title: 3,4- and 3,5-Disubstituted 2-Pyridones Using an Intermolecular Cycloaddition / Cycloreversion Strategy: Toward the Synthesis of Aristopyridinone A.
abstract: The intermolecular cycloaddition of pyrazinone precursors with alkyne substrates was evaluated. The resulting regioisomeric [2.2.2]-diketopiperazine alkene cycloadducts were diverted into 2-pyridone products through cycloreversion of the [2.2.2]-bicyclic intermediates. New insights into the regioselectivity of pyrazinone azadiene Diels-Alder reactions as well as cycloreversion reactivity were revealed in this study. Synthetic sequences using this [4+2]/r[4+2] strategy were determined that can produce predominantly the 3,5-disubstituted 2-pyridone alkaloid structures; pyridones featuring the 3,4-substitution pattern are observed as the minor regioisomeric products.
authors.affiliation: Department of Chemistry, The College of William & Mary, P. O. Box 8795, Williamsburg, VA 23187, USA.
authors.forename: Maren K
authors.initials: MK
authors.lastname: Leibowitz
authors.affiliation: Department of Chemistry, The College of William & Mary, P. O. Box 8795, Williamsburg, VA 23187, USA.
authors.forename: Ethan S
authors.initials: ES
authors.lastname: Winter
authors.affiliation: Department of Chemistry, The College of William & Mary, P. O. Box 8795, Williamsburg, VA 23187, USA.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Scheerer
keywords: 2-Pyridone; Aristolochia; Aristopyridinone; Cycloaddition/cycloreversion; alkaloid synthesis