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Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI
Published on: November 22, 2016
1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds
Vito A Fiore1, Chiara Freisler1, Gerhard Maas1
1Institute of Organic Chemistry I, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany.
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.
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