Acid chlorides, aromatic, diazoketones

Acid chlorides, reduction to aldehydes, 53, 55 Acid chlorides, aromatic, diazoketones from, 53, 37... 

DIAZOCYCLOHEXANONE, 51, 86 a-Diazoketones, reaction with trialkylborane, 53, 82 rearrangement, 52, 53 synthesis, 52, 53 >°-Diazoketones, aromatic, from acid chlorides, 53, 37 -Diazoketones, cyclic, alkylation of, 53, 82, 83 Diazomethane, in modified Arndt-... 

Thiophene- and benzo[6]thiophene-carboxylic acids undergo all the normal reactions of an aromatic carboxylic acid (63AHC(1)1, 70AHC(11)177). They can be converted to acid chlorides, amides and esters the esters can be used to make hydrazides. Benzo[6]thiophene-2-carboxylic acid chloride has been converted to the methyl ketone with dimethylcadmium and to the diazoketone with diazomethane. Bromodecarboxylation of the silver salts (Hunsdiecker reaction) has been used to prepare the dibromo compounds (340) and (341). 

The method described here, discovered by Newman and Beal,6 employs triethylamine (1 equivalent) to react with the hydrogen chloride thus only one equivalent of diazomethane is necessary. This modification is restricted to the preparation of aromatic diazoketones-aliphatic acid chlorides give a mixture of products. ... 

This valuable method for the conversion of an acid to its next higher homolog has been used to prepare aliphatic, aromatic, and heterocyclic acids. Excellent reviews of the reaction have been published. Diazomethane preparations are described elsewhere (method 500). The acyl chloride is added to an excess of diazomethane in ether or benzene solution. Diazoketones are usually not purified. 

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