Unsaturated enol acetates such as 20-a~ etoxy-A1~**~-dienes, readily obtainable by the reaction of A16-20-keto steroids with isopropenyl acetate, are convertible in excellent yield to the hitherto inaccessible 21-i0do-A~~-20-ketosteroids by treatment with N- iodosuccinimide in dioxane solution. Replacement of the halogen atom by acetate proceeds in nearly quantitative yield, thus opening a route to the A16-20-keto-21-acetates and ...
