RESEARCH
Liquid HF facilitates novel reactions Imidoyl fluorides and unusual malonamides prepared by reaction of olefins with nitriles in HF solvent Never-before isolated reaction intermediates and compounds difficult to make have been synthesized in liquid hydrogen fluoride by Dr. John R. Norell of Phillips Petroleum. His novel processes lead to imidoyl fluorides ( R N = C F R ' ) and unusual malonamides (N,N'-dialkyl-2-alkylaminomalonamides). Dr. Norell can isolate the intermediates in the reaction of a nitrile with an olefin or an alcohol by using liquid H F as both solvent and reactant. Such nitrile reactions in a sulfuric acid system are known generally as Ritter condensations. Only one Ritter condensation intermediate has been isolated—the iminosulfate from reaction of isobutylene and acrylonitrile in acetic acid-sulfuric acid mixture. Dr. Norell finds that the reactivity and low boiling point of liquid H F aid the reaction and facilitate isolation of the intermediate imidoyl fluorides in high purity. Anhydrous conditions are essential during the reaction and purification because water will quickly form amides. Dr. Norell usually begins the synthesis by addition of a secondary olefin—one which cannot form a tertiary carbonium ion—to a mixture of a nitrile and H F . After the reaction proceeds for 30 to 120 minutes at 0° to 40° C , excess H F is removed by vacuum distillation. An aprotic solvent such as ethyl ether is added, and then gaseous ammonia for neutralization. Ammonium fluoride precipitates and is removed by filtration. After evaporation of the solvent, the product is isolated by vacuum distillation. A protic solvent, such as ethanol, changes the product. If ethanol is
used instead of ether before neutralization in the isolation of an imidoyl fluoride, a mixture of an imido ester and an amidine forms. No imidoyl fluoride is found. With HCN. Dr. Norell at first obtained only "tar" when he used hydrogen cyanide as the nitrile. Later, by adjusting the relative concentrations of reactants, he obtained various N,N ; -dialkyl-2-alkylaminomalonamides in low yields (below 20%). Water is involved in the synthesis of these malonamides. The reaction is carried out at 0° to 50° C. using a slight excess of HCN. The mixture is then poured on ice, neutralized, extracted, and concentrated to give crude product. Propylene, cyclopentene, cyclododecene, and norbornene are among
Dr. J. Norell describes synthesis of malonamides in liquid HF solvent
the olefins that Dr. Norell finds will react with HCN. No malonamide product has been isolated using ethylene or a tertiary olefin such as 2-methyl-2-butene. Substitution of sulfuric acid for H F proved almost disastrous. Although at 0° C. no problems are encountered with mixtures of HCN and H 2 S 0 4 , at temperatures between 30° to 40° C. the mixture heats with almost explosive force, a fact not well documented in the literature. No such heating occurs with HCN and H F . New compounds. In his work on malonamide structure, Dr. Norell made several new compounds. N,N'diisopropyl - 2 - isopropylaminomalo namide reacts with methyl iodide and silver oxide to give methyl group substitution for the 2-amino hydrogen atom, with acetic anhydride to give acetyl substitution, and with hydrochloric acid and ether to give a hydrochloride. No reduction by lithium aluminum hydride of the amide groups in any of the malonamides has been detected. The 2-alkylamino group does not undergo some of the classical tests for secondary amines, such as the Hinsberg test or phenyl isothiocyanate test. Of several mechanisms proposed for the reactions leading to the malonamides, the one favored by Dr. Norell begins with formation of an isocyanide. If an olefin such as cyclohexene is added to a mixture of H F and HCN, cyclohexylformamide forms, followed by a splitting out of H F to make cyclohexyl isocyanide. The odor of isocyanides is prevalent. Then an isocyanide-protonation-hydride transfer sequence follows, giving the malonamide.
Liquid HF reactions lead to complex malonamides Liquid HF
Olefin imidoyl fluoride todionamide derivative
42 C&EN FEB. 23, 1970
