Titanium(IV) chloride induced reactions of ketones and C-acylimines with dimethylcyanamide

Article abstract of DOI:10.1002/jlac.199619961027

The reactions of ketones (benzophenone, 4-methylbenzophenone, acetophenone, acetone, and 2,2,4,4-tetramethyl-3-pentanone) and C-acylimines with dimethylcyanamide in the presence of titanium(IV) chloride were investigated. Benzophenone and 4-methylbenzophenone react with dimethylcyanamide to give 4,4-disubstituted 2-dimethylamino-3-aza-1-oxa-1,3-butadienes 5 and 4,4-disubstituted 2-dimethylanuno-1-N,N-dimethylcarbamoyl-1,3-diaza-1,3-butadienes 9. Ketones with enolizable hydrogen atoms undergo aldol reactions under these conditions. C-Acylimines 11b-11e, derived from benzil and substituted anilines, undergo [2 + 2] cycloaddition to dimethylcyanamide with subsequent ring opening to 1-(N,N-dimethylcarbamoyl)-2,3,4-triaryl-1,4-diaza-1,3-butadienes 15. 1,2-Diphenyl-2-(isopropylimino)ethanone (11a) reacts with dimethylcyanamide to give 2-dimethylamino-1-isopropyl-4,4-diphenyl-2-imidazolin-5-one (23) in a hitherto unknown multistep reaction. The structure of 23 was confirmed by an X-ray analysis. VCH Verlagsgesellschaft mbH, 1996.