Nitrogen-oxygen Bond Research Articles

Some recent developments in the preparative photolysis of organic nitrites

I N T R O D U C T I O N THE use of photochemical reactions in preparative organic chemistry I has increased considerably during the last twenty years. Many structures accessible only with difficulty by more conventional means have been made available by the agency of radiant energy. One of the most common primary photochemical processes is the homolytic dissociation of an appropriate bond to give rise to two fragments each containing an unpaired electron. The subsequent fate of these free radicals determines the synthetic usefulness of such photochemical processes. It would appear that the nitrogen-oxygen bond in organic nitrite esters is particularly susceptible to homolysis. The latter process does not necessarily have to result f rom photochemical activation: on the contrary, most of the literature on the decomposition of nitrites describes pyrolytic procedures. In the present review, however, special emphasis will be given to photolysis, since the fragments thereby produced are endowed with sufficient energy z to result in subsequent behavior not otherwise attainable. In fact, a very recent development in the field is the photolytic decomposition of nitrites to alkoxy radicals, followed by a stereoselective intramolecular hydrogen abstraction by the latter and recombination of the resulting carbon radicals with NO to form nitrose-monomers, dimers or oximes. This novel course we shall designate the Barton Reaction, in honor of the inventor, and experiments central and peripheral to its nature will form the core of this review.

Relations between force constants, bond orders, bond lengths, and bond frequencies for some nitrogen-oxygen bonds

Self-consistent molecular orbital (M.O.) bond orders for a number of the simpler nitrogen-oxygen compounds have been calculated. Attempts are made to correlate bond lengths and force constants, with bond orders for these molecules. An attempt is also made to correlate the stretching NO frequencies with the force constants and bond lengths for these simple oxides.

Catalytic Reduction of Heterocyclic Aromatic Amine Oxides with Raney Nickel. III. Reduction of Hydroxamic Acid-type N-Oxides.

In the catalytic reduction of hydroxamic acid and compounds possessing hydroxyl adjacent to the N-oxide group and forming a hydroxamic acid-type structure, Raney nickel catalyst was found to act specifically in severing the nitrogen-oxygen bond. 2-Hydroxyquinoline 1-oxide, 4-methoxy-and 4-ethoxy-2-hydroxyquinazoline 1-oxide, and benzohydroxamic acid were deoxygenated forming 2-hydroxyquinoline, 4-methoxy- and 4-ethoxy-2-hydroxyquinazoline, and benzamide. In 4-benzyloxy-2-hydroxyquinazoline 1-oxide, the reduction of benzyloxyl group preceded the reduction of N-oxide group and 2, 4-dihydroxyquinazoline was formed via its 1-oxide compound.

Studies on isoxazole derivatives. XI. Synthesis of 4-ethoxycarbonyl- and 4-cyano-5-aminoisoxazoles and their ring cleavage.

4-Ethoxycarbonyl-(III) and 4-cyano-5-aminoisoxazole (IV) were prepared by reacting hydroxylamine and ethyl α-ethoxymethylenecyanoacetate (I) or α-ethoxymethylenemalononitrile (II), respectively. These 5-aminoisoxazoles were very unstable toward bases compared with a compound (XI) substituted in 3-position and the ring cleavage occurred at the nitrogen-oxygen bond with subsequent isomerisation to their corresponding nitriles, (V) and (VIII).