N,N'-Bis(1,4-benzodioxane-2-carbonyl)piperazine (Doxazosin EP Impurity C) is an impurity in the synthesis of Doxazosin (D537500), a selective α1-adrenoceptor antagonist. Doxazosin relaxes smooth muscles of the prostate. Molecular Formula: C22H22N2O6 Molecular Weight: 410.42