Patent GB-1125139-A (GB)
Title: Manufacture of polyfunctional compounds by electrolytic reductive coupling
IPC: C25B3/29
Filed: 1965-09-15
Abstract: 1,125,139. Electrolytic reductive coupling of #, y-mono-olefinic compounds. MONSANTO CO. Sept.15, 1965 [Sept.15, 1964], No. 39386/65. Addition to 967, 956. Heading C7B. One or more #, y - mono-olefinic compounds having at least one hydrogen atom and also an electron withdrawing group linked to the α - carbon atom are subjected to reductive coupling by electrolysis in an aqueous solution containing a salt as a supporting electrolyte, coupling occurring at the #- position with saturation of the double bonds. The electron - withdrawing group may be a carboxylate (i.e. acid or ester) carboxamide, nitrile, phosphonate, phosphinate, phosphine oxide, sulphone, Z-pyridyl or 4 - pyridyl group. Substituents in the electron-withdrawing group and on the α- carbon atom may be C 1  to C 10  hydrocarbyl groups while substituents on the # - and ycarbon atoms may be hydrocarbyl or hydrocarbyloxy groups containing up to 20 carbon atoms. Numerous examples are given of olefinic compounds which may be subjected to reductive coupling, including not only allyl compounds but compounds containing one or more alkyl, aryl or alkyl-aryl substituents. The coupling may result either in a hydrodimer or in a compound with mixed functional groups, e. g. cyanoalkane carboxylates or carboxamides, carbalkoxyalkane phosphonates and pyridylalkane sulphones. Typically the initial concentration of each of the olefinic compound and of the salt is at least 5% by weight of the solution and preferably the solution contains 20% olefinic compound and 30% salt. To minimize polymerization the pH is kept above 7, preferably in the range 7 to 10. Inhibitors for free radical polymerization e. g. hydroxy benzene compounds may be included in the bath, but under non-acid conditions no special precautions are necessary in the presence of atmospheric oxygen. The supporting electrolyte salt may be an amine or quaternary ammonium salt of a sulphonic or alkyl sulphuric acid including saturated alkyl or aryl groups. A typical example is tetraethyl ammonium p-toluenesulphonate. Tetralkyl phosphorium or trialkyl sulphonium halides, sulphates phosphates, phosphonates and carboxylic acid salts may be used. Other salts which may be used are alkali metal, alkaline earth metal, rare earth metal, or aluminium salts of any of the abovementioned anions. Preferably the cathode has a hydrogen overvoltage greater than that of copper, specified suitable materials being Hg, Cd, Sn, Zn ,  Bi ,  Pb, A1, Ni and graphite. Specified anode materials are Pt, Au, Ni, carbon, nickel silicide, Duriron, Pb and Pb-Sb and Pb-Cu alloys. A cell for carrying out the process may comprise a glass container holding a layer of mercury as cathode with a platinum anode in a sintered alumina cup suspended in the catholyte, the anolyte being a solution of the electrolyte salt. For the production of 3:4-dimethyl adipate the catholyte may be a solution of tetraethyl ammonium p-toluene sulphonate and dimethylformamide containing ethyl vinylacetate. A small amount of a hydrotrimer of ethyl crotonate is also obtained. In another example allyl cyanide is hydrodimerized to 3:4-dimethyladiponitrile. Other hydrodimers referred to are 2:3-dimethyl - 1:4 - di (Z<SP>1</SP>-pyridyl)-butane; diethyl - 3:4 - diethoxy - 3:4- dimethyl-adipate; 3:4 - diethyladipamide -tetraethyl-2 3-dimethylbutane- 1:4 - diphosphonate; diethyl - 2:3 - dimethylbutane - 1:4 - bis (ethylphosphinate): 2:3 - dimethylbutylene - 1:4 bis (diphenylphosphine oxide); and 2:3 - dimethyl- 1:4 bis (methylsulphonyl) butane. Reference is also made to U. S. A, Specification 3, 193, 476 which describes coupling two different compounds selected from α, # - olefinic nitriles, esters, and carboxamides; U. S. A. Specification 3, 193, 475 which describes coupling cycloalk - 1 - ene carboxylates carboxamides and nitriles; U. S. A. Specification 3, 193, 478 which describes #- hydrocarbyloxy acrylic esters, amides, and nitriles; U. S. A. Specification 3, 249, 521 which describes coupling α, # - olefinic phosphonates, phosphine oxides and sulphones; U. S. A. Specification 3, 218, 246 which describes coupling pyridyl ethylenes; and U. S. A. Specification 3, 193, 481, 3,193, 482 and 3, 193, 493 which describe respectively coupling aliphatic a, # - olefinic nitriles, carboxylates and carboxamides; with the indication that these reductive coupling reactions may also be effected using the corresponding #, yolefinic compounds. It is suggested that the #, yolefinic compounds isomerize to the α, # - olefinic compounds under alkaline conditions resulting at the cathode from electrolysis and that the so-formed α, # compounds then undergo reductive coupling.