flammable limits. In particular, the critical FPV was compared with the laminar burning velocity (LBV) calculated using a PREMIX code employing GRI-3.0. In addition, fictitious species (F-N2/F-CO2) were used in the reaction mechanism to distinguish chemical effects. Conclusively, results showed that CO2 dilution reduced LBV significantly not only by its larger thermal capacity but also by its active involvement in the chemical reaction. [ABSTRACT FROM AUTHOR]

Published
2018
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73. Tandem Transformations via Friedel–Crafts Acylation Followed by a Ring-Expansion, Ring-Opening, and Cycloisomerization Sequence

Author

Kim, Hun Young and Oh, Kyungsoo

Abstract

A tandem synthetic route to a diverse array of cyclic compounds has been developed from Friedel–Crafts acylation of alkynes followed by the microwave irradiation of β-chlorovinyl ketone intermediates. The stereoisomeric β-chlorovinyl ketone intermediates smoothly underwent a thermal α-vinyl enolization and ring expansion to vinyl and carbocyclic furans as well as cyclopetene derivatives in good to excellent yields without the need for any catalysts.

Published
2018
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99. Regiodivergent Halogenation of (E)-β-Chlorovinyl Ketones via Soft α-VinylEnolization Strategy.

Author

Kim, Hun Young, Lee, Seokwoo, Kim, Sanghee, and Oh, Kyungsoo

Subjects
*HALOGENATION, *ENOLIZATION, *KETONES, *ELECTROPHILES, *HALOGEN compounds, *NUCLEOPHILIC reactions
Abstract

Thesoft α-vinyl enolization of (E)-β-chlorovinylketones was investigated in the presence of various halogen electrophiles.Depending on the nature of halogen electrophiles, the selective formationof three products, namely α,α-dichloropropargyl ketones,α,γ-dihaloallenyl ketones, and 3-halofurans, was observed.The observed regiodivergent nucleophilic pathways of (E)-β-chlorovinyl ketones demonstrate the diversity-orientedsynthesis strategy in which the nucleophilic reactivity of (E)-β-chlorovinyl ketones can be selectively modulatedby the choice of suitable hard and soft electrophiles. [ABSTRACT FROM AUTHOR]

Published
2015
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