Substitution reactions of 3-phenylsydnone and the behavior of 3-phenyl-4-bromosydnone suggest us that the sydnone nucleus is aromatic in character to a considerable extent. As many instances are known where a methyl substituent in aromatic heterocycles is oxidized to a carboxylic group, it seemed possible to oxidize 4-methylsydnones to corresponding 4- carboxylic acid derivatives. Although this was not realized, we found an interesting ...
