title: Synchronized aromaticity as an enthalpic driving force for the aromatic Cope rearrangement.
abstract: We report herein experimental and theoretical evidence for an aromatic Cope rearrangement. Along with several successful examples, our data include the first isolation and full characterization of the putative intermediate that is formed immediately after the initial [3,3] sigmatropic rearrangement. Calculations at the B3LYP/6-31G(d) level of theory predict reaction energy barriers in the range 22-23 kcal/mol for the [3,3]-rearrangement consistent with the exceptionally mild reaction conditions for these reactions. The experimental and computational results support a significant enthalpic contribution of the concomitant pyrazole ring formation that serves as both a kinetic and thermodynamic driving force for the aromatic Cope rearrangement.
authors.affiliation: Department of Chemistry, The University of Texas at San Antonio, San Antonio, Texas 78249, USA.
authors.forename: David J
authors.initials: DJ
authors.lastname: Babinski
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Bao
authors.forename: Marie
authors.initials: M
authors.lastname: El Arba
authors.forename: Bo
authors.initials: B
authors.lastname: Chen
authors.forename: David A
authors.initials: DA
authors.lastname: Hrovat
authors.forename: Weston Thatcher
authors.initials: WT
authors.lastname: Borden
authors.forename: Doug E
authors.initials: DE
authors.lastname: Frantz