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.

中文翻译：

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N-三氟乙丙酰胺，三苯基膦和活性亚甲基化合物形成的1,5- Ph甜菜碱

N-苯基-N-（三氟甲基磺酰基）丙酰胺与三苯基膦在各种活性亚甲基化合物CH ₂ XY的存在下以1：1：1的摩尔比反应，生成1- 1--5-氧杂甜菜碱，Ph ₃ P ⁺ –C（ R）= CH–C（O ^–）= CXY。这些甜菜碱相对于乙烯基双键优选但不排他地形成为E-非对映异构体。在某些情况下，通过分级结晶可实现两种非对映异构体的分离。通过X射线衍射分析确定结构，发现E和Z的CH–C（O ^–）单键周围明显的构象差异-异构体和阴离子部分中扩展的电荷离域。