Synthesis and reactions of Biginelli compounds, 13 - Isolation, conformational analysis and X-Ray structure determination of a trifluoromethylstabilized hexahydropyrimidine - An intermediate in the Biginelli reaction

Hexahydrgpyrimidine-5-carboxylic acid ethyl ester (8) was obtained from Big inelli-type condensation of ethyl trifluoroacetoacetate with urea and benza ldehyde. The conformational features of this hexahydropyrimidine were inves tigated by computational and X-Ray crystallographic studies. The geometries of the four possible diastereoisomers were fully optimized using semiempir ical (AM1, AM1/MM) methods. The structure of the thermodynamically most sta ble diastereoisomer was further studied by ab initio (HF/3-21G) methods.