Unsaturated reduction, 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 ... 

The diimide reduction again proceeds sluggishly and several recycles are essential to achieve complete conversion. The doubly unsaturated endoperoxide is the major product in the singlet oxygenation of 1,3,5-cyclooctatriene (Eq. 14). 

The relative reactivities toward diimide cover a range of -10, from 1,2-dimethylcyclohexene to norbornene (ref. 6). Electron attractive substituents increase the reactivity of the double bond towards diimide although the data to place compounds such as maleic acid or acrylonitrile on the scale for Garbisch s hydrocarbons is lacking (ref. 21b). Garbisch et al. found that the main factors that contribute to the observed reactivities in diimide reductions of unsaturated hydrocarbons, eqn. (3), are torsional strain, bond angle... 

It seemed prudent that the same ethers be examined in the absence of potentially labile functionality, thus removal of unsaturation in 262 and 263 was considered. Hydrogenation of 259 over Pd/C or Pt was unsuccessful in either case reduction of the peroxide group was problematical. Hydrogenation over Wilkinson s catalyst gave a new product, but with the unsaturation retained. While selective alkene hydrogenation can sometimes be achieved in the presence of a peroxide bond, the double bond of 259 was apparently too hindered in this case. Diimide, on the other hand, worked reasonably well for this reduction. Thus, treatment of 259 in dichlo-romethane solution with potassium azodicarboxylate followed by addition of acetic acid led, after several days, to roughly 60% conversion of 259 to the saturated version, 264. Now, ether formation as before provided the saturated methyl and benzyl ethers 265 and 266, respectively, in good yields. 

Table 2 Relative Reactivities of Unsaturated Acids Toward Reduction with Diimide " ...

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-... 

Another method of preparing saturated rubbers was developed (Harwood et al., 1973) using the diimide reduction. This method can be used to produce a high degree of saturation dependent on the type of reagent used however, side reactions can occur in this method. Generation of the diimide from p-toluenesulfonyl hydrides leaves an acidic fragment that may cause cyclization in some unsaturated elastomers. 

There are a number of methods used for the determination of the number and position of double bonds in unsaturated molecules. Reduction using hydrogen over palladium on carbon, or diimide... 

Alkene Reduction. Sulfonylhydrazides deconpose into di-imide and sulfonic acid when heated. For this reason, they have heen utilized in the reduction of unsaturated compounds. When 2,4,6-triisopropylbenzenesulfonylhydrazide (TPSH) is used, the diimide can be generated at room temperature in the presence of base to reduce mono- or disubstituted double bonds selectively in the presence of trisuhstituted alkenes (eq 15). This reduction method tolerates sensitive groups such as esters, ketones, or organocohalt complexes and has heen applied in the preparation of polymers and in the synthesis of natural products (eq 16). This reagent was not effective in the reduction of resin-hound cyclic peptides. ... 

Reduction of tosylhydrazones of a,/3-unsaturated ketones gives alkenes with the double bond being located between the former carbonyl and a-carbon atoms. This reaction is believed to proceed via an initial conjugate reduction followed by decomposition of the resulting vinylhydrazine to a vinyl diimide. 

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