Dimethylformamide → 2-Dimethylaminomethylene-4-acetamidocyclohexanone

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A reaction mixture was prepared from 15.5 g. of 4-acetamidocyclohexanone [prepared by the procedure of Fraser and Swingle, Can. J. Chem., 48, 2065 (1970)], 80 g. of the dimethylacetal of dimethylformamide, 1.5 ml. of triethylamine and 500 ml. of benzene. The benzene was distilled therefrom over a 1.5 hour period until the volume was reduced to about 1/2 of the original volume. An additional 250 ml. of benzene were added. The reaction mixture was heated just below the boiling point of benzene for about 2 hours and was then distilled again until the volume was about one-half of that originally present (250 ml.) The above process was repeated once more except that the volume was reduced to one-third of the original volume (167 ml.). The reaction mixture was then cooled and filtered. The filter cake consisted of dl-4-acetamido-2-dimethylaminomethylenecyclohexanone formed in the above reaction; weight=6.45 g. Evaporation of the filtrate to dryness yielded a residue, chromatography of a chloroform solution of which over 200 g. of Florisil using chloroform containing increasing amounts of methanol (0-5%) as an eluant, yielded more dl-4-acetamido-2-dimethylaminomethylenecyclohexanone; M.P.=132°-133° C. (from benzene); yield=5.55 g.; total yield=12 g.

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