Two carbon homologation of carboxylic acids via carbon radicals generated from the acyl derivatives of N-hydroxy-2-thiopyridone: Synthesis of Cn+2 α-keto-acids from Cn acids. (The ‘three carbon’ problem).
摘要:
Reaction of olefins containing a three carbon atom chain with carbon radicals generated from carboxylic acids furnishes adducts that are precursors of the corresponding two carbon atom longer alpha-keto-acids. The keto-acids are furnishes in high overall yield.
The invention of radical reactions. Part XXXIV. Homologation of carboxylic acids to α-keto carboxylic acids by Barton-ester based radical chain chemistry
Carboxylicacids can be transformed into the homologous α-ketoacids by Barton-esterbasedradicalchemistry. This method was especially successful when ethyl α-trifluoroacetoxy acrylate was used as a radical trap.
Radicals formed from the esters of thiohydroxamic acids readily add to electron deficient olefins to give adducts of potential synthetic value in variable yield. In certain cases the added sulphur function is easily eliminated with reformation of olefin.