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11.
Giuseppe Werber Francesco Buccheri Nicol Vivona Manlio Gentile 《Journal of heterocyclic chemistry》1978,15(8):1393-1398
The factors influencing the reactivity of α-thienylglyoxal monosemicarbazones when treated with cyclizing reagents (bromine/sodium acetate and hydrobromic acid in acetic acid) were investigated. Depending on the experimental conditions, on the position of the substituent on the semicarbazide residue, and on the cyclizing agent, the substrates 1a-e give the semicarbazone bromides 2a-b, 5 , the 1,3,4-oxadiazoles 3a-c , the 1,2,4-triazine 11 and the 2,3,4,5-tetrahydro-1,2,4-triazine-3-ones 6, 8 and 9 . Compound 6 by thermolysis undergoes ring contraction in the Δ2-1,3,4-oxadiazoline 12 , while treatment with base involves the conversion of 6 into 1,2,4-triazol-5-one 13 . Ir, nmr and mass spectra support the reported structures. 相似文献
12.
13.
NMR data have been used to assign the stereochemistry to some new (E)- and (Z)-α-phenyl-β-[2-(N-methyl)nitropyrrolyl]acrylic acids. The (E)-molecules are biased in the s-cis conformation showing NMR spectroscopic features strictly depending on the conformation.The analysis of the NMR spectra reveals that the (Z)-isomers exist also in the s-cis conformation. 相似文献
14.
Giovannelli Tommaso Liuzzi Giampaolo Lucidi Stefano Rinaldi Francesco 《Computational Optimization and Applications》2022,82(2):293-327
Computational Optimization and Applications - In this paper, mixed-integer nonsmooth constrained optimization problems are considered, where objective/constraint functions are available only as the... 相似文献
15.
16.
Franco Cristiani Francesco A. Devillanova Gaetano Verani 《Transition Metal Chemistry》1977,2(1):50-52
Summary White crystalline complexes of general formula ML2X2, where M = Zn, Cd, Hg; X = Cl, 13r, I and L = pyrrolidine-2-thione, were prepared and studied by i.r. spectroscopy in the 4000-200 cm–1 range. Evidence for coordination of the ligand to the metal through sulphur was found in each case. The previous assignment of the band present in the ligand at 1110 cm–1 to the(CS) fundamental is discussed.This work was supported by the National Research Council (C.N.R.) of Italy. 相似文献
17.
Francesco A. Devillanova Gaetano Verani D. N. Sathyanarayana 《Journal of heterocyclic chemistry》1978,15(6):945-947
An infrared investigation cm N-methyl-1,3-thiazolidine-2-thione and -2-selone in the range 4000-200 cm?1 is reported. The v CS and v CSe vibrations give contributions to the absorptions around 1000 cm?1 and below 600 cm?1. The assignments are supported by comparison of their ir spectra with those of S- and Se-methiodides. The π-bond orders of the thio- and seleno-ketonic links in these compounds are higher than those found for 1,3-imidazolidine-2-thione and -2-selone. 相似文献
18.
The determination by neutron activation of trace quantities of calcium, strontium and barium in single crystals of alkali halides has been studied. The matrix is eliminated before the irradiation by an ion-exchange procedure. Gamma spectroscopy after radiochemical separation is used to determine strontium and barium. Calcium is determined by measuring the β-activity of 49Sc formed by the decay of 49Ca. Long-lived radioactive tracers are used to determine the chemical yields. 相似文献
19.
Giuseppe Werber Francesco Buccheri Manlio Gentile 《Journal of heterocyclic chemistry》1977,14(7):1263-1265
The ambident nucleophilic behaviour of some 2-amino-5-H-1,3,4-thiadiazoles in alkylation, acylation and nitrosation reaction has been verified. The structures assigned to the 2-amino-1,3,4-thiadiazoles ( 1a-i ) and to the Δ2-1,3,4-thiadiazolines ( 2a-e ) agree with the spectral data. 相似文献
20.
Il contenuto di questo lavoro consiste nel mostrare che le fibrazioni dei near-field regolari di dimensionet+1 sul nucleo , quando , si ottengono da fibrazioni regolari con una operazione di scambio fra alcuni sistemi di matrici, che generalizza il procedimento di sostituzione di regoli con regoli opposti di quadriche rigate nel caso di dimensione due sul nucleo. 相似文献