At Last, 1,10-Phenanthroline-N,N′-dioxide, A New Type of Helicene, has been Synthesized using HOF⋅CH₃CN

For more than 50 years the synthesis of 1,10-phenanthroline-N,N′-dioxide (2) has been sought. The reason for the failure of all the earlier attempts is that the limited space in the bay area of the starting material 1,10-phenanthroline (1) cannot accommodate two oxygen atoms. The oxidation has now been achieved with the oxygen-transfer agent HOF⋅CH₃CN, and X-ray studies have revealed that the product is not planar but is a new type of helicene—in this way the “space problem” for the two oxygen atoms has been solved.