An Unusual Samarium Diiodide Mediated Reductive Ring Contraction of a Tricyclic Oxazine to a Highly-Functionalized Cyclopentane and Cyclobutane

[reaction--see text] Samarium diiodide mediated reductive ring contraction of a substituted tricyclo[2.2.2]oxazine at 25 degrees C leads to a mixture of cyclopentane and cyclobutane rearrangement products with complete diastereoselectivity in each case. At -78 degrees C, the anticipated amidocyclohexanol reduction product is obtained exclusively, while the cyclopentane is the sole product at reflux in THF.