Hydrogenolysis acid chloride

The hydrogenolysis of hydroxamic acids (22) and hydra2ides (23) has also been used to synthesi2e amides. One of the earliest methods for the preparation of amides consists of treating acid chlorides with dry ammonia or an amine (24). 

Aiyl esters, prepared from the phenol and an acid chloride or anhydride in the presence of base, are readily cleaved by saponification. In general they are more readily cleaved than the related esters of alcohols, thus allowing selective removal of phenolic esters. 9-Fluorenecarboxylates and 9-xanthenecarboxylates are also cleaved by photolysis. To permit selective removal, a number of carbonate esters have been investigated aryl benzyl carbonates can be cleaved by hydrogenolysis aryl 2,2,2-trichloroethyl carbonates, by Zn/THF-H20. 

The first, and still widely used, polymer-supported ester is formed from an amino acid and a chloromethylated copolymer of styrene-divinylbenzene. Originally it was cleaved by basic hydrolysis (2 N NaOH, FtOH, 25°, 1 h). Subsequently, it has been cleaved by hydrogenolysis (H2/Pd-C, DMF, 40°, 60 psi, 24 h, 71% yield), and by HF, which concurrently removes many amine protective groups. Monoesterification of a symmetrical dicarboxylic acid chloride can be effected by reaction with a hydroxymethyl copolymer of styrene-divinylbenzene to give an ester a mono salt of a diacid was converted into a dibenzyl polymer. ... 

Carboxylic acid chlorides can be converted to aldehydes by hydrogenolysis on a poisoned Pd/BaS04 catalyst. This is the classic Rosenmund reduction. Over more active catalysts, further hydrogenation gives the corresponding alcohols. Bases are used to react with the HCl. For example, 2,5-dimethylpyridine was used as base in a Rosenmund reduction.457... 

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. 

Acid chloride and benzyl alcohol Cleavage - Hydrogenolysis... 

Hydrogenolysis of Acid Chlorides to Aldehydes (the Rosenmund Reduction)... 

The catalytic hydrogenolysis of acid chlorides to aldehydes over Pd-BaSO. has been... 

The air-sensitive Cp-substituted hydridovanadium complex is obtained by hydrogenolysis of the corresponding methyl derivative. The corresponding anionic compound is obtained by reduction of CpV(CO)4 with sodium and protonation with water (Scheme 64). Thus obtained [CpVH(CO)3] (106) is a useful one-electron reductant to reduce bromo- and iodoalkanes, bromoalkenes, and arylbromides in THF. Furthermore, acid chlorides are reduced to the aldehydes. A similar reduction with (106) is performed by using phase-transfer conditions in the presence of tetrabutylammonium hydrogen sulfate. Nitro compounds and organic halides are reduced under these conditions. 

The typical reactions of the alcohol group include their conversion to ethers and esters by reaction with alkyl halides and with acid chlorides or anhydrides, respectively (Scheme 6.2). The benzyl ether group is readily cleaved by hydrogenolysis and is often used as a protecting group for alcohols. Primary alcohols are oxidized initially to the aldehyde and then to the carboxylic acid. 

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