Thianthrene cation radical perchlorate (1) reacted with azo-bis-2-phenoxy-2-propane (6) to give thianthrene (2), cisthianthrene-5,10-dioxide, 5-(p-hydroxyphenyl) thianthrenium perchlorate (10), acetone, phenol, and 5-(2-propenyl) thianthrenium perchlorate (11) when the mole trtio of 1 to 6 was 1:1. Among the products, 11 was a new compound. However, when the corresponding mole ratio was 5:1, 11 was not formed. Similar result was obtained for azo-bis-2-(p-nitrophenoxy)-2-propane.