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Sukwon Hong

Bio: Sukwon Hong is an academic researcher from Gwangju Institute of Science and Technology. The author has contributed to research in topics: Enantioselective synthesis & Catalysis. The author has an hindex of 22, co-authored 65 publications receiving 3082 citations. Previous affiliations of Sukwon Hong include University of Florida & Northwestern University.


Papers
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TL;DR: Sterically less encumbered ligand designs have been developed to improve reaction rates, and metallocene and nonmetallocene chiral lanthanide complexes have been synthesized for enantioselective hydroamination.
Abstract: Organolanthanides are highly efficient catalysts for inter- and intramolecular hydroamination of various C−C unsaturations such as alkenes, alkynes, allenes, and dienes. Attractive features of organolanthanide catalysts include very high turnover frequencies and excellent stereoselectivities, rendering this methodology applicable to concise synthesis of naturally occurring alkaloids and other polycyclic azacycles. The general hydroamination mechanism involves turnover-limiting C−C multiple bond insertion into the Ln−N bond, followed by rapid protonolysis by other amine substrates. Sterically less encumbered ligand designs have been developed to improve reaction rates, and metallocene and nonmetallocene chiral lanthanide complexes have been synthesized for enantioselective hydroamination.

935 citations

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TL;DR: This tutorial review highlights strategies and recent advances in cooperative bimetallic catalysts which have been developed for a variety of asymmetric transformations.
Abstract: The efficient synthesis of enantioenriched compounds is becoming increasingly important in modern organic, pharmaceutical, and materials chemistry. Recently, chiral cooperative bimetallic catalysts have emerged as a powerful tool to achieve high efficiency and selectivity in asymmetric transformations. This tutorial review highlights strategies and recent advances in cooperative bimetallic catalysts which have been developed for a variety of asymmetric transformations.

291 citations

Journal ArticleDOI
TL;DR: The optimized precatalyst, in situ generated [(4R,5S)-Ph(2)Box]La[N(TMS)(2)](2), exhibits good rates and enantioselectivities, comparable to or greater than those achieved with chiral C(1)-symmetric organolanthanocene catalysts.
Abstract: C2-symmetric bis(oxazolinato)lanthanide complexes of the type [(4R,5S)-Ph2Box]La[N(TMS)2]2, [(4S,5R)-Ar2Box]La[N(TMS)2]2, and [(4S)-Ph-5,5-Me2Box]La[N(TMS)2]2 (Box = 2,2‘-bis(2-oxazoline)methylenyl; Ar = 4-tert-butylphenyl, 1-naphthyl; TMS = SiMe3) serve as precatalysts for the efficient enantioselective intramolecular hydroamination/cyclization of aminoalkenes and aminodienes. These new catalyst systems are conveniently generated in situ from the known metal precursors Ln[N(TMS)2]3 or Ln[CH(TMS)2]3 (Ln = La, Nd, Sm, Y, Lu) and 1.2 equiv of commercially available or readily prepared bis(oxazoline) ligands such as (4R,5S)-Ph2BoxH, (4S,5R)-Ar2BoxH, and (4S)-Ph-5,5-Me2BoxH. The X-ray crystal structure of [(4S)-tBuBox]Lu[CH(TMS)2]2 provides insight into the structure of the in situ generated precatalyst species. Lanthanides having the largest ionic radii exhibit the highest turnover frequencies as well as enantioselectivities. Reaction rates maximize near 1:1 BoxH:Ln ratio (ligand acceleration); however, incr...

274 citations

Journal ArticleDOI
TL;DR: The highly stereoselective feature of aminodiene cyclization is demonstrated by concise syntheses of naturally occurring alkaloids, (+/-)-pinidine and (+)-coniine from simple diene precursors.
Abstract: Organolanthanide complexes of the general type Cp'(2)LnCH(TMS)(2) (Cp' = eta(5)-Me(5)C(5); Ln = La, Sm, Y; TMS = SiMe(3)) and CGCSmN(TMS)(2) (CGC = Me(2)Si(eta(5)-Me(4)C(5))((t)()BuN)) serve as effective precatalysts for the rapid, regioselective, and highly diastereoselective intramolecular hydroamination/cyclization of primary and secondary amines tethered to conjugated dienes. The rates of aminodiene cyclizations are significantly more rapid than those of the corresponding aminoalkenes. This dienyl group rate enhancement as well as substituent group (R) effects on turnover frequencies is consistent with proposed transition state electronic demands. Kinetic and mechanistic data parallel monosubstituted aminoalkene hydroamination/cyclization, with turnover-limiting C=C insertion into the Ln-N bond to presumably form an Ln-eta(3) allyl intermediate, followed by rapid protonolysis of the resulting Ln-C linkage. The rate law is first-order in [catalyst] and zero-order in [aminodiene]. However, depending on the particular substrate and catalyst combination, deviations from zero-order kinetic behavior reflect competitive product inhibition or self-inhibition by substrate. Lanthanide ionic radius effects and ancillary ligation effects on turnover frequencies suggest a sterically more demanding Ln-N insertion step than in aminoalkene cyclohydroamination, while a substantially more negative DeltaS( double dagger ) implies a more highly organized transition state. Good to excellent diastereoselectivity is obtained in the synthesis of 2,5-trans-disubstituted pyrrolidines (80% de) and 2,6-cis-disubstituted piperidines (99% de). Formation of 2-(prop-1-enyl)piperidine using the chiral C(1)-symmetric precatalyst (S)-Me(2)Si(OHF)(CpR)SmN(TMS)(2) (OHF = eta(5)-octahydrofluorenyl; Cp = eta(5)-C(5)H(3); R = (-)-menthyl) proceeds with up to 71% ee. The highly stereoselective feature of aminodiene cyclization is demonstrated by concise syntheses of naturally occurring alkaloids, (+/-)-pinidine and (+)-coniine from simple diene precursors.

163 citations

Journal ArticleDOI
TL;DR: The self-assembly through hydrogen bonding was confirmed by X-ray structure and by the 1H experiments revealing that the dimerization constant of the novel hydrogen-bonding capable salen ligand in 25% v/v CD3NO2/CDCl3 is 53 ± 21 M−1, proving the validity of self- assembly based approaches toward the efficient construction of chiral bimetallic catalyst system.
Abstract: Novel chiral dinuclear Co(II)-salen catalysts self-assembled through the pyridone/aminopyridine hydrogen-bonding pair have been developed. The self-assembled dinuclear Co(II)-Salen catalyst results in significant rate acceleration (48 times faster rate) as well as excellent enantioselectivity (96% ee vs 55% ee) in a nitro-aldol reaction, compared to the corresponding monomeric catalyst. A bimetallic mechanism is suggested by the kinetic experiment showing that the rate law is second order in [catalyst]. The self-assembly through hydrogen bonding was confirmed by X-ray structure and by the 1H experiments revealing that the dimerization constant of the novel hydrogen-bonding capable salen ligand in 25% v/v CD3NO2/CDCl3 is 53 ± 21 M−1. This result proves the validity of self-assembly based approaches toward the efficient construction of chiral bimetallic catalyst system.

159 citations


Cited by
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TL;DR: The fascinating story of olefin (or alkene) metathesis began almost five decades ago, when Anderson and Merckling reported the first carbon-carbon double-bond rearrangement reaction in the titanium-catalyzed polymerization of norbornene.
Abstract: The fascinating story of olefin (or alkene) metathesis (eq 1) began almost five decades ago, when Anderson and Merckling reported the first carbon-carbon double-bond rearrangement reaction in the titanium-catalyzed polymerization of norbornene. Nine years later, Banks and Bailey reported “a new disproportionation reaction . . . in which olefins are converted to homologues of shorter and longer carbon chains...”. In 1967, Calderon and co-workers named this metal-catalyzed redistribution of carbon-carbon double bonds olefin metathesis, from the Greek word “μeτάθeση”, which means change of position. These contributions have since served as the foundation for an amazing research field, and olefin metathesis currently represents a powerful transformation in chemical synthesis, attracting a vast amount of interest both in industry and academia.

1,696 citations

Journal ArticleDOI
TL;DR: Hydroamination of Alkenes and Alkynes under Microwave Irradiation and Nitromercuration Reactions 3878 9.8.4.5.
Abstract: 8.4.5. Nitromercuration Reactions 3878 9. Hydroamination of Alkenes and Alkynes under Microwave Irradiation 3878 * To whom correspondence should be addressed. Phone: +49 241 8

1,685 citations

Journal ArticleDOI
TL;DR: The results show clear trends in gold-Catalyzed C-H Bond Functionalization and Selective Reductions, and catalytic Hydrogenation of Alkenes and 1,3-Dienes, as well as in other areas of science.
Abstract: 2.7. Hydroxylation Reactions of Allenes 3282 2.8. Hydroamination Reactions of Allenes 3284 2.9. Hydrothiolation of Allenes 3284 2.10. Hydroalxoxylation of Alkenes and 1,3-Dienes 3286 2.11. Hydroamination of Alkenes and 1,3-Dienes 3287 2.12. Hydrothiolation of Conjugated Olefins 3289 3. Activation of Carbonyl/Imine Groups and Alcohols 3289 3.1. Condensation Reactions 3289 3.2. Addition Reactions 3291 3.3. Aldol Reactions 3294 3.4. Hydroand Carbosilylation Reactions 3295 3.5. Nucleophilic Substitution Reactions of Alcohols 3297 4. Gold-Catalyzed C-H Bond Functionalization 3297 4.1. Csp3-H Bond Functionalization 3298 4.2. Csp2-H Bond Functionalization 3299 4.3. Csp-H Bond Functionalization 3304 5. Gold-Catalyzed Selective Reductions 3305 5.1. Catalytic Hydrogenation of Alkenes 3306 5.2. Selective Reductions of R, -Unsaturated Carbonyl Groups and 1,3-Dienes 3306

1,358 citations