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Paper | Regular issue | Vol 51, No. 1, 1999, pp.77-84
Published online, 1st January, 1970
DOI: 10.3987/COM-98-8336
Isolation, Conformational Analysis and X-Ray Structure Determination of a Trifluoromethyl-stabilized Hexahydropyrimidine — An Intermediate in the
Biginelli Reaction

C. Oliver Kappe,* S. Fabio Falsone, Walter M. F. Fabian, and Ferdinand Belaj

*Institute of Organic Chemistry, Karl-Franzens-University Graz, Heinrichstr. 28, A-8010 Graz, Austria

Abstract

Hexahydropyrimidine-5-carboxylic acid ethyl ester (8) was obtained from Biginelli-type condensation of ethyl trifluoroacetoacetate with urea and benz-aldehyde. The conformational features of this hexahydropyrimidine were investigated by computational and X-Ray crystallographic studies. The geometries of the four possible diastereoisomers were fully optimized using semiempirical (AM1, AM1/MM) methods. The structure of the thermodynamically most stable diastereoisomer was further studied by ab initio (HF/3-21G) methods.