Patent GB-823336-A (GB)
Title: Fluorination of organic compounds with sulphur tetrafluoride
IPC: C07C51/60
Filed: 1957-11-04
Abstract: Organic compounds containing one or more oxygen atoms doubly bonded to carbon, any remaining atoms on the oxygen-carrying carbon being singly bonded to the carbon atom and at most one of the said remaining atoms being monovalent, are fluorinated by reacting them with sulphur tetrafluoride under anhydrous conditions.  The preferred compounds to be treated are those containing one or more oxygen atoms doubly bonded to carbon with one of any remaining valencies of each of the oxygen-carrying carbon atom or atoms being satisfied by a singly bonded carbon and the other by hydrogen, halogen, nitrogen, oxygen or carbon, and carbon monoxide, carbon dioxide, aldehydes, ketones, carboxylic acids, salts, esters, halides, anhydrides and amides are mentioned.  The carbonyl compounds treated may also contain other functional groups such as amino, hydroxyl or mercapto groups.  In the reaction the oxygen of the carbonyl group is generally replaced by two fluorine atoms and additional fluorine atoms may be introduced in certain carbonyl compounds.  The reaction is preferably carried out in an inert atmosphere using a mole. ratio of sulphur tetrafluoride to each carbonyl group in the reactant of between 1 : 1 and 6 : 1 at a temperature between 25 DEG  and 350 DEG C. and a pressure, usually autogenous, of between 5 and 50 atmospheres for between 25 and 48 hours.  The reaction may be carried out in the presence of a fluoride ion acceptor catalyst such as hydrogen fluoride, boron trifluoride, arsenic trifluoride, phosphorus pentafluoride, titanium tetrafluoride and silicon tetrafluoride; these catalysts are found to improve the yield of product and reduce the formation of by-products.  When solid reactants or highly reactive compounds are employed, the reaction mixture may be diluted with an inert solvent such as benzene, hexane, octane, cyclohexane or perfluoro compounds such as perfluoro-cyclohexane.  The examples describe the preparation of (1) 2 : 2-difluoropropane from acetone, (2) 1 : 1-difluorocyclohexane from cyclohexanone, (3) difluorodiphenylmethane from benzophenone, (4) as (3) in the presence of hydrogen fluoride, (5) 1 : 2-diphenyltetrafluoroethane from benzil, (6) 1 : 1-difluoroethane from acetaldehyde, (7) a  : a -difluorotoluene from benzaldehyde, (8) a  : a  : a 1 : a 1 - tetrafluoro - p - xylene from terephthalaldehyde, (9) fluoroform from formic acid, (10) 1 : 1 : 1 - trifluoroheptane from heptanoic acid, (11) benzotrifluoride from benzoic acid, (12) o-bis-(trifluoromethyl) benzene and o-(trifluoromethyl) benzoyl fluoride from phthalic acid, (13) p-bis-(trifluoromethyl) benzene and p-(trifluoromethyl) benzoyl fluoride from terephthalic acid, (14) 3 : 3 : 3-trifluoropropylene from acrylic acid, (15) o-bis-(trifluoromethyl) benzene from phthalic anhydride, (16) 1 : 1-difluoroethyldimethylamine from N : N-dimethylacetamide, (17) benzotrifluoride from benzamide, (18) a  : a -difluorobenzyldimethylamine from N : N-dimethylbenzamide, (19) m-chlorobenzotrifluoride from benzoyl chloride in the presence of hydrogen fluoride, (20) benzotrifluoride from benzoyl fluoride in the presence of hydrogen fluoride, (21) o-trifluoromethylbenzoyl fluoride from phthaloyl fluoride, (22) benzotrifluoride from methyl benzoate, (23) carbon tetrafluoride from carbon dioxide, (24) carbon tetrafluoride from carbon monoxide.  The use of sodium propionate to give 1 : 1 : 1-trifluoropropane/sodium benzoate to give benzotrifluoride and the use of other specified aldehydes and ketones including furfural, carboxylic acids including trifluoro- and trichloro-acetic acid and citric acid, anhydrides including maleic anhydride, amides, acid halides including adipyl bromide and chloroacetyl chloride and esters including phthalide and dimethyl and di-isopropyl carbonate is mentioned.