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Torquoselective Ring Opening of Fused Cyclobutenamides: Evidence for a Cis,Trans-Cyclooctadienone Intermediate
journal contribution
posted on 2015-12-17, 04:12 authored by Xiao-Na Wang, Elizabeth H. Krenske, Ryne C. Johnston, K. N. Houk, Richard P. HsungElectrocyclic
ring opening of 4,6-fused cyclobutenamides 1 under thermal
conditions leads to cis,trans-cyclooctadienones 2-E,E as transient intermediates,
en route to 5,5-bicyclic products 3. Theoretical calculations
predict that 4,5-fused cyclobutenamides
should likewise undergo thermal ring opening, giving cis,trans-cycloheptadienones, but in this case conversion to 5,4-bicyclic
products is thermodynamically disfavored, and these cyclobutenamides
instead rearrange to vinyl cyclopentenones.