?-Facial and Tautomeric Selectivities during Diels-Alder Capture of Isodicyclopentadienes by Highly Reactive Dienophiles

Article abstract of DOI:10.1021/jo00370a022

The reactions of isodicyclopentadiene (1) with hexafluoro-2-butyne, cyclooctyne, cyclobutadiene, and (methoxyvinylcarbene)tungsten pentacarbonyl have been investigated.Cycloaddition involving the two acetylenic dienophiles proceeds with exclusive below-plane stereoselectivity at room temperature and below.When the cyclooctyne reaction mixtures are warmed, increasing amounts of product arising from <4 + 2> addition to the <1,5> sigmatropic isomer of 1 make their appearance.Interestingly, cyclobutadiene was found to add only to 2.In the case of the Fischer carbene complex, rapid reaction occured to give the syn- sesquinorbornene adduct only.Oxidation of this product with dimethyl sulfoxide led to an ester identical with the adduct derived directly from methyl acrylate and 1.Structural assignments were made where appropriate on the basis of spectral data, X-ray crystal structure determination, and chemical interconversions.