Formation of new organoselenium heterocycles and ring reduction of 10-membered heterocycles into seven-membered heterocycles

Reacting 2,4-bis(phenyl)-1,3-diselenadiphosphetane-2,4-diselenide {PhP(Se)(μ-Se)}₂], Woollins’ reagent, with an equivalent of aromatic diol in refluxing toluene afforded 10-membered phosphorus-selenium heterocycles 1 and 2 with an O-P(Se)-Se-Se-P(Se)-O linkage. Two equivalents of aromatic diol and Woollins’ reagent in refluxing toluene gave seven-membered phosphorus-selenium heterocycles 3 and 4 with an O-P(Se)-O linkage together with 10-membered phosphorus-selenium heterocycles 1 and 2. It was also found that the diphosphorus species O-P(Se)-Se-Se-P(Se)-O rings 1 and 2 could be readily ring contracted into the monophosphorus rings 3 and 4 in almost quantitative yields via further reaction with another equivalent of corresponding aromatic diol. One representative X-ray structure is reported.