Cleavage, xxii

The results can be rationalized in terms of an oxidative addition-reductive elimination mechanism as illustrated with XXII. A similar mechanism has been proposed for the acid cleavage of Pt(II)-C sigma bond (57, 58). 

On the other hand, reaction of the disilacycloheptane (XIV n = 5) with sulfuric acid is not so energetic as that of the lower homologs and gives two major products with the silicon-silicon bond intact, (XVIII) and (XIX), in the ratio of about 1 1, along with three minor ones, (XX), (XXI), and (XXII). Only the last compound is a product arising from cleavage of the silicon-silicon bond. 

The mechanisms of two other reactions described in Sect. 2.2 involve slow proton transfer to unsaturated carbon. The general acid catalysed cleavage of vinyl mercuric halides [42, 50] for example, allyl mercuric iodide, CH2=CHCH2HgI (XXII), gives Bronsted exponents around 0.7. Linear Bronsted plots are obtained with carboxylic acid catalysts but, as observed in other A—SE 2 reactions, general acids of different structural types (for example, hydronium ion or bisulphate ion) show substantial deviations. Bronsted catalysis of the hydrolysis of diazo compounds (N2 =CR X) has been studied by the groups of Albery and Kreevoy. With... 

In DMF, benzaldehyde benzoylhydrazone (XXII) is reduced to a mixture of the anion of XXII (from XXII by deprotonation by EGB), benzamide and benzaldehyde, the latter formed from benzylideneimine. The cleavage of the N-N bond occurs after the uptake of... 

Isolated from Datura ferox L. 29), this product was hydrolyzed to (— )-3a,6/S-tropanediol and ( —)-tropic acid. A synthesis of XXI was achieved by hydrogenolytic cleavage (30) of A — )-hyoscine (XXII), obtained by total synthesis, and followed by separation of the diastereo-isomeric S( — )-tropoyltropanediols with dibenzoyltartaric acid. Feeding D. stramonium L. seedlings with hyoscyamine-(methyl-i4C) brought about its conversion to the 6 3-hydroxy derivative-(methyl-i C) 31). 

This assignment was confirmed by the work of Kaneko (9). Tuberostemonine was converted to the lactam XX which was transformed by reduction with lithium aluminum hydride followed by cleavage with cyanogen bromide into XXI. Debromination by hydrogen over palladium followed by reductive removal of the cyano group gave XXII. The... 

If structure VI for hydroxylycoctonine is correct the product of lead tetraacetate cleavage of hydroxylycoctonam (XX) should be XXI. This was confirmed by alkaline hydrolysis of XXII to the corresponding acid, which spontaneously cyclized to the lactone XXIII. 

Catalytically active metallic ions may play an important role in ageing of polymers. Their effect may become evident also in transformations of an antioxidation system. From this standpoint, data149 dealing with oxidative transformation of 2,6-di-tert-butyl-4-alkylphenols in the presence of Co(II) complexes of Schiff bases are interesting. The mixture of compounds which results in this case contains 2,6,2, 6 -tetra-tert-butyl-4,4 -dioxycyclohexadiene-l-one XCVIII and compounds formed by its cleavage, among them 2,6-di-tert-butyl-4-hydroxy-4-alkyl-2,5-cyclohexadiene-l-one of the type CX, 2,6-di-tert-butyl-l,4-benzoquinone XXII, and 3,5,3, 5 -tetra-tert-butyl-4,4 -diphenoquinone XX. 

Shono T, Matsumura Y, Hashimoto T, Hibino K, Hamaguchi H, Aoki T (1975) Electroorganic chemistry. XXII. Novel anodic cleavage of glycols to carbonyl compounds. J Am Chem Soc 97 2546-2548... 

Cleavage of Tricarboxylic Adds. Both citric and isocitric acids are reversibly split by enzymes found in various bacteria. Citritase splits citrate to oxalacetate and acetate (XXII). CoA does not participate in this reaction. Unlike the reaction catalyzed by the citrate condensing enzyme, which greatly favors citrate synthesis, the standard free enei ... 

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