Symmetrical spiro-phosphoroheterocycles from the selenation of carbohydrazides

2,4-Bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide (Woollins’ reagent) reacts with benzoic hydrazides in refluxing toluene to give new symmetrical spiro heterocycles in 48–76% isolated yields. However, under identical conditions, treating Woollins’ reagent with thiophene-2-carbohydrazide leads to an additional product, 1,3,4-selenadiazole (27% yield) together with the spiro phosphorus heterocycle in 44% yield. Three representative X-ray structures are reported.