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Paper | Regular issue | Vol 29, No. 4, 1989, pp.761-769
Published online, 1st January, 1970
DOI: 10.3987/COM-89-4882
Synthesis and Reactions of Biginelli-Compounds, Part II. Nitration of 6-Methyl-2-oxo-1,2,3,4-tetrahydro-5-pyrimidinecarboxylates

C. Oliver Kappe* and Urlike G. Wagner

*Institute for Organic Chemistry, Karl-Franzens-University Graz, Heinrichstrasse. 28, A-8010 Graz, Austria


The nitration of tetrahydro-5-pyrimidinecarboxylates (Biginelli-Compounds2) 1 and 4 does not yield 5-nitrodihydro-5-pyrimidinecarboxylic acids 2a,b as assumed earlier, but affords the corresponding 5-nitro-4-nitromethylidene-hexahydro-5-pyrimidinecarboxylates 3. Single-crystal X-ray studies show that 3a exists in the intramolecularly H-bondend (Z)-configurated form, whereas nmr spectra indicate that 3a can exist in both (Z)-and (E)-configurated forms, depending on the solvent used.