Synthesis and rearrangements of N-trichloroacetylfluoroacetimidoyl chloride and its phosphorylation products

The interaction of N-fluoroacetyltrichloroacetamide (1) with PCl5 leads to the formation of N-trichloroacetylfluoroacetimidoyl chloride (3), which is irreversibly isomerized to N-chloro(fluoro)vinyltrichloroacetamide (Z/E≈3:1) in the presence of the catalyst DBU. In the reaction of 3 with phosphites or phosphines, the substitution of chlorine atom by the phosphorus-containing groups is accompanied by the stereoselective 1,3-H transfer affording C-phosphorylated fluorovinylamides (6, 9), mainly with the E-configuration. With low-nucleophilicity phosphites, there is realized the [4+1]-cycloaddition, whereas with hydrophosphoryl reagents, the 1,2-addition to the CN bond occurs.