The Synthesis of Fluorinated Biaryls by Means of the Ullmann Reaction

The field of organic fluorine chemistry, although still in its infancy, has been explored with increasing intensity during the past two decades. The greatest hindrance to its earlier development has been the violent reactivity of fluorine, making direct fluorination of organic compounds impractical, especially from a laboratory standpoint. The discovery by Schiemann and Balz in 1927 of an improved method for indirect means of linking the fluorine atom to the benzene ring was perhaps the chief impetus toward research in chemistry of the aromatic fluorides. The writer, having had no previous experience in this particular field, became acquainted with the subject through a paper presented by Dr. John G. Surak at Marquette in 1947 in which several aspects of organic fluorine chemistry were discussed. A subsequent search of the literature revealed that comparatively little has been written on the subject, particularly in the form of books and monographs. Most of the information is confined to scattered and fairly recent reports in the various journals. One fact that stood out was that while some sort of bridgehead has been made in the study of the monoaryl fluorine compounds. Therefore, the aim of the research in this thesis has been directed toward the development of a satisfactory method of their synthesis, and toward the determination of some of their physical properties. As Remick states so concisely (39), a satisfactory preparative procedure demands: (a) that the proposed reaction be thermodynamically possible; (b) that the reaction take place with a sufficiently high velocity to be practicable; and (c) that there be as few side reactions as possible and that those which are inevitable take place much more slowly than the main reaction. As a means of preparing fluorinated biaryl compounds from monaryl fluorides, the Ullmann reaction appears to meet these conditions most satisfactorily. For this reason it has been chosen as the method of attack upon the problem