Diimide reducing agent

The carbon-carbon double bond can be reduced by diimide prepared in solution in a number of ways.34 183,184 Oxidation of hydrazine with oxygen (air) or H202 in the presence of a catalytic amount of Cu(II) ion was the first method to generate and use diimide in hydrogenation.183-185 Acid-catalyzed decomposition of alkali azido-dicarboxylates,185,186 as well as thermal or base-catalyzed decomposition of aromatic sulfonyl hydrazides,183,184 are also useful methods for preparing the diimide reducing agent. 

The available studies indicate that diimide has been used as a reducing agent for the preparation of HNBR. It has been used mainly as an alternative for hydrogenation of nitrile rubber latex. The use of diimide to hydrogenate low-molecular weight olefines is well known in the organic literature [93]. Diimide can be conveniently generated in situ by thermal treatment of solutions of p-tolu-enesulfonyl hydrazide or oxidation of hydrazine. 

In the 1960s diimide was recognized as a new reducing agent in the reduction of double bonds72-76. 

A limitation to the use of diimide as a reducing agent appears to be the relative rate at which diimide reacts with the unsaturated substrate. If the rate of reduction is sufficiently slower than that of the disproportionation of diimide, the latter reaction will dominate and no reduction will be accomplished. A fur-... 

The thermal instability of sulfonyl hydrazides allows them to be used for the reduction of carbon-carbon double bonds the reaction depends on the in situ formation of the highly reactive diimide intermediate (86), which is a good reducing agent for alkenes. Tosylhydrazide can be used for this reduction, but triisopropylbenzenesulfonyl hydrazide (87) is preferred because it decomposes to the diimide at low temperature. In the final step, the diimide reduces the alkene to the alkane, as indicated in Scheme 56. 

Reducing agents Aluminum hydride. Bis-3-methyl-2-butylborane. n-Butyllithium-Pyridine. Calcium borohydride. Chloroiridic acid. Chromous acetate. Chromous chloride. Chromous sulfate. Copper chromite. Diborane. Diborane-Boron trifluoride. Diborane-Sodium borohydride. Diethyl phosphonate. Diimide. Diisobutylaluminum hydride. Dimethyl sulfide. Hexamethylphosphorous triamide. Iridium tetrachloride. Lead. Lithium alkyla-mines. Lithium aluminum hydride. Lithium aluminum hydride-Aluminum chloride. Lithium-Ammonia. Lithium diisobutylmethylaluminum hydride. Lithium-Diphenyl. Lithium ethylenediamine. Lithium-Hexamethylphosphoric triamide. Lithium hydride. Lithium triethoxyaluminum hydride. Lithium tri-/-butoxyaluminum hydride. Nickel-aluminum alloy. Pyridine-n-Butyllithium. Sodium amalgam. Sodium-Ammonia. Sodium borohydride. Sodium borohydride-BFs, see DDQ. Sodium dihydrobis-(2-methoxyethoxy) aluminate. Sodium hydrosulflte. Sodium telluride. Stannous chloride. Tin-HBr. Tri-n-butyltin hydride. Trimethyl phosphite, see Dinitrogen tetroxide. 

The parent azo compound HN=NH, called diimide or diazene, is unstable but is useful as a reducing agent in organic chemistry, where it is typically generated in situ. Some standard methods for the generation of diimide are as follows ... 

Nonmetallic reducing agents can be used in alkene hydrogenation as well. Diimide (HN NH) is a good example. It is not stable under normal conditions and is made only as it is needed. Diimide exists in two forms, cis and trans, but only the less stable cis form is active in hydrogenation (Fig. 10.2). 

FIGURE 10.2 An effective nonmetaUic reducing agent for alkenes is diimide... 

The coincidence of these factors, which accelerate the oxidation of hydrazine to nitrogen via diimide and those which accelerate reduction, prompted the use of dipotassium diazodicarboxylate (PADA), or azidoformate, as a reducing agent. This substance undergoes acid-catalyzed, rapid and irreversible decomposition in water, with the obligatory intermediacy of diimide (Scheme 16.11). 

Dihydroxybenzoyl)acrylic acid, 95 3-(2, 4 -Dihydroxybenzolymethyl)-6-hydroxy-benzofuran-2-one, 96 Diimide, MA reducing agent, 42 Diisobutylene... 

Diimide (HNNH) is a reactive reducing agent. Draw its Lewis structure. Compare its Lewis structure with that of ethene. Based on molecular orbital theory, compare the hybridization of the two compounds. What is the H—N—bond angle in diimide ... 

Dia ene deductions. Olefins, acetylenes, and azo-compounds are reduced by hydrazine in the presence of an oxidizing agent. Stereochemical studies of alkene and alkyne reductions suggest that hydrazine is partially oxidized to the transient diazene [3618-05-1] (diimide, diimine) (9) and that the cis-isomer of diazene is the actual hydrogenating agent, acting by a concerted attack on the unsaturated bond ... 

In the above-mentioned reactions with hydrazine and hydroxylamine, the actual reducing species is diimide (NH=NH), which is formed from N2H4 by the oxidizing agent and from NH2OH by the ethyl acetate.The rate of this reaction has been studied.Although both the syn and anti forms of diimide are produced, only the syn form reduces the double bond, at least in part by a cyclic mechanism ... 

Schotman and co-workers tentatively assigned the new Raman peaks at 1625 and 1592 cm 1 observed during sulfur vulcanisation of squalene, to the formation of conjugated dienes and trienes, respectively [70]. When vulcanisation was carried out in the presence of l,3-di(citraconimidomethyl)benzene, this resulted in a reduced intensity of these two new peaks, corroborating that conjugated dienes and trienes, formed as a result of reversion, react with the diimide. Obviously, the diimide is not an anti-reversion agent in the sense that it prevents reversion, but it is in the sense that it repairs crosslinks when reversion has occurred. 

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