Alkyl halides hydrogenolysis

These can be made by various routes, including hydrogenolysis of Ln-C bonds thermolysis of alkyls and substitution of halide. Thus hydrogenolysis of the dimeric methyl-bridge cyclopentadienyl complexes (Ln, e.g., Y, Er, Yb, Lu) in THE affords [Cp2Ln(thf)(/u,-H)]2 ... 

C.vi. Alkyl Halides. Alkyl halides are reduced by lithium aluminum hydride to give a hydrocarbon in what is known as a hydrogenolysis reaction (R3C—X R3C—H sec. 4.8.E).6l Reduction of 1-bromobutane... 

Historically, simple Vz-alkyl ethers formed from a phenol and a halide or sulfate were cleaved under rather drastic conditions (e.g., refluxing HBr). New ether protective groups have been developed that are removed under much milder conditions (e.g., via nucleophilic displacement, hydrogenolysis of benzyl ethers, and mild acid hydrolysis of acetal-type ethers) that seldom affect other functional groups in a molecule. 

The synthesis of a benzamide with a somewhat more complex side chain starts by condensation of acid 144 with racemic cis-aminopiperidine 152. Removal of the benzyl group of 153 by hydrogenolysis gives the secondary amine 154. Alkylation on nitrogen with the halide 155 gives finally the dopamine antagonist, cisapride (156) [38,39]. 

The reactions of alkyl halides with Fe(II) deuteroporphyrin IX have been examined (Wade and Castro 1973). Three classes of reaction were observed (i) hydrogenolysis, (ii) elimination to alkenes, and (iii) coupling of alkyl free radicals. Further discussion has been given in Castro (1998). 

Acyl halides can be reduced to aldehydes1206 by treatment with lithium tri-f-butoxyaluminum hydride in diglyme at -78°C,1207 R may be alkyl or aryl and may contain many types of substituents, including N02, CN, and EtOOC groups. The reaction stops at the aldehyde stage because steric hindrance prevents further reduction under these conditions. Acyl halides can also be reduced to aldehydes by hydrogenolysis with palladium-on-barium sulfate... 

Protodehalogenation.1 This hydride is the reagent of choice for hydrogenolysis of alkyl halides. Lithium aluminum hydride is somewhat less powerful, particularly for reduction of alkyl chlorides. 

The hydrolysis of alkylmagnesium halides (Expt 5.3), and the hydrogenolysis of alkyl halides and of alkyl methane- or toluene-p-sulphonates (Expt 5.4). 

THE HYDROLYSIS OF ALKYLMAGNESIUM HALIDES, AND THE HYDROGENOLYSIS OF ALKYL HALIDES AND OF ALKYL METHANE- OR T0LUENE-/P-SULRH0NATES... 

Superhydride has also been used for the hydrogenolysis of alkyl toluene-p-sulphonates, and an illustrative example is given in Expt 5.4 for the preparation of cyclooctane from cyclooctyl toluene-p-sulphonate. A sodium borohydride hydrogenolysis of alkyl halides and of alkyl methane- and toluene-p-sulphonates under PTC conditions provides an interesting variant of this reaction.9... 

Three transmetallation reactions are known. The reaction starts by the oxidative addition of halides to transition metal complexes to form 206. (In this scheme, all ligands are omitted.) (i) The C—C bonds 208 are formed by transmetallation of 206 with 207 and reductive elimination. Mainly Pd and Ni complexes are used as efficient catalysts. Aryl aryl, aryl alkenyl, alkenyl-alkenyl bonds, and some alkenyl alkyl and aryl-alkyl bonds, are formed by the cross-coupling, (ii) Metal hydrides 209 are another partner of the transmetallation, and hydrogenolysis of halides occurs to give 210. This reaction is discussed in Section 3.8. (iii) C—M bonds 212 are formed by the reaction of dimetallic compounds 211 with 206. These reactions are summarized in Schemes 3.3-3.6. 

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