An attempt is made to directly observe an ethano-bridged (cyclopentyl) oxyallyl using a synthetic methodolgy which employs aprotic solvents and homogeneous conditions involving a novel organometallic reagent and which can be carried out at very low temperatures. However, even with preparation temperatures of -120 degrees C, the 2,5-dimethylcyclopentyl oxyallyl is not observable by in situ NMR spectroscopy. Products corresponding to an oxyallyl + oxyallyl dimerization are observed instead. The major dimer is a cis-dioxane compound, and the formation of this suggests a process under pericyclic control. An analysis of the allowed molecular orbital overlaps is presented, and it is concluded that the mutual overlap involves all three terminal orbitals (overlap 2 in Figure 2), with preferential bond formation taking place between carbon(A)-oxygen(B), oxygen(A)-carbon(B), where A and B are the two oxyallyl monomers. The dioxane product represents only one of four possible double-connectivity ways in which two oxyallyl units can be joined (see Figure 1). The initially formed cis-dioxane product is quite labile and is easily transformed in a sequential and stereospecific manner into products representative of two of the other three connectivity modes. The formation of the parent cyclopentyl oxyallyl was also studied under the same reaction conditions. In this case one sees no dimeric products, but the formation of the oxyallyl is indicated because [4 + 3] diene adducts of the putative oxyallyl can be trapped, in; accord with previous work in this area.