Methodology is described for the annulation of five-membered carboxylic rings onto cycloalkanones, using an intramolecular sulfur ylide reaction. Epoxybicyclo[x.3.0]alkanes (x = 3, 4, 5, 6) were obtained from cycloalkanones via the corresponding 2-[3-(phenylthio)propyl]cycloalkanones (2a-d, 7, 11), which were reacted successively with triethyloxonium tetrafluoroborate and potassium fert-butylate. An analogous annulation to give a six-membered ring epoxide from 14 also proceeds smoothly, whereas attempted seven-membered ring formation from 17 was unsuccessful. The stereochemistry of the various annulations was determined and compared with the stereochemistry of the epoxidations of the corresponding olefins (33a-d, 35, 38, 40). These olefins were obtained by intramolecular Wittig reactions. Mechanisms for the ylide cyclizations are discussed.
A process for the stereoselective construction of a cyclopentane ring onto a preexisting cycloalkanone is developed. 2-(3-Iodopropyl)cycloalkanones, obtained by known methods from the parent cyclic ketones, were converted to
Aus den Cycloalkanonen (I) entstehen mit Allylalkohol und Säure die Allyl‐cycloalkanone (II), die Thiophenol in Gegenwart von Azoisobuttersäurenitril (AIBN) zu (III) addieren und dann mit Triethyloxonium‐Salzen in (IV) übergeführt werden.
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