Cyclopropyl eight-membered rings

An intramolecular version of this acylation of homoallylsilanes leads to 2-cyclopropylcycloal-kanones 10. This reaction gives five-, six-, seven- and even eight-membered ring systems in a highly regiocontrolled manner. In all these cases, the 2-cyclopropyl ketones 7 were isolated as the sole product of intramolecular acylation. . 2-Cyclopropylcyclobutanones were not ob-... 

The ring expansion of the benzoxepinones 134 to benzoxocinones 136 involved a cyclopropanation with diazomethane in the presence of palladium acetate and a catalytic hydrogenation. The cleavage of the more labile internal bond in the cyclopropyl derivatives 135 leads to the eight-membered ketones 136 exclusively in excellent yields (90-95%). Reduction of ketones 136 with sodium borohydride affords the hydroxy derivatives 137 in a stereo-controlled manner (Scheme 34) <2002CC634>. 

The secondary marine metabolite (+)-acetoxycrenulide has unprecedented structural features which prompted L.A. Paquette et al. to embark on its total synthesis. The eight-membered carbocycle of the target was constructed via a Claisen rearrangement. The bicyclic p,y-unsaturated lactone was subjected to Simmons-Smith conditions, that delivered the cyclopropyl ring exclusively from the p-face of the molecule as a result of the predominant ground-state conformation. 

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