AbstractWe have developed a convenient synthetic approach to highly reactive N‐(arylsulfonyl)trichloro‐ and ‐trifluoroacetimidoyl chlorides 2 by reacting the corresponding N‐acylsulfonamides with PCl5. The interaction of the imidoyl chlorides with phosphites proceeds through different pathways depending on the substituents in the reagents, and leads to N‐arylsulfonyl‐N‐trichlorovinylphosphoramidates 4, 1‐arylsulfonylamino‐1‐chlorotrifluoroethylphosphonate 5, C,N‐bis(phosphorylated) N‐dihalovinylsulfonamides 8 and α‐(arylsulfonylamino)trifluoroethylidenebis(phosphonates) 10. A rare example of an aza‐Perkow reaction involving a trifluoromethyl group was discovered. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)