Galenko EE, Zanakhov TO, Novikov MS, Khlebnikov AF. Metal carbonyl mediated rearrangement of 5-(2-oxoalkyl)-1,2,4-oxadiazoles: synthesis of fully substituted pyrimidines.
Org Biomol Chem 2023;
21:2990-3001. [PMID:
36942559 DOI:
10.1039/d3ob00148b]
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Abstract
Variously substituted ethyl 6-oxo-1,6-dihydropyrimidine-5-carboxylates can be easily prepared by a metal carbonyl mediated rearrangement of ethyl 3-oxo-2-(1,2,4-oxadiazol-5-yl)propanoates. The irradiation of a mixture of oxadiazoles and Fe(CO)5 in wet solvents with a 365 nm LED at room temperature for 2 h followed by heating at 80 °C for 2 h gives pyrimidines in up to 90% yield. This procedure enables the preparation of 6-oxo-1,6-dihydropyrimidine-5-carboxylates with various aryl substituents at the C2 and alkyl or aryl substituents at the C4 position. 1-(1,2,4-Oxadiazol-5-yl)propan-2-ones analogously give 6-methylpyrimidin-4(3H)-ones, albeit in lower yields. Ethyl 6-oxo-1,6-dihydropyrimidine-5-carboxylates can be easily modified at the C6 position by bromination followed by cross-coupling reactions to give pyrimidine-5-carboxylates with pyridyl, amino and ethynyl substituents.
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