Halogen bonds, hydrogenolysis

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)) ... 

HYDROGENOLYSIS OF CARBON-HALOGEN BONDS WITH CHROMIUM(n)-EN PERCHLORATE NAPHTHALENE FROM 1-BROMONAPHTHALENE... 

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... 

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. 

Trichloroethylene (TCE) and perchloroethylene (PCE) require cleavage of the carbon-halogen bonds. Two methods of cleavage are P-elimination by dehy-drohalogenation, as shown in Equation (13.14), and nucleophilic substitution by either water or hydrogenolysis in Equation (13.15). The proposed pathways for reduction of chloroethylenes by zero-valent iron are as follows ... 

Besides carbon-halogen bonds, Bu3SnH is used routinely for hydrogenolysis of various carbon-heteroatom bonds. The deoxygenation from alcohols has been performed by a Barton-McCombie reaction where the addition of tin hydride to the triple bond is suppressed (Equation (2)).29-31... 

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