Ring-closing metathesis catalyzed by RuCl2(CHPh)(PCy3)2 has been used to synthesize calix[4]arenes in cone and 1,3-alternate conformations with upper and lower rim alkenyl bridges. Ester, methoxy, and hydroxy groups have been used to probe the effect of substituents on the mode of metathesis. With some substrates, intermolecular metathesis competes with the intramolecular process leading to oligocalix[4]arenes. X-ray diffraction has been used to reveal the molecular structures of two single-bridged calix[4]arenes and of a double-bridged calix[4]arene.

[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.