Investigation on possibility of rearrangement of pyrimidine-5-carboxylic acids esters

Abstract

A previously reported rearrangement of pyrimidine-5-carboxylic acids esters to 5-acylpyrimidones does not, in fact, occur in any of the examples studied by us.A report appeared in 1933 regarding the rearrangement of a pyrimidine-5-carboxylic acid ester (1b) which occurred in aqueous alkali medium to give the 5-acetylpyrimidone (2b) [1]. The presence of a ketone in the reaction mixture was confirmed by the formation of its oxime and phenylhydrazone. In the years 1982-2005 a series of papers appeared in which it was confirmed that the rearrangement has a very general character and occurs for a broad range of differently substituted pyrimidine-5-carboxylic acids esters 1a-d [2][3][4][5]. N N X R CO 2 Et N H N R X O O N N X R CO 2 H 2a-d KOH/H 2 O or KOH/EtOH 3a-d 1a-d 13 a X = Me, R = Bn; b X = Me, R = OH; c X = Me, R = SH; d X = NH 2 , R = SHThere is also work reported in which alkaline hydrolysis of the same pyrimidine-5-carboxylic acids esters gives the trivial result of formation of the corresponding acids which are isomers of 5-acetylpyrimidones. This reaction occurs under similar conditions and the substances obtained by different authors have very similar characteristics. The structure of the acids was quite reliably demonstrated and included a chemical route. Decarboxylation of the acids gives simple pyrimidines [6]. At the same time, proofs of the structure of the 5-acetylpyrimidones given in the articles [2-5] did not appear fully reliable.In our laboratory repeated attempts were made to synthesize certain 5-acetylpyrimidones by methods [2][3][4][5]. All proved to be unsuccessful. Against the authors claims, only the acids were obtained in the examples studied [7].