RING-CHAIN TAUTOMERISM, OXIDATION, AND NO -REACTION OF A STERICALLY HINDERED 1,3-DIHYDROXYIMIDAZOLIDINE

The bis-hydroxylamine 1 does not react with the hindered benzaldehyde 2 in ethanolic solution, in DMSO or DMF even at high temperatures. Rea ction only takes place after melting the components without any solven t at about 150 degrees C. The products shows ring-chain tautomerism in various solvents. Oxidation of both isomeric forms 3 and 4 leads to t he nitrosonitrone 5 and the cyclic stable nitroxide radical 6, respect ively. Compound 5 reacts with excess nitric oxide (NO) to yield the un stable hydronitrate of the 3,4-dihydroazet-1-oxide 9 which is converte d to the acyclic, unsaturated nitrone 10 in alkaline solution.