Summary.
The reactive 1:1 intermediate produced in the reaction between 2,6-dimethylphenyl isocyanide and dimethyl acetylenedicarboxylate was trapped by N,N′ -dimethylbarbituric acid to yield the isomeric products dimethyl 7-(2,6-dimethylphenylamino)-1,3-dimethyl-2,4-dioxo-4H-pyrano[3,2-d]pyrimidine-5,6-dicarboxylate and dimethyl (E)-2-((2,6-dimethylphenylamino)-(1,3-dimethyl-2,4,6-trioxo-pyrimidine-5-ylidene)-methyl)-but-2-enedioate in a nearly 1:1 ratio and an overall yield of 85%. Dynamic effects were observed in the 1H NMR spectra of these compounds and were attributed to restricted rotation around the aryl-nitrogen single bonds and the polarized carbon-carbon double bond.
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Received September 18, 2000. Accepted (revised) November 22, 2000
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Yavari, I., Hazeri, N., Maghsoodlou, M. et al. Dynamic 1H NMR Study of Aryl-Nitrogen Single Bond and Carbon-Carbon Double Bond Rotational Energy Barriers in Two Highly Functionalized Pyranopyrimidines. Monatshefte fuer Chemie 132, 683–687 (2001). https://doi.org/10.1007/s007060170082
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DOI: https://doi.org/10.1007/s007060170082