Labelled compounds of interest as antitumour agents .6. Isotopically efficient syntheses of [N-15]-nitrothiophenecarboxamides

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-nitrothiophene-3-carboxamide in high yield. Similarly, 2-cyanothiophene gives 4-nitrothiophene-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 [N-15]-nitrate, formed from [N-15]-nitric acid (95% isotopic enrichment), enables preparation of the corresponding [N-15]-nitrothiophene-carboxamides in high isotopic yield.