Introduction

   Fluorine-containing compounds have widely spread into our modern life from the kitchen utensils to steroids, with quite broad applications in electronic, agricultural and medicinal industries. Fluorine-containing compounds are classified in two main categories. One is a mono- or partly fluorinated compound and the other is a poly or perfluorinated compound. In the former case fluorine atom(s) are introduced into the organic compounds for enhancing the original functionality of the compounds, for example, bioactivity. In the latter case fluorine atoms are introduced for endowing various new functions such as low surface tension and/or resistances against the chemical reagents, thermal stress, sun light and so on.
   Our laboratory has been engaged in the study of the fluorine chemistry with an enthusiasm on the poly- and perfluoro systems in addition to mono- and partly fluorinated ones in order to find new fluorine-containing functional materials. To realize these goals, we have pursued the studies on synthetic methodology and on the fundamentals underlain in the functioning appeared by the introduction of fluorine atoms.

Main research work

1. Basic study on the development of low-global-warming alternatives of highly fluorinated compounds and their environmental effects
2. Study on Fuctional Fluoro Organic Compounds and Their Synthesis

Staff

Recent research activities

１. Basic study on the development of low-global-warming alternatives of highly fluorinated compounds and their environmental effects

   Hydrochlorofluorocarbons (HCFCs) and Hydrofluorocarbons (HFCs) have been selected as Chlorofluorocarbon (CFC) alternatives and utilized as refrigerants, blowing agents, and cleaning solvents in a global scale. Ozone depleting potential of these substances is nearly zero, but there is still a room for the improvement from the environmental point of view, especially due to their higher values of global warming potential (GWP) than those of CO₂ or methane. This higher environmental concerns on GWP has driven main advanced countries to regulate these substances in addition to Perfluorocarbons (PFCs) and widely used electric insulator of SF₆ through Kyoto conference (COP3) and/or other international assessment meetings. Multi-national efforts have recently been made for developing more environmentally benign alternatives with a lower GWP.
   Our main objective in this connection is the development of so-called third generation HFC alternatives, which satisfies the demands from both environment and functionality. Our strategy for devising such substances is based on a design of compounds fulfilling conflicting demands of stability and degradability (short life time on the surface), one required for the use and the other for environmental protection for the global warming. To realize this goal we synthesized various PFCs containing heteroatoms such as oxygen, nitrogen and sulfur and evaluated their profile from both functional and environmental viewpoints in the national project. In the course of the study we developed new synthetic methods for preparing perfluoro-imines and -vinylamines, which have proved to be a useful starting material for the synthesis of the said PFCs.

2. Study on Functional Fluoro Organic Compounds and Their Synthesis

   Fluorine is a very unique element with the highest electronegativity and the smallest size next to hydrogen, which endows various prominent functionality in the fluoro organic compounds. Due to its size hydrogen atoms of the hydrocarbons can be replaced with fluorine atoms to any extent from mono- to perfluoro-substitutions.
   Mono-fluoro or partly fluorinated compounds have been utilized mainly in agricultural and medicinal fields, while perfluoro compounds have been utilized as surfactants, energy transfer fluids or various fluoro polymers. A new application of partly fluorinated compounds includes liquid crystals. One peculiar application of perfluoro compounds includes an oxygen-transporting fluid. Perfluoro moiety has been introduced into the organic compounds for adding the functionality such as light resistance, both water- and oil-repellency, low surface tension, low friction property and so on.

   Our laboratory has pioneered in the fluorine chemistry in Japan and still actively worked in this field. Our long standing interest in the methodology for preparing perfluoro compounds has driven us to study the electrochemical fluorination and has led us to the invention of the direct liquid-phase photofluorination.
   Intensive study of electrochemical fluorination made it possible to prepare perfluoro cyclic ethers useful for oxygen-transporting fluids and N-containing perfluoro carboxylic acids, from which unique perfluoro imines and enamines can be derived. One example of application is oligomer-type fluorinated surfactants.

Fig.1 Structure of Oligomer-type Fluorinated Surfactants		Fig.2 Suface Tension of Aqueous Solutions of Oligomer-type Fluorinated Surfactants

   The study of direct fluorination leads us to the discovery of persistent perfluoroalkyl radicals, perfluoro-3-ethyl-2,4-dimethyl-3-pentyl (PFR-1) and perfluoro-3-isopropyl-2,4-dimethyl-3-pentyl (PFR-2), which are amazingly stable in any sense; GC-analyzable and resistant to various oxidizing reagents such as oxygen, halogens (100% fluorine itself in an extreme case), conc. mineral acids (HCl, HBr, H₂SO₄) and aq. NaOH and so on. PFR-1 is prepared by direct fluorination of hexafluoropropen trimers in ca. 90% yield. These radicals are potentially useful for ESR imaging and also promising as a standard for ESR measurement. When heated, thermal decomposition occurs with releasing trifluoromethyl radical, thus useful as a trifluoromethylating reagent and a radical initiator for the synthesis of fluoro polymers, which are now under investigation.
   We have developed a very unique fluorination method called liquid-phase photofluorination that compliments the traditional fluorination methods such as electrochemical and cobalt trifluoride fluorination. The scope and limitation are now under investigation.

Fig.3 Hydrocarbon Radical		Fig.4 Perfluoroalkyl Radical

   Rather recently, we have initiated the synthetic study on the fluoro amino acids and amine derivatives. Our discovery of novel conversion of a carbonyl group adjacent to a perfluoroalkyl group to an amino function leads to a new methodology for preparing fluoro amino acids and amine derivatives. An asymmetric version of this methodology was also developed and thus various biologically interesting fluoro amino acids or amine derivatives are now available in an enantiomerically pure form.

Previous research project

1. Development of new halon alternatives
2. Development of optical active fluorine-containng liquid crystals
3. Development of functionalistic membrance of fluoro polymers
4. Development of fluorine-containing organic semiconductors