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

Abstract

The addition of dialkyl acetylenedicarboxylates to strong CH-acids in the presence of triphenylphosphine leading to highly functionalized 1,4-diionic organophosphorus compounds is reported. These betaines possess two vicinal stereogenic centers and exist as a mixture of two diastereoisomers. Interconversion between the two diastereoisomeric forms of these 1,4-diionic compounds via C-H proton exchange reactions of the (Ph)3P+-CH moieties, preclude their separation. The assignments of the two diastereoisomeric forms of these systems are based on the high-field 1H, 13C and 31P NMR data.