Expanding the chemistry of ring-fused 1,4-diphosphinines by stable mono anion formation.

A new sulfur-enriched tricyclic 1,4-diphosphinine (2) was synthesized and novel reactivity studies on the phosphorus heterocycle were performed: a weak anionic nucleophile (KHMDS) adds selectively thus forming a stable anionic 1,4-diphosphinine derivative (3b) which was fully characterized. The substitution potential of 3b was demonstrated using Ph2PCl to give 4b, while oxidation of 3b using elemental iodine furnished cleanly the P-P coupling product 5.