ON THE CHLORINE ADDITION TO THE C(5)-C(6) BRIDGE AND THE N-OXIDATION OF 1,10-PHENANTHROLINE

It was found that under the influence of aqueous hypochlorite 1,10-phe nanthroline (1) is initially transformed into 5,6-dichloro-5,6-dihydro -1,10-phenanthroline (2) and 5-chloro-6-hydroxy-5,6-dihydro-1,10-phena nthroline (8). The latter readily undergoes subsequent transformations either into a mixture of 5,5-dichloro-6-oxo-5,6-dihydro-1,10-phenanth roline (4) and 5,6-dioxo-5,6-dihydro-1,10-phenanthroline (5) or into t he known 5,6-epoxy-1,10-phenanthroline (3) depending on the acidic or alkaline conditions, respectively. In contrast to the flat molecule of the starting 1, that of the dichloro derivative (2) being twisted at the central bond of the bipyridine system can be easily N-oxidized to di-N-oxide (11). Both 2 and its di-N-oxide (11) in the presence of sod ium isopropoxide at 0 degrees C freely lost hydrogen chloride and retu rned to the fully aromatic system of 5-chloro-1,10-phenanthroline (9) and its di-N-oxide (13), respectively.