Aroylspirophosphoranes bearing two naphth-1,8-diyl-8-oxy groups: synthesis, crystal structure, and np(Oapical)→π∗(Cdouble bond; length as m-dashO) charge transfer interaction

The reactions of aroyl chlorides with the lithium phosphoranide generated from bis(naphth-1,8-diyl-8-oxy)phosphorane 1 afforded aroylspirophosphoranes 3a–f. The p-anisoyl- and p-tert-butylbenzoylphosphoranes 3a and 3b bearing an electron-donating aryl group were stable to moisture on silica gel. The crystal structures of p-anisoyl-, p-tert-butylbenzoyl-, benzoyl-, and p-fluorobenzoylphosphorane (3a, 3b, 3d, and 3e) elucidated by X-ray structural analysis suggested effective intramolecular np(Oapical)→π∗(Cdouble bond; length as m-dashO) charge transfer stabilization to be operative.