Intramolecular carbon-hydrogen insertion on cupric sulfate assisted decomposition of diazomethyl ketones derived from four l-methylcycloalkanecarboxylic acids and (hexahydrophenyl)acetic, homopivalic, and enanthic acids is shown to yield mostly cyclopentanones. The yields are appreciable in the conformationally favorable cases, and insertion in the solvent cyclohexane can be avoided by the use of Freon TF as the solvent The conversion of a pimaradienic diterpene into a 14-iso-16-androstanone derivative shows the power of the new method of cyclopentanone synthesis.

Selenide (a) to selenoxide (b) or selenone (c) oxidation is a useful operation in organic synthesis, and a variety of reagents have been developed for this purpose. a b C Most investigations have focused on the preparation and reactivity of selenoxides,' but selenones have received little attention. Selenones have been prepared by oxidation of selenides using an excess of peroxycarboxylic acids,2 potassium permanganate,2 or hydrogen peroxide in the presence of seleninic acid.3 These methods have several disadvantages and can be applied only to selenides with limited structural features in the presence of selected solvents.Herein, we report that potassium hydrogen persulfate, commercially available as Oxone, can be used effectively for the direct conversion of selenides to selenones under very mild conditions. When selenides are treated with 3 mol equiv of Oxone in a methanolic, aqueous, buffered solution (pH 8.0-8.5) at room temperature, selenones are produced in good yield. The amount of buffered solution added in these reactions is crucial for success to selenone formation because the oxidation process involves the generation of acids, and Oxone has shown a strong pH dependence as ~x i d a n t .~ This protocol was applied to the oxidation of three classes of substrates: alkylaryl selenides, #?-methoxyalkyl selenides, and b-hydroxyalkyl selenides. The reactions can easily be monitored by TLC since selenones are more polar than selenides but less polar than selenoxide intermediates. Selenones exhibit a characteristic IR absorption at 870-970 and 912-1059 ~m -l ,~ and in 13C

and references therein.(11) Subtle differences of energy content of the two dienes 4 are noted also from a study of equilibration of their nuclear double bonds [E. Wenkert and Z. Kumazawa, ibid., 140 (1968)]. While 4a remained unfazed, acid-induced isomerization of 4b led to an equilibrium mixture of 2a, 4b, and sandaracopimaradiene.

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