Département de chimie moléculaire

The study of a general synthetic route to 1$\sigma$4,3$\sigma$2-diphosphaallenes involving the reaction of LiHMDS with C-phosphoniophosphaalkenes is reported. The choice of the base is crit. since the precursors are highly electrophilic species that react cleanly with Me-, butyl-, mesityl-, or tert-butyl-Li to afford C-phosphanylphosphonium ylides. The role of the substituents at the $\sigma$4-P center also was studied. One resulting phosphaallene [Ph2(iPr2N)P:C:PNiPr2] react cleanly with a Lewis acid and undergo [3+2] cycloaddn. with trimethylsilyl azide to afford a five-membered heterocycle (shown as I) in a three-step process. The crystal and mol. structures of iPr2NP:C:PPh2(NiPr2) and iPr2NP:C:PPh(NiPr2)2 were detd. by x-ray crystallog. [on SciFinder(R)]