Wang Xiao-Na, Krenske Elizabeth H, Johnston Ryne C, Houk K N, Hsung Richard P
Division of Pharmaceutical Sciences and Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53705, United States.
J Am Chem Soc. 2014 Jul 16;136(28):9802-5. doi: 10.1021/ja502252t. Epub 2014 Jul 3.
Electrocyclic 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.
4,6-稠合环丁烯酰胺1在热条件下的电环化开环反应会生成顺式、反式环辛二烯酮2-E,E作为瞬态中间体，进而生成5,5-双环产物3。理论计算预测，4,5-稠合环丁烯酰胺同样应发生热开环反应，生成顺式、反式环庚二烯酮，但在这种情况下，转化为5,4-双环产物在热力学上不利，这些环丁烯酰胺反而重排为乙烯基环戊烯酮。
