Labelled compounds of interest as antitumour agents - VI. Isotopically efficient syntheses of [15N]-nitrothiophenecarboxamides

Article abstract of DOI:10.1002/(SICI)1099-1344(199611)38:11<1015::AID-JLCR917>3.0.CO;2-6

Reaction of 3-cyanothiophene with one equivalent of potassium nitrate in concentrated sulphuric acid causes nitration, concurrent with hydrolysis of the nitrile, to give 5-nitro-thiophene-3-carboxamide in high yield. Similarly, 2-cyanothiophene gives 4-nitro-thiophene-2-carboxamide and 5-nitrothiophene-2-carboxamide, benzonitrile gives 3-nitrobenzamide and 4-methylbenzonitrile gives 4-methyl-3-nitrobenzamide. Extension of this process to use of potassium [¹⁵N]-nitrate, formed from [¹⁵N]-nitric acid (95% isotopic enrichment), enables preparation of the corresponding [¹⁵N]-nitrothiophenecarboxamides in high isotopic yield.