To estimate of the dispersion trend of 3H and 14C discharged from the Wolsung Nuclear Power Plants, the present level of 3H and 14C in environmental samples in the vicinity of the Wolsong site was studied. Tree-ring cellulose analyses were carried out for retrospective evaluation of 3H and 14C in the environment around the Wolsong Nuclear Power Plants. 3H released from the Wolsong Nuclear Power Plants has affected an area up to a 25-km radius from the site, while almost all 14C was deposited within a 2-km radius, reaching to a natural level over 2 km. Organically bound tritium concentrations in tree rings were strongly correlated with the gaseous tritium discharge rate, while delta14C (excess) in tree rings ranged from 204 per thousand to 460 per thousand, which did not significantly vary with year.
NH 4 OH promoted crystallization induced dynamic resolution (CIDR) of configurationally labile a-chloro acetamides has been investigated. CIDR of N-(S)-(1-phenylethyl)-a-chloro-a-aryl acetamides 2-4 has been successfully used for the asymmetric preparation of a-chloro carbonyl functionality up to 97:3 diastereomeric ratio in 95% yield. As an application of this methodology we have shown a stereospecific substitution reaction of (aS)-2 with KSAc for the asymmetric preparation of a-mercapto carboxylic acid derivative (aR)-5.Dynamic kinetic resolution of configurationally labile ahalo esters or amides having a chiral auxiliary has been recently recognized as an effective synthetic method for asymmetric syntheses of a-substituted carboxylic acids. 1 For the effective asymmetric transformation, there must be a significant difference in the rate of nucleophilic substitution reaction of one diastereomer over the other. In some cases that the enough substitution rate difference is not available, crystallization induced dynamic resolution (CIDR) could be an alternative approach for dynamic resolution, in which one of diastereomers crystallizes preferentially with high selectivity. 2 We have investigated the development of efficient dynamic resolution methods for a-halo acetamide which could be a synthetic precursor of optically active a-substituted carboxylic acids. Here we wish to report preliminary results on CIDR of N-(S)-(1-phenylethyl)-a-halo-a-aryl acetamides that contain one potentially labile stereogenic center in basic conditions. (S)-1-Phenylethylamine is chosen as a chiral inducer because it is stable, inexpensive and available in quantity in both enantiomeric forms (Figure). Initial studies on CIDR were carried out with 1:1 diastereomeric mixture of a-bromo-a-phenyl acetamide (aRS)-1, Et 3 N (1.5 equivalents) and tertrabutylammonium bromide (TBAB, 30 mol%) in toluene at room temperature by allowing solvent to slowly evaporate. After the complete evaporation of toluene, the reaction provided the optically active product 1 with 75:25 diastereomeric ratio and (aS)-diastereomer as a major isomer as shown in the Table (entry 1). The stereochemical outcome of this CIDR process was determined by 1 H NMR of crude reaction mixture. 3a No stereoselective CIDR was observed in the absence of base or halide source in toluene. Other solvents which evaporate faster such as THF, CH 3 CN and CH 2 Cl 2 gave lower selectivities as shown in the Table (entries 2-4). The reaction of a-chloro-a-phenyl acetamide (aRS)-2 provided 2 without any notable selectivity (52:48 diastereomeric ratio, entry 5) upon similar treatment with Et 3 N and benzethonium chloride (BC) for chloride source in toluene.Considering the important role of solvent for the appropriate CIDR conditions, we have focused on finding effective solvent system. It is necessary to find the solvent system in which the solubility of the substrate is good for both precipitation and equilibration processes. In an effort to control the solubility of (aRS)-1 and (aRS)-2 in t...
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