Wang, Xiao-Na Krenske, Elizabeth H. Johnston, Ryne C. Houk, K. N. Hsung, Richard P. Torquoselective Ring Opening of Fused Cyclobutenamides: Evidence for a <i>Cis,Trans</i>-Cyclooctadienone Intermediate Electrocyclic ring opening of 4,6-fused cyclobutenamides <b>1</b> under thermal conditions leads to <i>cis,trans</i>-cyclooctadienones <b>2</b>-<i>E</i>,<i>E</i> as transient intermediates, en route to 5,5-bicyclic products <b>3</b>. Theoretical calculations predict that 4,5-fused cyclobutenamides should likewise undergo thermal ring opening, giving <i>cis,trans</i>-cycloheptadienones, but in this case conversion to 5,4-bicyclic products is thermodynamically disfavored, and these cyclobutenamides instead rearrange to vinyl cyclopentenones. ci;bicyclic;cyclobutenamides 1;Fused Cyclobutenamides;case conversion;Torquoselective Ring;ring opening;vinyl cyclopentenones 2015-12-17
    https://acs.figshare.com/articles/dataset/Torquoselective_Ring_Opening_of_Fused_Cyclobutenamides_Evidence_for_a_i_Cis_Trans_i_Cyclooctadienone_Intermediate/2039205
10.1021/ja502252t.s004