title: Computational and experimental investigation of the Diels-Alder cycloadditions of 4-chloro-2(H)-pyran-2-one.
abstract: 4-Chloro-2(H)-pyran-2-one undergoes thermal Diels-Alder cycloaddition with electron-deficient dienophiles to afford, without any significant selectivity, 6-endo- and 5-endo-substituted bicyclic lactone cycloadducts. In contrast to 3- and 5-bromo-2(H)-pyran-2-one, 4-chloro-2(H)-pyran-2-one does not undergo thermal cycloadditions with electron-rich dienophiles. The regio- and stereochemical preferences of the cycloadditions of 4-chloro-2(H)-pyran-2-one and other related 2(H)-pyran-2-ones are investigated computationally. Calculations were carried out on the transition states leading to the four possible regio- and stereoisomeric cycloadducts using density functional theory (B3LYP/6-31G). These studies allow prediction of the regio- and stereoselectivity in these reactions which are in line with experimental observations.
authors.affiliation: Department of Chemistry, King's College, Strand, London WC2R 2LS, UK. kamyar.afarinkia@kcl.ac.uk
authors.forename: Kamyar
authors.initials: K
authors.lastname: Afarinkia
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bearpark
authors.forename: Alexis
authors.initials: A
authors.lastname: Ndibwami