2,4,8,10-Tetraoxaspiro[5.5]undecane, 3,9-diethylidene-

3,9-Diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane(DETOSU) it is mostly used as a liquid owing to its low crystallization tendency, it is relatively unstable. It hydrolyzes rapidly even in the presence of only water traces and spontaneously isomerizes during storage to the diallylacetal DVTOSU, which is inactive for the polymerization.

3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane is used as a reactive bifunctional monomer that forms biodegradable polyorthoesters by polyaddition with α,ω-diols.

3,9-Diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane is prepared in a rearrangement reaction of DVTOSU, it is an exothermic reaction that also occurs spontaneously with complete conversion.[2] For production on an industrial scale, the rearranged is carried out at elevated temperatures in the presence of catalysts.