Diels-Alder approach to biaryls: elucidation of competing tandem [2+2] cycloaddition/[1,3] sigmatropic shift pathway
Bradley O Ashburn1, Rich G Carter, Lev N Zakharov
1Department of Chemistry, 153 Gilbert Hall, Oregon State University, Corvallis, Oregon 97331, USA.
Abstract:
Reaction of 2-halo-6-nitrophenylacetylene with an electron deficient diene gives rise to a [4+2] cycloaddition/cycloreversion biaryl product and a bicyclo[4.2.0]octadiene resulting from a competing [2+2] cycloaddition pathway. The cyclobutene can be opened to give a mixture of cyclooctatriene and biaryl in varying amounts depending on heat and light exposure. The conversion of the cyclobutene into biaryl occurs through a [1,3] sigmatropic carbon shift followed by [4+2] cycloextrusion of ethylene gas.
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