Studies on Conformation and Reactivity. II. The Polyphosphoric Acid-catalyzed Ring Opening of 4, 5-Epoxy-3-oxo Steroids. 2. The Synthesis of 4-Ethylthio-17β-acetoxyandrost-4-en-3-one and its Analogs.

The efficient catalytic action of polyphosphoric acid, when used in the presence of alkylmercaptans as nucleophiles, of normal ring opening of 17β-acetoxy-4, 5-epoxyandrostan-3-one (VII), was reported. With ethanethiol in PPA-dioxane at room temperature, VII afforded 4-ethylthio-17β-acetoxyandrost-4-en-3-one(VIII), and a further product, 17β-acetoxy-3, 4-bis(ethylthio)androsta-3, 5-diene (IX), accompanied by the third product with a transparent ultraviolet spectrum, the structure of which was tentatively assigned as 4β-ethylthio-5α-hydroxy-17β-acetoxy-5α-androstan-3-one (X). Ethanedithiol and 2-mercaptoethanol also reacted with VII, as expected, affording 17β-acetoxyandrosta 3, 5-dieno [3, 4-b]dithiane (XI) and its oxathiane (XII) derivative respectively. Unique ultraviolet absorption data of the dithiane (XI) and oxathiane (XII) was referred to in connection with the suggestion of presence of some unique conjugation in the -S-C3=C4-S- and -O-C3=C4-S- systems in these compounds.