A facile synthesis and theoretical study of novel stable heterocyclic phosphorus ylides containing 2,4-dimethyl-3-acetyl pyrrole

The reaction between dialkyl acetylenedicarboxylates and 2,4-dimethyl-3-acetyl pyrrole in presence of triphenylphosphine, in ethyl acetate, led to stable phosphorus ylides derivatives 3(a-c) in good yields. The stable ylides involving 3(a and b) exist in solution as a mixture of the two isomers, while 3c indicate only one isomer. For this reason, assignment of more stable Z or E isomers as a (major or minor) was investigated using theoretical calculations.