title: Preference for the Diels-Alder addition of dienes syn to the O atom in cross-conjugated spirocyclic cyclohexadienones.
abstract: In the Diels-Alder reaction, the preferred addition of dienes syn to the O atom in cross-conjugated cyclohexadienones containing an oxa-spiro ring system is observed. The two structures reported here, namely rel-(1R,4aR,9S,9aS,10R)-4a,9,9a,10-tetrahydro-9,10-diphenylspiro[9,10-epoxyanthracene-1(4H),2'-oxiran]-4-one, C27H20O3, and rel-(1R,4aS,9R,9aS,10S)-4a,9,9a,10-tetrahydro-9,10-diphenylspiro[9,10-epoxyanthracene-1(4H),2'-oxetane]-4-one, C28H22O3, are the minor and sole products, respectively, of the reactions of diphenylisobenzofuran with two slightly different cyclohexadienones. These structures differ in the size of the oxa-spiro ring, by one C atom, and in the relative configuration at the spirocyclic ring C atom, leading to some minor conformational differences between the two compounds.
authors.affiliation: Evans Chemical Laboratories, Department of Chemistry, The Ohio State University, Columbus, Ohio 43210, USA. gallucci.1@osu.edu
authors.forename: Judith C
authors.initials: JC
authors.lastname: Gallucci
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Tamura
authors.forename: Leo A
authors.initials: LA
authors.lastname: Paquette