Reductive cleavage by metallic sodium in liquid ammonia of cotton lignin

Twofold cleavage with sodium in liquid ammonia of the dioxane lignin and fourfold cleavage of the native lignin from cotton stems have shown that the uncleaved parts of lignin have molecular masses 2–4 times lower than the initial lignins and consist of 15–17 phenylpropane structural units.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 412–416, May–June, 1989.     

Reductive cleavage by sodium in liquid ammonia of the lignin of cotton-plant stems

Summary 1. The reductive degradation by metallic sodium and liquid ammonia of the lignin of green cotton-plant stems has confirmed the presence in them of three types of structural units: syringyl, guaiacyl, and p-hydroxycoumaryl.2. The preliminary sonication of the plant with ultrasound leads to a decrease in the amount of products containing methoxy groups in the aromatic nucleus, particularly syringyl structures.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 643–646, September–October, 1976.     

Deoxygenation of sugar trifluoromethanesulfonates by sodium metal in liquid ammonia and by photolysis

Several trifluoromethanesulfonyl(TFMS) derivatives of sugars were prepared and treated with sodium in liquid ammonia or subjected to ultraviolet irradiation. Three 3-$\text{O}$-TFMS derivatives gave the corresponding 3-deoxy compounds, but a 2-$\text{O}$-TFMS derivative gave a branched-chain sugar.     

Cleavage by sodium in liquid ammonia of kenaf lignins and the biological activity of the cleavage products

The natural lignin of kenaf stems and fractions of the dioxane lignin of kenaf stems isolated previously were cleaved by sodium in liquid ammonia in order to study their structure. It was established that the kenaf lignins consist of three types of structural units: p-coumaryl, guaiacyl, and syringyl, with a predominance of the guaiacyl types. An antioxidation activity of the monomeric products of the degradation of the kenaf lignins has been found.Institute of the Chemistry of Plant Substances of the Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 738–742, September–October, 1987.     

Cleavage by sodium in liquid ammonia of kenaf lignins and the biological activity of the cleavage products

The natural lignin of kenaf stems and fractions of the dioxane lignin of kenaf stems isolated previously were cleaved by sodium in liquid ammonia in order to study their structure. It was established that the kenaf lignins consist of three types of structural units: p-coumaryl, guaiacyl, and syringyl, with a predominance of the guaiacyl types. An antioxidation activity of the monomeric products of the degradation of the kenaf lignins has been found.     

Rupture of sulfides of the thiophene series by sodium in liquid ammonia

Summary By tne action of sodium in liquid ammonia, alkylthienyl sulfides are readily dealkylated with formation of the corresponding mercaptans of the thiophene series.     

Reductive cleavage of cyclopropyl ketones

Aryl substituted cyclopropyl ketones are cleaved to acyclic ketones with zinc and zinc chloride or with zinc alone in refluxing alcohol.     

Reductive cleavage of dichalcogenide bonds

Electrochemical reduction of 1,2-di(2,4,6-triphenylpyridinium-l)ethane, 1,4-di(2,4,6-triphenylpyridinium-1)butane, 1,6-di(2,4,6-triphenylpyridinium-l)hexane, 1,4-di(N-methyl-4,6-diphenylpyridinium-2)benzene, and 2,7-di(N-methyl-4,6-diphenylpyridinium-2)fluorene in solutions of DMF and MeCN in the potential range from−0.8 to −1.7 V (SCE) was studied by CV. The successive formation of stable radical cations, biradicals, and dianions was investigated by semiempirical MO calculations at the PM3 level.     

Reductive cleavage of 4,5-cycloalkanoisoxazolines

Different variants of the reductive cleavage of 4,5-cycloalkanoisoxazolines under the influence of Raney nickel in the presence of acids were studied. The compositions, structures, and properties of the reaction products are discussed.See [1] for our preliminary communication.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 972–976, July, 1988.     

Reductive cleavage of dichalcogenide bonds

The kinetics of reductive cleavage of the dichalcogenide bond in dimeric Schiff's bases ArEEAr (E=S, Te) induced by indirect electron transfer byin situ generated bridged bispyridinium radical cations and biradicals was studied by cyclic voltammetry. It was shown that the dependence between the apparent rate constants of intermolecular electron transfer and the electron-withdrawing properties of diaryldichalcogenides is violated. The mechanisms of homogeneous (chemical) and heterogeneous (electrochemical) reductive cleavage of diaryldichalcogenides were discussed. For Part 2, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1522–1526, August, 1999.