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141.
Yu. Yu. Popelis É. É. Liepin'sh Ya. P. Stradyn' 《Chemistry of Heterocyclic Compounds》1980,16(2):116-123
The1H and13NMR spectra of t-nitrofuran and 17 2-substituted 5-nitrofurans were investigated. The Δ1H and Δ13C substituent increments [Δ = δ(2-X-5-nitrofuran) δ(5-nitrofuran)] in the spectra of these compounds were analyzed by comparison
with the analogous 5-methylfuran and furan derivatives, and the change in the sensitivity of the chemical shifts of the ring
protons and the carbon atoms to the effects of substituents X as a function of the electronic character of substituent R was
also analyzed. The chemical shifts and the spin-spin coupling constants were used to determine the preferred orientation of
the substituents relative to the furan ring. It was found that medicinal preparations of the 5-nitrofuran series (5-nitrofurfurylidenehydrazones)
exist in the form of s-trans conformers in solutions in dimethyl sulfoxide and water, whereas furagin has primarily the structure
of the E s-trans form.
Translated from Khimiya Geterotsiklichesklkh Soedinenii, No. 2, pp. 167–176, February, 1980.
The authors thank N. O. Saldabol, M. A. Trushule, and K. K. Venter for providing us with samples of the compounds, the synthesis
of which has been described in the literature. 相似文献
142.
Edmunds Lukevics Pavel Arsenyan Juris Popelis Olga Pudova 《Phosphorus, sulfur, and silicon and the related elements》2013,188(4):639-647
Lithiation of 2-trimethylsilyl- and 2-trimethylgermylthiophenes by n -BuLi and subsequent silylation or germylation by dichlorodimethylsilane or dichlorodimethylgermane give bis[2-(5-trimethylsilyl-(germyl)thienyl]dimethylsilanes and -germanes ( 1a-d ). Their oxidation with 4 equivalents of m -chloroperbenzoic acid leads to formation of corresponding thiophene-1,1,1'1'-tetroxides ( 2a-d ). Nucleophilic addition of secondary amines to thiophene-1,1,1'1'-tetroxides ( 2a-d ) has been studied. It has been shown that the basicity of amine and the nature of solvent determine the reaction pathway. In water, the addition of two dimethylamine or piperidine molecules and only one diethylamine or morpholine molecule to each thiophene-1,1,1'1'- tetroxide fragment of the sulfone was accompanied by complete desilylation and degermylation. In organic solvents (benzene, THF) the addition of two piperidine molecules to each thiophen-1,1-dioxide fragment of bis[2-(5-trimethylsilyl)thienyl]dimethylsilane was observed. In this case the desilylation of both trimethylsilyl and dimethylsilyl groups occurred. 相似文献
143.