Reductions hydrogenolysis

In contrast to chemical reactions in which elimination and nucleophilic displacement are alternatives and may occur simultaneously, microbial elimiuation is less common. This term is also used for the reactiou iu which, for example, 1,2-dihaloethaues are transformed to ethene, in contrast to dehydro-halogenation in which a haloethene is produced or reductive hydrogenolysis to a haloethaue. Degradatiou iuvolviug elimiuation is found in several degradations ... 

Reduced furans are formed in two types of oxypalladation processes on substrate a,ft- and y,<5-unsaturated alcohols. In an unusual reaction, allyl alcohol is converted into 4-methylenetetrahydrofurfuryl alcohol, among other products (Scheme 57)97 the formation of propene is thought to arise by reductive hydrogenolysis of allyl alcohol. 

FIGURE 3.3 Deprotection of functional groups by reduction. Hydrogenolysis of benzyl-based protectors.1 Attack by electrons liberates the protector as the benzyl anion because the latter is stabilized by resonance. This is a simplified presentation of the reaction. 

Reductive dechlorination or reductive hydrogenolysis is a common transformation of 1- and 2-carbon chlorinated aliphatics under methanogenic conditions [373,374]. 1,1,1-Trichloroethane (l,l,l-TCA),for example,is converted to 1,1-dichloroethane (1,1-DCA) [375], and Perchloroethylene (PCE) is successively converted to TCE, cDCE, VC, and ethane [274]. Each reductive dechlorination is a two-electron transfer reaction. 

Ethers do not undergo this reaction, because —Q— is a much weaker nucleophilic site than — S—. L Reduction (Hydrogenolysis)... 

Reactions of the carbonyl group of inososes include the addition of diazoalkanes, dithioacetal formation, reduction, hydrogenolysis, and phenyl-hydrazone formation. The epoxide CXXX, which is formed from scyllo-inosose pentaacetate and diazomethane, is the starting material for a considerable series of seven-carbon derivatives.1 Some of the newer compounds of this group are discussed on pages 187 and 188. 

In the past, derived liquids have been prepared from coals by extraction, chemical reaction (reduction, hydrogenolysis, alkylation, etc.) and destructive distillation (pyrolysis). Depending on the conditions of liquefaction, the chemical changes have varied considerably in depth. These preparation processes are very complex and some assumptions are always necessary in describing the chemistry involved. 

Hydrogenation of anilines usually affords a saturated amine as the major product, but several side reactions, including hydrogenolysis, reductive hydrolysis, and reductive coupling, may accompany and even dominate the reduction. Hydrogenolysis is important only in certain activated molecules (10). 

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