title: Multiple Cycloaddition Reactions of Ketones with a β-Diketiminate Al Compound.
abstract: A β-diketiminate Al compound (1) with an exocyclic double bond reacts with two equivalents each of benzophenone and 2-benzoylpyridine in a [4+2] cycloaddition to generate bicyclic and tricyclic compounds 2 and 3, respectively. Compound 2 consists of six- and eight-membered aluminium rings, whereas 3 has two five- and one eight-membered ring. Compounds 2 and 3 were characterized by a number of analytical tools including single-crystal X-ray diffraction. The quantum mechanical calculations suggest that the dissociation of the solvent molecule from 1 would lead to an active species 1A having two 1,4-dipolar 4π electron moieties, in which the electrophilic site is the Al atom and the nucleophilic positions are polarized exocyclic and endocyclic C=C π bonds. The detailed mechanistic study shows that the dipolarophiles, benzophenone, and 2-benzoylpyridine undergo double cycloaddition with two 1,4-dipolar 4π electron moieties of 1A. Herein, the addition of one molecule of the dipolarophile promotes the addition of the second one.
authors.affiliation: Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen (Germany).
authors.forename: Sankaranarayana Pillai
authors.initials: SP
authors.lastname: Sarish
authors.affiliation: Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen (Germany).
authors.forename: Prinson P
authors.initials: PP
authors.lastname: Samuel
authors.affiliation: Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, 37077 Göttingen (Germany). hroesky@gwdg.de.
authors.forename: Herbert W
authors.initials: HW
authors.lastname: Roesky
authors.affiliation: Ernst-Moritz-Arndt-Universität, Institut für Biochemie, Arbeitskreis Bioanorganische Chemie, Felix-Hausdorff-Strasse 4, 17487 Greifswald (Germany). carola.schulzke@uni-greifswald.de.
authors.forename: Carola
authors.initials: C
authors.lastname: Schulzke
authors.affiliation: Department of Chemistry, National Institute of Technology Calicut, NIT Campus P.O., Kozhikhode 673 601 Kerala (India).
authors.forename: Karikkeeriyil
authors.initials: K
authors.lastname: Nijesh
authors.affiliation: Department of Chemistry, National Institute of Technology Calicut, NIT Campus P.O., Kozhikhode 673 601 Kerala (India).
authors.forename: Susmita
authors.initials: S
authors.lastname: De
authors.affiliation: Department of Chemistry, National Institute of Technology Calicut, NIT Campus P.O., Kozhikhode 673 601 Kerala (India). param@nitc.ac.in.
authors.forename: Pattiyil
authors.initials: P
authors.lastname: Parameswaran
keywords: 2-benzoylpyridine; aluminium; benzophenone; cycloaddition; heterocycles