2-Phenyl-1,3,2-dioxaphosphorinane rearranges at 250°C to afford 2-phenyl-2-oxo-l,2-oxaphospholane which is, in turn, converted into the 2-thio derivative by P 4 S 10 . This cyclic thiophosphinate reacts with nickelocene and allyl iodide to yield (L = 2-phenyl-1,2-oxaphospholane) by reduction—complexation. The same scheme is successfully applied to the 1-oxa-2-phosphacyclohepta -4,6-diene nucleus. Thus, the P IV =S reduction—complexation process works with ...