A facile synthesis of diastereoisomeric 1,4-diionic organophosphorus compounds

The addition of dialkyl acetylenedicarboxylates to strong CH-acids in the p resence of triphenylphosphine leading to highly functionalized 1,4-diionic organophosphoms compounds is reported. These betaines possess two vicinal s tereogenic centers and exist as a mixture of two diastereoisomers. Intercon version between the two diastereoisomeric forms of these 1,4-diionic compou nds via C-H proton exchange reactions of the (Ph)(3)P+-CH moieties, preclud e their separation. The assignments of the two diastereoisomeric forms of t hese systems are based on the high-field H-1, C-13 and P-31 NMR data. (C) 1 999 Elsevier Science Ltd. All rights reserved.