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A Facile Method for the Synthesis of Hydrazine‐4‐oxothiazolidine and Imino‐5‐oxothiadiazine Derivatives from 1,4‐Disubstituted Thiosemicarbazides 下载免费PDF全文
Alaa A. Hassan Ashraf A. Aly Tarek I. M. Bedair Alan B. Brown Talaat I. El‐Emary 《Journal of heterocyclic chemistry》2014,51(1):44-49
1,4‐Disubstituted thiosemicarbazides reacted with dimethyl acetylenedicarboxylate with formation of (2‐hydrazono‐4‐oxothiazolidin‐5‐ylidene)acetates and, in one case, a (2‐imino‐1,3,4‐thiadiazin‐5‐on‐6‐ylidene)acetate. Several mechanistic options involving nucleophilic interaction are presented. The structures of all newly synthesized compounds were identified by 1H NMR, 13C NMR, COSY, HMQC and HMBC spectral data. 相似文献
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A Comparative Study of 8‐Hydroxyquinoline and 8‐Hydroxyquinoline‐5‐sulfonic Acid for Antimony(III) Determination by AdSV. Substituent Effect on Sensitivity II 下载免费PDF全文
A sensitive and selective method for the determination of Sb3+ based on the formation of its complexes with 8‐hydroxyquinoline (HQ) and 8‐hydroxyquinoline‐5‐sulfonic acid (HQS) is proposed. The best analytical conditions are: pH 5.4 and 2.2 for HQ and HQS, respectively; CHQ from 15.0 to 25.0 µmol L?1 and CHQS from 70.0 to 200.0 µmol L?1. The detection limits are 100.0 and 14.0 ng L?1 (tacc=30 s) for Sb3+ with HQ and HQS, respectively. The method using HQS as ligand has a 2.2‐fold higher sensitivity than that with HQ and the former was chosen for Sb3+ determination. 相似文献
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María Casimiro Dr. Pascual Oña‐Burgos Dr. Jens Meyer Steffen Styra Dr. Istemi Kuzu Prof. Dr. Frank Breher Prof. Dr. Ignacio Fernández 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(2):691-701
2D 7Li,15N heteronuclear shift correlation through scalar coupling has successfully been applied to several lithium organyls consisting of polydentate N ligands such as N,N,N′,N′‐tetramethylethylenediamine (tmeda), N,N,N′,N′,N′′‐pentamethyldiethylentriamine (pmdta) and (?)‐sparteine. Structural insights on the conformation of benzyllithium ? pmdta ( 5 ) in a toluene solution and the strength of ion pairing in combination with PGSE NMR measurements, 1H,1H‐NOESY and 1H,7Li‐HOESY experiments are presented. By studying in detail the formation of 5 in solution, a transient species has been observed for the first time and assigned to a pre‐complex of nBuLi and pmdta. In addition, the solution behaviour of the complex formed between benzyllithium and (?)‐sparteine ( 8 ) has been studied by PGSE and multinuclear NMR spectroscopy. The straightforward synthesis and first applications in asymmetric lithiations are also reported, which show that the new system benzyllithium ? (?)‐sparteine ( 8 ) provide poorer enantioselective induction than the classical nBuLi ? (?)‐sparteine ( 6 ). The results were supported by deprotonation experiments confirming that the formation of 8 relies on two relevant factors, namely temperature and lithiating reagent. The existence of 8 may thus interfere with the asymmetric induction when the system nBuLi ? (?)‐sparteine is used in the enantioselective deprotonations of N‐Boc‐N‐(p‐methoxyphenyl)‐benzylamine conducted in toluene. 相似文献
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献