Isocyanates constitute an important class of compounds in organic chemistry. Because of their instability and high reactivity the heterocyclic isocyanates have however not got the same attention as the respective aromatic compounds in synthesis and reacti vity studies. We have recently shown that the introduction of a nitro group in the pyridyl ring stabilizes the isocyanate. This fact makes the heterocyclic nitropyridyl isocyanates available as interesting new 5ubstrates similar to aromatic isocyanates in general, and we have now the opportunity to investigate the chemistry of nitropyridyl isocyanates. We will explore whether the utility of aromatic isocyanates in organic reactions may include the heterocyclic nitropyridyl isocyanates as well. We propose to utilize 3-nitro-4-pyridyl isocyanate and 5-nitro-2-pyridyl isocyanate as substrates for the formation of a series of heterocyclic compounds; pyridoxazolidinone, pyridoimidazolone, pyridopyrimidinone, 3-pyridyl oxazolidin-2-one, imidazolidine -2,4-dione, naphtyridine, pyridooxadiazolinone, polyurethanes and a potential heterocyclic conducting polymer. Many of these heterocyclic systems are present in pharmaceuticals.