Torquoselective Ring Opening of Fused Cyclobutenamides: Evidence for a <i>Cis,Trans</i>-Cyclooctadienone Intermediate
作者:Xiao-Na Wang、Elizabeth H. Krenske、Ryne C. Johnston、K. N. Houk、Richard P. Hsung
DOI:10.1021/ja502252t
日期:2014.7.16
Electrocyclic ring opening of 4,6-fused cyclobutenamides 1 under thermal conditions leads to cis,trans-cydooctadienones 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-cydoheptadienones, but in this case conversion to 5,4-bicyclic products is thermodynamically disfavored, and these cyclobutenamides instead rearrange to vinyl cyclopentenones.