• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2711-2718
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• 2012

The alkylation of the ambident enolates of a methyl glycinate Schiff base with ethyl chloride was studied at B3LYP and MP2 levels with $6-31+G^*$ basis set. The free (E)-enolates and (Z)-enolate are similar in energy and geometry. The transition states for the alkylation of the free (E)/(Z)-enolate with ethyl chloride have similar energy barriers of ~13 kcal/mol. However, with a lithium ion, the (E)-enolate behaves as an ambident enolate and makes a cyclic lithium-complex in bidentate pattern which is more stable by 11-23 kcal/mol than the (Z)-enolate-lithium complexes. And the TS for the alkylation of (E)-enolate-lithium complex coordinated with one methyl ether is lower in energy than those from (Z)-enolate-lithium complexes by 4.3-7.3 kcal/mol. Further solvation model (SCRF-CPCM) and reaction coordinate (IRC) were studied. This theoretical study suggests that the alkylation of ambident enolates proceeds with stable cyclic bidentate complexes in the presence of metal ion and solvent.

• Bulletin of the Korean Chemical Society
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• 제32권spc8호
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• pp.2887-2888
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• 2011

• Bulletin of the Korean Chemical Society
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• 제21권8호
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• pp.767-768
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• 2000

• Bulletin of the Korean Chemical Society
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• 제20권3호
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• pp.325-328
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• 1999

In the reactions of the enolates of various 2-piperidineacetates with iodomethane or trisyl azide, the anti isomer was always predominant over the syn one, independent of the stereochemistry of the piperidineacetates. The piperidineacetates having OTBDMS moiety at C5 proceeded more diastereoselectively than the compounds without the substituent. The diastereoselectivity could be explained by perpendicular model for the electrophilic substitution reaction.

• Bulletin of the Korean Chemical Society
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• 제35권6호
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• pp.1851-1854
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• 2014

• Archives of Pharmacal Research
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• 제14권3호
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• pp.266-270
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• 1991

Synthesis of C-(2-furyl)-N-(4-nitrophenyl)methanohydrazonyl bromide 2 is described. Treatment of 2 with uncleophiles affords the corresponding substitution products 3-7. Also, compound 2 reacts with selenocyanate anion and thiocyanate anion and give the corresponding selenadiazoline and thiadiazoline 8 and 9, respectively. Moreover, reaction of 2 with enolates of various active methylene compounds afforded the pyrazole derivatives 17-20.

• Bulletin of the Korean Chemical Society
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• 제23권5호
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• pp.749-757
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• 2002

Chiral oxazolidin-2-one is easily prepared from D-mannitol and demonstrated to undergo highly diastereoselective alkylation reactions via lithium imide Z-enolates of its N-acyl derivatives to afford ${\alpha}-branched$ products. Evans syn and non-Evans sy n aldol products were also selectively obtained using this new auxiliary in high diastereomeric purity by simply changing the stoichiometry of TiCl4 and the nature of the amine base. Also, this new auxiliary is employed in diastereoselective Staudinger-type ${\beta}-lactam$ syntheses. Using 2-chloro-1-methylpyridinium iodide as the dehydrating agent, the reaction of auxiliary tethered acetic acid with trans imines gave the desired ${\beta}-lactams$ with cis-selectivity.

• Bulletin of the Korean Chemical Society
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• 제32권10호
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• pp.3738-3742
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• 2011

Bismuth tribromide ($BiBr_3$) catalyzed Mannich-type reactions of N-acyliminium ions which generated in situ from N-benzyloxycarbonylamino p-tolylsulfones have been developed. In the presence of catalytic amount of $BiBr_3$, N-benzyloxycarbonylamino p-tolylsulfones prepared from aromatic and aliphatic aldehydes reacted with silyl enol ether and silyl enol ester under mild reaction conditions to afford N-Cbz-protected ${\beta}$-amino ketones and N-Cbz-protected ${\beta}$-amino esters in moderate to good yield, respectively.

• Bulletin of the Korean Chemical Society
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• 제5권5호
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• pp.191-193
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• 1984

6, 6-Diiodopenicillanic acid was prepared from 6-aminopenicillanic acid using iodine-sodium iodide systems in good yield (60%). Enolates derived from 6-chloro-6-iodo-, 6,6-diiodo-penicillanate have been generated in situ by a metal-halogen exchange process at -$78^{\circ}C$ using methylmangnesium iodide and reacted with acetaldehyde to yield aldols. As the size of remaining halogen atom increases, the proportion of ${\beta}$-face attack was increased. In the case of 6,6-diiodopenicillanate, only ${\beta}$-face attack was observed yielding a single isomer (6S, 8R).