A novel one-step method for mildly converting cyclic ethers into dibromo compounds is reported. Alcohols, oximes, aldehydes, and ketones are known to react under Appel or Corey-Fuchs reaction conditions, but apparently these have never been applied to oxetanes or larger cyclic ethers. Treatment of 3,3-dimethyloxetane (1) with tetrabromomethane and triphenylphosphine gave the corresponding dibromo compound 1,3-dibromo-2,2-dimethylpropane (2). The less-strained homologue oxolane (6) was also reacted giving 1,4-dibromobutane (7) in a 93% yield. Mechanistic interpretations are offered to explain the observed reaction rates of the conversions described.

In the course of our investigation of the intermolecular reactions of foiled carbenes of the norborn-2-en-7-ylidene type, we have investigated the decomposition of methoxyoxadiazoline 1 in alcohols. Most of the reactions performed lead to products with an anti configuration confirming the participation of the double bond to the stabilization of the transition states. The thermal behavior of spirooxadiazoline 1 is quite different from the behavior of the parent 2-methoxy-2,5,5-trimethyl-∆ 3 -1,3,4-oxadiazoline. Photolysis of 1 leads to the carbene after prior formation of the diazo compound whereas thermolysis cleanly generates an extremely unstable carbonyl ylide 4 that immediately decomposes to the stabilizednucleophilic carbene 5 and methyl acetate without genera-

Bromination of the polycyclic oxetane 2,4-oxytwistane (rac-(1R,3S,4R,7S,9R,11S)-2-oxatetracyclo[5.3.1.0(3,11).0(4,9)]undecane) was undertaken in order to form 2,4-dibromotwistane. The oxetane was subjected to the mild reagent combination CBr4/Ph3P in a fashion similar to that for the Appel and Corey-Fuchs reactions. NMR spectroscopy revealed that the isomeric dibromo compound 2,8-dibromoisotwistane (2,8-dibromotricyclo[4.3.1.0(3,7)]decane) was inadvertently formed. The conversion was prevented by migration of a C-C bond within the geometrically stressed C10 framework. Computational chemistry was used to model the structure of the polycyclic oxetane and to assess the component of total ring strain energy due to the four-membered heterocycle. Mechanistic aspects behind the skeletal rearrangement are also discussed.

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