2-Aminoperfluoropropene has been prepared by the Mg-promoted defluorinative N-silylation of N-p-methoxyphenyl hexafluoroacetone imine and has been employed as a synthon of trifluoroalanine for the preparation of trifluoroalanine dipeptides.

Mg-promoted defluorination of N-(p-methoxyphenyl)bis(trifluoromethyl)imine 1 gave perfluoroenamine 2, which was readily transformed to N-Cbz-2-trifluoromethyl-3,3-difluoropyrrolidine 10. Chemoselective defluorination from the trifluoromethyl group of 10 by LHMDS-promoted dehydrofluorination in THF provided 3,3-difluoro-2-difluoromethylenepyrrolidine 11. The product 11 was converted to 3,3-difluoroproline dipeptides 16 upon treatment with aminoesters.

A Novel Route to Dipeptides via Noncondensation of Amino Acids: 2-Aminoperfluoropropene as a Synthon for Trifluoroalanine Dipeptides. -The method enables the C-N bond formation for peptide synthesis under very mild conditions with complete preference of the amino group [cf. (XVIII)]. -(GUO, Y.; FUJIWARA, K.; UNEYAMA*, K.; Org. Lett. 8 (2006) 5, 827-829; Dep. Appl. Chem., Fac. Eng., Okayama Univ., Tsushima, Okayama 700, Japan; Eng.) -R. Steudel 28-182

2-N-(p-Methoxyphenyl)(trimethylsilyl)aminoperfluoropropene was prepared in 95% yield by the Mg-promoted C-F bond activation in an Mg-TMSCl-DMF system. The fluorinated enamine is very electrophilic so that it reacts with a variety of α-amino esters in a triethylamine-DMF system at room temperature, affording trifluoroalanine dipeptides in 70-90% yields via one-pot process. The reaction proceeds via three steps; addition of amino group of amino esters, subsequent dehydrofluorination leading to the corresponding imidoyl fluoride, then acid-catalyzed hydrolysis of the imidoyl fluoride. The protocol is applicable for alanine tripeptides. 462