Carbon-hydrogen bonds Hydrogenolysis

Hydrogenolysis of hydrocarbons involves the rupture of carbon-carbon bonds and the formation of carbon-hydrogen bonds. The simplest hydrogenolysis reaction of a hydrocarbon is the conversion of ethane to methane... 

Concomitant hydrogenolysis of a benzyl ester and hydrogenation of a diene were performed in one step over Pt02 in AcOEt.207 In contrast, 10% Pd(OH)2/C in AcOEt or EtOH at room temperature for 1 hour under hydrogen was used for the hydrogenolysis of a benzyl group without the saturation of a cyclic carbon-carbon double bond.208... 

If hydrogen gas is added to the reaction mixture of J, and 11 the hydrogenolysis reaction of thorium-to-carbon sigma bonds (J-1 22) allows interception of species 13 and thus, catalytic hydrogenation of the inserted carbon monoxide functionality. At 35 C under 0.75 atm initial H2 pressure with [JJ =9.0 x 10" M and [ 1JJ = 6.5 x 10" M, hydrogenation and isomerization are competitive and both the enolate and the alkoxide reduction product 14 are produced (eq.(13)). Under these conditions, turnover fre-... 

Hydrodehalogenation - that is, hydrogenolysis of the carbon-halogen bond -involves the displacement of a halogen bound to carbon by a hydrogen atom. This chapter is devoted to dehalogenations mediated by transition-metal complexes (Eq. (1)) ... 

Among the electron-rich alkenes, vinylsulfides are especially amenable to cation-radical reduction an important feature is the absence of hydrogenolysis of carbon-sulfur bonds. The reduction of [(phenylthio)methylene]cyclohexane is efficient (88%), and the retention of the phenylthio group clearly contrasts with catalytic hydrogenation (Mirafzal et al. 1993). This provides versatile functionality for further synthetic operations. 

For the replacement of halogen by hydrogen - hydrogenolysis of the carbon-halogen bond - many reduction methods are available. Since breaking of carbon-halogen bonds is involved, the ease of hydrogenolysis decreases in... 

Unsaturated epoxides are reduced preferentially at the double bonds by catalytic hydrogenation. The rate of hydrogenolysis of the epoxides is much lower than that of the addition of hydrogen across the carbon-carbon double bond. In a, -unsaturated epoxides borane attacks the conjugated double bond at -carbon in a cis direction with respect to the epoxide ring and gives allylic alcohols [660], Similar complex reduction of epoxides occurs in a-keto epoxides (p. 126). 

Hydrogenation of phthalic anhydride over copper chromite afforded 82.5% yield of the lactone, phthalide, and 9.8% of o-toluic acid resulting from hydrogenolysis of a carbon-oxygen bond [1015]. Homogeneous hydrogenation of a,a-dimethylsuccinic anhydride over tris(triphenylphos-phine)rhodium chloride gave 65% of a,a-dimethyl- and 7% of )S,)S-dimethyl-butyrolactone [1016]. 

Acid chlorides can be selectively hydrogenated in the presence of a catalyst (palladium deposited on a carrier, which is usually barium sulphate but is occasionally charcoal). The reaction, which involves the hydrogenolysis of the carbon-halogen bond, is known as the Rosenmund reduction and has been widely used for the synthesis of aromatic and heterocyclic aldehydes. 

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