Reactions of amides with nitrogen compounds

A -Diphenylformamidine 85 6 Formanilide (2.4 g, 0.02 mole) is added slowly, in small portions, to a cooled solution of PC15 (4.8 g, 0.023 mole) in chloroform (20 ml). When the reaction subsides, a chloroform solution of freshly distilled aniline (1.9 ml, 0.02 mole) is added, causing an immediate precipitation. The mixture is heated under reflux for 2.5 h, then cooled in an ice-bath and filtered. The solid amidine salt is collected, washed with cold acetone, and dried in a vacuum. The free amidine base was obtained therefrom by treatment with alcoholic sodium ethoxide solution. The crude amidine crystallizes in an ice-bath and is filtered off, washed with cold alcohol, dried, and extracted with acetone. Pouring the acetone solution into water precipitates the amidine. One more precipitation from acetone by water gives material of m.p. 140-141° (2.6 g, 66%). 

Bredereck and his co-workers857 858 have prepared a number of amidines in good yield when using phosphorus oxychloride in benzene  

/V1 -Dimethyl-/V2-phenylformamidine A mixture of dimethylformamide (27.4 g) and anhydrous benzene (50 ml) at 20-25° was treated, with stirring and exclusion of moisture, with phosphorus oxychloride (23.1 g) in anhydrous benzene (50 ml) dropwise, and then left overnight at room temperature. On the next day aniline (11.6 g) in anhydrous benzene (40 ml) was dropped in at approximately 35°, while the yellow oil that separated was kept in suspension by rapid stirring. Stirring was continued for a further 3-4 h, after which the supernatant benzene was decanted and the residue was kneaded with anhydrous benzene (50 ml) the benzene was decanted and the kneading and decantation were repeated. To convert this material into the free base it was dissolved in ice-water, the solution was covered with a layer of the equal amount of benzene, and the mixture was made strongly alkaline with cold 2n sodium hydroxide solution. The mixture was shaken, the benzene layer was separated, and the aqueous phase was extracted twice more with benzene. The benzene solutions were united, dried over potassium carbonate, and evaporated. The residue was purified by distillation in a vacuum, giving the amidine, b.p. 119-122°/10 mm, D20 1.5955 (15.6g, 85%). 

Arl-Dimethyl-Ar2-phenylacetamidine was obtained analogously from A,A-dimethyl-acetamide. 

When ureas are used as the amide component, guanidines are formed analogously.858 If the amine component contains a suitably reactive group, the amidine may on occasions react further to give a heterocycle for instance, benzothiazole is obtained in 85% yield from o-aminothiophenol, dimethylformamide, and phosphorus oxychloride.859 

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