No abstract

N-Phenyl-N-(trifluoromethylsulfonyl)propiolamides react with triphenylphosphane in the presence of various active methylene compounds CH2XY in a 1:1:1 molar ratio to furnish 1-phosphonium-5-oxabetaines, Ph3P+–C(R)=CH–C(O–)=CXY. These betaines are formed preferentially, but not exclusively, as E-diastereoisomers with respect to the vinylic double bond. In some cases, separation of the two diastereoisomers was achieved by fractionating crystallization. Structure determination by X-ray diffraction analysis revealed marked conformational differences around the CH–C(O–) single bond of E and Z-isomers and extended charge delocalization in the anionic part.

N-Phenyl-N-triflylpropiolamides react with iodine chloride or iodine bromide by an intramolecular electrophilic ipso-halocyclization/nucleophilic halide addition sequence to furnish cyclohexadiene-spiro-γ-lactams. These products can undergo cleavage of the amide bond with primary amines and of the N–Cspiro bond with secondary amines, leading to N-alkyl-2-iodo-3-phenylacrylamides and N-(4-halophenyl)-2-iodo-3-(2-triflylamino)phenylacrylamides, respectively.

The uncatalyzed silylphosphanylation of acetylenic N-trifluoromethylsulfonyl-carboxamides by Ph2P–SiMe3, formally an insertion of a C,C triple bond into a P–Si bond, is reported. Some characteristic functional group transformations of the resulting 3-PPh2-2-SiMe3-N-triflyl-acrylamides were briefly explored: transamidation of the N-triflylamide group with allylamine, P oxidation and protodesilylation. A hydrophosphorylation of the acetylenic triple bond with chloro(diphenyl)phosphane is also reported.