title: Torquoselective ring opening of fused cyclobutenamides: evidence for a cis,trans-cyclooctadienone intermediate.
abstract: 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.
authors.affiliation: Division of Pharmaceutical Sciences and Department of Chemistry, University of Wisconsin , Madison, Wisconsin 53705, United States.
authors.forename: Xiao-Na
authors.initials: XN
authors.lastname: Wang
authors.forename: Elizabeth H
authors.initials: EH
authors.lastname: Krenske
authors.forename: Ryne C
authors.initials: RC
authors.lastname: Johnston
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.forename: Richard P
authors.initials: RP
authors.lastname: Hsung
mesh_terms: D001643:Bridged Bicyclo Compounds / Q000737:chemistry; D003500:Cyclization; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D008958:Models, Molecular; D013329:Structure-Activity Relationship; D013449:Sulfonamides / Q000737:chemistry*; D014753:Vinyl Compounds / Q000737:chemistry
chemical_list: D001643:Bridged Bicyclo Compounds; D013449:Sulfonamides; D014753:Vinyl Compounds