Studies into the photochemistry of steroidal nitronate anions and n-alkyloxaziridines

The photochemistry of nitro-compounds is well documented in the literature. However the photochemical behaviour of nitronate anions has not been widely reported. We have studied the photochemical behaviour of a number of steroidal nitronate anions and found that the major products are hydroxamic acid. ketone and alkene. It was found that the yield of products is influenced by the position of the nitro-group. The hydroxamic acids were found to be the major products in the photolysis of 17-nitronate anions. However, it was observed that in these systems the yield of hydroxamic acid was influenced by the CID ring geometry. In the photolysis of nitronate anions derived from 3.6 and 20-nitro steriods only tentative evidence for hydroxamic acid formation was found in the photolysis of the 6-nitronate anion. The formation of hydroxamic acids from the 17-nitronate anions was observed to be both regio - and stereo-specific and it was postulated that these reactions proceeded via a N-hydroxyoxaziridine anion intermediate. In order to further investigate the possible intermediary of an oxaziridine the synthesis of steroidal N-alkyl oxaziridines was carried out. and their photochemical behaviour examined. It was found that the N-alkyl-17-spiro-oxaziridine rearranged efficientlytoa lactam whereastt-eN-alkyl-20-oxaziridine only gave a poor yield of amide. These results were consistent with those obtained for the nitronate anions. However the lactam formed was of different regio-chemistry to that observed in the photochemical formation of hydroxamic acid. However the observed photochemical rearrangement of the steriodal oxaziridines was fully in accord with theoretical predictions.