Carboxylic acid halides: aliphatic, synthesis aromatic

Notable examples of general synthetic procedures in Volume 47 include the synthesis of aromatic aldehydes (from dichloro-methyl methyl ether), aliphatic aldehydes (from alkyl halides and trimethylamine oxide and by oxidation of alcohols using dimethyl sulfoxide, dicyclohexylcarbodiimide, and pyridinum trifluoro-acetate the latter method is particularly useful since the conditions are so mild), carbethoxycycloalkanones (from sodium hydride, diethyl carbonate, and the cycloalkanone), m-dialkylbenzenes (from the />-isomer by isomerization with hydrogen fluoride and boron trifluoride), and the deamination of amines (by conversion to the nitrosoamide and thermolysis to the ester). Other general methods are represented by the synthesis of 1 J-difluoroolefins (from sodium chlorodifluoroacetate, triphenyl phosphine, and an aldehyde or ketone), the nitration of aromatic rings (with ni-tronium tetrafluoroborate), the reductive methylation of aromatic nitro compounds (with formaldehyde and hydrogen), the synthesis of dialkyl ketones (from carboxylic acids and iron powder), and the preparation of 1-substituted cyclopropanols (from the condensation of a 1,3-dichloro-2-propanol derivative and ethyl-... 

Reactions have been described for RH = amines, alcohols, aromatics, aliphatics, perfluoroalkyls, hydrogen halides, and thiols (167). Another recent use of S2OfiF2 in organic chemistry has been in the synthesis of lactones by the remote oxidation of carboxylic acids using a... 

Silver salts of carboxylic acids react with bromine or chlorine in an inert solvent to give carbon dioxide, a silver halide, and the halide containing one less carbon atom than the acid. The method has been reviewed. " Both low- and high-molecular-weight aliphatic bromides have been prepared. "t i i The degradation of silver salts of aromatic acids is complicated by nuclear halogenation." The procedure is valuable as a step in the synthesis of oi-bromo esters (C, to C,) from dicarboxylic acids. ... 

Carboxyl Activation Synthesis of Esters and Amides from Carboxylic Acids. 4-(Dimethylamino)pyridinium chlorosulfite chloride is more reactive than either thionyl chloride or thionyl chloride/pyridine for carboxyl activation. Aliphatic and aromatic, as well as amino acids (in racemic form), undergo activation (via the acyl halide) and subsequent esterification by reaction with an alcohol at — 20 °C (eq 1). The esterification step requires the addition of a second equivalent of DMAP and this method has been applied to a range of functionalized carboxylic acids. 

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