Features of the Synthesis of Thiobarbituric Acid Arylidene Derivatives in the Presence of Triethylamine

The synthesis of thiobarbituric acid arylidene derivatives proceeds in two steps, which include 5-(2-hydroxy-2-phenyl)ethyl derivative formation and dehydration. The triethylamine promotes increase in the negative charge on the 5th carbon atom (from -0.399 to -0.638) and positive charge on the aldehyde CH=O group carbon atom (from 0.288 to 0.300) in the transition state due to associative interaction (analysis by quantum-chemical method AM1), and it also promotes dehydration by "pushing out" the hydroxy group. The yield of thiobarbituric acid arylidene derivatives reaches 92-99%.