• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2527-2530
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• 2010

The stereoselectivity of the intramolecular Diels-Alder reactions of 1 and its derivatives were investigated by ab initio calculations. The stereoselectivity mainly originates from the steric repulsion and the orbital interactions. The additional s-cis and s-trans conformations by introducing the carbonyl group at the neighbor of diene or dienophile may change the stereoselectivity, hence this kind of substitution can be utilized for stereoselectivive asymmetric synthesis.

• Journal of Photoscience
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• v.10 no.1
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• pp.49-60
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• 2003

How stereo selectivity in singlet and triplet photocycloaddition and photocyclization reactions, respectively, is linked to spin selectivity and how this link affects our understanding of photochemical reaction mechanisms, is described in this review. As illustrative examples, the Paterno-Buchi reaction and the Norrish-Yang cyclization are described with emphasis on triplet biradical structure and dynamics.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.13-14
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• 2003

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.169-170
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• 2002

It has been well known for the stereoselectivity in pharmacodynamic effects of many xenobiotics including therapeutic agents, which have lead to the development of enantiomer drugs. Compared to pharmacodynamic stereoselectivity, stereoselective pharmacokinetics of each enantiomer has not been seriously considered in the development of enantiomer drugs although many reports have been demonstrated the stereoselective absorption and metabolism of racemic drug (e.g verapamil). (omitted)

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.355-356
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• 1997

• Journal of Photoscience
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• v.4 no.1
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• pp.7-10
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• 1997

The structures of 8-membered azalactone isomers produced from photocyclization of 2-(N,N-dibenzylamino)ethyl benzoylacetate were determined by the X-ray structure analysis to clarify the stereochemical behavior of a 1,8-biradical. The remarkable stereoselectivity in cyclization of the 1,8-biradical to form cis- and trans-isomers of the azalactone was not observed. The ring conformations were boat-chair like and dihedral angles between C$_5$- and C$_6$- phenyl groups were ca 45$\circ$ in the both isomers. The 1,8-biradicals in the transition state for the cyclization would have nearly same boat-chair like conformation and twisted configuration with the dihedral angle of ca 45$\circ$ as the corresponding isomer, and this is responsible for luck of stereoselectivity in long-chain biradical cyclization.

• Bulletin of the Korean Chemical Society
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• v.23 no.6
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• pp.856-861
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• 2002

The general reducing charagteristics of a newly synthesized reducing agent, lithium(2.3-dimethyl-2-butyl)-${\iota}$-butoxyborohydride (Li $Thx'BuOB_2$, 1), in tetrahydrofuran (THF) toward selected organic compounds containing representative fundtional groups under practical has been examined. The reagent revealed an interesting and unique reducing characteristics. Especially, the stereoselectivity in the reduction of cyclic ketones was extraordinary. Thus, the introduction of bulky alkyl and alkoxy groups into the parent borohydride affonds a high stereoselectivity. In general, the reducing power of the reagent is somewhere between the dialiylborohydride and the parent borohydride. This permits the reagent to be a reagent of choice for selecitive reduction of organic compounds with an improved selectivity.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.591-598
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• 2013

A series of chiral prolinamide compounds with pyridine-2, 6-dicarboxylic acid moieties derived from L-proline have been designed and synthesized, their catalytic properties for direct asymmetric aldol reactions were also studied in this article. These catalysts gave the aldol product in high yield (87%) and high enantioselectivity, up to 85%, of the anti-structure at room temperature but gave disappointing results at a lower temperature or when additive was added. Conditions, including solvents, temperature and additives were screened for the reactions. Moreover, the influence of presence of water on yield and stereoselectivity was also discussed.

• Bulletin of the Korean Chemical Society
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• v.16 no.1
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• pp.37-42
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• 1995

Reactions of alkenes and alkynes with the recently discovered isopinocampheylhaloborane-methyl sulfide (IpcBHX·SMe2, X=Cl, Br, I) were investigated in detail in order to establish their usefulness as hydroborating agents. The reagents readily hydroborated alkenes at 50 ℃ and alkynes at 25 ℃ with excellent regioselectivity in placing the boron atom exclusively at the less hindered carbon atom. Especially, the selectivity achieved by the iodo derivative reaches essentially 100%. In addition to that, IpcBHX·SMe2 was applied to the reduction of cyclic ketones to examine its stereoselectivity. The halogen substituent in these reagents plays an important role in the stereoselective reduction. The stereoselectivity increased dramatically with increasing steric size of the substituent. Finally, the iodo derivative achieved highly stereoselective reduction, such selectivity being comparable to that previously achieved with trialkylborohydrides.

• Bulletin of the Korean Chemical Society
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• v.15 no.6
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• pp.478-483
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• 1994

Reactions of alkenes and alkynes with thexylhaloborane-methyl sulfide (ThxBHX${\cdot}$SMe$_2$, X= Cl, Br, I) were investigated in detail in order to elucidate the effect of halogen substituent in thexylborane and hence establish their usefulness as hydroborating agent. The reagents readily hydroborated alkenes at $50^{circ}C$and alkynes at $25^{circ}C$ in exceptional regioselectivity. Especially, the selectivity achieved by the bromo and iodo derivative reaches essentially 100%. In addition to that, $ThxBHX{\cdot}SMe_2$ was applied to the reduction of cyclic ketones to examine its stereoselectivity. The halogen substituent in thexylborane plays an important role in the stereoselective reduction. The stereoselectivity increased dramatically with increasing steric size of the substituent. Finally, the iodo derivative achieved highly stereoselective reduction, such selectivity being comparable to that previously achieved with trialkylborohydrides.