70388-71-5Relevant academic research and scientific papers
Thermolysis of Compounds with a Geometrically Fixed Vinyloxirane Unit: Stereospecific Synthesis of 4,5-Fused cis- and trans-2,3-Dihydrofurans
Eberbach, Wolfgang,Seiler, Wilhelm,Fritz, Hans
, p. 875 - 901 (2007/10/02)
The conformationally fixed vinyloxiranes 7c - f, 8a - f, and 9b - d are transformed thermally into the bicyclic ethers 23 - 25.Starting with the spiro-derivatives c - f, which are monosubstituted at the vinyl group, the ring expansion takes place with high stereospecificity leading to 4,5-fused cis-(c/e) and trans-2,3-dihydrofurans (d/f), respectively.On heating 8b and 9b in the presence of dimethylfumarate besides the isomerisation to 24b/25b two cycloadducts are formed in each case to which the structures of 29/31 and 30/32 have been assigned.Oxapentadienyl dipoles (3) are proposed as intermediates in which the rotation of C/O-bonds is energetically more favorable than rotation of C/C-bonds.The activation parameters for the transformation 8b -> 24b are determined and discussed together with the reported date of some analogous ring expansion reactions.
