General Synthesis of Phosphonates from Heteroniaanthracene Cations and Their Use in Wittig-Horner Reaction

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Abstract
Heteroaromatic cations such as 9-heteroniaanthracene (acridinium, xanthylium, and thioxanthylium) and 1-thionianaphthalene (thiochromenylium) ions reacted with trimethyl phosphite in the presence of sodium iodide in acetonitrile at room temperature to give the corresponding phosphonates (2 and 4) respectively in 76–92% yields. The phosphonates were deprotonated with butyllithium in THF at −78 °C, and the resulting carbanions reacted with p-tolualdehyde, cinnamaldehyde, and 4,4′-dichlorobenzophenone to afford the corresponding exomethylene containing heterocyclic compounds, respectively, in 52–96% yields. However, the phosphonate carbanions derived from 2 did not react with cycloalkanones and butanal.