title: Cyclobutenone-Based Syntheses of Polyquinanes and Bicyclo[6.3.0]undecanes by Tandem Anionic Oxy-Cope Reactions. Total Synthesis of (+/-)-Precapnelladiene.
abstract: The addition of ethenyllithium derivatives to the carbonyl of dialkyl squarate-derived bicycloheptenones, e.g., 1a and 6a, initiates a low-temperature anion-accelerated oxy-Cope rearrangement to provide polyquinanes by a transannular aldol reaction of the intermediate bicyclo[6.3.0]undecadienone 4. Additional functionality is introduced by alkylation of the enolate 3 resulting from the oxy-Cope rearrangement. Phosphorylation or triflation of enolate 3 provides an entry into the bicyclo[6.3.0]undecane ring system. An application of this new methodology is demonstrated by the total synthesis of the sesquiterpene natural product (+/-)-precapnelladiene from diisopropyl squarate (10 steps, 12%).
authors.affiliation: Department of Chemistry, University of California, Irvine, California 92697-2025.
authors.forename: James M.
authors.initials: JM
authors.lastname: MacDougall
authors.forename: Vincent J.
authors.initials: VJ
authors.lastname: Santora
authors.forename: Sharad K.
authors.initials: SK
authors.lastname: Verma
authors.forename: Philip
authors.initials: P
authors.lastname: Turnbull
authors.forename: Cameron R.
authors.initials: CR
authors.lastname: Hernandez
authors.forename: Harold W.
authors.initials: HW
authors.lastname: Moore