A new method for synthesizing fluorinated open chain β-enamino ketones and cyclic β-enamino diketones using perfluoroalkanoyl fluorides and ketimines

Reacting 2-isopropyliminopropane with perfluoropropionic and perfluorobutyric acid fluoride gave the respective 5-amino-1,1,1,2,2-pentafluorohex-4-en-3-one and 5-amino-1,1,1,2,2,3,3-heptafluorohept-5-en-4-one, whereas 2-isopropyliminopropane or 2-isopropylimino-2-phenylethane with tetrafluorosuccinic and octafluoroadipic acid difluoride in a 2:1 ratio yielded the corresponding 2,9-bisamino-5,5,6,6-tetrafluorodeca-2,8-dien-4,7-dione, 1,8-bisamino-1,8-diphenyl-4,4,5,5-tetrafluoroocta-1,7-dien-3,6-dione, 2,11-bisamino-5,5,6,6,7,7,8,8-octafluoro dodeca-2,10-dien-4,9-dione and 1,10-bisamino-1,10-diphenyl-4,4,5,5,6,6,7,7-octafluorodeca-1,9-dien-3,8-dione. Changing the stoichiometry to 1:1 surprisingly, the fluorinated 1′-isopropylamino substituted 1-ethylidene-3,3,4,4-tetrafluorocyclopentane-2,5-dione, 1-benzylidene-3,3,4,4-tetrafluoro cyclopentane-2,5-dione, and 1-ethylidene-3,3,4,4,5,5,6,6-octafluorocycloheptane-2,7-dione, 1-benzylidene-3,3,4,4,5,5,6,6-octafluorocycloheptan-2,7-dione were obtained. The molecular structures of one open chain and two cyclic compounds in the solid state reveal short intramolecular N(H)⋯OC distances and considerable electron delocalisation in the β-enamino fragments. In the 19F NMR spectra of 1-benzylidene-3,3,4,4-tetrafluorocyclopentane-2,5-dione, a two step temperature dependent dynamic process was proposed, causing an AA′BB′ system.