B. Example. Selenadiazoles 2a and 2b. A 1: 9 Z/E mixture of semicarbazone 1 (2.18 g, 8.4" 01) in 40 mL of anhydrous tetrahydrofuran was treated with selenium dioxide (1.85 g, 16.8" 01) and stirred for 72 h under nitrogen. The reaction mixture was passed through Dicalite, and the cake was washed well with methylene chloride. Concentration of the filtrate and washings supplied a brown oil, which was triturated three times with hot ethyl acetate/ ...
